Three hundred billion dollars. That’s the money needed to stop the rise in greenhouse gases and buy up to 20 years of time to fix global warming, according to United Nations climate scientists. It’s the gross domestic product of Chile, or the world’s military spending every 60 days.

The sum is not to fund green technologies or finance a moonshot solution to emissions, but to use simple, age-old practices to lock millions of tons of carbon back into an overlooked and over-exploited resource: the soil.

“We have lost the biological function of soils. We have got to reverse that,” said Barron J. Orr, lead scientist for the UN Convention to Combat Desertification. “If we do it, we are turning the land into the big part of the solution for climate change.”

Rene Castro Salazar, an assistant director general at the UN Food and Agriculture Organization, said that of the 2 billion hectares (almost 5 billion acres) of land around the world that has been degraded by misuse, overgrazing, deforestation and other largely human factors, 900 million hectares could be restored.