As temperatures rise, tropical forests absorb less carbon

A large-scale scientific study involving over 225 researchers across three continents has found that rising temperatures are measurably reducing tropical for...

What Happened

A large-scale scientific study involving over 225 researchers across three continents has found that rising temperatures are measurably reducing tropical forests' ability to absorb carbon dioxide from the atmosphere.
The research, synthesising decades of forest monitoring data from South America (RAINFOR), Africa (AfriTRON), and Asia (T-FORCES), shows that by the 2010s, the average carbon absorption capacity of tropical forests had dropped by one-third compared to earlier decades.
Forests absorb CO2 through photosynthesis and release it through respiration; when temperatures rise, respiration rates increase faster than photosynthesis can compensate, tipping the carbon balance toward net emission.
A critical thermal tipping point has been identified at 32.2°C (average daily maximum temperature during the warmest month): beyond this point, long-term carbon storage declines steeply, with each additional degree releasing four times more CO2 than below the threshold.
If global average temperatures rise 2°C above pre-industrial levels, an estimated 71% of tropical forests will be pushed past this tipping point, transforming forests from carbon sinks into carbon sources.

Static Topic Bridges

The Carbon Cycle and Forest Carbon Sinks

Forests are a critical component of the global carbon cycle, acting as "carbon sinks" by absorbing more CO2 than they release. Through photosynthesis, trees convert atmospheric CO2 into biomass; through respiration (especially root and soil respiration), some of this carbon is returned to the atmosphere. Net Ecosystem Productivity (NEP) is the difference between these two processes and represents a forest's net contribution to carbon storage.

Tropical forests cover roughly 12% of Earth's land surface but store approximately 25% of terrestrial carbon.
A 1°C rise in tropical land surface temperature was found to push an extra 3.5 petagrams (billion tonnes) of CO2 into the atmosphere per year.
Globally, each 1°C rise in maximum temperature reduces carbon storage in tropical forests by approximately 7 billion tonnes — roughly equivalent to total US annual carbon emissions over five years.
Drier tropical forests are more vulnerable because water stress compounds heat stress, increasing tree mortality rates.

Connection to this news: The study quantifies for the first time how a well-defined temperature threshold — not just gradual warming — can trigger a non-linear collapse in forest carbon absorption, directly affecting India's climate commitments and UPSC discourse on climate tipping points.

Climate Tipping Points and Feedback Loops

A climate tipping point is a threshold beyond which a component of the Earth system undergoes a self-reinforcing or irreversible shift. Once crossed, these tipping points can trigger cascading consequences for the broader climate system. Positive feedback loops — where an effect amplifies its own cause — are particularly dangerous: warmer temperatures reduce forest carbon sinks, leading to higher atmospheric CO2, which causes further warming.

The Amazon rainforest, already experiencing dieback in its southeastern portions, has been flagged as one of nine major Earth system tipping points.
Forest-atmosphere feedbacks include evapotranspiration (which cools local climates), albedo effects, and the biotic pump hypothesis, all of which may weaken as forests degrade.
The IPCC Sixth Assessment Report (2021–22) specifically identified tropical forest carbon sink weakening as a high-confidence finding.

Connection to this news: The study's identification of a hard thermal tipping point at 32.2°C gives concrete scientific grounding to the abstract concept of tipping points, making it directly relevant to Mains answers on climate feedback mechanisms and India's climate vulnerability.

India's Climate Commitments and NDCs

India's Nationally Determined Contributions (NDCs) under the Paris Agreement include a target to create an additional carbon sink of 2.5 to 3 billion tonnes of CO2 equivalent through additional forest and tree cover by 2030. India updated its NDCs in 2022, pledging to reduce emissions intensity of GDP by 45% from 2005 levels and achieve 50% cumulative electric power from non-fossil sources by 2030.

India's forests currently cover about 21.7% of its geographical area (State of Forest Report 2021).
The Green India Mission under the National Action Plan on Climate Change (NAPCC) targets enhancing forest cover on 5 million hectares of degraded land.
India ratified the Paris Agreement in October 2016.

Connection to this news: If tropical and subtropical forests globally weaken as carbon sinks, the ecological basis for India's NDC forest-carbon targets comes under pressure, raising the stakes for domestic forest conservation policy.

Key Facts & Data

32.2°C — average daily maximum temperature (warmest month) at which tropical forest carbon storage capacity begins a steep non-linear decline.
One-third — reduction in tropical forests' average carbon absorption capacity by the 2010s relative to peak rates.
3.5 petagrams CO2/year — additional CO2 released into the atmosphere for each 1°C rise in tropical land surface temperature.
71% of tropical forests face being pushed past the tipping point if global warming reaches 2°C above pre-industrial levels.
225+ researchers across three forest monitoring networks (RAINFOR, AfriTRON, T-FORCES) contributed to the study.
Tropical forests span South America, sub-Saharan Africa, and Southeast Asia — regions with the highest biodiversity and significant overlap with developing nations' land-use pressures.
Closing leaf stomata (pores) to prevent water loss under heat/drought stress is one mechanism by which trees reduce CO2 uptake, directly limiting photosynthesis.