This week, world leaders are hashing out a binding agreement in Paris at the 2015 U.N. Climate Change Conference for curbing greenhouse gas emissions. And for the first time, they’ve made the capture of carbon in soil a formal part of the global response to the climate crisis.

“This is a game changer because soil carbon is now central to how the world manages climate change. I am stunned,” says André Leu, president of IFOAM — Organics International, an organization that promotes organic agriculture and carbon farming worldwide.

Leu is referring to the United Nations Lima-Paris Action Agenda, a sort of side deal aimed at “robust global action towards low carbon and resilient societies.” On Dec. 1, countries, businesses and NGOs signed on to a series of new commitments under the agenda, including several on agriculture.

Currently, the Earth’s atmosphere contains about 400 parts per million of carbon dioxide. Eric Toensmeier, a lecturer at Yale and the author of The Carbon Farming Solution, a book due out in February, says the atmosphere’s carbon dioxide levels must be cut to 350 parts per million or lower to curb climate change.

Toensmeier and Leu are among a growing number of environmental advocates who say one of the best opportunities for drawing carbon back to Earth is for farmers and other land managers to try to sequester more carbon in the soil.

“Reducing emissions is essential, but eventually it still gets us to catastrophic climate change,” says Toensmeier, who’s attending the Paris talks on behalf of the group Project Drawdown. “The level of emissions in the atmosphere now is already past a tipping point. That means we have to sequester carbon.”