How did the Amazon become a carbon source in 2023?

Question

Hans Steiner · Accepted Answer

Extreme drought and heat tipped the balance

In 2023 the Amazon, long regarded as a crucial carbon sink, shifted temporarily to releasing more carbon than it absorbed. The turn came during an exceptional combination of drought and record heat that stressed vegetation across vast areas. Researchers estimate the region emitted up to about 170 million tonnes of CO₂ that year, a reversal driven more by weakened plant uptake than by fire alone.

A few key points explain the change:

Atmospheric stress: an anomalously warm season—about 1.5°C above the 1991–2020 baseline in places—reduced plants’ capacity to photosynthesize and store carbon.
Drought impacts: reduced soil moisture and canopy stress limited the forest’s growth and carbon sequestration, so living vegetation pulled in less CO₂ even where trees did not burn.
Fires contributed but were not the dominant factor: studies find vegetation physiology and drought-related declines in uptake explain a larger share of the net loss.

Why this matters

Climate feedbacks: if such extreme events become more common, the Amazon could shift from buffering climate change to amplifying it, shortening the time available to cut emissions globally.
Ecosystem health: repeated stress weakens forests, increases tree mortality, and raises vulnerability to pests and fires, with long recovery times.

What can be done

Protecting and restoring intact forest reduces susceptibility to drought-driven collapse.
Policies that cut global greenhouse‑gas emissions lower the odds of extreme, ecosystem‑level heat and drought events.
Better monitoring—satellites and field networks—helps track rapid shifts in carbon balance so policymakers and managers can respond.

The 2023 event is a stark example of how climate extremes can undermine natural climate solutions and why rapid emissions reductions and forest stewardship are both essential.