Feature Cover story

Anthropocene: An epoch of our making Humans have affected the Earth in myriad ways, be it through agriculture, mining or urbanisation.

But are our impacts epochal? Absolutely, says Figure 1. An enterprise to reckon with. Human manipulation of their environment began in earnest during the Industrial Revolution and accelerated markedly after the 1950s, as IGBP's Great Acceleration graphs show. James Syvitski. Modified after Steffen W et al. (2004).

s rapidly receding ice sheets brought whole. But now we regularly decelerate but pristine and strongly under the Athe Pleistocene epoch to an end around and accelerate natural processes, focus influence, if not control, of society. 12,000 years ago, the warmer and more energy in extraordinary ways and alter, Epochs are by themselves merely stable climate heralded the inception of destroy or create ecosystems. Stealthily subdivisions of Earth’s geologic the holocene. No longer constrained by at first, but then at an astonishing pace, timescale; it is what happens during these the ice age, humans were free to finally we have left the holocene behind and intervals that gives epochs their unique make their mark. and make their mark embraced the Anthropocene (Box 1). characteristics. The progression from they did. We moved from hunting and Momentum is building to officially one epoch to another is marked by some gathering to farming; we built major declare the Anthropocene a new geological easily distinguishable, global stratigraphic cities and civilisations. We came to rely epoch (Syvitski and Kettner 2011; ‘event’, such as a mass extinction, bulk more and more on technology. at some Zalasiewicz et al. 2011), prompting change in the composition of sedimentary point, we graduated from adapting to high-profile publications and scientific rocks or shift from one climate regime our environment to making it adapt workshops/conferences to discuss the to another. The traits of past epochs can to us. The effects on the Earth were relative merits and demerits of doing so. be inferred from the rocks that were gradual at first: it is huge, after all, and Interestingly, while portions of society deposited during those time intervals. its biogeochemical and physical systems still refuse to acknowledge the role of have our activities created a biological, are extremely resilient. as long as our humans in affecting global climate, geochemical or sediment signal that will numbers were few and ambitions modest, they appear more willing to accept be preserved as a rock record for millions we had little impact on the planet as a that the modern world is anything of years (Zalasiewicz et al. 2011) and that

12 ❚ Global Change ❚ Issue 78 ❚ March 2012 Figure 1. An enterprise to reckon with. Human manipulation of their environment began in earnest during the Industrial Revolution and accelerated markedly after the 1950s, as IGBP's Great Acceleration graphs show. Modified after Steffen W et al. (2004).

Background image created by Gregor Aisch; http://driven-by-data.net/about/global-digital-divide/.

will be sufficiently different from that of driver of change (see also page 20 of this the holocene epoch? If so, where does the issue), a trend that continues to date. past two centuries comparable with, say, holocene end and the Anthropocene begin? those of the Pleistocene ice ages? Do they IGBP’s Great acceleration graphs How big is our humans have changed the Earth in a permit the recognition of a new epoch? (Figure 1), part of the programme’s footprint? number of fundamental ways (Syvitski first synthesis (Steffen et al. 2004), The big regional ice sheets of the and Kettner 2011), many of which are far collectively highlight the accelerating Pleistocene epoch removed the soil cover less known than global warming. This human enterprise and its impacts on the of is not surprising when you consider the biophysical Earth system. From these rapid changes portrayed by the Great higher latitude regions, reorganised data we can infer that the Anthropocene acceleration graphs. Since the 1950s, continental drainage patterns, left large began sometime around the Industrial human population, urbanisation, resource regional areas covered with thousands revolution in Europe (circa 1800), when consumption and even the number of of lakes and marshes, and mantled new and powerful ways of manipulating Macdonald’s restaurants have all grown continental-scale tracts of land with ice-sheet the environment became available. by leaps and bounds. Granted there are deposits. Life and ecosystems had to adjust Things progressed relatively slowly for a large regional variations, but the impacts accordingly. Things changed drastically century and half before the stage of great on at least some components of the during the Holocene, when everything acceleration (1950 onwards). Consumption biophysical Earth system have been global from ocean circulation to river hydrology brought on by affluence and technology and represent similar temporal trends. or land vegetation responded to the end of overtook population as the greater atmospheric carbon dioxide, global surface the ice age. And of course, human activities accelerated. But are the effects during the Global Change ❚ Issue 78 ❚ March 2012 ❚ 13 Feature Cover story

temperatures and human- Box 1. The emergence of a paradigm induced nitrogen fluxes to the coastal zone have all increased. Particularly striking is the The concept of the Anthropocene has manifested itself in the scientific literature for over extent and rate at which we a century under various guises. In the 1990s the term Anthroposphere was widely used have modified Earth’s surface. in the Chinese science literature under the influence of Chen Zhirong of the Instute of Deforestation for wood and Geology and Geophysics at the Chinese Academy of Sciences in Beijing. New York Times land clearing for cultivation is journalist Andrew Revkin introduced the terms Homogenocene and Anthrocene in his an obvious example; the direct 1992 book Global Warming. Sometimes the concept appeared without a moniker, as in effects include soil erosion, hill Vitousek et al. (1997). slope failure and downstream sedimentation. But infrastructure The Anthropocene was formally introduced in 2000 by Nobel laureate and former IGBP – dams, cities, transportation vice-chair Paul Crutzen and colleague Eugene Stoermer (1934-2012) in IGBP’s Global networks and coastal-management Change magazine (then a newsletter). Professor Stoermer, an ecologist, had been using measures – has led to lasting the term since the eighties. In one 1995 email, Stoermer described terrestrial and neritic and profound impacts. Prior to oceanic production during the Anthropocene. The term and concept quickly caught on, human interference, the world’s nicely encapsulating IGBP science (Steffen et al. 2011). Before 2003, the term yielded rivers collectively delivered 15 416 web hits; by 2011 that number had increased to over 450,000. gigatons (Gt) of sediment per year to the coastal ocean. We Still, the Anthropocene isn’t as well known as global warming, which two out of three now easily match the capacity people had heard of by 2008, according to a Gallop Poll (http://www.gallup.com/ of rivers to move sediment in poll/117772/Awareness-Opinions-Global-Warming-Vary-Worldwide.aspx). But the diverse ways. In the 1930s, a former is a more effective paradigm in describing the cumulative impact of civilisation, proliferation of small farms making global warming and its consequences but one of many ways in which humans employing poor tilling at a time have modified the Earth. Narrow focus on global warming might suggest that we simply of drought in the US Great Plains need to stop emitting greenhouse gases and use renewable energy to abate the planet’s region led to one of the world’s pressures. The human footprint is much larger than that. largest erosion events: 12.5 Gt of topsoil was removed over more than 9 million hectares. had on our planet, but over a for one or more of the so-called The construction of the Palm much shorter period of time. tipping points to be crossed? What Islands will add 520 km of Clues to our impact are being can we do to prevent this from beaches to the city of Dubai, recorded in sediments that will happening? We need to have a United arab Emirates, and form part of the rock record in cold hard look at the available displace more than 3 Gt of the future. Be it a rapid sediment evidence and continue to collect rock, sand and limestone. pulse, a sudden change in missing information. as this is But we are also sequestering composition or evidence for a an unfolding story of a change more sediment on land than mass extinction, it will not be hard in our Earth system, we must would be sequestered naturally to distinguish the Anthropocene continue to deploy and maintain (Figure 2). The large dams we from the holocene millions of appropriate observing systems. have built during the past two years into the future. Cities could But we need to do better than centuries trap more than 2.3 Gt of make for particularly interesting repeat the business-as-usual sediment every year in reservoirs. deposits, as an article in the May approach that favours observations This starves deltas of sediment 28 issue of The Economist points of the more easily sensed and, in combination with the out cheekily (http://www. atmosphere and surface oceans. mining of water, oil and gas, has economist.com/node/18741749). Monitoring the complexities of led to a situation where large the terrestrial environment more deltas are sinking at four times Living in an effectively is just as important. the rate of sea-level rise. humans Anthropocene If addiction is a recurring now irrigate deserts throughout world compulsion to engage in the world. We have delayed the The preceding discussion might some specific activity despite flow of freshwater to the ocean have given the impression the knowledge of its harmful by weeks to months through that we know a lot about our consequences, humans are diversions and reservoirs. By What are the footprint. and we do indeed. certainly afflicted by one. any unbiased and quantitative thresholds we But there is much that we know as discussed on page 20, we measure, humans have affected need to worry little about. For example, what continue to extract and consume the surface of the Earth at a are the thresholds we need to resources at rates that are clearly magnitude that ice ages have about? worry about and how likely is it unsustainable. Can we change

14 ❚ Global Change ❚ Issue 78 ❚ March 2012 Figure 2. Sediment trapping by large dams. Reservoirs around the world retain sediment that would otherwise have been transported to the ocean. Source: GWSP Digital Water Atlas (2008). Map 51: Sediment Trapping by large Dams (v1.0). Available online at http://atlas.gwsp.org. our behaviour and embrace a JaMES P M SYvITSKI, IGBP’s more sustainable way of living, includes the International Council Chair, is the Executive Director and if so, how? Unfortunately of Science, the International Social of the Community Surface this is proving to be a far tougher Science Council, big funders Dynamics Modeling System, question to answer, for the of global-change research and University of Colorado-Boulder, constraints are not merely poor some UN agencies. The Planet Campus Box 545, Boulder, information or less sophisticated Under Pressure conference in Co 80309-0545, USa. models. What if the answer entails London this year might be a Email: james.syvitski@ a transformation of our societies, good place to find out how an colorado.edu political systems, economies and even international power relations? integrated approach to solutions Clearly, answering the might look like (http://www. big questions pertaining to We have entered the planetunderpressure2012.net/). sustainability requires diverse Anthropocene, without question. expertise and a solutions-based Some of the changes, for example REfERENcEs approach. Existing global-change those brought about by large vitousek P M et al. (1997). Science 277 research programmes like IGBP reservoirs and megacities, are (5325): 494-499. have contributed immensely to here to stay for hundreds if not our understanding of the Earth thousands or even millions of Crutzen P J and Stoermer E F (2000). system and of its modification by years. We will simply have to get Global Change Newsletter 41: 17-18. humans. It is now time to build used to and find a way of living on this foundation and harness with such changes. But there Steffen W et al. (2004) Global Change this knowledge to explore creative are things we can and should and the Earth System: a Planet under solutions to the planet’s problems. change to keep improving human Pressure. The IGBP Book Series. Berlin, The current research on global wellbeing and to avoid crossing Germany: Springer. change needs to be supplemented potentially dangerous thresholds. Steffen W et al. (2011). Philosophical by that on societies, policy and our strength as humans is the Transactions of the Royal Society economics. Inputs from industry capacity to recognise problems, to A 369: 842-867. doi:10.1098/ will need to be solicited, for it will understand them and to develop rsta.2010.0327. need to be part of any solution. solutions. The final chapter of The structures that do this aren’t the Anthropocene story is yet to be the final Syvitski J P M and Kettner A J (2011). in place yet, but the planned written: the narrative will depend chapter of the Philosophical Transactions of the Royal Future Earth initiative is a step on our collective self-awareness Society A 369: 957-975 in the right direction. Contours and the capacity to correct Anthropocene of the initiative are being worked our course, for the relentless story is yet to Zalasiewicz J et al. (2011). out at the moment by a team pressure on our planet portends Philosophical Transactions of the Royal reporting to an alliance that unprecedented destabilisation. ❚ be written. Society A 369: 835-841.

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