Is the Amazon about to flip into savanna? Where scientists agree and disagree
Many scientists think a threshold may exist; studies disagree about whether it is at 20 percent clearing or at 4 °C of warming, and how soon it might come.
▶ Start the storyThe honest answer is that many scientists think a tipping point is real, but they disagree about where it is, and about when it might come. The basic worry goes like this. The Amazon recycles moisture, so the forest helps make the rain that feeds it. If enough forest is lost, whether to drought, fire or clearing, there is less rain downwind, which stresses and kills more trees, and eventually a threshold may be crossed beyond which large parts of the remaining forest die off and turn into drier forest or , particularly in the drier south and east.
Different studies put the threshold in different places. One summary of research says it could be reached at about 20 to 25 percent deforestation, and that this change would take decades. Another account of modelling research says a near system-wide transition across 62 to 77 percent of the forest could be triggered by 1.5 to 1.9 °C of warming combined with 22 to 28 percent deforestation, and that large transitions would need 3.7 to 4.0 °C of warming without deforestation. Even the count of what is already gone differs: about 20 percent deforested in 2022 in one account, 17 to 18 percent cleared in another.
Clearing alone
- About 20 to 25% deforestation (one summary)
- would take decades
Warming alone
- 3.7 to 4.0 °C with no deforestation
- Lower with deforestation: 1.5 to 1.9 °C plus 22 to 28% cleared
Timing is more disputed still. In 2019 Brazilian scientist Carlos Nobre warned that at the current pace the forest could reach a tipping point within 20 to 30 years. A 2022 study found that the rainforest has been losing since the early 2000s, but it cannot determine exactly when, or if, a tipping point will be reached. Different models do not even agree on whether rainfall in the basin will go up or down.
The Amazon has also shown toughness: it survived glacial periods when the climate was drier. The sensible reading is not doom or all-clear but a serious risk with uncertain edges.
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Recap
The risk is real but its threshold and timing are uncertain, so numbers need a source, a model and a date.
💡 A trick to remember it · A dimmer switch, not a light switch: scientists see the forest dimming, but they argue about where the click is.
Surprising fact · Different studies place the threshold at about 20 to 25 percent deforestation or at several degrees of warming.
Sources (3)
No source, no claim. Every fact in this lesson (15 claims) cites at least one of these.