How is tropical deforestation linked to climate change

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Open access

Highlights

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Recent tropical deforestation increased heat exposure relative to forested areas

Work in deforested areas was associated with disproportionate lost safe work time

Deforestation was associated with >0.5 h/day of lost safe work for 4.9 million people

Additional global climate change will worsen heat exposure in deforested areas

Science for society

Recent research has highlighted the effects of global warming on low- and middle-income countries in the tropics. Additionally, tropical deforestation remains an issue of global concern for climate change mitigation. We link these bodies of research by examining how tropical deforestation exacerbates local impacts of global warming and leads to unsafe thermal environments for outdoor workers. We show that deforestation across the tropics is associated with increases in humid heat exposure large enough to exceed established thresholds for outdoor worker health. These findings suggest that tropical deforestation is hastening the arrival of climate change impacts. Furthermore, this work shows that local ecosystem services provided by tropical forests are important for the resilience of vulnerable populations.

Summary

Climate change has increased heat exposure in many parts of the tropics, negatively impacting outdoor worker productivity and health. Although it is known that tropical deforestation is associated with local warming, the extent to which this additional heat exposure affects people across the tropics is unknown. In this modeling study, we combine worker health guidelines with satellite, reanalysis, and population data to investigate how warming associated with recent deforestation (2003–2018) affects outdoor working conditions across low-latitude countries, and how future global climate change will magnify heat exposure for people in deforested areas. We find that the local warming from 15 years of deforestation was associated with losses in safe thermal working conditions for 2.8 million outdoor workers. We also show recent large-scale forest loss was associated with particularly large impacts on populations in locations such as the Brazilian states of Mato Grosso and Pará. Future global warming and additional forest loss will magnify these impacts.

Keywords

Deforestation

climate change

humid heat

climate impacts

resilience

climate mitigation

labor

© 2021 The Authors. Published by Elsevier Inc.

This article is more than 3 years old

Deforestation and the carbon cycle

Forests store large amounts of carbon. Trees and other plants absorb carbon dioxide from the atmosphere as they grow. This is converted into carbon and stored in the plant’s branches, leaves, trunks, roots and in the soil.

When forests are cleared or burnt, stored carbon is released into the atmosphere, mainly as carbon dioxide. Averaged over 2015—2017, global loss of tropical forests contributed about 4.8 billion tonnes of carbon dioxide per year (or about 8-10% of annual human emissions of carbon dioxide).

Whilst forests are important carbon sinks, meaning they draw down carbon dioxide from the atmosphere, the carbon stored in these sinks is part of an active, relatively quick carbon cycle. As living things (including trees) die and decay, the carbon that they once stored is released back into the atmosphere.

By contrast, carbon stored underground in the form of fossil fuels such as coal, oil and gas, is much more stable, and is part of a much slower carbon cycle. Without the influence of humans burning these fossil fuels for energy, this carbon would be unlikely to reach the atmosphere. When fossil fuels are burned, carbon from dead and decayed plants, animals and phytoplankton that lived hundreds of millions of years ago (before dinosaurs existed), is released into the atmosphere in the form of carbon dioxide.

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Deforestation and climate change

Burning fossil fuels, in combination with destruction of carbon sinks due to deforestation and other activities, has contributed to more and more carbon dioxide building up in the atmosphere – more than can be absorbed from existing carbon sinks such as forests. The build-up of carbon dioxide in the atmosphere is driving global warming, as it traps heat in the lower atmosphere. Carbon dioxide levels are now at their highest in human history.

It is not effective to “offset” greenhouse gas pollution from burning fossil fuels by storing carbon in forests. This is because fossil fuels are pumping much more carbon dioxide into the atmosphere than existing forests can absorb. At the same time, carbon stores in forests and other natural carbon sinks will become increasingly unstable as climate change progresses. Droughts, tropical storms, heatwaves and fire weather are increasing in severity and frequency because of climate change. This will continue to result in increases in forest losses, contributing to more and more carbon dioxide being released into the atmosphere. Risks are significantly reduced but not avoided by keeping the rise in global temperature well below 2°C.

The future

Protecting natural ecosystems and sustainably managing and re-establishing forests are important ways to reduce greenhouse gas emissions and slow down temperature rise in the short term by drawing down carbon dioxide from the atmosphere. At the same time, we must deeply and rapidly reduce global greenhouse gas emissions levels from fossil fuels – coal, oil and gas. If we do only the former and not the latter, we risk transforming more and more of our carbon sinks into carbon sources as climate change progresses.

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To learn more about this topic, read our report:

Land Carbon: No Substitute for Action on Fossil Fuels

By Annika Dean  /  21 August 2019