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The land provides —
Land use is a big problem that could be a big solution.
Scott K. Johnson
– Aug 8, 2019 11: 06 pm UTC
Enlarge / Forest being cleared for palm oil cultivation.
During the negotiations leading up to the 2015 Paris Agreement, nations agreed to reduce greenhouse gas emissions. But they also gave climate scientists some extra homework. In addition to the periodic IPCC reports assessing the latest in climate science, nations wanted some specific reports focused on topics that hadn’t really been covered before. As some nations demanded a new and more stringent goal of limiting global warming to 1.5°C rather than 2°C, they needed a report on what that would take—and how much risk it could avoid.
Today saw the release of another report, this one focused on land use. The report is the result of volunteered efforts of 107 scientists from 52 countries, referencing research from some 7,000 studies. It covers the ways that human agriculture, forestry, and land use contributes to climate change, the way climate change is impacting these activities, and what we can do about both of those things.
Human land use contributes almost a quarter of our current greenhouse gas emissions. Clearing forests takes the carbon in the vegetation and adds it to the atmosphere as CO2. Farming can also result in a release of carbon as CO2, nitrous oxide from fertilizer, and methane from (primarily) livestock and rice paddies.
Land ecosystems naturally take up carbon from the atmosphere, and some of humanity’s emissions have ended up in these ecosystems (or the ocean) rather than the atmosphere—without this helpful uptake, the world would be warming even faster. But if you add all the greenhouse gas fluxes together, land ecosystems are soaking up a little less than our land use is emitting. In addition, the amount these ecosystems can soak up in the future will very likely change as the impacts of climate change worsen.
On top of the global climate change caused by our emissions, land-use changes themselves can have more local climate impacts, including the loss of evaporative cooling as forests are cut down or agricultural practices reduce soil moisture.
The report states that “climate change has already affected food security due to warming, changing precipitation patterns, and greater frequency of some extreme events.” In particular, the report identifies food-supply instability, water scarcity, wildfires, and permafrost degradation as risks that are growing rapidly as the world continues to warm. It’s important to note, though, that climate isn’t the only influence on many of these risks. The report points out that everything from population and consumption changes to technology to land management practices can also make a big difference.
Enlarge / Illustration of increasing risks in different categories at different amounts of global warming.
And that brings us to what we can do about it. Much of the report focuses on the many ways we can minimize the impacts of climate change while also reducing the greenhouse gas emissions that cause it. Fortunately, most of these actions are win-win-win in that they also provide benefits beyond climate resilience and emissions. These additional benefits include things like improving farmers’ financial stability and making land use sustainable for the long term. Some actions—like dietary shifts away from resource-intensive foods like beef or reductions in food waste—even make the other actions much easier by reducing the overall demand for land.
Familiar agricultural practices, like prevention of soil erosion and reduction of inefficient water and fertilizer use, have a big role here. The biotech world will need to provide more drought-resistant crop varieties for dry regions at risk of losing their farmland to desertification, for example, or insect-resistant varieties to combat changes in the geographic ranges of pest species.
Some problems are less about technical solutions and more about socioeconomic ones. Reducing deforestation, for example, often requires addressing the vulnerabilities and lack of options that drive people to clear land.
Trade-offs
There are also trade-offs to balance. Some strategies to reduce or counteract our overall emissions rely on biofuel crops, either to fuel transportation or burn in power plants that can capture the CO2 for storage underground. Those biofuel crops may compete for land with food crops or reforestation plans. The local details really matter, and the report emphasizes that the best mix of options will vary from place to place, depending on the situation.
To that end, the report calls for “mutually supportive climate and land policies.” Preserving or restoring land pays great dividends, but so do actions that reduce underlying problems like poverty.
The report highlights the fact that land-use factors actually make up a big portion of the difference between emissions scenarios that lead to 1.5 or 2°C warming instead of 3°C. So doing these things effectively could be incredibly important. And to turn that around, the report adds, “Delaying climate mitigation and adaptation responses across sectors would lead to increasingly negative impacts on land and reduce the prospect of sustainable development.”