Amazon Forest Degradation Weakens Carbon Storage Capacity

Long-term study reveals biodiversity loss is reshaping the Amazon’s ability to store carbon, threatening its role as a key carbon sink.

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A recent study analyzing over 1,200 tree species across 271 forest plots in Brazil has uncovered alarming changes in tropical forest degradation and carbon storage capacity. The research, published in Nature Ecology & Evolution, highlights how forest composition is shifting due to ongoing degradation.

Large-seeded tree species, which dominate healthy forests, are in decline, particularly in human-modified landscapes. The loss of key biodiversity components, such as seed-dispersing wildlife, has allowed faster-growing trees with smaller seeds—dispersed by birds and bats—to thrive instead. This transition significantly impacts the Amazon rainforest’s ability to store carbon.

How Degraded Forests Reduce Carbon Storage and Resilience

Beyond biodiversity loss, these shifts have severe climate change implications. Degraded forests are losing their structural integrity, with replacement trees exhibiting softer wood, faster growth, and lower carbon sequestration capacity. These species are also more vulnerable to forest fragmentation, fire, and drought, leading to shorter lifespans and further reducing long-term carbon storage.

In 2023 alone, approximately 3.7 million hectares of primary tropical forest were lost—an area equivalent to nearly ten football fields per minute. While this marks a 9% decline from 2022, the destruction continues at an alarming rate, nearly matching the annual size of Switzerland.

Landscape Fragmentation and Local Disturbances Accelerate Forest Degradation

The interactions between forest fragmentation, logging, and local disturbances like fires and hunting are complex. Research leader Bruno Pinho stresses that while deforestation's impact on biodiversity is well known, the consequences of forest fragmentation remain underexplored.

The team found that dense-wood tree species relying on medium to large seed-dispersing animals are declining. Key regions such as Paragominas, south of Belém, exemplify severe degradation. Even when landowners comply with Brazil’s Forest Code, maintaining 35-80% natural vegetation coverage, many forests suffer from selective logging and fire damage.

One particularly vulnerable species is the Brazil nut tree (Bertholletia excelsa), which depends on seed dispersal by the agouti. However, these animals require extensive, unfragmented forest ecosystems to thrive. The Brazil nut tree is now listed as vulnerable on the IUCN Red List and considered threatened by Brazil’s Ministry of Environment and Climate Change.

Declining Carbon Storage Capacity in the Amazon Rainforest

Long-term monitoring reveals a worrying decline in the Amazon's ability to function as a carbon sink. Research indicates that the Amazon absorbed 30% less carbon in the 2000s compared to the 1990s. Data from 321 forest plots spanning three decades show a marked reduction in carbon accumulation rates.

The rate of above-ground biomass increase has declined by one-third over the past decade compared to the 1990s. This reduction is driven by a combination of:

  • Increased tree mortality
  • Slower long-term growth trends
  • Shorter carbon residence times due to faster-growing species replacing longer-living trees
  • Climate variability exacerbating feedback effects

The Urgent Need for Conservation and Forest Restoration

Experts stress the need for immediate action to mitigate the impact of tropical forest degradation on carbon storage. Essential conservation strategies include:

  • Enhancing forest conservation efforts to protect biodiversity and improve carbon sink stability
  • Controlling logging and fires in degraded landscapes
  • Restoring forest quality by promoting wildlife corridors and protecting fauna critical for seed dispersal
  • Preventing forest fragmentation to maintain ecosystem resilience

With the Amazon rainforest storing an estimated 150-200 Pg C in its living biomass and soils, protecting these ecosystems is critical to combating climate change. The findings highlight the importance of not just preserving forest cover, but ensuring forest quality remains intact to sustain long-term carbon sequestration.

Environment + Energy Leader