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The last time the atmosphere contained as much carbon dioxide as it does now, birdlike dinosaurs roamed what was then a verdant landscape. The earth’s lushness was at least partly caused by the abundance of CO₂, which plants use for photosynthesis. That has led to the idea that more CO₂ in the atmosphere could create a literally greener planet.

Today, plants and soil around the world absorb roughly a quarter of the greenhouse gases that humans release into the atmosphere, helping the Earth avoid some of the worst effects of climate change. In an ideal situation, as levels of carbon dioxide increased, plants would soak up more of these emissions, helping to fuel their growth.

But in a study published Wednesday in the journal Nature, researchers found that under a warming climate, rather than absorbing more greenhouse gas emissions, plants and soil may start absorbing less, accelerating the rate of change.

“We have this image of the planet getting very, very green as we move into the future,” said Pierre Gentine, a professor in the Department of Earth and Environmental Engineering at Columbia University and an author of the study. “But it may be the opposite .”