Tree mortality in the Amazon rainforest is a critical problem with significant ecological, climatic and economic consequences. The Amazon, often referred to as the “lungs of the Earth,” plays an important role in sequestering carbon dioxide and thus regulating the global climate. However, several factors are contributing to an alarming rate of tree mortality in this vast rainforest.
Tree mortality in the Amazon is being driven by increasing droughts, extreme weather events and deforestation. The dying trees, which absorb carbon through photosynthesis during their lifetime, release carbon into the atmosphere as they decay. The increasing tree mortality could transform the rainforest from a carbon sink into a carbon source.
Fragile carbon reserves and biodiversity reserves
Home to an enormous diversity of plants and animals, the Amazon rainforest plays a critical role in addressing the impacts of climate change by storing enormous amounts of carbon while helping to regulate temperatures and rainfall at regional and global scales.
Using models that predict tree death and the resulting changes in carbon balance, a new study in the journal The future of the earth has found that some regions of the Amazon rainforest could reach a tipping point by the middle of this century.
“The Amazon rainforest biome is critically important due to its vast but fragile carbon and biodiversity reserves. Intact Amazon forests support more than 20% of terrestrial species, store 100 billion tonnes of carbon, absorb atmospheric CO2, and regulate regional and continental climate through moisture recycling,” the authors wrote.
“Despite these important functions, the stability and spatial continuity of the forest are threatened by climate extremes such as droughts and storms, large-scale deforestation in the south, east and southwest, and forest degradation in adjacent areas.”
According to the researchers, these factors increase the risk of reaching a tipping point at which intact forests could become carbon sources and even collapse within a few decades.
“It is therefore crucial to reduce uncertainties, better understand the likelihood of such a tipping point, and take countermeasures to preserve the health and resilience of the Amazon rainforest.”
Simulation of tree death in the Amazon region
The experts used ORCHIDEE-CAN-NHA, a groundbreaking land surface model to simulate tree death and regrowth in the Amazon during droughts. This model was calibrated and evaluated using historical data from previous droughts.
The scientists combined the use of this land surface model with four climate scenarios to predict future changes in carbon movement and tree loss by the end of the century.
Although the climate models produced different results – such as differences in humidification and drying – they all found a warming trend for the next few decades, particularly throughout the northeastern Amazon rainforest.
“These climate models show different patterns of climate change across the Amazon. The simulation performed with the HadGEM climate model shows the clearest trend toward drying, suggesting that the Guiana Shield and the east-central Amazon are approaching a tipping point,” the researchers noted.
“These two regions are expected to transition from carbon sinks to carbon sources by the mid-21st century, with the Brazilian Shield following around 2060. This transition is attributed to increased carbon loss in the future due to drought.”
Localizing the hotspots of tree death in the Amazon region
A better understanding of which areas of the Amazon rainforest are most at risk of drying and dieback will help scientists understand the region’s carbon footprint and provide valuable information on how to protect this ecosystem from the impacts of a rapidly changing climate.
“This study represents an important step forward by providing a spatial picture of the probability of drought risks and predicting the evolution of the future net carbon balance of the Amazon rainforest by using a well-calibrated model that accounts for tree mortality caused by hydraulic failure and subsequent recovery from demographic processes, including the recruitment and growth of surviving trees,” the study authors write.
“The predicted potential threat to the Amazon rainforest required further investigation and consideration of mitigation measures.”
—–
Like what you read? Subscribe to our newsletter for exciting articles, exclusive content and the latest updates.
Check out EarthSnap, a free app from Eric Ralls and Earth.com.
—–
