When people talk about technologies that might offset climate change, they often evoke not-yet-invented marvels, like planes spraying chemicals into the atmosphere or enormous skyscrapers gulping carbon dioxide from the clouds.

But in a new report, Oxford University researchers say that our best hopes might not be so complex.

In fact, they are two things we already know how to do: plant trees and improve the soil.

Both techniques, said the report, are “no regrets.” They’ll help the atmosphere no matter what, they’re comparatively low-cost, and they carry little additional risk. Specifically, the two techniques it recommends are afforestation—planting trees where there were none before—and biochar—improving the soil by burying a layer of dense charcoal.

Between now and 2050, trees and charcoal are the “most promising” technologies out there, it said.

It also cautioned, however, that these so-called “Negative Emissions Technologies” or NETs should only be seen as a way to stave off the worst of climate change.

“NETs should not be seen as a deus ex machina that will ‘save the day,’” its authors wrote. NETs should instead be seen as one of several tools to meet the international goal of avoiding climate change greater than 2 degrees Celsius. Another crucial tool is reducing emissions.

It’s a solution that makes sense, as forest management is one of the oldest ways that humans have shaped their environment. Before the arrival of Europeans, Native communities in the Americas had been burning forest fires for millennia to support the growth of desirable plants like blueberries and to manage ecosystems. British communities have long practiced coppicing, a tree-cutting technique that keeps forests full of younger trees.

In other words, humanity has been “geoengineering” with trees for a very long time. The authors of the Oxford report add that afforestation will need global support in order to be successful.

“It is clear that attaining negative emissions is in no sense an easier option than reducing current emissions,” it says (emphasis mine). “To remove CO2 on a comparable scale to the rate it is being emitted inevitably requires effort and infrastructure on a comparable scale to global energy or agricultural systems.”