Maxplanckresearch 3/2020

03 | 2020 Using a tree’s natural defenses 03 ECOLOGY GIVE TAKE AND | 2020 MAX PLANCK The light convertersThe NANOCHEMISTRY Research Risky cooling CLIMATE RESEARCH 2 Max PlanckResearch ·3 | 2020 who are suffering from the from who suffering are In the corona crisis, politics politics crisis, corona the In S Researchers are following are Researchers fundamentally, away from level of savings in privatelevel in of savings households never been has businesses and individuals on even to taking breaking both developments with with developments both in savings accounts. in Germany have changed Germany in new debts so that moneynew is debts that so great interest. great crisis. At the same time, the the time, At same the crisis. available to support support to available setting aside 150 EUR setting billion Germans with high, so ave or spend?

ILLUSTRATION: ALESSANDRO GOTTARDO EDITORIAL

Dear reader,

“To give is more blessed than to receive” – these words from the New Testament just about sum up the most important things that can be said on this subject. However, in a survey conducted by the Bertelsmann Stiftung in February of this year, 41 percent of respondents agreed with the statement “People do not care about their fellow human beings.” Then the coronavirus came along and changed everything. A wave of helpfulness has now swept the country. Neighbors have been helping neighbors, shopping services have been set up for elderly people, and regular customers have been collecting money for small stores and cafés that had to close during the lock- down. Another survey conducted in June showed that only 21 percent of respondents still believed that people do not care about their fellow human beings.

However, it is also clear that the coronavirus is deepening the social divide: people who were already disadvantaged have been hit particularly hard by the lock- 3 down and its economic effects. This is intensifying the social inequality that had already been growing in our country for some time – a subject that we examine in greater depth in the “Focus” section of this magazine.

The coronavirus crisis has also brought about astonishing changes in the relationship between the government and the economy. Over the last few decades, political leaders and their policies have disengaged from economic activities and public duties and services have been privatized. This trend now shows signs of reversing – and not only in the field of crisis management.

Covid-19 can affect anyone, but the course it takes varies widely. This has focused attention on our immune system. The immune system is also regulated by a certain give and take, a balance between the body’s ability to defend itself and the undesirable effect of the body attacking itself and developing autoimmune diseases.

On that note: stay healthy, and use your time for some exciting reading!

Your editorial team

Max Planck Research · 3 | 2020 4 A skin cancer cell like this this like cell cancer A skin 40 to the human immune system. immune human to the one presents a challenge challenge a presents one

ENDANGERED

48 Christof Paar is a Max Planck aMax is Paar Christof Director – and chose his his chose –and Director educational path later on in life. later on in path educational

SKILLED 56 40 Max Planck Research Research Planck Max · 3 Black poplars deploy poplars Black aspecial 56 against pests. against strategy to protect themselves themselves protect to strategy | 2020

SHREWD Volcanoes are inspiring new new inspiring are Volcanoes 70 70 climate heating. climate ideas forideas to halt aprocedure

LEARNED 48 70

PHOTOS: SCIENCE PHOTO LIBRARY / STEVE GSCHMEISSNER (TOP LEFT); LARA WITTHAUT, FOTO-OSTERMANN.DE FOR MPG (TOP RIGHT); ANDREAS BÖCKLER / MPI FOR CHEMICAL ECOLOGY (BOTTOM LEFT); PICTURE ALLIANCE / ASSOCIATED PRESS | ICHIRO OHARA (BOTTOM RIGHT) CONTENT

20 | VIEWPOINT Trees stand for strength and steadfastness. This is because trees can neither run Global migration and the “great nor hide from enemies. Nevertheless, trees reshaping” are by no means defenseless.

The coronavirus pandemic, economic 62 | Beyond the emergency recession and climate change are the three global crises that will reshape the future Five years ago, the arrival of thousands of of societies and have a significant impact on refugees within a short period of time migration. presented the administrative offices of the German municipal authorities with 5 a huge challenge. How did they handle FOCUS the situation? Give and take 64 | The light converters 26 | Underestimated inequality The sun sends more energy to Earth than Social inequities are increasing, yet no broad humanity needs. Special materials are alliance for a greater redistribution of wealth designed to put this supply to use for a has emerged in democratic countries. whole host of purposes. Why is this the case? And how do immigration and poverty influence attitudes towards 70 | Risky cooling state intervention? Experts are discussing whether geoengineering involving the targeted release 34 | Not just in times of crisis of the gas could reduce global warming. An analytical look at the state’s economic and financial activities shows that rather 78 | POST FROM ... than leaving everything to the market, the state has begun playing an active role in Rehovot, Israel economic policy.

40 | Immunity – a balance between 80 | COMMUNITY NEWS attack and defense Everything has its price – especially health. 82 | FIVE QUESTIONS But what might the evolutionary costs of About environmental protection perfect immunity be? And why are we not in Brazil equipped to fight all pathogens?

83 |IPUBLISHER’S INFORMATION

Max Planck Research · 3 | 2020 THE MOST ACCURATE WEIGHING SCALE IN THE WORLD: THE KATRIN EXPERIMENT IN KARLSRUHE.

Quarks, leptons, photons, gluons – the world of physics features a bewildering diversity of particles – a veritable “particle 6 zoo”. What’s more, some of these minuscule building blocks of matter occur in several different forms. One of the most abundant particles in the universe, the neutrino, exists in three types that are constantly transforming into one another in a phenomenon known as oscillation. This has wide-ranging consequences. For a long time, it was assumed that neutrinos had no mass – in other words, that they weighed nothing at all. But with absolutely no mass, oscillation between the three types of neutrino would quite simply be impossible.

Now, in order to measure the tiny mass of a neutrino, scientists have developed the most precise weighing scale in the world. Dubbed KATRIN, this scale is located at the Karlsruhe Institute of Technology (KIT) and consists of a high-precision spectrometer and an extremely strong tritium source. When this heavy variant of hydrogen undergoes radioactive decay, one electron and one neutrino are emitted. The energy released in this process is divided between the two particles – and the neutrino carries off at least as much energy as corresponds to its mass. Accordingly, the spectrometer data allows the scientists to draw conclusions about the “weight” of the neutrino.

The team led by Susanne Mertens from the Max Planck Institute for Physics is part of this international experiment. In 2019, the researchers calculated the mass of a neutrino for the very first time. The result: its mass is less than an electron volt. This is the world’s most accurate value so far, but the KATRIN scientists are certain that far greater precision can be achieved.

Max Planck Research · 3 | 2020 Max PlanckResearch ·3 | 2020 LOCATION ON ON

PHOTO: MARKUS BREIG/KIT 7 8

“It’s really amazing how quickly PHOTO: DEREK HENTHORN FOR MPG; ILLUSTRATION: HENNING BRUER research into CRISPR-Cas9 and its possible applications has developed in recent years.”

Max Planck Research · 3 | 2020 NOBEL PRIZE IN CHEMISTRY

EMMANUELLE CHARPENTIER

CRISPR-Cas9 as an adaptive im- also relatively straightforward in mune system that bacteria and ar- terms of its operation, it’s hard to chaea use to defend themselves imagine laboratory work without it CRISPR-Cas9 contains two molecules of RNA from attacks by viruses. In 2011, nowadays. However, CRISPR-Cas9 that can be combined Emmanuelle Charpentier and her has not only revolutionized basic into a single molecule. research groups, who were con- research, but has also become an A recognition sequence ducting joint research at Umeå indispensable tool in medicine, matching a specific University and the University of biotechnology, and agriculture. In- 9 sequence on the DNA Vienna at the time, described deed, physicians around the world strand directs the enzyme Cas9 to the location where tracrRNA – an RNA molecule that are working flat out to convert the it should cut the strand. activates the CRISPR-Cas9 CRISPR-Cas9 technology into system. A year later, Charpentier therapies for as-yet-untreatable and Doudna published their fin- diseases. Microorganisms with dings describing exactly how modified genetic material are in- CRISPR-Cas9 homes in on the tended to improve the efficiency of correct location in the DNA strand food and medicine production. With some discoveries, it seems like it and how the system can be used as And agricultural crops whose ge- will only be a matter of time before a tool for modifying genetic mate- netic material has been modified they are honored with the Nobel rial. using CRISPR-Cas9 promise Prize, and the CRISPR-Cas9 higher yields and greater resis- gene-editing scissors were one The key discoveries that paved the tance to diseases and environmen- such discovery. In early October, way for the award are therefore just tal impacts. the time had finally come: the nine years old. This unusually Royal Swedish Academy of Sci- short time frame for the awarding But as with any new technology, the ences awarded the Nobel Prize in of a Nobel Prize serves as a testa- gene-editing scissors also involve Chemistry 2020 to Emmanuelle ment to the colossal importance of some risks. So far, there has been Charpentier for her work on the research conducted by Em- barely any research into the envi- CRISPR-Cas9. She shares the manuelle Charpentier and Jennifer ronmental impacts of the release of prize with Jennifer Doudna, a mo- Doudna. In the ensuing period, re- genome-edited plants and animals. lecular biologist at the University searchers have refined CRISPR- Moreover, the genetic modifica- of California, Berkeley. Charpen- Cas9 into a precise genetic tool tion of cells in the human germline tier is the Director of the Max that can correct defective DNA as (e.g. to create “designer babies”) is Planck Unit for the Science of easily as if it were a document in a highly controversial from an ethi- Pathogens in Berlin and is consid- word-processing program. This cal perspective. It is up to society ered one of the world’s leading ex- technique is therefore also referred and political leaders to weigh up perts on the infectivity and immu- to as genome editing and can be the pros and cons of genome edi- nity of pathogenic bacteria. In the used to study a whole host of scien- ting and to establish a legal frame- 2000s, researchers identified tific questions. As the method is work for its use.

Max Planck Research · 3 | 2020 10

“The Nobel Prize

is a fitting honor PHOTO: DEREK HENTHORN FOR MPG; ILLUSTRATION: HENNING BRUER for the team that has worked incredibly hard for 30 years to make us better.”

Max Planck Research · 3 | 2020 NOBEL PRIZE IN PHYSICS

REINHARD GENZEL

Cosmic swarm: the black hole at the heart of the Milky Way reveals itself by the pull it exerts on nearby objects. This image shows the paths of Reinhard Genzel and his group have longer wavelengths by the very stars as they orbit the achieved a number of ground- strong gravitational field of the gravitational monster at varying degrees of breaking results. For over three black hole and therefore appears proximity. Reinhard decades, the researchers have been with a reddish color. This change Genzel and his team have using infrared instruments to in wavelength is exactly in line worked relentlessly for study the center of our galaxy. with the prediction made by Ein- many years to track the There, they follow the movement stein’s general theory of relativity. 11 stars’ movements, thereby of stars swirling around the invisi- In the spring of this year, Reinhard gaining valuable astrophysical insights. ble object like moths around a light. Genzel and his colleagues pu- Based on these observations, the blished their results from another astronomers have determined the series of observations: the orbit of gravitational giant’s mass – with a the star S2 does not remain sta- very high degree of accuracy – to tionary in space, but instead moves be around 4.3 million solar masses. slowly forward – so that multiple Deep in the heart of the Milky Way Because this mass is concentrated orbits of S2 create the shape of a lurks a massive black hole. At a dis- within a small space, the research- rosette. This is another effect that tance of 26,000 light-years from ers believe that a black hole is the was predicted by Einstein’s theory. Earth, this behemoth is hidden be- most plausible explanation. hind dense curtains of gas and The astronomers made their observa- dust. Nevertheless, the phantom Further studies by the team have re- tions using sensitive instruments has been exposed by astronomers, vealed, for example, that stars in such as Gravity, Sinfoni and Naco, chief among whom are Reinhard the center of the galaxy exhibit an all of which are operated at the Genzel, Director at the Max unusual mass spectrum. Moreover, Very Large Telescope (VLT) of the Planck Institute for Extraterre- the scientists have discovered in- European Southern Observatory. strial Physics in Garching, Ger- frared flares that are thought to The instruments were built under many, and the American re- arise from gas close to the inner ac- the direction of the Max Planck searcher Andrea Ghez from the cretion disc of the black hole. Gen- Institute for Extraterrestrial University of California. In recog- zel’s group has also found that gas Physics and scan the sky in the in- nition of their work, the two scien- is swirling around the black hole at frared region. By combining the tists are sharing one half of the a speed equal to 30 percent of the light from the four eight-meter 2020 Nobel Prize in Physics. The speed of light. mirrors within an underground other half of the prize has been laboratory, the researchers create awarded to the British theorist In 2018, the researchers succeeded in what is known as an interferometer. Roger Penrose for his detailed verifying the so-called “gravita- This virtual telescope has a diame- mathematical description of black tional redshift” of a star for the ter of 130 meters, and its detail resolu- holes as a consequence of the gen- first time. The light from S2, as tion is so precise that you could dis- eral theory of relativity. the star is known, is stretched to cern a one-euro coin on the moon.

Max Planck Research · 3 | 2020 12

VIRTUAL VISIT PHOTO: CYBER VALLEY THE CHANCELLOR’S Valley into being, came and informa Angela MerkelAngela wanted to im form an Tuebingen play and Stuttgart a key visit, which in she originally had jects. The visit also included The visitjects. also aproject presentation of start-ups by the three pression of Cyber Valley, artificial the tion about pro- its research current tour, a brief overview of how Cyber tended took the person, to make in field.this The InstituteMax Planck now is that Europe’s in facility largest form of aone-hour video conference for Intelligent Systems’ in campuses intelligence (AI) research consortium role in this venture.role this The Chancellor’s in on October 21on October and included avirtual SUSAN TRUMBORE age and slow growth rates of certain tropical tree tree tropical of certain rates slow and age growth have, great the forher team example, determined Trumbore Susan research. and system to Earth measurements radiocarbon played introducing in role she critical cycle the and carbon into the Trumbore’s to research contribution remarkable emphasized Thejury dynamics. system for her work field the Prize in Earth of Balzan awarded 2020 the been has Biogeochemistry for Planck Institute of Max the The Director AWARD-WINNING - - -

The Chancellor appears to have appears The Chancellor been Karliczek, Baden-Wuerttemberg’sKarliczek, Minister President Winfried Kret President Winfried Minister lor, web the conference attended was have initiative. from the that arisen by Federal Anja Minister Research impressed. “Cyber Valley demonst- rates the attractiveness of Germany attractiveness the rates ness leaders workness and hand in hand cabinet. ence Minister in Kretschmann’s in ence Minister applications and business models,” business and applications location. and Scientists AI busi an as show how excellent be can research schmann, and Bauer, Theresia schmann, Sci Merkel.said Along Chancel the with to innovative transferred successfully

projects involvingprojects young scientists. flowinto research will of 750,000 francs Swiss money of prize the Half sciences. natural and humanities the between alternation in annually awarded is Prize The Balzan soils. in stored be can at which carbon rates the overestimating are research also proves that current global models global proves current that also research of for Their up to ten years. periods carbon supply short in is when by carbon storing survival their ensure trees that They discovered species.

Max Planck Research Research Planck Max an insight into the workings workings insight into the an of the Max Planck Institute Planck Institute of Max the Digital whistle-stop tour: whistle-stop Digital in Tuebingenin by video. for Intelligent Systems for Intelligent Angela Merkel gained Merkel gained Angela · 3 | 2020 - - - -

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------PHOTO: MPI FOR BIOCHEMISTRY / ANNA SCHROLL PHOTO: SOUTH AFRICAN RADIO ASTRONOMY OBSERVATORY (SARAO) 20 more added.20 to be telescopes, with of 64 consists currently observatory MeerKAT radio the Tuned to space: in

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FATALITIES

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FEB MAR IN BRIEF IN MAR MAR MAR ·3 APR APR | 2020 APR APR MAY

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PHOTO: NASA / JPL-CALTECH / UCLA / MAX PLANCK INSTITUTE FOR SOLAR SYSTEM 19 STUDIES / GERMAN AEROSPACE CENTER / IDA / PLANETARY SCIENCE INSTITUTE GLOBAL MIGRATION AND THE “GREAT RESHAPING”

The future of societies worldwide is currently being reshaped at a fundamental level by concurrent crises: the coronavirus pandemic, the resulting economic recession and climate change. Steven Vertovec considers how these three crises are seriously affecting global migration. He describes the complex factors that relate to global migration and outlines the challenges that loom ahead.

National politics, international institutions, legal parameters and economic structures and social practices are already undergoing a process of fundamental change today. Until now, migration has been an important driver of economic vitality, social transition and political changes all over the world. However, the pandemic has had a hugely negative impact on global migration. Now that borders are largely closed and economies are constrained, millions of migrants have been made destitute. As key workers, many migrants are disproportionately exposed to the risk of infection with Covid- 19 in hospitals and care homes, food factories and agricultural businesses. Whether or not they are seen as being highly skilled or low skilled, currently migrants all over the world are also particularly affected by job losses.

At the same time, national politics, international institutions, legal and economic structures and social practices are already undergoing a process of fundamental change. As a result of the pandemic, the International Monetary Fund, the World Bank and the European Union all forecast the worst economic breakdown since the Great Depression. In fact, this breakdown has already started. A reduction in demand for goods and services, the interrup- tion of supply chains and the resulting bankruptcy among businesses are all leading to large scale unemployment. The recession is also taking its toll in the developing countries. Before the outbreak of Covid-19, the amount of money transferred by migrants to their home countries totaled more than USD 554 billion. That corresponds to triple the amount of money contributed

Max Planck Research · 3 | 2020 VIEW POINT

STEVEN VERTOVEC

Steven Vertovec, who is from the U.S., studied anthropology and religious science. He gained his doctorate at the University of Oxford, where he eventually became Professor for Transnational Anthropol- ogy and the Director of the ILLUSTRATION: SOPHIE KETTERER SOPHIE ILLUSTRATION: Centre for Migration, Policy and Society. In 2007, he was appointed Director at the Max Planck Institute for the Study of Religious and Ethnic Diversity in Goettingen. He has worked as an expert and an adviser on migration issues on behalf of various British ministries, the World Bank, the European Commission, the G8 and UNESCO. His core theories on migration are reflected in his concept of “superdiversity”, which describes the growing complexity of many societies around the world.

Max Planck Research · 3 | 2020 by the industrial nations as development aid. These transfers have already decreased by 20 percent, and further reductions will follow. For dozens of countries and countless households, this money is essential in order to survive. Now that these payments are being reduced, a large number of people will inevitably fall into extreme poverty

The climate crisis will have significantly worse and more far-reaching consequences on global migration than the pandemic and economic crisis. The Intergovernmental Panel for Climate Change assumes that by 2050, global warming will be at least 1.5 degrees above pre-industrial levels, and possibly even higher (particularly in certain regions). Both MIGRATION IS “rapid” changes are expected, such as extreme weather events and flooding, as well as “slow” changes through ongoing A HOUSEHOLD droughts, a rise in sea levels and a decrease in the supply of food and clean water. Estimates of how many “climate migrants” STRATEGY: will be created as a result vary widely. The International Organiza- tion for Migration estimates that by 2050, between 200 million ONE MEMBER and one billion people will have to leave their homes due to LEAVES HOME the climate crisis. 22 IN ORDER TO Before the pandemic, there were around 272 million migrants worldwide (or 3.5 percent of the total global population). We SUPPORT THE know from research that migration is never a question of obvious push-and-pull factors or clear differentiations between voluntary OTHERS FROM and enforced migration. When viewed as a system, migration FAR AWAY is so multi-faceted that it makes sense to apply complexity theories used in mathematics and physics. Important factors here are the growing number of migrants and their increasing differen- tiation with regard to age, gender, level of education, nationality and legal status. These features are increasingly interacting and mixing, creating emergent new systems. All this leads to unforeseeable processes and unpredictable chains of events.

The reasons why people are leaving their home countries also vary widely. Instead of the simple concept that persecution leads to “refugees” and poverty leads to “economic migrants”, we have to understand that migration always has several causes that are interwoven. Among others, these include political reasons, such as when a state riddled with corruption, suppression and violence, failing to provide for its people. Other causes are of a social nature, such as the desire for education, health and wellbeing, or the causes may also be economic and demographic, arising from increasing competition for resources due to a growth in the population, for example. Finally,

Max Planck Research · 3 | 2020 VIEW POINT

there are ecological reasons for migration, such as destruction of the environment and climate-related disasters. All of these causes are interdepen- dent, continuously reinforcing and compounding each other.

Migration only rarely entails the movement of entire groups of people (for example due to wars or flooding). Instead, it is usually a strategy employed by an individual household, from which one or more members move away in order to gain access to resources with which they can support those who have stayed behind. For people in rural areas, the first step can be moving to a city, while migration to a neighboring country is often the next option; long-distance international migration is a more radical, though often necessary, option. In all cases, economic resources are an essential requirement for people who decide to migrate. For this CONSEQUENTLY, reason, the people who migrate from a country are not usually THERE ARE the absolute poorest, unless they are forced to leave. NUMEROUS Among those who migrate to another country, the destination, mode of travel and the conditions under which they leave are POSSIBLE PATH- determined by several factors. So-called regular channels involve numerous immigration regulations and visa programs that apply WAYS OF ‘INTE- to the individual states, with complex preconditions that have to 23 GRATION’ THAT be met in each case. Programs for uniting families make it easier in different ways for relatives to follow on. By constantly experi- A MIGRANT menting with migration regulations, governments have attempted to meet the demands of employers and to control public opinion. MIGHT FOLLOW, Migration that occurs beyond the framework of immigration mea- EACH DEPEND- sures and employment migration measures is termed “irregular”. The lack of opportunities for international migration via regular ING ON AN channels often leads to exploitation by people smugglers. Refu- gees are defined as people who are officially recognized as being INTERSECTION persecuted and in need of protection. Generally, migration channels tend to correspond to specific combinations of nationality, OF FACTORS ethnic origin, religion, age, gender, education and class. Over the past 30 years, the configurations of these characteristics of migrating populations worldwide have changed considerably, creating a condition of “superdiversity” that is markedly more complex than social structures of the past.

After a migrant arrives in a destination country, what happens next depends on yet another series of influences. There is no uniform “integration” process. Rather, integration is a broad concept referring to an array of areas: the labor market, housing, language acquisition, education, legal administration, every-

Max Planck Research · 3 | 2020 day interactions, social services and healthcare. One’s ability to participate in each of these areas often depends on factors including legal status, linguistic competence, age, gender, work skills, social networks, and education levels.

As part of the Max Planck Society research initiative on migration, integration and exclusion, we have learned that the “integration” of those migrants who came to Germany during the mass migration of 2015/16 was dependent on the interplay of elements, including asylum policies, adjustments in the law, municipal and civil reactions, discrete approaches of local authorities and migrants’ own needs and resources. Minor WHEN WEALTHY contextual differences, such as administrative structure, type of accommodation, or even the specific town or city to where an COUNTRIES asylum-seeker was sent, led to fundamental differences in the SEAL THEIR procedure, speed and success of a person’s “integration”. BORDERS, THE The fact that national policies, legal frameworks and economic structures are currently undergoing a process of fundamental TRANSFER change will influence all these elements and processes surrounding global migration, likely limiting opportunities for 24 OF MONEY TO migrants. The pandemic has already led to numerous restrictions on international mobility. Covid-19 and the risk of future pan- POOR COUNTRIES demics have led to specific measures designed to limit the risk DECREASES of infection and restrict cross-border migration. The economic crisis will lead to high levels of unemployment, which in turn will AND THE LEVEL decrease demands for imported labor, and possibly also reduce the level of public acceptance of economic migrants. In develop- OF HARDSHIP ing countries of the global South in particular, the climate crisis GROWS will lead to insufferable conditions, which will cause a further deterioration of the economic situation and further intensify the complex causes of migration. The decline of agriculture and fish- ing will lead to a wave of migration to cities, which will in turn create enormous social, economic and ecological strain. While some countries might promote migration as a kind of pressure valve, others, particularly those that are currently considered to be fragile, might collapse, triggering mass displacement.

Some international observers are calling for a special status for “climate refugees”. However, this looks highly unlikely. Since there is a wide range of reasons why people migrate due to climate change, it will be very difficult to develop a specific concept of refugee “protection”. Also, however the term “climate refugees” is defined, there will be far too many of them for the world

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to be able to meet their needs. A vicious circle is looming: the more the wealthy countries try to limit global migration, the more money transfers to poor countries will decrease. This in turn will increase the level of hardship among the people in those countries in which ecological, economic, social and political conditions are steadily worsening. This will lead to the desperate need for even more migration. What can we do?

We need political decision-makers to start developing future-oriented ideas now. The standard approach of considering problems in isolation and then offering conventional, short-term solutions must be aban- doned. Instead, systemic, complexity-oriented research, ONE ANSWER assessments and answers are needed. Despite a number of different ideas (including the “Global Compacts”), there is no COULD BE international system for regulating migration. One possible TEMPORARY coordinated, multi-faceted answer could be the establishment of new, large-scale, more comprehensive cooperation CIRCULAR programs for temporary, circular migration between developing and wealthy countries. Such programs are already exist, MIGRATION such as the Canadian program for seasonal agricultural PROGRAMS workers. In the receiving countries, these programs offer important sectors (for instance, care work, agriculture and 25 construction) the workers they will still significantly need despite the great reshaping, as well as money transfers for the families of migrants and foreign capital for their countries of origin. Due to their temporary nature, programs such as these are often more acceptable to the members the host country. An integrated set of new technologies could make it easier to administer, safeguard and “healthproof” such programs. These include technologies for data processing and screening for competence and disease, as well as for monitoring working conditions, facilitating return travel home and providing international money transfers and investments. If they are introduced on a large scale, bilaterally or even globally, these time-limited, circular migration programs could offer many advantages that might help alleviate some of the effects of the three crises – the pandemic, economic depression and climate change.

This “great reshaping” marks the beginning of a new age that presents us with urgent and momentous challenges. Global migration should not be regarded as part of the problem, but as an opportunity to take remedial action.

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GIVE AND TAKE

26 | Underestimated inequality 34 | Not just in times of crisis 40 | Immunity – a balance between attack and defense

26 ILLUSTRATION: ALESSANDRO GOTTARDO FÜR MPG

Max Planck Research · 3 | 2020 FOCUS

UNDERESTIMATED INEQUALITY

TEXT: RALF GRÖTKER

Despite the fact that social inequities are increasing, no broad alliance for a greater redistribution of income and wealth has emerged in democratic countries. Lisa Windsteiger, Andrea Martinangeli and Marco Serena are conducting research into the reasons for this at the Max Planck Institute for Tax Law and Public Finance. They are also studying the ways in which immigration and poverty influence people’s attitudes towards state intervention.

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Andrea Martinangeli, Lisa Windsteiger and Marco Serena (from left) are researching social inequality issues at the Max Planck Institute for Tax Law and Public Finance.

“The higher one’s personal income, the higher one presumes the average income to be.”

LISA WINDSTEIGER

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The gap between rich and poor has been widening for a boration with her colleague Andrea Martinangeli. long time. The same trajectory was observable in all in- “We present test subjects with very specific issues in dustrialized countries throughout the entire 20th cen- these experiments,” she explains. “For example, we tury. Even before the First World War, the incomes of show them short teaser videos in which already known the richest – as well as their share of the total national facts are presented about such things as immigration or income – had already reached peak values. The two poverty.” Their hypothesis is that the effect observed world wars were followed by a phase of realignment when already familiar topics are tested serves as an in- and equalization, but the highest earnings soon began dicator of the effect a dominant media topic will have to rise again, more or less benefiting from the momen- on the public over an extended period. tum of the downward trend, once again reverting to the conditions of the early 20th century. The richest ten percent of the German population currently owns WEALTH DISTRIBUTION IN GERMANY 67 percent of the country’s assets, and more than half of these – i.e. 35 percent of the country’s total assets – 90% of adults own around are owned by just one percent of the population. In 33% of total assets contrast, the poorer fifty percent of Germans have just 1.4 percent of their nation’s total assets at their disposal.

A majority opposes the inheritance tax

How are such conditions possible in a democracy? Should we not expect the less affluent majority to come together to demand higher taxes from the rich and to distribute a greater proportion of public funds to those on the losing side in terms of income and wealth distribu- GRAPHIC: GCO ACCORDING TO THE SOCIOECONOMIC PANEL (SOEP), 10 % of adults own around tion? Lisa Windsteiger, an economist at the Max 67 % of total assets 29 Planck Institute for Tax Law and Public Finance, cites PHOTO: STEFANIE AUMILLER FÜR MPG the “demand for redistribution” as one explanation for the fact that even a functioning democracy offers no guarantees against inequalities in income and wealth. These experiments are conducted via an online platform. Knowledge and the lack of it plays a role in this context. Between two and four thousand test subjects are in- According to recent surveys, for example, around vited to participate per experiment, and all have volun- seventy percent of Germans generally consider the tarily registered with a commercial survey panel pro- inheritance tax (which is rather low in this country) to vider. Windsteiger explains: “Although we pay more be unfair. Yet, the fact is that, if one assumes two heirs than the statutory minimum wage for completing a per tax case, only one in thirteen inheritances is survey that takes about a quarter of an hour, these actually taxable, which means that the vast majority of clearly aren’t people who do this kind of thing full- Germans are not subject to the inheritance tax. And yet time. I myself, for example, am registered with a survey a political majority has not formed in favor of panel provider and get inquiries every now and then. I inheritance tax reform, which would require wealthy not only do this because I’m interested in how others heirs in particular to pay a lot more. structure their surveys, but also because they often involve political issues on which I would like to voice an However, Windsteiger finds how people react when con- opinion.” fronted with certain issues more important than what people know or don’t know. “We generally assume that people’s preferences or value-based attitudes are essen- The influence tially constant and don’t change in relation to the pre- vailing situation,” she says. “However, people do adapt of social isolation their behavior under certain circumstances – when certain issues come to their attention, they suddenly Step by step, Windsteiger tests various hypotheses that agree with different statements about redistribution are partly based upon one another, and for which she than before, while rejecting others. We refer to this as has usually already developed mathematical models. ‘demand for redistribution’.” What influence does social isolation (i.e. when people interact exclusively with others of a similar social Windsteiger conducts survey-based experiments to re- standing) have on opinions about redistribution? What search this demand for redistribution, often in colla- effect does the degree of homogeneity have within

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CHICAGO 1970

0–45 %

45–60 %

60–75 %

75–125 %

125–150 %

150–200 %

>200 %

AVERAGE HOUSEHOLD 30 INCOME IN RELATION TO THE AVERAGE INCOME WITHIN THE ENTIRE METROPOLITAN AREA

these isolated social pockets? How does thinking about that people misjudge their own position on the wealth such issues as immigration or poverty change the de- and income scale and therefore hold a distorted view of mand for redistribution? In addition to surveys, labo- the extent to which others have significantly more or ratory experiments are carried out at the Institute’s fewer resources at their disposal, and that the prevai- premises in Munich involving a smaller number of ling level of homogeneity within such isolated social participants (mostly students), who use computers to bubbles increases those distortions. What the survey play through situations that primarily focus on interac- experiment showed was that the higher one’s own in- tion. As Windsteiger explains: “In this kind of setting come is, the higher the average income of others is as- one can, for example, closely study how a participant’s sumed to be. In relative terms, people earning a lower expectations of another person can change in certain income underestimated the average national income to situations.” an even greater extent. As a result, their expectations of the additional income they could personally gain Isolation, for example: increasing inequality is often ac- through social redistribution are probably lower than companied by an equal increase in socio-economic iso- what could actually be achieved. The experiment also lation – “segregation” – which is particularly evident in showed that the greater one’s own social isolation, the relation to the gentrification of urban districts. A sur- more distorted one’s perception of the income of others vey-based experiment was carried out to identify the is (and thus of one’s own position on the income scale). causes and effects in this context. The basic hypothe- This effect also leads to division into rich and poor: the ses (which were set out in a mathematical model) were example of Chicago shows that people are increasingly

Max Planck Research · 3 | 2020 FOCUS

CHICAGO 2012 GRAPHIC: GCO ACCORDING TO DANIEL HERTZ

Division into rich and poor: the example of Chicago shows that people are increasingly congregating in 31 certain residential districts according to their income levels, which promotes the formation of isolated social bubbles.

congregating in certain residential districts according migrants to withdraw their support for redistribution to their income levels, which promotes the formation and aid programs for the socially deprived. The reason: of isolated social bubbles. The conclusion that a conse- long-term residents suspect that the immigrants – quence of isolated social bubbles is that people who with whom they themselves feel little social affinity – earn less, in relative terms, underestimate the gap that benefit most from the relevant services. Another hy- separates them from the wealthy. As a result, their ex- pothesis is that while immigrants are certainly viewed pectations of the additional income they could person- as competitors by population groups who themselves ally gain through social redistribution are probably are in the low-wage sector, they nevertheless favor re- lower than the actual reality. distribution, as this competition may well put them in a situation in which they themselves might need social support. On the other hand, higher wage earners are Contrasting reactions more likely to withdraw support for such programs because, as net contributors to the social security system, to controversial topics they worry that their burden will increase.

Immigration and poverty are another set of issues, in re- The results of the survey experiments partially confirm lation to which several different initial hypotheses these hypotheses. When confronted with the issue of were posited. One of them is that higher levels of ethnic immigration, lower wage earners actually respond by diversity due to increased immigration causes non-im- increasing their demands for (progressive) tax in-

Max Planck Research · 3 | 2020 FOCUS

“When the number within senior management circles. The role of politics in all of this is in dispute. Inequality increased in virtu- of disadvantaged ally all industrialized nations, not after, but before con- servative governments had come to power and had be- people becomes gun to reduce redistribution. There is something else that suggests that the role of politics is rather less do- too great, the minant: using game theory, Marco Serena – like Lisa Windsteiger a Research Fellow at the Max Planck In- tendency is towards stitute in Munich – conducted research into how inequality can influence elections. He reached the per- less redistribution.” haps surprising conclusion that, rather than it being a larger percentage of financially disadvantaged citizens who vote in favor of greater redistribution, on the con- MARCO SERENA trary, election results tend towards less redistribution when the group of disadvantaged people exceeds a certain size.

This effect can be best explained by using a highly simpli- creases, whereas middle-class income groups reduce fied example. Peter, Marie and Sabine differ in terms their demands under the same conditions. High in- of wealth. While Sabine has four gold pieces, Peter and come earners – show no reaction. When confronted Marie have just one each. An election with the issue of poverty, none of the groups showed is being held, in which a decision on any change whatsoever in the demand for progressive redistribution of gold will be made. In taxation. On the whole, however, the issue of poverty the event of a tie, the decision will be SUMMARY has a positive effect on another factor – the demand for made by flipping a coin. All three are public expenditures on education. But a more detailed now considering whether it is worth The social exclusion of analysis shows that this effect is due solely to the be- the effort to sacrifice their free time on income groups in society havior of the middle income groups. Low wage earners, a Sunday to go to the polling station, means that people 32 on the other hand, withdraw their support for spend- which results in a complex nexus of underestimate the real ing on public education when confronted with the is- mutual expectations and possible out- average income and therefore also the impact of sue of immigration. comes. If all three go to the polls, Peter redistribution. and Marie will gain the majority and will be able to enforce redistribution, Topics that are covered by A simulated Matthew effect as a result of which each of the three the media, such as the would have two gold pieces, i.e. Sabine immigration of refugees, Deriving clear policy advice from these observations is would lose two gold pieces, whereas leads to an increase in support for redistribution in difficult. Instead, the results reveal how complex the Peter and Marie would each gain one poorer groups of the situation is. Should a party with a social redistribution gold piece. Peter and Marie are thin- population, while agenda more openly broach the issues of poverty or im- king that, based on this probable out- decreasing among the migration, or not? “What our results show,” says come, Sabine may not even take part middle classes. Windsteiger, “is that different voter groups often react in the election, although she stands to very differently, even in opposite ways, to specific the- lose more than either of them could A game-theoretic simulation shows for small groups that matic messages.” But, she adds, this does not make win. In this case, however, it would be redistribution tends to be strategic issue management impossible. “To be able to sufficient for only one of them, Peter supported during elections predict the impact that specific effects will have on the or Marie, to cast a vote for both to re- when the number of poor whole, it is necessary to understand them very pre- ceive one gold piece. However, the does not exceed the number cisely.” The behavioral experiments conducted at the problem is that, if both think the same of rich to a very high degree. Institute of Tax Law and Public Finance provide the way and neither Peter nor Marie go to foundation for this. the polls, there will be no redistribution as Sabine may anticipate their The economic causes of increasing inequality include glo- strategic considerations and, therefore, be sure to go to balization, technological change, and, above all, the the polls herself. Even this simple example involving Matthew effect of accumulated advantage, i.e., the only three people shows that accurately modeling pos- concept that “the rich get richer”, rather like the Bible sible scenarios – which in turn have an effect on mutual quotation: “Whosoever hath, to him shall be given.” behavioral expectations and therefore on voter partici- The non-economic causes of increasing inequality in- pation – is no trivial matter. It is now possible to use the clude limited mobility within the labor market, self-iso- model developed by Marco Serena to precisely track lating elites and, in terms of income, the self-reinfor- the effect that group size and wealth disparity have on cing tendencies in remuneration practices, especially an election’s outcome. “Mathematically, the most dif-

Max Planck Research · 3 | 2020 FOCUS

ficult thing was to represent the asymmetrical benefit,” the probability that a single vote changes the election’s Serena explains. “This leads to several tipping points, outcome is negligible. at which the situation changes in favor of either the haves or the have-nots.” However, a rule of thumb can be derived for smaller groups based on Serena’s model: redistribution would take place only if the number of have-nots were smaller Rule of thumb for small groups than the number of rich people squared. So if there were ten rich people in a village and less than a hun- Summing up his innovation, Serena explains that “This dred poor people, there would be a good chance that is in fact the first model capable of mathematically pre- the mayor would be permitted to redistribute the tax dicting the conditions under which those voters in an revenues. But no redistribution would take place if unequal group (who are among the have-nots but are in there were exactly one hundred or more poor voters. the majority) would have no incentive to vote.” In real Serena’s summary of this methodological approach is terms, the model analyzes election processes based on also applicable to the work of the other two researchers: the majority voting system in relatively small groups, “We are focusing on a single effect, which could plausi- such as a supervisory board. The reason: it is only in bly play a role in the overall event. We are not claiming such smaller groups that voters can expect their votes that there are no other effects. But if we had models for to make a difference. “In municipal or national elec- all of the effects that have a bearing on a situation, we’d tions,” says Serena, “people tend to vote because they be able to create an overall model that would make very feel a moral obligation to do so or because they wish to far-reaching predictions.” express their political beliefs in some way.” In this con- www.mpg.de/podcasts/wert (in German) text, specific expected benefits cannot be calculated, as

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NOT JUST IN TIMES OF CRISIS

TEXT: WOLFGANG MULKE

Leon Wansleben, a sociologist at the Max Planck Institute for the Study of Societies in Cologne, takes an analytical look at the state’s economic and financial activities. It appears that, rather than leaving everything to the market, the state has begun playing an active role in economic policy.

Max Planck Research · 3 | 2020 FOCUS

ILLUSTRATION: ALESSANDRO GOTTARDO FOR THE MPG

Max Planck Research · 3 | 2020 FOCUS

Certain dyed-in-the-wool market economists are cur- central banks. “The dominance of central banks is rently rubbing their eyes in disbelief. The state is doing characterized by their robust independence, increa- everything possible to counter the economic conse- sing media attention, and the leading role they play in quences of the Covid-19 crisis. Public authorities are countering financial and economic crises,” Wansleben even investing directly in private companies, some- explains. These are indicators of their increasing thing that was barely conceivable in recent decades. power over recent decades. The central banks ensure that inflation remains low; they stabilize the economy “For many years,” as Leon Wansleben, a sociologist at the and help floundering states to stay afloat. There is Max Planck Institute for the Study of Societies ex- hardly a newscast in which the name of a central bank plains, “governments around the world have been vig- is not mentioned. orously supporting markets while cutting back on the public sector.” Now, he goes on, we are seeing the direct opposite – the state has become very active in fis- Central banks as cal matters. For example, it is counteracting the current crisis by taking on a heavy national debt load. crisis managers “This process is particularly evident in relation to the Covid-19 crisis,” says Wansleben. The 38-year-old re- In the past, central banks, such as the German Bundes- searcher has been head of the “Sociology of Public bank, controlled inflation via the amount of money in Finances and Debt” research group at the Max Planck circulation. Whenever they raised interest rates, con- Institute in Cologne since 2019. There are still many sumers and companies would reduce their spending, unanswered questions in this field: what influences preferring instead to invest their money, as a result of state economic policy, and who are the ones taking ac- which pricing pressures decreased. Reducing interest tion? Which rationale are they following, and which in- rates produced the opposite effect. Today, rather than 36 terests and concepts are playing a role in the back- stabilizing economies through the money supply, cen- ground? tral banks adjust their interest rate policy to align with price developments within the goods and services markets. However, there is a problem with this approach, The merging of markets as it does not take asset markets, e.g. those for equities and real estate, into account. When they burst, price and the state bubbles in these markets can rapidly lead to economic crises. The 2007 to 2009 financial crisis showed just Among other things, the research group is devoted to ex- how quickly this can happen. amining economic sociology and, according to the group’s thesis, the traditional, ideal-typical notions While the increasing influence of the Bundesbank, the about the market and the state are no longer applicable. U.S. Federal Reserve (aka the Fed), and other central Many economists treat them as two separately opera- banks was initially based on different approaches to the ting, homogeneous units, yet the market and the state threat of inflation, the inflation problem increasingly overlap in many areas, such as the energy markets, receded into the background to be replaced by con- where municipalities often have to compete with pri- cerns about weak growth, falling real interest rates and vate suppliers. Wansleben wants to ascertain the actual the expansion of the financial sector. The world’s cen- structure of these markets and what role the public sector plays in them. The relevant projects are part of an extensive study into the role of the state as an economic stakeholder. The state’s economic interventions take many different forms, ranging from direct investment in private companies that have encountered difficul- ties as a result of various crises (e.g. Lufthansa and the “Covid-19 has Commerzbank) to investment funds, or from Germa- ny’s state-owned development bank KfW to municipal wiped the market- companies. dogma off the table.” Wansleben is looking into why, since the 1980s, parlia- ments and governments have gradually withdrawn from economic governance and ceded control to the LEON WANSLEBEN

Max Planck Research · 3 | 2020 FOCUS

Dizzying: the European Central Bank (ECB) headquarters building in Frankfurt am Main is one of the tallest buildings in Germany. However, many observers consider the ECB’s balance sheet total (which currently accounts for 50 percent of the economic output within the euro zone) to also be extraordinarily high. PHOTO: CARO / BASTIAN / FOTOFINDER

tral banks became the most important crisis managers by the financial markets. They curb uncertainties when, for example, the dotcom bubble burst at the turn within the markets, particularly through a predictable of the millennium or after the terrorist attack on the interest rate policy, as well as by converting private World Trade Center in 2001. loans into sovereign payment instruments – by pur- chasing bonds, for example. The extent of these stabi- When describing his research project, Wansleben ex- lization efforts can be seen in the central banks’ ba- plains, “What I’m trying to figure out is why central lance sheet totals. The ECB’s balance sheet total al- banks were able to be so successful in spite of the finan- ready accounts for half of the eurozone’s economic out- cial crisis brewing in the background, and which insti- put, and that of the Fed accounts for about 30 %. This tutional conditions fostered their increase in power.” is where the sociological research approach comes into He had already been exploring this subject prior to re- play. Why is it, Wansleben asks, that national parlia- locating to Cologne, when he was still teaching at the ments and governments have for so long neglected to London School of Economics and Political Science. exercise not only their authority, but also their deci- One of his findings is that the central bankers are, so to sion-making powers and responsibilities regarding speak, the stabilizing force in an economy dominated economic policy?

Max Planck Research · 3 | 2020 FOCUS

This voluntary self-disempowerment is evident in tax business orientation of municipal companies, appar- policy, which has been used less and less for redistribu- ently due to exaggerated concerns about scandals that tion purposes in recent decades. Nor, to a large extent, could arise from their decisions. Instead, the public de- have these powers been used to address political chal- bate over municipal policies tends to focus on marginal lenges such as climate change. Wansleben, however, issues. foresees the next change on the horizon. He says, “There are many signs that central banks are currently In another project, Wansleben and his research group are reaching the limits of legitimacy and effectiveness with also investigating the public sector investments being their concepts for economic governance, as well as made by municipal authorities in Germany. In general, their specific interventions.” cities and municipalities reduced their investment budgets at the start of this century. “That was followed by a process of divergence,” says the sociologist. The A lack of transparency communities’ development went in different direc- tions. Some communities, particu- in municipal enterprises larly in the wealthy southern German states, started reinvesting more in Central bank policies have long been seen as controversial. their infrastructure, while treasurers They spend vast amounts of money on buying up go- in other regions continued to cut SUMMARY vernment and corporate bonds to revive the economy costs. The consequences quickly be- and want to increase lending to the economy through a came evident to local residents. The Many years after the state zero-interest policy. However, neither of these mea- infrastructure deteriorated, many had withdrawn from its sures is having the desired effect. Critics in Europe, for schools became dilapidated and were economic activities and control of economic policies, example, fear that the ECB is indirectly communiti- insufficiently maintained, or the con- the trend is now reversing. 38 zing the national debt of southern European states by struction of new housing was ne- buying more and more of their state bonds. Achieving glected. Wansleben suspects that, The central banks’ ability to the inflation target of two percent is also a long way off. “Faced with cost-cutting pressures avert economic crises is in Wansleben asserts that democratic institutions now following the reunification of Ger- doubt and a greater political need to develop new approaches and instruments of many, the federal system began exert- commitment is required. economic governance. ing fiscal pressure on the municipali- Municipal enterprises play ties.” High fixed expenditures for an important role in the His other two projects at the Max Planck Institute in Co- such things as social services have de- provision of public services. logne are still in the early stages, yet hopes for exciting prived poorer cities and municipali- results are high. One of Wansleben’s research projects ties of the funds needed for invest- More state investment in infrastructure is also concerns the state’s municipal institutions. Using Co- ments. Their income from trade taxes required. logne as an example, he is investigating the economic is also very low. activities of the public authorities, whereby the focus is on public services – a term which, as he notes, is not “This whole subject has a certain explo- precisely defined but “formulated in a deliberately siveness these days,” as the researcher vague manner.” The state may take action if there is a knows. Population growth in the cities has been greater public interest in doing so, a precondition, which the than expected. They simply must develop their infra- city of Cologne interprets rather loosely. It acts, for ex- structures. Then there are also the investments neces- ample, as a telecommunications network operator sary for climate protection, such as improvements in through the municipal company Netcologne, and has public transport services. The Covid-19 crisis is cur- acquired a shipping company that is active throughout rently providing clear evidence of the more active role Europe. According to Wansleben, the question of what the state is again playing. The federal government is the state is permitted to do and what it is economically providing the municipalities with substantial financial sensible to do is “really fascinating.” support; after all, the most important tasks in the practical management of the pandemic must be undertaken But a glance into the engine room of the state ought to also by the cities and municipalities. One recent example of reveal who is influencing the actions of its institutions. this is the announcement by the federal government In this context, Wansleben has identified a lack of that it is expanding the public health authorities. The transparency in the decision-making process, espe- federal and state governments want to create 5000 new cially in municipal enterprises. Therefore, politicians jobs, as well as implement a digital upgrade within the are loathe to engage in democratic discourse about the departments.

Max Planck Research · 3 | 2020 FOCUS

INVESTMENTS PER CAPITA in 2018 (in EUR)

800 600 400 200 GRAPHIC: GCO BASED ON RESEARCH LEON BY WANSLEBEN / MPI FOR THE STUDY SOCIETIES OF

Dissimilar conditions: while many cities and municipalities in central and northern Germany will have to continue to save money, most municipalities in Bavaria and Baden-Wuerttem- berg can afford to invest generously.

However, Wansleben identifies a requirement for action demic is positive. “The market dogma has been wiped on one central issue. He is calling for at least partial off the table,” Wansleben says and sees the aid pack- debt relief for over-indebted municipalities, because ages as a reasonable mix between economic stimulus without it they will be unable to solve their structural and investment. “This has now revealed a major disad- problems. He asserts that debt repayments and restric- vantage of the U.S. system,” he concludes. There, the tions on municipal supervision have left no room for federal government is refusing to provide financial investment, which in turn has a negative impact on the support to the individual states. This means, Wansle- development of these municipalities. In other words, ben explains, that the U.S. states are having to bear the over-indebtedness triggers a downward spiral. Al- costs of the Covid-19 crisis, while losing revenue at the though acting Finance Minister Olaf Scholz came up same time. The German model, in contrast, is based with a debt relief plan, it was not accepted by the gov- on cooperative federalism in which the federal, state erning coalition due to long-standing reservations. Ac- and local governments redistribute funds among cording to its critics, the plan would reward poorly themselves and between levels, i.e. they act in solida- managed cities and communities. Conversely, the re- rity, especially in times of crisis. searcher’s evaluation of the state’s response to the pan- www.mpg.de/podcasts/wert (in German)

Max Planck Research · 3 | 2020 FOCUS

ILLUSTRATION: ALESSANDRO GOTTARDO FOR MPG

Max Planck Research · 3 | 2020 FOCUS

IMMUNITY – A BALANCE BETWEEN ATTACK AND DEFENSE

TEXT: CATARINA PIETSCHMANN 41

Everything has its price – especially health, of course. At the Max Planck Institute for Evolutionary Biology in Ploen, Tobias Lenz and his team are researching what the evolutionary costs of perfect immunity might be and why we are not immune to all pathogens.

Max Planck Research · 3 | 2020 FOCUS

The MHC genes encode the information for the production of proteins on the surface (orange) of an immune cell. These can bind to molecular fragments from a virus, referred to as antigens, from the interior of a cell and present them to a T cell of the immune system (right). The T-cell can then trigger a defensive response. We’ve rarely been so keen to discuss pathogens and im-

munity as we are right now. The corona pandemic has HOW THE BODY’S IMMUNE SYSTEM RECOGNIZES PATHOGENS highlighted the importance of having a robust immune system. But why do viruses, bacteria, and other mi- crobes overcome our body’s defenses time and time again? Isn’t all-inclusive protection possible, and how much would it cost? Tobias Lenz and his team are analyzing the battle between defenders and attackers. They use computer-based approaches to investigate how the immune system reacts to pathogens, such as leprosy bacteria and HI viruses. Their research focus EVOLUTIONARY BIOLOGY is on “MHC” genes.

Antigen T cell GRAPHIC: GCO TOBIAS FROM LENZ / MPI OF MHC stands for “major histocompatibility complex” and refers to a group of genes possessed by all vertebrates. Humans possess six such genes, here named “human leukocyte antigen” (HLA). They encode proteins that are responsible for the immune system’s ability to recognize invaders. These proteins bind molecular frag- The great variability in MHC genes ensures that a ments that are left behind by pathogens that have pe- matching MHC protein exists for almost every netrated cells and that are displayed, like in a shop win- intruder. Hence, if a specific pathogen is circulating in dow, on the cell surface. Patrolling immune cells re- a population, those individuals with the matching cognize them as foreign molecules and put the MHC variant will be at an evolutionary advantage. immune system on alert. Their carriers will become only mildly ill or perhaps 42 not at all. And consequently, the frequency of this variant will increase within the population. To remain successful in the future, the pathogen needs to mutate and evolve in such a way that MHC variants cannot continue to provide protection. The mutated pathogen then needs to be matched by another MHC gene “It might well be that variant, and the evolutionary race enters the next round. The process can always result in evolution we possess too many taking a different direction. Advantages can be rendered useless from one day to the next. However, HLA genes for the not only do attackers quickly mutate from one genera- tion to the next, they occasionally only appear in modern day life we certain places and times. “In the long term, this means that no single variant will dominate the population, but live today.” that instead different ones will coexist,” explains Tobias Lenz. This is what evolutionary biologists refer to as a “balanced polymorphism.” TOBIAS LENZ Lenz and his colleagues simulate the interplay between MHC genes and pathogens on the computer. With the help of specialized programs, they can observe the co-evolution of the adversaries in time-lapse. The re- However, given the sheer immeasurable multitude of searchers can also compare present-day genetic infor- viruses, bacteria, fungi, and other parasites, how do mation with that of the past and, thus, learn how the such a small number of genes succeed in ensuring that MHC variants have changed over time. For example barely any invaders avoid detection? The key lies in from skeletons from a medieval graveyard in Denmark. these genes’ extremely high variability. They are the Here, the dead were from a leper colony. Such colonies most variable genes in the entire genome. “The were frequent in the past and up to the modern era, in HLA-B gene, one of the human MHC genes, for order to prevent the spread of this often fatal disease. instance, has more than 4000 known variants,” says Thanks to antibiotics, most cases of leprosy are now Tobias Lenz. curable.

Max Planck Research · 3 | 2020 PHOTO: ACHIM MULTHAUPT FOR MPG Max PlanckResearch FOCUS ·3 | 2020 addition to his work on human MHC genes, Lenz also also Lenz work genes, MHC addition to his on human diversity of MHC variants in the fish also an playsalso fish the in diversity of variants MHC investigates those of sticklebacks, whose immune immune whose of sticklebacks, those investigates important role in their defense against parasites. defense against role their in important Tobias Institute’s In room. his in aquaria Lenz system is similar to that of humans. The great The great of humans. to that similar is system 43 FOCUS

To this day, leprosy still occurs sporadically in Southeast strated that some variants are able to present a particu- Asia. Some people there have an HLA variant that in- larly large number of different HIV antigens. This creases their susceptibility to the disease. Is it possible makes HIV more visible for the immune system, so it that most of the people in Europe who contracted le- can be fought more efficiently.” In contrast, the less ef- prosy possessed this variant? “In collaboration with re- fective variants may confer resistance to another patho- searchers from the University of Kiel, we have indeed gen. HLA variants may also be involved in the fact that discovered that the HLA variant that makes people SARS-CoV-2 causes severe symptoms in only a small more susceptible to leprosy is found at a higher fre- percentage of those infected. As coronaviruses have quency in these bones from the Middle Ages,” says circulated among humans for many years, most of us Lenz. possess gene variants that can recognize the viruses. “We’re susceptible to SARS-CoV-2, because it’s relatively new, but thanks to thousands of years of natural A variant with advantages selection, most people’s immune systems can limit its effects,” says Tobias Lenz. Along with colleagues from and disadvantages around the world, he is currently investigating the extent to which HLA genes may be involved. Although But why has this gene variant persisted over the centuries thousands of different HLA variants exist in humans, and not been eliminated by natural selection? “We now each one of us has only a handful of them. High vari- know that this variant isn’t solely disadvantageous. Yes, ability, it turns out, also has a drawback: autoimmunity. it provides poor protection against leprosy, but it also helps protect those who carry it from hereditary type 1 MHC proteins are adapted to bind molecules from bacte- diabetes,” explains Tobias Lenz. Hence, the negative ria, viruses, and other parasites and present them on selective pressure due to leprosy is counterbalanced by the cell surface. There, these foreign molecules are re- the positive selective pressure of better protection cognized by a particular type of immune cell known as against diabetes. That might explain why this HLA T cells. A selection process for T cells occurs in the variant still exists in the population. embryo: those that recognize foreign molecules are retained, while those that recognize the body’s own mo- HIV is another example for a balanced polymorphism: lecules are removed. However, this process isn’t perfect, 44 some HLA variants in the immune system are better at and so T cells that recognize the body’s own molecules keeping HIV in check than others. “We’ve demon- keep emerging. The more HLA variants a person

Degenerated pigment cells from the skin. An immune system with a large variety of HLA types is better able to recognize and fight such cancer cells. As a consequence, immunotherapy is more effective in skin cancer patients with a high variability of these genes, but in such patients, treatment can also frequently trigger inflammatory reactions. PHOTO: SCIENCE PHOTO LIBRARY / STEVE GSCHMEISSNER

Max Planck Research · 3 | 2020 FOCUS

IMMUNITY AT AN OPTIMUM

The relationship between MHC diversity and an individual’s fitness (black

FITNESS curve). The greater the diversity of MHC variants, the better the body is protected against pathogens Self-tolerance Recognition of and parasites. At the same pathogens time, however, the immune system’s tolerance towards the body itself decreases. The body’s optimal MHC diversity is located at the apex of the curve.

INDIVIDUAL MHC DIVERSITY GRAPHIC: GCO TOBIAS FROM LENZ BIOLOGY / MPI EVOLUTIONARY OF

SUMMARY

MHC genes produce an abundance of differing proteins that help the immune system to possesses, the more foreign molecules This can occur when one of the mutations frequently 45 recognize intruders. they can present – in the case of pathogens manifesting in tumors causes the immune system to that can mutate as rapidly as HIV, that’s a suddenly recognize the tumor cells as foreign and at- Some MHC variants huge advantage! Unfortunately, however, tack them. provide protection against this will also lead to more of the body’s specific pathogens but can own molecules being presented. This can also trigger autoimmune diseases. cause the immune system to turn against More effective treatment itself, resulting in autoimmune diseases. The more of these variants Multiple sclerosis, type 1 diabetes, celiac Together with oncologists from the Memorial Sloan Ket- a person possesses, the disease, psoriasis, ankylosing spondylitis, tering Cancer Center in New York, Tobias Lenz and better they are equipped to and many more – all are associated with his team have investigated the influence a cancer pa- fight pathogens. The price, however, is a higher risk certain HLA variants. Throughout evolu- tient’s own contingent of HLA genes has on the suc- of developing autoimmune tion, the diversity of HLA genes seems to cess of immunotherapy. Such a treatment with “check- diseases. have settled at an optimal level. “This point inhibitors” aims to induce immune cells to act means we’re well protected against patho- against the body’s own cells that are multiplying un- gens, while at the same time the risk of au- controllably. “Our results have shown that immuno- toimmune diseases is minimized,” says therapy is more effective in patients with metastatic Tobias Lenz. But is this still the case in our hy- skin cancer if they possess a broad diversity of HLA giene-oriented society? Autoimmune diseases are on variants,” says Lenz. However, HLA genes are also as- the rise in many countries. Does this suggest that the sociated with common side effects of immunotherapy, balance between infection defense and autoimmune such as skin rashes or liver and intestinal inflammation. disease has shifted in favor of the latter? “It’s possible In cancer as well, the immune system has to maintain a that we possess too many HLA genes for the age we balance between combating tumor cells on the one live in.” Hence, the diversity of immune genes influ- hand and avoiding autoimmune diseases on the other. ences our susceptibility to both infectious and autoim- The price for possessing a perfect defense against mune diseases. The immune system and the HLA pathogens would be that such a system could turn genes may also play a role in cancer, as immune cells against one’s own body – too high a cost to bear. Thus, can recognize and eliminate cells that are dividing un- the legions of pathogens will keep discovering ways to controllably. This helps to destroy some tumors at an outsmart our immune system. early stage. Also, a tumor, even one at an advanced www.mpg.de/podcasts/wert (in German) stage, can occasionally shrink in a seeming miracle.

Max Planck Research · 3 | 2020 INFOGRAPHIC HOW THE ECONOMY GROWS

GROWTH IN GDP (represented with an initial value of 100 for 1994) GREAT BRITAIN SW 150 Consumption-oriented GB growth model

140 • High current account deficit: imports exceed exports CONSUMPTION ORIENTATION CONSUMPTION 130 • High consumer spending • High demand for services, also IT from moderately skilled and low GE 120 skilled providers

110

100 1995 1997 1999 2001 2003 2005 2007

The years between 1994 and 2007 saw the longest period of sustained growth in the OECD since the beginning of the oil crisis in 1974/75. Important economic factors • Financial services 46 • Oil industry / petrochemicals • Gas turbines

EXPORT SHARE OF GDP (in percentage of GDP)

50 ITALY 45 Growth model neither consumption-oriented nor export-oriented 40 • Small export sector, specialization 35 in labor-intensive goods • Real Euro exchange rate too high in relation to economic performance 30 • Low consumption

25 Important economic factors 20 • Tourism GB SW IT GE • Footwear and fashion • Wine 1995 2001 2007 • Furniture Exports are price-sensitive, particularly when industrial products are involved. This means that an export-oriented economy profits from low wages.

Max Planck Research ·· 33 | 20202020 INFOGRAPHIC

Until about 30 years ago, growth in Europe was fueled by rising wages and growing consumption. However, national and international developments started undermining this model in the 1990s. Since then, Germany has strengthened its reliance on exports, while Britain, Sweden and Italy have branched out onto other paths. Lucio Baccaro from the Max Planck Institute for the Study of Societies in Cologne has been analyzing the various possibilities.

GROWTH IN REAL WAGES (represented with an initial value of 100 for 1994) SWEDEN 140 Consumption-oriented GB SW and export-oriented growth 130 model

• Simultaneous growth in export 120 and consumption • Price-insensitive exports: particularly IT services 110 • Wage growth in industry and the service sector GE 100 IT

90 1995 1997 1999 2001 2003 2005 2007

The majority of economic performance still depends on private household consumption and consequently on disposable income. Important economic factors • Research and development services 47 • Flat steel • Refined copper • Timber

PRIVATE HOUSEHOLD DEBT (as percentage of available net income)

180 GERMANY 160 Export-based growth model 140 • Sustained current account surpluses: exports exceed imports 120 • Real Euro exchange rate too low in relation to economic performance 100 • Growing inequalitybv due to low 80 wages in the service sector 60

20 Important economic factors GCO ACCORDING TO GESELLSCHAFTSFORSCHUNG OECD, THE 1/2020, WORLD BANK, WSI • Aircraft construction 0 • Machine construction GB SW IT GE • Automobile construction 1995 2001 2007 Borrowing boosts spending and consequently economic growth. However, this type of “growth on credit” is also viewed critically. EXPORT ORIENTATION

Max Planck Research ·· 33 | 20202020 HUNTING FOR SPIES IN COMPUTER CHIPS

Becoming a Max Planck Director via “second- an apprenticeship, but it doesn’t sound as if he re- chance” education is probably something of grets going into a skilled trade – indeed, he says an exception. But that is precisely what happened that, even as a young boy, he enjoyed tinkering with things and was fascinated by technology. His in the case of Christof Paar, one of the founders parents were actually quite accepting of his deci- of the Max Planck Institute for Security and Privacy sion to learn a trade, even though his father was an in Bochum, where his work now includes tracking academic. Having qualified as a tradesman, Paar down hardware Trojans on computer chips. then took something of a roundabout route into the world of science. After all, switching from a skilled trade to an academic career was harder in 48 TEXT: KLAUS JACOB those days – almost 40 years ago – than it is today. Paar first attended a specialized upper secondary school. He graduated after one year and then spent half a year working as a journeyman at a small Christof Paar has fond memories of the construction three-man firm. “I used to ride my motorbike to of the Colonius telecommunications tower in Co- the building sites.” He then pondered “for weeks”, logne. In 1980, the soaring stairwell that provides whether to become a master craftsman or switch to access for the fire service had to be fitted with studying for a degree. His boss urged him to stay, loudspeakers: four of them at every ten meters of taking the view that a career as a master craftsman height. This laborious task fell to an apprentice in offered much more security than becoming an en- his first year – namely, to Christof Paar. Since gineer. In the end, Paar opted for the academic then, the former telecommunications technician route and signed up to study telecommunications has climbed to the upper echelons of science to be- at Cologne University of Applied Sciences. “It was come one of the founding Directors of the Max a rational decision,” he says, adding that the higher Planck Institute for Security and Privacy in Bo- earning potential was the decisive factor. chum. His research work at the Institute is also of great political relevance – and he’s a good contact On his detour through so-called “second-chance edu- when it comes to Huawei and 5G networks or the cation”, Paar managed to fulfill many of the ex- protection of companies against hackers. pectations one has of a Director of a Max Planck Institute: his excellent academic performance was When you look at the individual milestones on Chris- impressive, not least because he was – and still is – tof Paar’s résumé, it is clear that his journey to be- enthusiastic about his subject. His eyes light up coming a Max Planck Director is something of a when he talks about fast microprocessors or the rags-to-riches story. In the beginning, things fight against hackers. The 57-year-old Director is didn’t look all that promising. While attending an talkative, easy to get along with and full of laughter, academic-track high school, Paar struggled with and takes a relaxed approach to team meetings. Al- languages and therefore switched to an intermedi- though most of his team members are young re- ate secondary school, where he obtained his “Mit- searchers, Paar treats them as equals; he is open to tlere Reife” diploma. He then went on to complete criticism, and is on familiar terms with everyone.

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CHRISTOF PAAR

49 PHOTO: LARA WITTHAUT, FOTO-OSTERMANN.DE FOR MPG

A passion for technology: Christof Paar hunts for security flaws in computer hardware.

Max Planck Research · 3 | 2020 VISIT TO PHOTO: LARA WITTHAUT, FOTO-OSTERMANN.DE FOR MPG

50 Youthful and fit: it’s no surprise that Christof Paar is in such good shape, especially thanks to his tri-weekly karate training sessions.

Meetings with Paar have a relaxed, collegiate at- known as an “embedded system” – in other words, mosphere – with pizza and coffee at the ready. In- a combination of a computer and a physical device. deed, Paar looks much younger than his years, This is the area of research that Paar still works on partly thanks to his lean physique. Thrice-weekly today – and even then, at the age of 24, he knew ex- karate sessions help him to keep fit. actly what he wanted his future career to look like. “I wanted to become a professor, without a shadow Paar graduated from Cologne University of Applied of a doubt.” Indeed, his main motivation in those Sciences at the top of his class – and was one of days was teaching. only a handful of graduates to complete the degree within the prescribed period of study. He met a Of course, this meant that he would first have to do a group of fellow students who spurred each other doctorate, which wasn’t possible at a university of on to high achievements. “The A-Team,” he says applied sciences in those days. So with that, to- with a smile. It was in those early days, while work- gether with the A-Team, he switched to the Uni- ing as a teaching assistant for math, that he disco- versity of Siegen, where he was largely spared the vered his passion and talent for teaching. For his need to complete the basic course of studies. How- dissertation, he developed an electronic control ever, as an acknowledged conscientious objector, system for flip-disk displays such as those on he first had to complete his civil service as substi- buses, where the names of the respective stops are tute for the compulsory military service – and he displayed by an array of tiny disks that flip to show was in luck: the audiologist Hasso von Wedel, who either their black or white side. To this day, a large had made a name for himself as a tinnitus re- display of the same type notifies traders of current searcher, was offering two research-related posi- prices at the Frankfurt Stock Exchange. The tech- tions for conscientious objectors at the University nology, which was very advanced in those days, is Hospital of Cologne. Paar secured one of the posi-

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tions and was responsible for the technology used cated mechanisms that operate in the background in the experiments. As a result, he actually ma- to ensure that even scratched CDs can be played naged to turn this forced career break to his advan- without errors. The technology even makes it pos- tage. During his civil service, he attended lectures sible to drill a hole with a diameter of up to three in physics and mathematics at the University of millimeters into the disk without affecting play- Cologne, and toward the end he began his studies back. Paar simplified the algorithms for real-time at the University of Siegen. error correction, which are implemented directly in the form of special hardware circuits, in order to From Siegen, he moved to the U.S. to write his second make them significantly smaller, faster and more thesis – at Michigan Technological University. energy-efficient – a method that was later put to But why would someone who had to switch schools commercial use. because he struggled with foreign languages move to the U.S.? “Of course, my thirst for adventure After completing his doctorate, Paar planned to em- was a key factor,” says Paar. Moreover, he had al- bark on an academic career in the U.S. so that he ready hitchhiked across the U.S. twice during his could be with his girlfriend, whom he had met two time at Cologne University of Applied Sciences, years earlier and later married. “Two years of and had found it much easier to learn the language long-distance relationship were enough.” In 1995, by conversing with Americans than he did in he was offered a position as assistant professor at

Paar works on the implementation of new

encryption methods in hardware and 51 software. He is one of the experts who established this area of research.

school. He even went on to marry an American Worcester Polytechnic Institute in Massachusetts, woman. “My English teacher would be pretty a private university that is funded by tuition fees amazed,” he laughs. and therefore places a lot of value on high-quality teaching. As part of the application process, Paar Paar spent a long, cold winter in Michigan working was required to deliver not only a research lecture, on his Master’s thesis. Once again, he chose a topic but a teaching lecture as well – and with that he that was at the cutting edge of technical develop- outdid his competitors. The freedom he now en- ment: active noise cancellation, a technology that joyed as a professor allowed him to introduce a new is intended for use in cars, for example; it cancels subject at the university: cryptography. out undesired noise using what is colloquially known as “anti-noise.” Paar has a habit of combi- The word cryptography conjures up images of the se- ning different fields within his projects: physics cret codes that children find so fascinating, or of with computer technology, engineering with the Enigma, the Nazi encryption device whose mathematics, classical hardware with software. code was cracked by the Allies. As a research disci- His doctoral thesis at the University of Essen is an- pline, however, cryptography still led a marginal other example. This time, his focus was on error existence in the 1990s. There was only a single correction in digital technology – a technology textbook, which was brand new at the time – and that is used in data transmission from satellites to the subject was only offered at a few universities. Earth or in CD players, for example. Very few peo- Paar had backed the right horse. “Luck was also on ple who listen to a CD are aware of the sophisti- my side,” he says. Back then, the rapid expansion

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of the dot-com bubble was making cryptography he returned to Germany – partly to be closer to his and data security increasingly important. Their im- elderly parents, but also for the opportunity to help portance has also been bolstered by cases such as establish the Horst Görtz Institute for IT Security that of the whistleblower Edward Snowden, who re- at the Ruhr University in Bochum. The initiative vealed just how brazenly intelligent agencies inter- for founding the Institute came from Horst Görtz, cept data and how important it is to protect them. the owner of a medium-sized business who made Another of the countless examples is the scandal his fortune in IT security during the dot-com boom. surrounding Crypto AG, a Swiss company that It was born of his desire to use his foundation to manufactured encryption devices during the Cold launch an influential research institute in Germany. War. It later emerged that the company had been Paar’s two older children, Noah and Maja, found the selling manipulated devices on behalf of the CIA move to Germany easy – they had been raised bilin- and the German Federal Intelligence Service gually and entered elementary school here, while his (BND), allowing the secret services to conduct espi- younger daughter, Flora, was born in Germany. For onage in over 100 countries. Paar’s wife, the transition was more challenging from a career perspective. In the U.S., she had However, Paar’s work doesn’t focus primarily on the taught at a community college – a type of higher edu- development of new encryption methods, but rather cation that doesn’t exist in Germany. She now works on their implementation in hardware and software. as a lecturer in biology at the Ruhr University in Bo- Indeed, he is one of the experts who established this chum. “The job brings her a lot of satisfaction,” says area of research within the scientific community. Christof Paar.

52 Subtly manipulating just a few transistors is often enough to deactivate vital safety functions.

Together with his colleague Çetin Koç, he launched In any case, things are going well for him: not least the Conference on Cryptographic Hardware and thanks to the Horst Görtz Institute, Bochum is now Embedded Systems (CHES) in 1999. Although the one of the world’s leading locations for IT security conference was actually intended to be a relatively and is home to 1,000 students in the field. However, small workshop, the first CHES was attended by the Institute has caused a stir not only within the over 150 international specialists from academia and scientific community – in 2008, Paar and his col- industry and was even covered in the New York leagues succeeded in cracking the security system Times. Today, CHES has evolved into one of the used in an electronic door opener that controls mil- most important international conferences in the lions of car and garage doors. To do this, the re- field of cryptography. searchers first had to analyze the electronics using a very laborious process known as reverse enginee- But let’s turn our attention back to Christof Paar’s ring. The resulting insights allowed them to produce journey from a mere apprentice to becoming a Max a sort of master key that could open garage doors Planck Director. Paar stayed in the U.S. for seven and the doors of some cars. This was a major story years, during which he rejected a number of offers to for the media. “We were overrun by journalists for join start-ups – because he enjoyed university life weeks,” says Paar. and the combination of research and teaching that it offered him. He was also worried that getting in- Such “vulnerability research” projects like these are volved in a start-up would mean he would no longer part of Paar’s everyday work – after all, those who have enough time for his wife and children. In 2001, seek to improve security need to be aware of a

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53 PHOTO: LARA WITTHAUT, FOTO-OSTERMANN.DE FOR MPG

Secure monitoring: Christof Paar’s team is developing technology that can be used to check whether nuclear warheads are stored securely. The monitoring cannot be circumvented, because the warheads record an electromagnetic signature that is specific to the storage site. It is this connection to physical characteristics that links the project to research into computer hardware.

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Scanning components: this image from a scanning tunneling microscope reveals details in the chip structure that help the researchers in Bochum to search for hardware Trojans.

state and are excluding it from the rollout of 5G technology. Paar is all too aware that manipulations of this kind are possible. After all, he also studies hardware Trojans – and he has received an ERC Advanced Grant on this very topic, one of Europe’s

GRAPHIC: KRIMINALTECHNISCHES INSTITUT DES BKA 52 - KT most prestigious research awards. Hardware Trojans – in other words, circuit manipulation within a computer chip – can be used for espionage and could even allow attackers to shut down entire system’s weaknesses. But Paar goes one step further: industrial systems. he also wants to know what makes hackers tick, what their thought processes are, and where their mental Non specialists could be forgiven for thinking that ma- restrictions lie. This has led him to develop a new nipulation of this kind can’t be too hard to find – but area of research in collaboration with Nikol Rum- they would be mistaken. Chips such as those inside mel, a cognitive psychologist at Ruhr University smartphones or in 5G-connected computers con- Bochum. The two researchers were confronted with tain many millions of transistors that measure just a a problem: professional hackers are reticent. They few nanometers across and whose schematics are a 54 keep their cards close to their chest, even when carefully guarded secret. Christof Paar and his team working for companies that have hired them to seek have found that subtly manipulating just a few of out vulnerabilities in their products. Paar and Rum- these transistors is often enough to deactivate vital mel had to make do with students from Ruhr Uni- safety functions. To understand circuits of this kind, versity who volunteered to participate. Through the researchers must laboriously analyze the chips this research, they discovered that the speed at layer by layer, with the help of ablation techniques. which a hacker makes progress is correlated with the Meanwhile, they have developed an automated hacker’s working memory. From cognitive psycho- method for analyzing the high-level structure of the logy, we know that most people can process a maxi- computer chip. For example, this allows them to mum of seven units of information at the same time. identify the sub-modules of the chip in which en- One approach to preventing hacking attacks is cryption takes place – sections that are especially therefore to design hardware and software so that suited for introducing Trojans. Until now, these attackers have to grapple with significantly more in- analysis techniques were only available to powerful formation. Christof Paar and the French researcher intelligence agencies and a small number of specia- Gilles Barthe became the founding Directors of the lized firms. However, Paar’s research will help the new Max Planck Institute in Bochum in 2019. Now, entire international research community gain a bet- Paar can spend more of his time on research – for ter understanding of hardware manipulation, so which he also works with the Federal Criminal that new safeguards can be developed. Police Office, or BKA, and companies such as Google. That being said, he doesn’t want to give up Exactly how attacks by governmental or semi-govern- on teaching altogether. “The difference is that, now, mental organizations can be foiled is the subject I can cherry-pick the most interesting topics,” he of research at the Cluster of Excellence “Cyber Se- says. A highlight is Paar’s introductory lecture on curity in the Age of Large-Scale Adversaries” cryptography that he successfully introduced in the (CASA), of which Christof Paar is one of the spea- U.S., albeit in an updated form. kers. “As we know from Edward Snowden’s revela- tions, intelligence services sometimes go to absurd The current wrangling over Huawei highlights the im- lengths to circumvent security solutions,” says Paar. portance of Paar’s research area. The U.S. and Bri- It seems unlikely that he will run out of work any- tain suspect the company of spying for the Chinese time soon.

Max Planck Research · 3 | 2020

USING A TREE’S NATURAL DEFENSES

TEXT: CATARINA PIETSCHMANN

Trees stand for strength and steadfastness. However, the latter can also be a handicap. This is because trees can neither run nor hide from 56 enemies. Nevertheless, trees are by no means defenseless. Sybille Unsicker from the Max Planck Institute for Chemical Ecology in Jena is investigating how black poplars defend themselves against voracious insects. Predators also have to cope with these For her diploma thesis, she examined constantly changing and locally vary- tree crowns on the Ivory Coast. She is ing conditions. In the plant kingdom, currently conducting research in a ri- a common way to spoil the appetite of parian forest on Küstrin-Kietz, an is- Not only the ravages of time but also a attackers is to produce very indiges- land in the Oder River, which is a na- multitude of large and small herbi- tible or even toxic substances. Howe- ture reserve directly on the German– vores, bacteria, fungi, and viruses eat ver, there are hardly any toxins that Polish border. The more than 300 away at a tree throughout its life. keep all predators equally at bay. What black poplars (Populus nigra) growing Which pests infest which parts of a is toxic to one species may be attrac- along the banks of the Oder are among tree depends, among other things, on tive to another. For example, the nico- the last naturally occurring black its age (and that of its leaves), the sea- tine in tobacco plants, the caffeine in poplars in Germany. While elsewhere son, and the weather. Different condi- coffee plants, or the piperine in pep- more competitive species make life tions also prevail within the tree per plants are produced to make the difficult for them, the battles at the crown. Leaves can have different mi- leaves or fruits of their respective end of the Second World War de- cro-climates, depending on how high plants inedible. And this works stroyed almost all the vegetation here. they are off the ground, the direction against most insects. But for humans, This was a stroke of luck for these they face, and their position on the these substances are popular stimu- trees because they are weak competi-

tree. “You have to think of a tree as lants. True to the motto: “The enemy tors. As seedlings, they can rarely pre- PHOTO: ANDREAS BÖCKLER / MPI FOR CHEMICAL ECOLOGY more like a meadow in which there are of my enemy is my friend,” other vail against other plants. various ecological niches,” explains plants get external help for defense. Unsicker. The tree as an ecosystem, And Unsicker aims to find out exactly “I was eager to study a native tree species so to speak. how these alliances work. that occurs in an ecosystem with great

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BIOLOGY & MEDICINE

Using professional climbing equipment, Sybille Unsicker can examine the treetops even at these heights.

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Maybe not pure herbivores after all? In addition to leaves, the caterpillars of the gypsy moth (Lymantria dispar) like to eat fungi. The orange-colored spore deposits of poplar leaf rust alter the mixture of odorous substances that the poplars Luptati veris release from their leaves. asperib eatus.Ebis et omnisit aut lautaeptatem faccab incto commos voluptusam quunt. Apistrum hiligent laborum fugitio bero odit pra et facereptat.Beatemp biodiversity. Riparian forests are hot oremquae rem spots of biodiversity. The fact that velite id moluptas black poplars have become rare in Eu- audis et, autatis rope has given me additional motiva- dolla nossunt ut aut quibus ma acea tion. Our results might even contri- santio id ent que bute to the preservation of these lab ipitae trees,” says Unsicker. Since 2009, she and her team have been studying how poplars react to insect attack – both in the field and in the laboratory. For this purpose, Unsicker has equipped several trees in the riparian forest with ropes. Researchers can use these 58 to climb into the tree crowns and take leaf samples from different heights. They regularly encounter caterpillars of the gypsy moth, a moth that is about three centimeters in size. The investigations have shown that the insects prefer to feed on older, already hardened leaves. The difference between the damaged through its skin to the outside and pu- To avoid having to climb into the tree- and the undamaged leaves is enor- pate. At this stage, the caterpillar be- tops every time they want to observe mous. “Infested leaves produce large haves as if it were under the control of the interplay between caterpillars and quantities of volatile compounds, an external force and even defends its poplars, Unsicker and her team have which give crushed leaves their cha- deadly tenants against attackers. Its planted poplar cuttings from the racteristic odor. We can also detect strength is eventually exhausted, and floodplain forest in their greenhouse sesqui- and monoterpenes, aromatic it dies. The volatile analysis shows in Jena. For their analyses, the re- hydrocarbons, and nitrogen-contai- that the parasitoid wasps can detect searchers wrapped the branches in ning volatiles, including benzyl cya- the odorant molecules from the in- fine nets and placed gypsy moth ca- nide,” says Unsicker. jured leaves extremely well. Faced terpillars inside. “You can easily smell with the choice between the odor of that the insects change the smell of Is this the “cry for help” we are looking intact or damaged leaves, they clearly the leaves,” says Unsicker. Once the for – the message to the enemy of the prefer the damaged leaves. Only a few caterpillars have begun to destroy the enemy? The team had colleagues odorant molecules are required for leaves, the researchers replace the from Austria send one of the caterpil- the highly sensitive antennae of the nets with gas-impermeable bags. lars’ most formidable enemies: para- parasitoid wasps to locate their prey. These collect the volatile substances sitoid (i.e., Braconid) wasps. These But is this also the situation in the of the trees that are being attacked. insects deposit several eggs inside the wild, where – in addition to poplars – The researchers then capture the vo- body of the caterpillars. The hatched other plants also release their volatiles latiles with a filter. The filter content braconid wasp larvae feed on the tis- and the wind swirls all the scents to- is rinsed with solvent and analyzed sue of their hosts but spare the vital gether? To find out, the researchers using gas chromatography and mass organs. The caterpillar thus conti- placed the presumed attractants on spectrometry. nues to live until the wasp larvae bore glue traps in the riparian forest. “Af-

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rent substances than when they are can be found in plants is highly com- infested by caterpillars. But how does plex and used in a variety of ways. a leaf know what is causing it harm? Only in this way is it possible to con- “Leaves can recognize insects by their ceive that a poplar tree – which saliva, which penetrates the leaf tis- reaches sexual maturity no earlier sue. They also perceive the way an than the age of 10 years and then lives animal eats and how much leaf area is on for another 90 years – can survive lost in the process,” explains Un- the attacks of its extremely diverse sicker. “Sucking aphids trigger a dif- predators. ferent reaction than caterpillars that feed on large areas, or leaf beetles that This is supported by the fact that the PHOTO: FRANZISKA EBERL punch small holes in the leaves.” volatiles that summon the parasitoid wasps can be produced very easily. The trees can thus not only call for out- The starting point is the amino acid side help but also warn parts of the phenylalanine, which is converted crown that may not have been in- into benzyl cyanide in only two steps. fested yet. After all, branches of large The intermediate stage, phenylacetal trees are often many meters apart. oxime, can accumulate in the leaf and “Communication within the tree is toxic. The higher the concentration crowns via volatiles would thus be comparatively quick. It would take much longer to send information through the tree’s supply lines, from 59 the leaf to the branch to the trunk, and from there back to another branch and so on,” says Unsicker. In the coming years, Unsicker hopes to find out exactly how one leaf per- ceives the odor of another as well as SUMMARY which receptors and transport mole- ter only a short time, we had braconid cules carry the volatiles through the Black poplars emit odorous wasps and other parasitic insects such cell membranes. substances from their leaves; these attract parasitoid wasps. as ichneumonid wasps in the traps,” The insects parasitize says Unsicker. caterpillars and thus help the Caterpillar toxins trees keep the voracious Examinations of the cuttings in the larvae at bay. greenhouse confirmed the findings. in the leaves As soon as the researchers removed Odorous substances are also suitable media for the caterpillars from the leaves, the But why don’t the attacked poplar leaves transporting information concentration of the nitrogen-con- produce toxins that would repel the from tree to tree as well as taining volatiles dropped to zero. Be- caterpillars like tobacco, coffee, and within the tree crown. They cause the wasps are attracted to these pepper plants do? “The leaves of the reach their destination very odors, it was clear: “We had black poplars also contain substances relatively quickly and are easy found the distress call molecules pro- that are toxic in high concentrations. to produce. duced by the trees,” says Unsicker. For example, salicinoids can be toxic, Leaves infested with fungi Poplars produce volatiles mainly especially for generalists (i.e. cater- also release characteristic during the day when they also carry pillars that feed on various tree spe- volatiles. Their smell attracts out photosynthesis. At night, howe- cies) like gypsy moth caterpillars. But butterfly caterpillars, which ver, they largely stop production. The there is a considerable danger that apparently do not live a kinds of volatiles released by the such a toxin would also affect all the purely vegetarian life but also eat the fungi as a source of leaves depend on the type of injury many beneficial insects that live on nitrogen. they sustain. If they are cut with scis- and in a tree.” Unsicker suspects that sors, for example, they release diffe- the arsenal of defense molecules that

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of this substance in the leaves eaten by think it’s great that someone has ma- the greenhouse with rust spores and gypsy moth caterpillars, the higher naged to draw attention to the forest also put gypsy moth caterpillars on the mortality of the caterpillars. “The ecosystem,” says Unsicker. the leaves. An analysis of the leaf production of these toxic substances scents showed that leaves exposed to thus serves not only the indirect but While Wohlleben promotes greater ap- such a double attack gave off a com- also the direct defense. The tree es- preciation of trees and the forest, Un- pletely different odor profile than sentially has a double defense stra- sicker and her team continue to col- leaves on which only caterpillars had tegy,” explains Unsicker. lect scientific data. In addition to the chewed. “The leaves smell a bit like gypsy moth, trees usually have to deal mushrooms. The proportion of ter- The poplars communicate not only with with a host of other enemies. For ex- penes is considerably lower, but the the parasitoid wasps but also example, black poplars are often at- samples contain hydrocarbons that change information with each other – tacked by rust fungi, which can are typical for fungi,” explains Un- a phenomenon that has been commu- spread to most of the tree crown in sicker. The nitrogen-containing sub- nicated to the public as well, thanks in late summer. The fungal spores are stances that predominate in the dis- part to the books by Peter Wohlleben. blown onto the leaves by the wind or tress call to the parasitoid wasps are It has been known since the 1980s that washed by rain onto lower parts of the not affected by the rust. trees can pass on information about crown. They then penetrate the pests with the help of volatiles. Trees leaves through the stomata. After a are also connected to each other via few days, they form spore deposits Caterpillars fungal networks at the roots, the my- that penetrate the leaf surface as or- corrhizae. However, critics accuse ange pustules from which new spores love fungi Wohlleben of humanizing trees. are released. In a pilot study, “Even for my taste, he sometimes em- Unsicker’s co-worker Franziska Eberl In particular, fungi can change the phe- bellishes the facts too much. But I sprayed some of the small poplars in nol content of leaves. For example,

60 VOLATILE-MEDIATED COMMUNICATION

PROTECTION AGAINST HEAT AND OXIDATIVE STRESS

POLLINATION

SEED DISPERSAL Communication between plants

PROTECTION AGAINST HERBIVORES Mutual inhibition of growth PROTECTION AGAINST PATHOGENS

ABOVE GROUND GRAPHIC: GCO BY ADAPTED SYBILLE FROM UNSICKER PROTECTION AGAINST Communication HERBIVORES between plants?

PROTECTION AGAINST Mutual inhibition PATHOGENS of growth BELOW GROUND

Volatiles released from plants perform various tasks – both above and below ground. Trees thus attract beneficial insects such as pollinators, seed dispersers, and enemies of herbivorous insects. They are also in contact with each other – some volatiles can inhibit the growth of their neighbors or warn them of heat and pests.

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GLOSSARY

GYPSY MOTH (LYMANTRIA DISPAR) Moth belonging to the family of owlet moths. The name refers to the behavior of its larger caterpillars, which generally migrate each day from the leaves to rest in shaded spots. The eggs are laid on the trunks of the trees and survive the winter. The caterpillars hatch in the spring; they prefer to eat oak leaves but

do not reject the foliage of other PHOTO: SYBILLE UNSICKER / MPI FOR CHEMICAL ECOLOGY deciduous and coniferous trees. Gypsy moths are among the most feared pests in oak forests. A single caterpillar can destroy one square meter of leaf surface from the time it hatches to the time it pupates. Their mass propagation can defoliate entire oak forests and cause permanent 61 damage to the trees. The researchers capture the gaseous odor signals of the leaves in plastic bags and pass them through a filter. They then determine the chemical structure of these volatile substances in the laboratory.

they trigger the formation of cate- were thought to be pure herbivores. The extent to which the findings can be chins, the basic building blocks of “We therefore conducted the same ex- transferred from poplars to other tree various tanning agents, in the leaves. periment with the closely related Or- species is not yet fully understood. These are harmful to the fungus. Be- gyia antiqua – with the same result: it For example, during some years, oaks cause rust can pervade the treetops in is also crazy about the rust.” can suffer severe damage from mas- late summer, it could also influence sive infestations of gypsy moths. Fo- the prevalence of other natural ene- rest rangers and forest owners cur- mies of the poplars. But the real sur- High protein diet rently spray forests with pesticides in prise for the researchers was that the order to limit the economic damage. fungal odor apparently does not At first, Unsicker suspected that the fun- “From an ecological point of view, it is bother the caterpillars! On the con- gus-infested leaves might produce quite natural that species like the trary: faced with the choice between fewer toxins because the caterpillars gypsy moth repeatedly appear in healthy and fungus-infested leaves, develop faster on them and pupate great numbers. Nature would nor- the caterpillars clearly prefer the lat- earlier. But that is not the case. It is mally regulate this itself in each case ter. Long-term observations even rather the components of the fungi because the natural enemies respond show that especially very young cater- that are the cause: the spores are rich to the increased food supply and pillars are attracted by the odor. They in nitrogen and contain many amino decimate the gypsy moth population first nibble the rust from the leaves acids and B vitamins essential for the again. Pesticides should therefore before they attack the leaves them- development of the caterpillars. be used only in such a way – if at all – selves days later. “Fungi and other microorganisms that enough predators will be left to might therefore have had a stronger keep future moth populations in The researchers initially considered influence on the communal evolution check.” their findings to be a measurement of plants and insects than previously error – the gypsy moth caterpillars assumed,” says Unsicker.

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BEYOND THE EMERGENCY

TEXT: EVA VÖLKER

Five years ago, the arrival of um-sized towns (with 165,000 and thousands of refugees within 130,000 inhabitants) and one small town (with 80,000 inhabitants) in a short period of time presented Lower Saxony, she analyzed examples the administrative offices of of the structures and administrative the German municipal authori- procedures that were in place when ties with a huge challenge. the refugees were received. In 2015/16, Taking three towns in Lower the three towns took in up to 100 new arrivals every week. This presented We’ve arrived: during Saxony as an example, Miriam them with an enormous challenge, the peak of the 2015/16 Schader from the Max Planck since no information was provided in migration, over 100 advance as to how many people would people seeking Institute for the Study of protection arrived in Religious and Ethnic Diversity arrive and what their particular cha- German towns and racteristics or requirements were. in Goettingen studied how the municipalities every Furthermore, the legal framework in week. This presented a municipal authorities handled Germany was repeatedly changed by challenge to the local the situation. a large number of new or amended authorities, but it was one that they were able laws, which were passed in quick suc- to meet. cession from 2015 onwards. The indi- 62 vidual local authorities also found it hard to retain an overview of EU po- “We can do this.” With these words, Ger- litical developments. many’s Federal Chancellor Angela Merkel attempted to reassure the Although the authorities often had to re- country at the end of August 2015. act spontaneously and an enormous Just a short time previously, Germany amount of work was involved, the lo- For example, the middle town of the had suspended the Dublin Regulation cal structures certainly didn’t col- three that were studied temporarily for Syrians. This meant that the refu- lapse during this period. Instead, the refused to accept any more asylum gees were no longer sent back to the administrations in many local autho- seekers. When significantly fewer country in which they first entered rities made sure that the new arrivals asylum seekers entered Germany fol- the territory of the European Union. were received properly and that the lowing the closure of the Balkan route On 4 September 2015, the German departments involved coordinated in the spring of 2016, the local autho- and Austrian governments decided to with each other. “With reference to rities quickly resumed their normal accept thousands of people seeking Merkel’s famous words, the munici- everyday business. Nothing was protection who had become stranded palities can say: ‘We made it’,” says changed with regard to some struc- in Hungary. Almost overnight, towns Miriam Schader, the author of the tures, and reception capacities were and municipal authorities had to find study. The administrations in all quickly reduced again. Today, for ex- accommodation for the new arrivals. three towns studied first initiated an ample, there is now just a part-time With incredible speed, gymnasiums “emergency operation” so that deci- employee working in the office for in- were turned into temporary accom- sions could be made quickly. This en- tegration in the municipal authority, modation, and food and medical sup- abled them to overcome the period of and with ten new asylum seekers ar- plies were organized. uncertainty in the short term. Howe- riving every week, reception capaci- ver, clear differences emerged be- ties are already fully stretched. The Today, five years later, the question tween the local authorities, particu- two other municipal authorities de- arises as to whether Merkel’s opti- larly in terms of how they handled the veloped a very different strategy. mism was justified. Miriam Schader, medium- to long-term challenges. They turned a period of uncertainty a sociologist at the Max Planck Insti- This was ascertained by the scientist into a period of fundamental change, tute for the Study of Religious and following numerous interviews with by actively shaping the situation Ethnic Diversity, has been looking for staff working in the administrative of- themselves and improving the struc- scientific answers. In two medi- fices at different levels. tures for migration and integration

Max Planck Research · 3 | 2020 CULTURE & SOCIETY PHOTO: PICTURE ALLIANCE | ALEXANDER / DPA KOERNER

that had previously been in place. For flect the migration and diversity did not fit in, and for disciplining example, the largest of the three among the local population in the those who preferred to be cautious for towns studied merged two adminis- long term. In this way, two of the fear of being assigned to a certain ac- trative areas responsible for migration three municipal authorities studied commodation building,” Schader ex- and integration in order to make it proved their ability to cope and to de- plains. easier for refugees to access various velop a sustainable strategy. state support payments, such as child Overall, the study concludes that munic- allowance, the services provided in However, the measures designed to im- ipal authorities made little use of ori- accordance with the Asylum Seekers prove participation also went hand in entation aids such as best practice Benefits Act, and Hartz IV social sup- hand with a process of exclusion. models. This also created a patchwork port funds. The smallest of the three Much of the accommodation offered of different municipal models for re- towns set up an advice center for ad- was simply buildings that had been ceiving refugees. The experience of ministrative and legal issues, which quickly converted, which were only the people seeking protection there- worked closely with voluntary inte- suitable for habitation to a limited ex- fore varied between one place and ano- gration advisers. On its own initiative, tent, and which offered almost no pri- ther. The opportunity was not used it created a new bus link to the accom- vate space, even though large num- everywhere of making long-term modation housing the asylum seekers, bers of people lived there for longer changes in order to receive the refu- which was located outside the town periods of time. Other buildings were gees. According to the Miriam center. Asylum seekers were also is- located in the middle of industrial es- Schader’s findings, this omission sued with an electronic health insur- tates. By only housing men in accom- indicates a lack of far-sightedness. ance card. These measures and the modation facilities, the refugees were After all, it’s only a question of time new structures in two of the towns further isolated in some cases, since before more people arrive in were not only intended to deal with there was no support from volunteers, Germany seeking asylum. the consequences of the immigration for example. “Some buildings were wave in 2015/16, but also to better re- also used for disciplining those who

Max Planck Research · 3 | 2020 KNOWLEDGE FROM

A riot of color in the laboratory: among other projects, Lars Grunenberg, Bettina Lotsch and Julia Kröger (from left) are investigating the wavelengths of light at which their photocatalysts produce hydrogen from water. Here, Lars Grunenberg takes a sample to determine the gas content.

Max Planck Research · 3 | 2020 MATERIALS & TECHNOLOGY

THE LIGHT CONVERTERS

TEXT: KARL HÜBNER

The sun sends more energy to Earth than humanity needs. 65 Researchers led by Bettina Lotsch, Director at the Max Planck Institute for Solid State a material that could do both at the honorary professor at LMU Munich Research in Stuttgart, are same time: convert sunlight into elec- and the University of Stuttgart. “We trical energy – and then directly store create functional materials and teach working on materials that can this energy. As the headline on the In- them new tricks, especially with re- help us put this abundant supply stitute’s website said at the time, the gard to their energy conversion and to use for a whole host of researchers had created a “solar cell storage,” explains Lotsch. “Some of purposes – even beyond the and battery combined.” them are indeed all-rounders.” One energy revolution. such group of materials are carbon ni- The material responsible for this break- trides, which are so appealing to re- through is called poly(heptazine im- searchers because they are not only ide) (PHI) and belongs to the class of highly stable, but also simple, sustai- materials known as carbon nitrides. nable and inexpensive to produce.

PHOTO: WOLFRAM SCHEIBLE FOR MPG Every photovoltaic cell shows that sun- Akin to polymers, these molecules light can be converted into an electric feature a strict alternation of carbon Initially, the group did not intent to de- current. But, anyone who intends to and nitrogen atoms arranged into re- velop a solar battery material. The store this solar power for later use first curring patterns. Although the mo- discovery was a “by-product,” so to has to charge a separate battery, and lecular layers themselves are two-di- speak, of research into another prop- this battery is generally based on lead mensional, they are stacked on top of erty of carbon nitrides – namely, their or lithium-ion technology. The rea- each other – layer by layer – in a struc- ability to do photocatalysis. This term son behind this separation is that, un- ture resembling “holey” graphite. is used by chemists to describe the til now, the production and storage of process where a substance absorbs solar power has relied on completely Bettina Lotsch has been investigating (sun) light and uses this energy to different materials and components. this group of materials for a long time. drive a chemical reaction. Photocata- Against that backdrop, a group of sci- The chemist is now the Director of lysis is one of the research foci in entists at the Max Planck Institute for the Nanochemistry Department at Bettina Lotsch’s Department, where Solid State Research caused a minor the Max Planck Institute for Solid the production of clean hydrogen sensation in 2018 when they revealed State Research in Stuttgart and an from water is one of the key reactions

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in the team’s experimental work. This produced from natural gas and is using titanium dioxide as a photocata- reaction also serves as a model for therefore not only a fossil energy lyst – but this approach never became other interesting applications of pho- source, but also – for technical widely used in industry. Modern tocatalysis, such as the synthesis of reasons – insufficiently clean for its research focuses on more promising important basic chemicals by the re- use in applications such as fuel cells. material candidates, including carbon duction of carbon dioxide or atmo- Although hydrogen could also be nitrides, which can now be observed spheric nitrogen. However, hydrogen obtained electrolytically from water in action at a laboratory in Stuttgart. is also of interest because it is consi- using renewable electricity, the more At the bottom of a brightly illumi- dered to be not only a clean fuel and economically viable – and more ele- nated glass apparatus, a yellow-co- hence, energy storage medium, but gant – solution would be to split water lored powder is visible, immersed in a also an environmentally friendly raw directly into its components using liquid. “The powder is a carbon material for the future. Indeed, there sunlight. In other words, by using nitride, the liquid is water, and the is a good reason why the German photocatalysis. reason why the whole thing is so federal government adopted a bright is that we’re illuminating it “National Hydrogen Strategy” in June from above with a solar simulator,” 2020, in which hydrogen is described Electrons transfer explains Filip Podjaski, a physicist in as a “key component of the energy Bettina Lotsch’s research group. transition.” At present, however, energy to water there is a lack of widespread infra- Podjaski explains the underlying princi- structure for handling this flammable In principle, this process was already ple: “The light excites certain elec- gas. Moreover, most hydrogen is still demonstrated almost 50 years ago, by trons in the material, which in turn

66 PHOTO: WOLFRAM SCHEIBLE FOR MPG

Max Planck Research · 3 | 2020 MATERIALS & TECHNOLOGY

transfer their energy to the water and even over the course of several days. thereby produce hydrogen from it.” In fact, the electrons remained in this SUMMARY But the exact processes involved are state until the scientists added the not that simple. On the one hand, the co-catalyst, which triggered the hy- Photocatalysts such as poly(heptazine imide) (PHI) absorbed light must be sufficiently drogen production to begin immedi- or suitable covalent organic energetic to excite an electron that can ately. This phenomenon was an excit- frameworks (COFs) use drive this reaction. On the other, the ing – indeed an “electrifying” – dis- energy contained in (sun) photogenerated electrons must be ex- covery for the researchers. All of a light to drive chemical tracted from the material before they sudden, they seemed to be able to de- reactions and, for example, return to their ground state and lose couple light absorption and catalysis produce hydrogen from water. their energy. To prevent this, the re- for a long period of time – just as na- searchers in Stuttgart add com- ture does with the light and dark reac- PHI can store energy pounds that provide electrons readily tions in photosynthesis, during which harvested from light and to the photocatalyst – “electron do- light energy is absorbed first and make it available at later nors” – so that the ground state be- sugar is then produced in a subse- times, either for a chemical reaction or in the form of comes populated again, and the ex- quent process. So now, energy could electricity. cited electrons remain available for actually be stored temporarily, like in use. Besides, there is also the “co-cata- a battery, and then be used for a chemi- This property could be used lyst,” which plays a crucial role in hy- cal reaction at the touch of a button to create a solar battery that drogen production by acting as a and at any point in time – even at is charged directly by light, matchmaker between the reaction night. In the scientific community, to produce hydrogen or other substances, or to partners. To facilitate most experi- the paradoxical term “dark photoca- power microswimmers. mental purposes, the researchers cur- talysis” began making the rounds. rently use the common – albeit rare And so, the idea of the solar battery and expensive – metal platinum as was born. their catalyst. However, they are also 67 working on possible alternatives with a view towards developing a more eco- Hydrogen propulsion nomical and sustainable solution for future applications. without a tank

In principle, such hydrogen production Since then, the scientists have been already works well at the laboratory working on understanding the under- scale, but there are a number of tech- lying charging and storage mecha- nical issues to be resolved before a nism. After all, how can it be possible process of this kind is ready for wide- for so many negatively charged elec- spread use, including in commercially trons to accumulate in such a small available systems. However, as an space? The researchers have since aside to their research, the team also learned that positively charged ions asked themselves: what would happen from the material itself and from the if we simply left out the co-catalyst? surrounding aqueous electrolyte play Testing nanomaterials: Theoretically, with continued expo- a stabilizing role. the Max Planck team in sure to light, more and more electrons Stuttgart uses a specially would become excited but would have A material that can store light energy developed reactor to analyze nowhere to go. “Usually, the electrons electrically would be useful in a vari- how efficiently photocata- then decay to their ground state while ety of applications. For example, Filip lysts can produce hydrogen. releasing – or emitting – their energy Podjaski envisages hydrogen engines The gas produced at the catalyst-coated electrode without practical use, and heat is cre- that could work without a fuel tank: (light blue) is not visible. ated,” says Filip Podjaski. “You could use light to accumulate The bubbles seen here electrons in PHI at any time and then stem from the noble gas However, that was not the case with one release them whenever you wanted in argon, that is used by the particular material, namely with PHI. order to produce the required hydro- researchers to remove Provided that an electron donor was gen from water.” For Bettina Lotsch, oxygen from the reaction solution, which otherwise present, the photoexcited electrons the battery-like behavior raises the would distort the measure- retained their energy permanently possibility of “choosing whether to ment. and accumulated within the material, use the stored energy as electricity as

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well.” With a simple switch, users However, Lotsch also envisages medical could then decide for themselves applications of photocatalysis outside whether they wanted to use the of the body. For example, microswim- charged battery to produce hydrogen mers could potentially aid the chemi- for a car or to operate a lamp and re- cal breakdown of metabolic products frigerator instead. In other words, in the bloodstream during dialysis. this technology could provide a versa- Similar applications are conceivable tile solar battery for every household. in wastewater treatment – essentially, Moreover, the ability to decouple light a photocatalytically active swimmer absorption from photocatalysis has that would conduct light-powered pa- now proven beneficial for a com- trols through dirty water in order to pletely different application – namely, remove unwanted substances. In the light-driven “microswimmers”, future, the researchers led by Bettina which are key topic of research at the Lotsch want to pursue ideas such as neighboring Max Planck Institute for these in collaboration with their col- Intelligent Systems (see MaxPlanck- leagues at the Max Planck Institute Research 3/2016). It was shown that for Intelligent Systems. PHOTO: WOLFRAM SCHEIBLE FOR MPG these swimming micromachines can also be made from PHI particles, But carbon nitrides such as PHI aren’t while photocatalysis can be used to the only materials that the group uses propel them efficiently through a li- for their photocatalysis research. The quid. scientists also have great expectations for a group of materials known as co- 68 valent organic frameworks (COFs). Microswimmers for Much like carbon nitrides, COFs form extended layers that then ar- medicine and environ- range on top of one another. These mental protection materials are characterized by their high porosity, with specific surface areas that can reach half the size of a Researchers have long known that this soccer field per gram. This is an ideal type of photocatalytic propulsion characteristic for a photocatalyst, be- system works, but the ability to store cause it is the surface on which re- provided by sunlight. On the other the absorbed energy in PHI has now actions catalyzed. hand, if carbon nitrides are used, ab- opened up a raft of new applications. sorption is limited to blue light only. “A microswimmer of this kind is But the key advantage of COFs is that There is a simple reason why the re- not only powered by direct exposure they can, in principle, be constructed searchers are mostly interested in ma- to light, but also continues to move from almost any kind of organic terials that absorb light over a broad in the dark,” says Bettina Lotsch. building blocks, and these precursor spectrum: the more light a photocata- The chemist even envisages that these molecules are subject to just a few ba- lyst can absorb from the solar spec- microswimmers could one day sic requirements. In other words, they trum, the more charge carriers it can be designed for use in the human provide huge scope for molecular de- supply for catalysis. body – once charged, they could sign. This is particularly beneficial continue to swim (in the dark) inside for chemists, in that it allows key Or rather, the more it can potentially the organism. Another idea is to properties of a COF to be “tailored” – supply – because, in order to actually load microscopic vehicles of this kind as Lotsch puts it – by choosing sui- put the absorbed energy to use, it’s with drugs for delivery to a specific table building blocks. In the context of also important that the electrons re- location in the body. And perhaps, photocatalysis, one key characteristic tain it for as long as possible and pass says Lotsch, a microswimmer is light absorption, and the COF de- it on efficiently. So far, COFs have made from a photocatalyst could signers in Stuttgart have now created been unable to rival the effectiveness even use catalysis to produce the novel varieties that absorb from violet of the carbon nitrides, but Bettina necessary active agent in situ from to orange – thereby covering almost Lotsch’s group is working to change substances available in its environ- all of the visible spectrum, which re- that by subtle variations of the COF ment. presents about 50 percent of the energy building blocks. One day, this may

Max Planck Research · 3 | 2020 MATERIALS & TECHNOLOGY

Searching for the optimum catalyst: Filip Podjaski, Bettina Lotsch, Lars Grunenberg and Julia Kröger (from left) discuss the electronic processes involved in splitting water molecules. An understanding of these processes helps them to develop materials that work more efficiently.

GLOSSARY pave the way for something the renewable,” says Lotsch. In this context, searchers have high hopes for: the di- her colleague Filip Podjaski points out GROUND STATE rect, stable storage of solar energy in a that, for historical reasons, the che- The electronic state of an atom or completely new type of battery. mical industry can obtain many of its molecule in which it has a minimum of energy. Electrons can important basic chemicals – and be excited by (visible) light with a Yet the question of sustainability re- therefore also the derived products, suitable energy – that is, light of a mains unanswered. Indeed, the team such as the COF building blocks – suitable color. The so absorbed in Stuttgart isn’t merely looking for from a hydrogen/carbon monoxide energy can then be transferred functional materials that are particu- mixture known as syngas. And al- and, hence, released in different larly effective at tasks such as photo- though these two components have ways, while the electrons return to their ground state. catalysis. “Of course, we also want previously been obtained from fossil these substances to be easy and su- sources, they could also be produced COVALENT ORGANIC stainable to produce, ideally from re- from water and carbon dioxide with FRAMEWORKS newable resources,” explains Lotsch. the help of photocatalysis. Therefore, Known as COFs for short, these Carbon nitrides are absolutely perfect if suitable recycling concepts were in- materials are made from organic for this, because they can be readily corporated, these versatile light con- building blocks; they have a large specific surface area and are highly obtained from urea – a natural re- verters could pave the way for a fun- variable in terms of their structure source. Depending on the building damentally sustainable circular econ- and composition, which is blocks used, COFs are still ultimately omy, as Podjaski explains. One day, due to the variety of potential derived from crude oil, but it doesn’t therefore, photocatalysis could poten- starting materials. stay that way. “As they are organic tially turn large parts of chemical pro- substances, they are potentially reduction ”green”.

Max Planck Research · 3 | 2020 KNOWLEDGE FROM

RISKY COOLING

TEXT: TIM SCHRÖDER

Volcanoes are sources of ideas. When they erupt, they emit large amounts of sulfur dioxide, cooling the climate. This has 70 prompted experts to discuss whether geoengineering involving the targeted release of the gas could reduce global warming. Ulrike Niemeier from the Max Planck Institute for Meteo- rology in Hamburg is investiga- were blasted into the stratosphere, canic eruptions in the previous cen- ting the feasibility of the idea three times higher than commercial tury, so intriguing. and the dangers it might entail. airliners fly. The mountain shook for hours, simultaneously spewing out “The eruption clearly proved that sulfur eight million metric tons of sulfur di- dioxide has a measurable effect when oxide. Within just a few days, long- it enters the atmosphere,” explains range air currents in the stratosphere Ulrike Niemeier, a scientist at the dispersed the gas over the entire Max Planck Institute for Meteorology northern hemisphere. And this led to in Hamburg. For years, Niemeier has The Pinatubo eruption was enormous. an interesting phenomenon: the sought to describe how the sulfur di- When the Philippine volcano blew off Earth became cooler. oxide and ashes emitted by volcanoes its summit in June 1991, a gigantic ash affect the Earth’s atmosphere. She cloud ascended into the sky. It We’ve long known why such cooling oc- uses computer simulations to model plunged the island of Luzon into curs. Sulfur dioxide reacts in the at- the effects of volcanic gases on the cli- darkness in the middle of the day. mosphere with water vapor to form mate. These include major eruptions Huge amounts of ash rained down on sulfuric acid, which reacts further to in prehistoric times of so-called su- an area as large as Baden-Wuerttem- form sulfate particles. These remain per-volcanoes, which were many berg, Bavaria, and Hesse combined. It airborne for a period, reflecting a por- times more powerful than Pinatubo.

buried streets under a layer that was tion of the Sun’s rays striking the The eruptions of the Yellowstone vol- PHOTO: PICTURE ALLIANCE / ASSOCIATED PRESS | ICHIRO OHARA sometimes several meters deep. Hun- Earth. This cools the underlying lay- cano about two million years ago, for dreds of people died, and tens of thou- ers of the atmosphere, explaining why example, released approximately 200 sands lost their homes. The eruption climate researchers find the eruption times more matter than Pinatubo did was so powerful that ash and gases of Pinatubo, one of the strongest vol- in 1991. Using computer simulations,

Max Planck Research · 3 | 2020 ENVIRONMENT & CLIMATE

Models for climate engineering: active volcanoes such as Nishinoshima, 1000 kilometers south of Tokyo, release huge amounts of sulfur dioxide. Particles form from this gas and remain suspended in the atmosphere, reflecting sunlight back into space.

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A change of course in research: Ulrike Niemeier researches the impact of volcanic eruptions on the climate, increasingly focusing on the possible effects of seeding the Earth’s atmosphere with sulfur dioxide.

PHOTO: TOM PINGEL FOR MPG

Max Planck Research · 3 | 2020 ENVIRONMENT & CLIMATE

Niemeier has calculated how these gi- down the pipeline into a depleted na- meters to several micrometers in size, gantic quantities may have been dis- tural gas reservoir under the North which are so small and light that once tributed throughout the Earth’s atmo- Sea. they have been thrown up into the at- sphere – how the matter cooled down mosphere, they almost never sink and ultimately altered the global cli- back to the ground. Sulfate particles mate. A controversial in the stratosphere are also aerosols. Ulrike Niemeier was able to use her Over the last 15 years, volcanic sulfur di- idea model to calculate how quickly and ef- oxide’s cooling effect has led to a shift of Niemeier’s research from her original The second climate engineering cate- focus – the role volcanoes play in the gory, known as radiation manage- climate – toward a different field of ment, includes methods that directly climate research. The impetus has impact the Earth’s heat balance. One SUMMARY been anthropogenic warming of the particularly bold idea in this category Earth’s climate, raising the question is solar radiation management (SRM), Geoengineering, or climate of whether we might be able to artifi- shading the Earth in space with huge engineering, is viewed as one cially cool it down. One of the first sunshades – a plan that is still consid- way of halting anthropogenic scientists to suggest this idea was the ered to be in the realm of science fi- climate change – whether atmospheric chemist Paul Crutzen, ction. But there are also options on a through reforestation, subterranean storage of carbon who for many years was the Director smaller scale: aircraft, for instance, dioxide, iron fertilization of the of the Max Planck Institute for Che- could scatter particles into the atmo- ocean, or shading the Earth by mistry in Mainz. Crutzen published a sphere, which could then reflect some means of sulfate particles provocative paper on the subject in of the Sun’s radiation back into space. produced from sulfur dioxide. 2006. To counteract the impact of the This idea, however, exposed Paul continuous increase in carbon dioxide Crutzen to a storm of indignation. It According to simulations, the average global temperature emissions, he asked whether humani- is always hubris, so the detractors, to could be maintained at the level ty might need to use technology to in- try to alter the Earth’s radiation bud- of 2020 without reducing tervene in the climate in the future to get using technology. Furthermore, greenhouse gas emissions if five mitigate the worst effects of climate the impact of such a massive climate to eight times more sulfur 73 change. Such climate fixes became intervention would be impossible to dioxide were released into the atmosphere each year than from known as geoengineering or climate predict in the various regions of the the 1991 Pinatubo eruption. engineering (CE), which now encom- world. After many years of research, passes a wide range of technical stra- Ulrike Niemeier agrees with this view. According to the calculations, tegies. Targeted climate interventions “While CDR only reduces carbon di- the reduction in energy input generally fall into two categories: car- oxide concentration in the atmo- from the Sun would disrupt bon dioxide removal (CDR) and radi- sphere, radiation management influ- large air currents in the tropics, for example, with unforeseeable ation management. The aim of CDR ences the amount of solar energy consequences for the global is to remove carbon dioxide from the reaching the whole of the world’s sur- climate. Aerosols formed from air, bind it, and safely store it in the face.” sulfur dioxide would also likely long-term. The reforestation of huge, reduce average global rainfall. previously unforested areas is under This could trigger conflicts discussion, as is fertilizing the sea Aerosols could slow between nations, some choosing unilaterally to go on releasing with iron to stimulate algal growth. down heating the gas and others suffering from “At present, the most realistic and rea- the reduction in rainfall. sonable solution appears to be systems that filter carbon dioxide out of All the same, Paul Crutzen’s paper trig- the air or capture it from the exhaust gered considerable scientific interest gases of power stations and industrial in climate engineering. As experts in plants,” says Ulrike Niemeier. This simulating sulfur clouds from volca- method is known as carbon capture nic eruptions and their impact on the ficiently small sulfate particles form and storage (CCS). The Dutch are al- climate, Ulrike Niemeier and her col- from sulfur dioxide, and how quickly ready working on implementing it. As league Claudia Timmreck were also they clear up once again by gradually part of the Porthos project, in the much in demand. At that time, they clumping together and sinking down coming years, a pipeline is to be laid at had just developed a unique simula- from the stratosphere. PHOTO: TOM PINGEL FOR MPG the Port of Rotterdam parallel to the tion tool: a stratospheric aerosol refineries, power plants, and cement model, which could be employed to “At the time, along with colleagues we works, into which carbon dioxide calculate the impact of sulfur dioxide tried to clarify whether climate from exhaust gases will be fed. The or sulfate particles in the stratosphere. change induced heating of the Earth carbon dioxide will then be pumped Aerosols are particles of a few nano- could theoretically be compensated

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for by sulfur dioxide,” explains Nie- CO2 emissions would continue to rise maintain 2020’s climate through to meier. Their investigations were part in the coming years. The Implicc 2100 with the help of sulfur dioxide of Implicc, a large EU project led by partners calculated that the tempera- alone, humanity would have to release her colleague Hauke Schmidt, which ture level of 2020 could be maintained five to eight times as much sulfur di- examined “Implications and risks of by means of large-scale sulfur dioxide oxide into the stratosphere each year engineering solar radiation to limit injections into the atmosphere. “On than that from the 1991 Pinatubo climate change.” The findings were average, the climate would remain eruption,” says Niemeier. That would clear and – much like Crutzen’s arti- milder worldwide,” says Ulrike be absurd. A Japanese research team cle – controversial: yes, global warm- Niemeier. “However, average global arrived at similar conclusions, calcu- ing could indeed be compensated for, rainfall would slightly decrease.” lating that 6,700 airplanes would have even in the worst-case scenario out- to distribute sulfur dioxide in the lined by RCP8.5, the Intergovern- This would however be problematic to stratosphere every day to reduce mental Panel on Climate Change. In put into practice. “If, despite rising global warming by one single degree

this “business-as-usual” scenario, CO2 emissions, we were aiming to Celsius. For comparison, at London’s

METHODS OF GEOENGINEERING

AEROSOLS IN THE ATMOSPHERE Aircraft, balloons, or drones, for example, SO introduce sulfur dioxide 2 into the stratosphere. SO2 There, particles form that SO reflect a portion of the 2 SO2 sunlight. SO SO 74 2 2 SO2 SO 2 SO2 SO2 SO2

SO2

CO2 CAPTURE AND STORAGE The greenhouse gas is separated from the exhaust gases of power and cement plants, for example, and pumped into former oil and natural gas sites or into deep aquifers.

DIRECT CAPTURE OF CO2 Huge filters extract

CO2 from the air, which is then stored underground.

SUBTERRANEAN

CO2 STORAGE

SUBTERRANEAN

CO2 STORAGE ENVIRONMENT & CLIMATE

Heathrow Airport, 1,200 aircraft take gradient between the two regions, tion would lead to the collapse of the off every day at peak times. Ulrike which could weaken air currents. The QBO,” says Niemeier. “We have no Niemeier also stresses that such sulfur quasi-biennial oscillation (QBO), one way of predicting what impact this dioxide releases would have signifi- of the large stratospheric air currents would have on the global climate.” cant side effects. Bright blue skies in the tropics, would be affected. would be likely to take on a milky ap- Every two years it changes its direc- Andreas Oschlies from the GEOMAR pearance. Worldwide, rainfall would tion – from west to east and then back research center in Kiel considers re- decrease on average, and the monsoon again. Coupling her aerosol model search such as Ulrike Niemeier’s to be and large air currents in the atmo- with the MPI-ESM, the large climate groundbreaking. “She’s one of the sphere would change due to our ef- model of the Max Planck Institute for very first to have analyzed in detail forts to reduce solar energy input. So- Meteorology, Ulrike Niemeier inve- the chemical-physical processes in lar radiation would drop more steeply stigated what would happen to the the stratosphere,” says Oschlies, who in the tropics than at the poles, QBO. “The calculations clearly show is an expert in climate engineering. thereby reducing the temperature that a large-scale sulfur dioxide injec- “She has supplied quantitative, robust

SUNSHADES IN SPACE Countless mirrors or lenses are deployed as a sunshade in a stable orbit around the Earth. They deflect a portion of the sunlight away from the Earth.

SO2 75 SO2

SO2 GRAPHIC: GCO

REFORESTATION Plants, especially trees,

bind CO2, removing it from the atmosphere.

IRON FERTILIZATION OF OCEANS Iron sulfate is a micronutrient for algae, causing them to pro-

liferate and absorb CO2. When they die, they sink to the seaf loor.

Max Planck Research · 3 | 2020 KNOWLEDGE FROM

data, which can be used to correctly stratosphere over a period of one theless, investigating climate engi- calculate the climate in the future if month would result in far less particle neering is important. If the climate we implement such climate enginee- clumping than daily releases. Not were to change extremely rapidly, cli- ring.” The discovery, for example, only that, the cooling effect was mate management measures could at that sulfate particles clump together highly dependent on where on Earth some point be placed on the political over time has been pivotal. In other the sulfur dioxide was released. The agenda as an emergency option – the words, it won’t help to pump ever models suggest that injections at sev- lesser of two evils in comparison to more sulfate into the stratosphere, be- eral points around the tropics would massive climate impacts. “If it ever cause the aerosols will just clump and have the greatest impact. came to that, we would need to know sink at a higher rate. Saturation is precisely what we would be getting bound to occur at some point, no mat- Such findings make it sound like into.” Nor can it be ruled out that at ter how much sulfate airplanes spray. Niemeier and other experts have al- some point in this century, individual “Niemeier’s findings have been essen- ready worked out a climate-engineer- countries may embark on climate en- tial in enabling us to assess how effec- ing master plan. But, according to gineering on their own initiative – tive such radiation management Ulrike Niemeier, nothing could be without consulting the worldwide methods might be,” says Oschlies. further from the truth. “I believe community of nations. Politically, Ulrike Niemeier has also analyzed the there’s only one way to halt climate that would be a fiasco, as it would af-

effect of different sulfur dioxide re- change: reduce CO2 emissions as fect the whole world. A solo initiative lease methods, for example, whether quickly as possible. Because one by individual nations or a small group daily releases of the gas or releases at thing’s clear: radiation management of nations could therefore lead to con- other particular intervals would be would only be treating the symptoms. flicts, for example if rainfall de- more effective. She discovered that It wouldn’t do anything to solve the creased in other countries. Hence, for releasing large quantities into the real problem, carbon dioxide.” Never- Ulrike Niemeier, the Ceibral project

Historical cooling effect: Ulrike Niemeier has calculated how the sulfur dioxide cloud that formed after the eruption of the Yellowstone volcano about two million years ago is likely to have spread over the Earth. Her results indicate that after eleven days, it covered large areas of the northern hemisphere. After about a month, it covered almost the entire northern hemisphere. GRAPHIC: GCO MICHAEL FROM BÖTTINGER/DKRZ

Max Planck Research · 3 | 2020 ENVIRONMENT & CLIMATE

has been one of the most interesting she has worked on. Together with Hauke Schmidt, lawyers, political scientists, economists, and philosophers, she helped investigate whether and how climate engineering could be for chemistry uniformly regulated internationally. The focus was on whether individual & life sciences nations could be held liable for damage caused by their climate engineering activities. From chemists to chemists – In her work for Ceibral, Ulrike Niemeier make full use of the GDCh attempted to deduce from models where the world’s winners and losers network: of climate engineering measures would be. “However, it’s incredibly  Job market – online and in difficult to causally link damage to a the Nachrichten aus der Chemie particular climate engineering mea-  CheMento – The mentoring sure,” she says. “As an example, a program for young chemists five-week drought in Poland led us to  Publications about career paths ask whether climate engineering measures in Australia  Workshops GLOSSARY were to blame.” She couldn’t  Job fairs and lectures give a definitive answer. “But it AEROSOLS was enormously exciting work- are particles dispersed in the ing with experts from the other atmosphere, ranging in diameter disciplines, while developing a from a few nanometers to several common language and mutual micrometers. They reflect solar

understanding of each other.” radiation but also play a role in ADVERT It became clear that, at present, the formation of cloud droplets. it would be difficult to prose- RADIATION MANAGEMENT cute a nation for climate engi- is a method of climate enginee- neering activities. No court in ring which would shield the Earth the world has ever tried such a from a portion of the Sun’s light case. Which institution would by means, for example, of sulfate aerosols. be responsible? “And in this respect, I think climate engineering also represents a crucial political issue,” says Ulrike Niemeier. “Should we ever actually consider climate engineering, humanity will have to be extremely vigi- lant not to stumble into starting wars. At any rate, an international agreement regarding the matter of liability should be ratified beforehand.”

Her collaboration in the Ceibral project and also her long-standing cooperation with other climate researchers as an expert in aerosols have shown Ulrike Niemeier how important academic exchange between disciplines is. “We have no idea whether we’ll ever employ climate engineering,” says Niemeier. “But we still need to prepare ourselves for it and, above all, be aware of the risks.”

Gesellschaft Deutscher Chemiker

Max Planck Research · 3 | 2020 www.gdch.de/karriere The Koffler Tower is not just the symbol of the Weizmann campus, but also contains particle accelerators, PHOTO: EDDIE GERALD / ALAMY STOCK PHOTO an observatory and a seminar room with a breathtaking view.

Max Planck researchers co- 78 operate with partners in more than 120 countries. Here they were due to close early before the start other particles their mass. I’m also in- write about their personal ex- of the Shabbat. My husband and I terested in any new particles we could were immediately made to feel wel- be searching for. As it happened, a periences and impressions. come. new model was presented just before I The physicist Elina Fuchs arrived, and my colleagues and I were spent four years conducting We are both physicists and had both able to use it to produce some very in- research at the Weizmann been given a job at the Weizmann In- teresting results. I also got to be in- Institute in Israel after recei- stitute in Rehovot. For researchers, volved in the development of a new Israel is a paradise for a number of dif- method at the interface between par- ving a scholarship from the ferent reasons. The laboratories and ticle and atomic physics. Minerva Stiftung, a subsidiary the infrastructure are phenomenal, from the Max Planck Society. and there are plenty of opportunities Israel is also a good place for pregnant She reports on generous hospi- for networking as well. Since we women and young parents. Children weren’t far away, we met with particle are given a very high priority in a na- tality, unusual public holidays physicists from Tel Aviv, Haifa, Jeru- tion with the highest birthrate of all and colleagues who were salem and Be’er Sheva nearly every industrial countries (3.1). Since nearly happy to help. week, and discussed new research. all Israelis serve in the army before Also, guest scientists were very often they study, with the women serving invited to the Institute, and it was for two years, and the men for three, On the first day, we were given a taste of great to be able to discuss ideas with it’s no exception for doctoral students the incredible hospitality in Israel. A them and make contacts. to have a child. In fact, it’s generally colleague collected us at the airport the rule. During my pregnancy and and gave us a short guided tour of the In my research, I focus on which parti- after the birth of our daughter, we campus site. When we entered our cles might exist beyond the Standard benefited from flexible working apartment that evening in October Model, and how existing models can hours, working from home and the 2015, we saw that someone had filled be tested and excluded. I am particu- Institute kindergarten. We were also the refrigerator with food. It turned larly interested in how the properties offered help by individual colleagues. out that the secretary had bought food of the Higgs boson change in new One Weizmann employee, whom we for us, so that we would have enough models. Discovered in 2012, it is an ele- always came across on the train in the to eat the next day, when the shops mentary particle which helps give morning, gave us huge quantities of

Max Planck Research · 3 | 2020 POST FROM

REHOVOT, ISRAEL

79 baby clothes. And when our daughter spent in Israel, I had a few surprises was born, two colleagues brought when it came to the way people be- home-made food to our door. haved. If you see someone approach- ing you on the sidewalk, it’s better to Of course, the greatest experience was get out of the way, otherwise they

the birth of our daughter. We were might simply barge into you. In Israel, PHOTO: PRIVATE also very moved by the various festi- it appears to be socially accep- vities and family dinners to which we table to talk loudly on the phone in were invited. One colleague invited us buses and trains, or to watch films to celebrate Pesach (Passover) with without headphones. him and his family twice. This is the equivalent of a professor inviting a Overall, I really enjoyed the scientific postdoc from another country to and cultural and human experiences Elina Fuchs spend Christmas Eve at home with during my stay, and can thoroughly their family. recommend a visit to Israel, whether 32, studied physics in Goettingen and Helsinki. For as a tourist or a researcher. You’ll dis- her Masters thesis, she switched Overall, I found the Jewish holidays very cover delicious dishes, see breathta- to DESY in Hamburg, where interesting. The biggest “culture king landscapes and be astonished by she also gained her doctorate shock” was Passover. This comme- places of historical interest. You’ll be from 2012 to 2015. Since then, morates the departure from Egypt, smothered in hospitality – and on she has conducted research which is why most Jews do not eat Yom Kippur, the most important na- into theoretical particle physics beyond the Standard Model, leavened food, such as bread. A reli- tional holiday, when the country and worked for four years as a gious neighbor asked us to buy his en- comes to a standstill, you can cycle postdoc at the Weizmann tire stock of cornflakes, toast and spa- along the freeway. Institute of Science in Israel, with the support of the Institute ghetti for a token amount, since he For information was not allowed to own leavened food. on the Minerva Stiftung, see: and the Minerva Stiftung of the After Passover, he bought everything minerva.mpg.de/ Max Planck Society. She is currently researching at the back, insisting that he pay more than Fermilab and the University we had paid him. In the four years I of Chicago as a Feodor-Lynen fellow.

Max Planck Research · 3 | 2020 “AN ESSENTIALLY CREDIBLE SCENARIO”

The ARD feature film Ökozid shows the legal re-appraisal of the climate crisis in the not so distant 2034. The two scriptwriters consulted experts at the Max Planck Institute for Comparative Public Law and International Law, including the scientific

advisor and coordinator PHOTO: RBB/ZERO ONE FILM / JULIA TERJUNG Alexandra Kemmerer.

Unease among the population: the film Ökozid paints a dark picture of the future. In 2034, the Ms. Kemmerer, in the film, Federal Republic of Germany is facing criminal charges for breaching its international statutory 31 countries of the global South obligation to counteract the increase in the concentration of CO2 worldwide. sue Germany before the Inter- national Court of Justice because Did people from the Institute also In what way? Germany had done too little benefit from the cooperation? to combat climate change. There has been an incredibly dynamic de- How realistic is such a scenario? Definitely. As a lawyer, you are trained to as- velopment in the area of climate complaints. sess facts in court proceedings retrospec- Just to name a few examples: in December 80 tively. For the film, however, we had to 2019, the Dutch Supreme Court ordered the ALEXANDRA KEMMERER: Of course, a imagine ourselves in the year 2034 and cre- country’s government to meet its climate feature film must always make compromises ate scenarios for the future. That is a com- targets. This July, the Irish Supreme Court between real-life circumstances and a story pletely different way of thinking. Instead of ordered the government to draw up a new that is exciting and understandable for the assuming existing constraints, it is possible climate plan for the period up to 2050. Pro- audience. However, despite the necessary to open up potential spaces. This kind of ceedings are also under way at the Hamm reduction in complexity, the scriptwriters thinking is certainly relevant to the legal Higher Regional Court, the Federal Consti- Andres Veiel and Jutta Doberstein have suc- field. Ministries often seek expertise in legal tutional Court, and the European Court of ceeded in conveying basic legal principles impact assessment. When drafting bills, it is Human Rights, all of which are concerned and an essentially credible scenario. essential to think ahead and classify future with climate protection. developments. In science, too, such “thin- How did the cooperation work? king in scenarios” based on precise factual Do you think that climate protection and legal knowledge opens up possible solu- will actually be enforced by courts I had met Jutta Doberstein at a conference in tions and promotes dexterity and flexibility in the future? 2018. In the summer of 2019, she told me in dealing with unforeseen risks, conflicts, about the film project and asked whether we and environmental changes. In this respect, That is my assumption – but we also should would be able to support it. Jutta Doberstein we have learned a lot from the exchange with not overestimate the role of the judicial sys- and Andres Veiel are known for their tho- the scriptwriters. tem. The film itself is quite realistic, I guess. roughly researched and scientific work – both It also shows the tension between courts and for their film documentaries and fictional Were you involved in the film produc- democratic procedures. Courts can lead the material. So I was happy to support them. A tion in any other way? way in climate protection – but they remain year ago, we held a kind of workshop at the embedded in political processes and public Institute with the two scriptwriters and se- During the process, there were always ques- debate. In the film, interaction with the veral scientists. For a whole day, we went tions of detail – for example about legal ter- public plays a major role. Subversive forces through options on how such a process minology or how lawyers and judges behave use social media bots to incite the population could be conducted and what the verdict in court. Of course, we helped – even if not against the plaintiffs and their concerns. In would be. It was a joint effort – an exchange everything that we suggested was imple- the end, there are large public protests. in which my colleagues Tom Sparks and mented. I was also able to read the finished This shows that the biggest challenge is to Guillaume Futhazar and our Director Anne script in advance and got the cut version for convince the broad majority that climate Peters were also substantially involved – and a screening. One interesting development protection is important. Courts alone cannot just simply a consultation session. Of was that the scenario we discussed a year ago not create the global solidarity that is essen- course, we cannot accept any liability for the has now turned out to be far less fictional tial to meet the challenges of climate change. result. than we had thought. Interview: Mechthild Zimmermann

Max Planck Research · 3 | 2020 COMMUNITY NEWS

WE DON’T HAVE TO LIVE IN A DOG-EAT-DOG SOCIETY In the first round of the new event format over thousands of years, the economic “Science Meets Literature”, Matthias models of the last decades try to per- Sutter, Director at the MPI for Research suade us to do something else,” the au- on Collective Goods, and Marc Elsberg, thor explains. “This is being refuted and author of bestsellers such as Blackout or it is demonstrated that what people like Zero, discussed Elsberg’s novel Greed, to do – namely to work together – is the which was published in 2019. right thing to do.” It was a lively and exciting discussion We don’t have to live in a dog-eat-dog moderated by Maja Brankovic, editor at society. Instead, the principle of sub- the Frankfurter Allgemeine Zeitung. sidiarity should be rethought: we should KUCHAR URSULA PHOTO: The topic: cooperation as a basic model all work together – unless “together” of the economy – a departure from pre- doesn’t make sense. This would result in vious doctrines such as competition and a completely different organization of subsidiarity or even the model of homo society. According to Sutter, however, oeconomicus, which assumes that peo- studies have shown that simply knowing 81 ple think exclusively in economic terms. that cooperation means success for ever- The novel is based on calculations by the yone does not automatically lead to the London Mathematical Laboratory, the appropriate behavior. The most im- purpose of which is to question currently portant driver is communication, such widespread economic models. Marc Els- as the promises of cooperation and, even berg developed the farmer’s fable from a better, the positive experience of cooper- part of these complicated mathematical ation. Both strengthen trust in the calculations. It illustrates the fact that principle. On the question of when the merging and dividing is not a zero-sum ability to work together arises, Sutter game, but leads to increased prosperity cited studies showing that small for all concerned. children appear to have a natural pre- But as positive as cooperation may disposition for cooperation. seem in fiction, there are limits in reality. Marc Elsberg emphasizes the fact that How does cooperation work? According to Elsberg, this is the case, for merging and sharing do not create a For his novel Greed, author Marc example, when the effort involved in or- communist or socialist society: “All Elsberg looked at the results of basic ganizing and coordinating cooperation ‘-isms’ kill cooperation – be it commu- mathematical research. is greater than the resulting benefit for nism, socialism, fascism or liberalism. those involved. Sutter mentioned three Because cooperation needs difference, additional factors that are essential for which leads to increased growth – so it functioning cooperation: successful doesn’t mean that everybody is the same. communication, the fact that people can Competition is not bad per se, but it is rely on each other and on what has been given a different role.” However, agreed upon, and institutions that en- Matthias Sutter comments that “re- sure that agreements are honored. search also shows that the more different Elsberg believes it is quite possible the participants, the more difficult co- that the idea could cause a similar epi- operation becomes.” phany as in the book because people ave always cooperated intuitively. The idea Are you interested in different aspects of mutual support and sharing is embed- of how cooperation works in fiction and science? Watch the discussion on the ded in the DNA of many philosophies Max Planck Society‘s Youtube channel: and religions. “The paradox is: although youtube.com/watch?v=sQEGMzHjtvE humans have successfully cooperated (in German)

Max Planck Research · 3 | 2020 FIVE QUESTIONS

ABOUT ENVIRONMENTAL PROTECTION IN BRAZIL

FOR RAQUEL SIROTTI

The Brazilian government under for producing data on deforestation in the huge economic problems because of the President Jair Bolsonaro has been Brazilian rainforest was dismissed after an- coronavirus pandemic, everything related the target of international criticism nouncing that deforestation had risen by to investments, money, and donations is very for its lax environmental policies. 88% during the first year of Bolsonaro’s ad- important – even more so than before the The outrage was particularly ministration when compared to the previ- crisis. great when, at a cabinet meeting ous year. His position was also given to 82 in April, environment minister someone from the military, generating a lot This year, the fires in the Amazon Ricardo Salles suggested taking of debate about the continued reliability of rainforest are raging stronger advantage of the coronavirus crisis data published by that agency. than they have done in a long time. to relax the rules on protecting Is there resistance to the slash- the rainforest. Did the protests Is no one doing anything and-burn clearances among against this have any effect? to resist this process? the Brazilian population?

RAQUEL SIROTTI Since the video of the At the beginning of May, Brazilian federal Yes, definitely! Even though there is a large meeting was published by court order, Jair prosecutors filed a lawsuit against Ricardo group of people involved in agribusiness, as Bolsonaro’s government has received in- Salles, the minister of the environment, in well as landowners, who have a great vested tense criticism – especially from interna- which they accused him of violating his duty interest in laxer environmental laws, the tional investors and funds supporting con- to protect the environment and called for his rainforest in Brazil is generally seen as one servation projects. They threatened to with- dismissal. So there is a movement going in of our greatest assets – one that should be draw their capital if the government didn’t the opposite direction, trying to replace preserved, maintained, and not sold to inter- KETTERER SOPHIE ILLUSTRATION: do more to protect the rainforest. In re- Salles with someone more concerned with national interests. The left-wing and more sponse, the president announced a decree environmental policies. progressive parties are very concerned about banning slash-and-burn clearance for the deforestation, and there is also a great 120 days. The government is attempting to How can the international community deal of dissatisfaction among the middle distance itself from the idea that it is open- influence Jair Bolsonaro to protect class – even those who voted for Jair ing the rainforest up to profiteers. the rainforest in the long term? Bolsonaro in the election.

Is compliance with the decree I think the most successful strategy has been Interview: Barbara Abrell being monitored? the threat by international investors and en- trepreneurs to pull money out of Brazil if the There is a governmental agency called environment minister continues to open up Ibama, which is in charge of monitoring the rainforest to investors to do whatever compliance. The problem here is that Bol- they please there. Import restrictions on Raquel Sirotti is a researcher at the Max sonaro has replaced a number of Ibama offi- Brazilian products may also be useful. Un- Planck Institute for European Legal History, cials with members of the military with no fortunately, that appears to be the only lan- where she studies the development of experience in environmental policies. Simi- guage that Bolsonaro understands. Espe- criminal law in Latin America, as well as larly, the director of the agency responsible cially now that his government is facing political crime.

Max Planck Research · 3 | 2020 RESEARCH ESTABLISHMENTS

SCHLESWIG- HOLSTEIN Institute / research center Plön Rostock Sub-institute / external branch Other research establishments MECKLENBURG- Associated research organizations VORPOMMERN Hamburg

Bremen The Netherlands BRANDENBURG Nijmegen LOWER SAXONY Berlin Italy Hannover Rome Potsdam Florence Magdeburg Münster USA NORTH RHINE-WESTPHALIA SAXONY-ANHALT Jupiter, Florida Göttingen Bochum Dortmund Mülheim Halle Brazil Manaus Düsseldorf Leipzig SAXONY Cologne HESSE Dresden Luxembourg Bonn Jena Luxembourg Marburg THURINGIA Bad Münstereifel Bad Nauheim RHINELAND PALATINATE Mainz Frankfurt

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Max Planck Research · 3 | 2020