To Paris via land
Authors: None The Lancet Planetary Health
Journal: The Lancet Planetary Health (2019)

On August 2–7, the IPCC convened to approve a new report, Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. As the report outlines, the continuing growth of the world's population and wealth has so far depended heavily on the expansion of land use for forestry and agriculture, with more than 70% of the ice-free surface of the Earth now being directly affected by human activity. However, as land use intensifies, so too do the risks of land degradation, desertification, and increasing greenhouse gas emissions that contribute to climate change, further enhancing these threats to food security and biodiversity. Central to understanding climate change is that land can be both a source and a sink of greenhouse gases: the net effect depends on the use this land is put to and the way that it is managed. CO2 sequestration by soils and vegetation, for example, act to reduce the concentration of atmospheric greenhouse gases, while methane emissions from rice cultivation and ruminant livestock rearing, and the conversion of excess nitrogen fertilisers to nitrogen oxides are contributors to the growth in atmospheric greenhouse gases. During 2007–16, land acted as a sink for an estimated 11·2 GtCO2 per year, or roughly 29% of total CO2 emissions, according to the report. However, whether the land can continue to sustain this sink is directly threatened by climate change. Together agriculture, forestry, and other land uses are estimated to produce the equivalent of 12·0 GtCO2 per year, or 23% of anthropogenic greenhouse gas emissions. As such, land-based adaptation and mitigation responses are crucial to addressing climate change. Probably the most discussed of the responses included in the IPCC report are those related to food systems, particularly diets. Like previous reports on sustainable food systems, it discusses the potential benefits of populations adopting more varied and balanced diets incorporating more plant-based foods, as well as the use of more sustainable agricultural practices and strategies to reduce food waste. However, the report is not confined to food, and the authors present other possible mitigation and adaptation approaches across a range of settings, including sustainable forest management, direct interventions to prevent or reverse desertification, and conservation of high-carbon ecosystems such as peatlands. The problems facing the way we use land are closely interrelated, and consequently so are the solutions, with most options having many potential co-benefits. For example, approaches aiming to restore degraded land could also enhance its ability to act as a carbon sink, as well as provide benefits to local biodiversity and/or food security. While land-based mitigation will be essential to keeping the global temperature increase below 1·5°C, or even 2°C, there are limits to what this can achieve. As well as the clear logistical and financial challenges involved, there are also huge cultural ones, such as those involving dietary change. Land ownership and access is another thorny issue; in many of the most vulnerable communities, the people working the land and most exposed to the effects of degradation and climate change are not recognised as land owners. Without secure land tenure, it is difficult to implement any long-term plans to enhance sustainability, but any solutions involving land ownership reform will require significant political will behind them. The intrinsically finite area of land available for mitigation, food production, wildlife, cities and almost everything else we do is also a key challenge. Large-scale conversion of land for purposes such as afforestation and reforestation—and especially growth of crops for bioenergy—need to be implemented carefully to avoid creating new risks for land degradation and food security, among other problems. Despite the challenges There is much that must be accomplished through careful land use and management. The IPCC report makes it clear that two of the most important prerequisites for achieving meaningful change will be having a clear climate target and identifying which combinations of solutions nations are willing to implement. The Paris Agreement largely addresses the former, whereas the latter will need discussion and implementation in the imminent future. What is certain is that change is needed, and it is needed soon. With the close links between land and climate, deferring action is only going to make these challenges steeper.