COMMENT since 1970 (0.8 million km2). Land is also increasingly traded. Since 2000, states including the United Kingdom and China have together bought a total area of farmland in Africa and elsewhere that is bigger than Germany to grow food. And 3.0 IGO BY-SA ESA/CC countries are producing more crops for export — global cereal exports rose sixfold between 1960 and 2010, according to the Food and Agriculture Organization of the United Nations. Although food trade can lessen local shortages, it exposes around 200 million poor people in countries such as Algeria, Mexico and Senegal to price shocks when exports from major producers, such as the United States, Russia and Vietnam, col- lapse. Some countries such as Egypt are reli- ant on imported food. Yet global land management is not on the political table. By contrast, climate-change mitigation has been negotiated inter­ nationally for 30 years. Air, ice and water are proclaimed officially as global com- mons — shared resources in which everyone has an equal stake. Treaties protect the atmos- phere, Antarctica and the high seas. Land has no safeguard. The reason: its diverse purposes and stakeholders. Intensive livestock rearing in Iowa, high-rise prop- erty in Singapore and timber logging in the Amazonian rainforests are each regulated differently. The European Union’s Common Agricultural Policy is a rare example of inter- national cooperation on land, but remains largely unsustainable. The United Nations’ Sustainable Development Goals (SDGs) don’t The Putoransky State Nature Reserve in northern Central Siberia seems untouched by humanity. call explicitly for global coordination of land uses. This is despite access to land resources being central to the goals — notably those on hunger, cities, production and consumption, climate and life on land. Govern land as a Things are beginning to change. This year, the UN Convention to Combat Desertifica- tion will publish its Global Land Outlook, addressing land management in the con- global commons text of sustainable development. The Inter­ governmental Panel on Climate Change Felix Creutzig calls for international coordination of (IPCC) will release a report on land use and land use to ensure everyone has access to its fruits. climate change in 2019. But a stronger case is needed: one that will bring all parties together to coordinate land uses around the world to he world’s land masses can seem ‘Growing pressure’). By 2050, we will need achieve sustainability. immense. When I crossed Siberia by twice as much productive ground as now I argue that land must be considered train after finishing my PhD, I passed sits idle2. Feeding more people will demand as a global commons — conceptually by Tbirch trees day and night. Later I traversed 10–20% more cropland3 (or 1.5 million to researchers and legally by the international Patagonia, counting one cow every ten min- 3.0 million square kilometres). To seques- community. Carbon sequestration and eco- utes. Such places are far from the busy cities ter atmospheric carbon dioxide, an area the system services, such as clean water, medical of Europe and North America. But they are size of India will probably be needed to grow resources, nutrient recycling and recreation increasingly interconnected. Even the most energy crops, and a similar area could be depend on land and are universal public remote landscapes are under rising pressure required for afforestation4. Up to one-fifth of goods6. Excluding people from the basic from human population growth, economic natural forests, grasslands and savannahs will goods and services that land furnishes, such development and climate change. be destroyed3. Meanwhile, 2% of the world’s as food and housing, breaches the Universal Globally, land is becoming a scarce most fertile land (0.3 million km2) will be Declaration of Human Rights. Researchers resource1. Today, almost two-thirds (63%) of paved over by 2030 as cities expand5. Humans and policymakers should focus on one goal: the world’s ice-free land is used for agriculture are driving mass extinctions: one-fifth of the providing sufficient fruits of the land to sup- or settlements, or is covered by forests (see Brazilian Amazon rainforest has been lost port all livelihoods, now and in the future. 28 | NATURE | VOL 546 | 1 JUNE 2017©2017 Mac millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. COMMENT COMMON GROUND In the absence of a major power, such as People’s rights to land have been debated by GROWING PRESSURE China or the United States, with a vested philosophers since at least John Locke and More productive land than currently lies idle interest in advancing the interests of the Hugo Grotius in the seventeenth century. In will be needed by 2050 to feed a larger commons, scientists and experts should SOURCE: REFS 1–4 population, grow energy crops, store carbon 2012, philosopher Mathias Risse made a pow- and expand cities. explain the benefits to the public. erful case for humanity’s collective ownership Part of the evidence will be supplied by of Earth in his book On Global Justice7. But scientific assessments, such as the Global few environmental scientists or policymakers Urban Cropland Pasture Land Outlook, assessments of biodiversity are considering these arguments. by the Intergovernmental Science-Policy The Declaration of Human Rights states Platform on Biodiversity and Ecosystem Forest and Bioenergy Aorestation that everyone should have an “adequate” shrubland Services (scheduled for 2018) and the IPCC standard of living, including food, clothing, 2019 land-use report. In addition, an over- housing and medicines — all products of the arching case for land as a global commons Total current 1 million km2 land. What is adequate is open to question. land use: 84 million km2 is required; it could be commissioned by Providers of food aid assume that a mini- the UN secretary-general. Better links are mal diet should include a certain number needed between international organizations, of calories. The second SDG also, rightly, including the UN agencies that are responsi- emphasizes nutritional needs. ble for food, shelter, energy, biodiversity and Some philosophers go further and argue terrestrial carbon storage. that access to land resources should be shared A nested regime for international govern- equally by all citizens of Earth; one such is ance will be necessary, including regulatory Gopal Sreenivasan at Duke University in changes in four areas. First, international Durham, North Carolina8. This might be financing of conservation and efforts to achieved by taxing land or by redistributing store carbon on land must be scaled up. produce and other profits derived from land. Second, ambitious conservation standards Private property will remain protected with should be harmonized. Third, innovative the common ownership of global land. The approaches to technology and management associated bundle of rights and duties, how- must be transferred to improve yields and Unused productive ever, will shift towards more stewardship of land: 4 million km2 food storage. Fourth, we will need sustain- land and protecting future generations and able patterns of consumption that reduce the people living elsewhere. Already now, land- amount of land embedded in trade. These owners in Iowa may practise industrial live- Additional land demand four areas must be reflected in international stock production only if they do not damage in 2050: 10 million km2 public and private laws, such as World Trade or devalue neighbouring properties. Organization regulations. States should commit to efficient land- GLOBAL GOVERNANCE management principles. Financial instru- Nordic welfare states such as Sweden provide The extra land requirement by 2050 ments such as land taxes could share the fruits all their citizens with adequate food, shelter corresponds roughly to the size of China. of land justly in modern economic systems. ■ and natural spaces for recreation. But many of the goods needed are imported and feed on Felix Creutzig heads the Land Use, land resources globally. Only global coopera- units of agricultural land by area incentivizes Infrastructures and Transport working group tion can achieve an open world-trade system the production of higher yields while preserv- at the Mercator Research Institute on Global that manages land-based production and ing wilderness and biodiversity10. Commons and Climate Change, Berlin, consumption footprints in a sustainable and Land-use rights can be assigned for a lim- Germany, and is a professor at the Berlin equitable way. ited period. For example, Chinese property Technical University. Because many diverse stakeholders are law limits them to 40, 50 or 70 years. And e-mail: [email protected] involved, coordinating land uses internation- benefits can be spread to future generations twitter: @efesce ally will be harder than governing Antarctica through approaches such as the Alaska 1. Lambin, E. F. & Meyfroidt, P. Proc. Natl Acad. Sci. or meeting treaties on climate change. Crit- Permanent Fund, which captures 25% of USA 108, 3465–3472 (2011). ics might suggest that securing one issue at the state’s oil revenue and redistributes an 2. Canadell, J. G. & Schulze, E. D. Nature Commun. 5, 5282 (2014). the time, such as food security or maintain- annual dividend to residents. 3. Smith, P. et al. Phil. Trans. R. Soc. B 365, ing biodiversity, is sufficient. But these issues Economist Elinor Ostrom and her col- 2941–2957 (2010). intersect. leagues have identified eight principles for 4. Smith, P. et al. Nature Climate Change 6, 42–50 Global cooperation on land use can build managing local commons that should be (2015). 11 5. Bren d’Amour, C. et al. Proc. Natl Acad. Sci. USA on and learn from successful local schemes. applied globally . These include: clearly http://dx.doi.org/10.1073/pnas.1606036114 These range from communal tenure of high defining group boundaries; matching rules (2016).