Averting catastrophic warming requires rapid, global changes to land use and food production, the assessment says.

Unsustainable land use and greenhouse gas emissions are delivering a one-two punch to natural ecosystems that are key to the fight against global climate change. And without sweeping emissions cuts and transformations to food production and land management, the world stands no chance of staving off catastrophic planetary warming.

That’s according to a dire new United Nations assessment of the complex relationship between terrestrial landscapes and climate change. The report from the Intergovernmental Panel on Climate Change, or IPCC, the leading U.N. body of researchers studying human-caused global warming, warns that the unfolding crisis poses a serious threat to global food security.

“Climate change has already affected food security due to warming, changing precipitation patterns, and greater frequency of some extreme events,” the report says. An estimated 500 million people live in areas where once productive land has dried out and turned to desert, including North Africa, East Asia and the Middle East.

Climate change has taken a toll on natural environments by fueling drought, extreme weather, wildfires, coastal erosion and the thawing of Arctic permafrost. And those risks are forecast to become “increasingly severe with increasing temperatures,” according to the findings. At the same time, humans have altered as much as 76% of the planet’s ice-free land. Agriculture, deforestation, urban development and other types of land use account for approximately 23% of total human greenhouse gas emissions and have left swaths of the global landscape degraded.

As the report details, land can be a major contributor to climate change. It can also be a tool for solving it. Earth’s natural landscapes continue to act as a buffer against warming, absorbing 29% of all carbon dioxide emissions, the report found.