Tropical Carbon Sink

A tropical carbon sink refers to the capacity of tropical forests to absorb more carbon dioxide (CO₂) from the atmosphere than they release, thereby acting as a net sink for global carbon. Tropical forests, particularly the Amazon, Congo Basin, and Southeast Asian rainforests, are among the most significant terrestrial carbon sinks on Earth. By sequestering carbon through photosynthesis and storing it in biomass and soils, these ecosystems play a central role in regulating the global carbon cycle and mitigating climate change.

Mechanism of Carbon Sequestration

Tropical forests capture carbon through a combination of biological and ecological processes:

• Photosynthesis: Trees absorb atmospheric CO₂ and convert it into organic matter, building biomass in trunks, branches, leaves, and roots.
• Soil Carbon Storage: Carbon is transferred into soils through leaf litter, root turnover, and organic matter decomposition.
• Long-term Storage: Mature forests store carbon in large trees and deep soil layers, acting as reservoirs for centuries.

While forests also release CO₂ through respiration, decomposition, and disturbances such as fire, a healthy tropical forest typically absorbs more carbon than it emits.

Global Importance

Tropical forests are estimated to store around 250–300 billion tonnes of carbon, representing more than half of the world’s terrestrial carbon stock. They also account for nearly 40% of the global land-based carbon sink, making them vital for meeting international climate targets such as those outlined in the Paris Agreement.
Key roles include:

• Regulating atmospheric CO₂ concentrations.
• Moderating global temperatures by offsetting greenhouse gas emissions.
• Maintaining rainfall patterns and hydrological cycles essential for agriculture and ecosystems.

Regional Examples

• Amazon Rainforest: The largest tropical carbon sink, historically absorbing around 1–2 billion tonnes of CO₂ per year. However, deforestation and climate stress are weakening its capacity, with some areas now becoming carbon sources.
• Congo Basin: The second-largest tropical carbon sink, critical for stabilising African climate systems.
• Southeast Asia: Tropical peatlands store vast amounts of carbon but are highly vulnerable to deforestation, drainage, and fire.

Threats to the Tropical Carbon Sink

Several anthropogenic and environmental factors threaten the stability of tropical carbon sinks:

• Deforestation and Logging: Removal of trees reduces carbon storage capacity and releases stored CO₂.
• Forest Degradation: Selective logging, mining, and infrastructure development weaken forest resilience.
• Climate Change: Rising temperatures and prolonged droughts reduce tree growth and increase mortality.
• Wildfires: Often exacerbated by land-use change, fires release significant amounts of stored carbon.
• Conversion to Agriculture: Clearing forests for crops or grazing disrupts long-term carbon storage.

Scientific Observations

Recent studies indicate a declining capacity of tropical forests to act as carbon sinks. For instance:

• The Amazon has shown signs of transitioning from a carbon sink to a carbon source in parts of its basin due to human activity and warming trends.
• African tropical forests, though still strong carbon sinks, are projected to decline in sequestration capacity by the end of the century if emissions continue.
• Tropical peatlands, which contain disproportionately high carbon stores, are highly vulnerable to disturbance, with long-lasting effects when damaged.

Conservation and Policy Relevance

The preservation of tropical carbon sinks is critical to climate mitigation strategies. Conservation policies focus on:

• Reducing Emissions from Deforestation and Degradation (REDD+): An international framework incentivising forest protection.
• Protected Areas and Community Forest Management: Ensuring forests remain intact and resilient.
• Reforestation and Afforestation: Enhancing carbon uptake through tree planting and restoration of degraded lands.
• Sustainable Land Use: Integrating agriculture and forestry to reduce pressures on natural forests.

Significance for the Future

The tropical carbon sink is central to achieving net-zero carbon goals. If tropical forests lose their sink capacity, global warming could accelerate significantly, undermining efforts to stabilise the climate. Maintaining their function requires urgent action to curb deforestation, promote restoration, and address climate-induced stressors.
The tropical carbon sink thus stands as a cornerstone of Earth’s natural climate regulation system, balancing atmospheric CO₂, supporting biodiversity, and sustaining human livelihoods across the tropics and beyond.