Amazon Carbon Sink: Flipping to Source?

For decades, the Amazon rainforest has served as the planet’s most critical safety valve against climate change. Known as a massive carbon “sink,” it historically absorbed vast amounts of carbon dioxide from the atmosphere. However, recent scientific findings suggest a terrifying shift. Driven by relentless drought and human-caused deforestation, significant portions of this vital biome are flipping roles. They are no longer storing carbon but are actively releasing it.

The Science of the Shift

The concept of the Amazon acting as the “lungs of the Earth” is biologically inaccurate but metaphorically useful. Plants absorb CO2 to grow. When forests are healthy, they lock this carbon away in their biomass and soil. However, when trees die, rot, or burn, that stored carbon returns to the atmosphere.

A landmark study led by Luciana Gatti, a researcher at Brazil’s National Institute for Space Research (INPE), provided the first concrete evidence of this reversal. Published in Nature, the study utilized vertical profiling—flying small planes over the forest to measure gas concentrations at different altitudes.

The results were alarming. The southeastern Amazon, which has faced the heaviest pressure from logging and agriculture, has become a net source of carbon. This region is now emitting more CO2 than it absorbs. The study indicates that this part of the forest releases about 1 billion tonnes of carbon dioxide annually. This is roughly equivalent to the annual emissions of a major industrial nation like Japan.

Why the Southeast is Suffering First

The Amazon is not uniform. The western section remains relatively moist and healthy. However, the eastern and southeastern sections are closer to major population centers and agricultural frontiers. This proximity leads to specific stressors:

• Temperature Spikes: During the dry season, the southeastern Amazon is now roughly 3.1 degrees Celsius (5.6 degrees Fahrenheit) hotter than it was in the pre-industrial era.
• Moisture Loss: Deforestation breaks the forest’s ability to recycle its own water. Fewer trees mean less evapotranspiration, which leads to less rainfall. This creates a feedback loop where the forest dries out, making it more susceptible to fire.

The Role of Historic Droughts

The snippet provided highlights drought as a primary driver of this carbon flip. In late 2023 and early 2024, the Amazon experienced one of the most severe droughts in recorded history. This event was driven by a combination of the El Niño climate pattern and unusually warm waters in the northern Atlantic Ocean.

The physical impact was visible and measurable. In October 2023, the Rio Negro in Manaus dropped to 13.59 meters. This was the lowest level recorded since measurements began in 1902.

Drought as a Carbon Emitter

Drought turns a sink into a source through two distinct mechanisms:

1. Tree Mortality: Trees in the Amazon are not evolved to withstand prolonged dryness. When water tables drop, massive trees die. As these trees decompose on the forest floor, they release their stored carbon slowly over time. This creates a “carbon debt” that will be paid into the atmosphere for years after the drought ends.
2. Increased Flammability: A dry rainforest burns easily. While natural fires are rare in a healthy rainforest, human-ignited fires (used to clear land for cattle or soy) escape control much faster during a drought. These fires release massive pulses of CO2 immediately.

The Tipping Point: Savannization

Scientists like Carlos Nobre have long warned of a “tipping point.” This is a threshold of deforestation—estimated between 20% and 25% of the total biome—where the rainforest can no longer sustain its own weather systems. Once this line is crossed, the rainforest will irreversibly degrade into a dry, savanna-like ecosystem.

Current data suggests roughly 17% of the Amazon has been clear-cut, while another 17% is degraded. We are dangerously close to the threshold. If “savannization” occurs, the forest will release roughly 123 billion tons of carbon. This is equivalent to several years of total global fossil fuel emissions.

The Agriculture Connection

The economic drivers pushing this tipping point are specific and powerful. The expansion of cattle ranching accounts for the vast majority of illegal deforestation. Soy production follows closely behind, often taking over land that was previously cleared for cattle.

Major global traders and meatpackers, such as JBS and Cargill, have faced intense scrutiny regarding their supply chains. Despite pledges to eliminate deforestation from their sourcing, the complex network of “indirect suppliers” (farms that sell to other farms before reaching the slaughterhouse) makes it difficult to track the true origin of the beef. This economic pressure keeps the chainsaws running, further weakening the forest’s ability to hold carbon.

Restoration and Political Will

The situation is dire, but the flip is not yet total. The western Amazon still functions as a sink, although a weakening one. Halting the transition from sink to source requires immediate, specific actions.

Since taking office in 2023, Brazilian President Luiz Inácio Lula da Silva has empowered agencies like IBAMA (the Brazilian Institute of Environment and Renewable Natural Resources) to crackdown on illegal miners and loggers. Data from INPE showed a significant drop in deforestation alerts in the first half of 2024 compared to previous years.

However, stopping the saws is only half the battle. Reforestation is necessary to rebuild the carbon sink. Projects like the Amazon Fund, supported significantly by Norway and Germany, act as financial vehicles to pay for this preservation. The goal is to reach “zero deforestation” by 2030, a target agreed upon by over 100 nations at the COP26 climate summit.

Conclusion

The Amazon is no longer just a victim of climate change; parts of it are becoming an accomplice. The transition of the southeastern region from a carbon sponge to a carbon emitter acts as a siren for the rest of the planet. While the western Amazon holds the line, the combination of extreme heat, El Niño droughts, and industrial agriculture threatens to push the entire ecosystem past the point of no return. The science is clear: keeping the Amazon as a sink is not just about saving trees. It is about preventing a catastrophic release of carbon that would make global climate goals impossible to reach.

Frequently Asked Questions

Is the entire Amazon now a carbon source? No. Currently, only the southeastern part of the Amazon is confirmed to act as a net carbon source. The western Amazon generally remains a carbon sink, absorbing more CO2 than it releases. However, the sink capacity of the entire forest is declining.

How does drought release carbon? Drought causes trees to die from lack of water. As these dead trees rot, they release stored carbon dioxide. Additionally, dry conditions make the forest highly flammable, leading to fires that release carbon immediately.

Can the forest recover if deforestation stops? Yes, but only if the “tipping point” has not been crossed. If deforestation stays below the 20-25% threshold, the forest has a chance to regenerate and restore its water recycling cycles. If it crosses that line, the damage becomes irreversible.

What is the “tipping point” percentage? Scientists estimate the tipping point is between 20% and 25% of total deforestation. We have currently lost about 17% of the forest to clear-cutting, with significant additional areas suffering from degradation.

Who is Luciana Gatti? Luciana Gatti is a senior researcher at Brazil’s National Institute for Space Research (INPE). She led the pivotal study published in Nature that used aircraft sensors to prove parts of the Amazon are now emitting more carbon than they absorb.