The Amazon rainforest and the looming threat of drought

The Amazon rainforest, often referred to as the “lungs of the Earth,” plays a vital role in the global carbon cycle by absorbing and storing large amounts of carbon dioxide from the atmosphere. This critical ecosystem service helps regulate the Earth’s climate and mitigate the impacts of climate change. However, the rainforest’s ability to store carbon is under threat due to various factors, including deforestation, climate change, and increasing incidents of drought.

A recent study involving 80 scientists from Europe and South America has shed light on how different regions within the Amazon rainforest are likely to respond to drier conditions brought about by climate change. 

The study, led by Dr. Julia Tavares and Professor David Galbraith of the University of Leeds, reveals that trees in the western and southern Amazon face the greatest risk of dying due to drought. The death of these trees, and consequently the loss of their ability to store carbon, could have significant implications for the global carbon cycle and climate change mitigation efforts.

Historically, scientific investigations have focused on the central-eastern region of the forest, which is the least vulnerable to drought. This means that the potential impacts of drought on the entire Amazon rainforest may have been underestimated. The current study offers the first comprehensive assessment of how different regions of the Amazon might respond to an increasingly warm and dry climate.

Professor Galbraith highlighted the importance of understanding the stress limits that the Amazon forest can endure:  “Our study provides new insights into the limits of forest resistance to one major stressor – drought.”

The Amazon is not a single, homogenous forest. It is composed of numerous forest regions that span various climate zones, ranging from extremely wet to very dry. Dr. Tavares explained that the research aimed to examine how these diverse forest ecosystems were coping with the stresses they faced.

Published in the scientific journal Nature, the study’s findings remove a “major knowledge bottleneck of how climate change will impact this critical ecosystem.” 

How the research was conducted 

The research team, known as the “tree doctors,” collected measurements and samples from 11 separate sites across the western, central-eastern, and southern Amazon – covering Brazil, Peru, and Bolivia – over the course of a year. This comprehensive data set allowed the scientists to evaluate the drought resistance of 540 individual trees across 129 species.

Despite the southern part of the Amazon Forest demonstrating the greatest degree of adaptation to cope with drought, the study revealed that trees in this region still faced the highest risk of dying due to drought. This increased vulnerability is likely a result of rapid climate change and disruption to rainfall patterns caused by deforestation, which have pushed trees to the limits of their adaptability.

Conversely, tree species in the wettest parts of the Amazon Forest exhibited the lowest levels of adaptation to drought, yet were considered the safest in terms of future climate change risks. This is because these areas have not yet been significantly impacted by changes in rainfall.

The researchers emphasize that their findings should be used to update and refine existing models on how the Amazon may be impacted by drier conditions, as previous studies may have underestimated the vulnerability of certain forest regions to climate change. With a more nuanced understanding of the Amazon rainforest’s response to drought, scientists and policymakers can better assess the potential consequences of climate change and develop targeted strategies to preserve this vital ecosystem.

More about carbon storage in the Amazon rainforest 

Carbon storage in the Amazon rainforest plays a significant role in regulating global climate. The vast expanse of the Amazon, covering approximately 6.7 million square kilometers, is home to an estimated 390 billion individual trees belonging to over 16,000 species. These trees absorb carbon dioxide (CO2) from the atmosphere and store it in their biomass through the process of photosynthesis.

The Amazon rainforest is responsible for storing an estimated 76 to 96 billion metric tons of carbon, making it one of the largest terrestrial carbon sinks on the planet. This carbon storage capacity helps offset human-induced greenhouse gas emissions, thereby mitigating the impacts of climate change. Furthermore, the vastness and diversity of the Amazon contribute to the stability of weather patterns, influencing precipitation and temperature.

However, this vital ecosystem service is under threat from various factors. Deforestation, often driven by logging, agriculture, and infrastructure development, directly results in the loss of trees and, consequently, their ability to store carbon. When trees are cut down or burned, the stored carbon is released back into the atmosphere, contributing to increased greenhouse gas concentrations and exacerbating climate change.

Climate change and drought also pose significant threats to the Amazon’s carbon storage capacity. As temperatures rise and rainfall patterns change, some regions within the rainforest become drier, increasing the likelihood of tree mortality. The recent study led by Dr. Julia Tavares and Professor David Galbraith revealed that trees in the western and southern Amazon face the highest risk of dying due to drought. This could lead to a decrease in the forest’s ability to absorb and store carbon, further accelerating climate change.

To preserve the Amazon’s carbon storage capacity, it is crucial to implement targeted conservation strategies, such as sustainable forest management, reforestation efforts, and the reduction of greenhouse gas emissions. In addition, enhancing our understanding of the Amazon rainforest’s response to climate change and drought will help inform policies and actions to maintain its health and resilience.

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