Amazon is a net carbon source: 15 years of aircraft data

A new study in Nature, reported by eurekalert.org, shows that the hotter, drier Amazon rainforest is a net source of global carbon emissions. The work was done by an international team, including researchers from the University of Kansas, and led by Brazil's National Institute for Space Research (INPE). Only in the wettest years does the forest remain closer to carbon neutral, the authors report eurekalert.org.

The paper rests on 15 years of airborne measurements of atmospheric carbon. Research planes sampled the air at different elevations above the rainforest eurekalert.org. The lead author is Luciana Gatti of INPE and the Nuclear and Energy Research Institute in Brazil.

Why airborne profiling

Co-author Jen Johnson, assistant professor of ecology and evolutionary biology at KU, said that tropical carbon is harder to track than extra-tropical carbon. Satellites looking from above are often blocked by persistent cloud cover, and ground-based networks are limited. In her words, airborne vertical profiling is the most direct way to quantify carbon exchange between tropical land ecosystems and the atmosphere at the regional scale eurekalert.org.

The team used the newest version of the long-term Amazon airborne dataset. It classified each of the last 15 years into one of three groups, according to climatic stress and the level of human activity in the region eurekalert.org.

Land use as the main control

Johnson said the comparison between groups points to human land-use change as the dominant control on the Amazon's net carbon balance. Global climate and climate-related stress modulate it. She added that bringing deforestation down to zero is required to manage net emissions from the region eurekalert.org.

The investigators found that 2024 had the highest annual emissions in the time series. It fell into the third group, which combined very warm temperatures, very low precipitation and high rates of fire-driven deforestation eurekalert.org.

Johnson also said that for many decades there has been concern about a tipping point. In that scenario, gradual drying and forest loss could reinforce themselves and shift the ecosystem toward types that store much less carbon eurekalert.org.

The team plans to add new trace gases to the monitoring program. This would let it separate the gross fluxes in and out of the atmosphere and define the components of the net carbon budget more precisely, Johnson said eurekalert.org.

Amazon rainforest is a net carbon source, 15 years of aircraft measurements in Nature study show

Why airborne profiling

Land use as the main control

Sources · 2

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