Chapter 4: Amazonian ecosystems and their ecological functions

ORCID

Correa: https://orcid.org/0000-0003-4466-6923

MSU Affiliation

College of Forest Resources; Department of Wildlife, Fisheries and Aquaculture

Creation Date

2026-03-30

Abstract

Climate change is already impacting critical mechanisms of the functioning of the Amazon’s ecosystems. The observed increase in temperature, precipitation changes, and increase in climate extremes affect ecosystem services, carbon uptake, and the duration of the dry season, among other effects. It also affects biodiversity, selecting species that can adapt quickly to the changing climate, including freshwater fish and other ectothermic groups able to do the same. In particular, fisheries’ yields are important to food security and have been impacted by climate change in unpredictable ways. Moreover, projections indicate that climate change will have significant adverse impacts on pollination and seed dispersal, essential ecosystem services for the maintenance of natural and agricultural ecosystems because of changes in species distributions, and decoupling of biotic interactions. Rainfall in the Amazon is sensitive to seasonal and interannual variations in sea surface temperature, as well as El Niño and La Niña. The increase in intensity and frequency of droughts and floods have important impacts on carbon cycling. Levels of water at Óbidos have significantly increased over the last 30 years, and the runoff of the Xingu catchment has risen by 10%, possibly owing to 40% deforestation in the Xingu catchment. The Amazon was a strong carbon sink in the 1980s, and recent measurements show a much weaker carbon sink in the forests. The mean net carbon uptake for the 1990s was -0.59 ± 0.18 Pg C y-1, and the decade of 2010s had a carbon uptake of -0.22 ± 0.30 Pg C y-1. In dry years, such as 2005 and 2010, the forest loses carbon to the atmosphere, increasing greenhouse gas concentrations. Increases in climate extremes are reducing carbon uptake by the Amazonian ecosystem. Biomass-burning emissions have significant negative impacts on the ecosystem, such as high ozone concentrations that affect the stomatal opening and human health. Aerosols from biomass burning alter the radiation balance, increasing diffuse radiation compared with direct radiation affecting carbon cycling. The increase in surface albedo associated with deforestation changes surface temperature and energy partitioning. Forest degradation could be as crucial as deforestation in terms of carbon emissions. Our current scientific understanding points to Amazonian forests becoming increasingly susceptible to wildfires and droughts. Feedbacks between climate change and Amazonian ecosystems’ functioning are substantial and must be better known and quantified, especially for carbon and water vapor feedback. We need more integrated studies involving biodiversity loss with the changing climate, including resilience. Additionally, there is a need for a comprehensive network of Amazonian environmental observations to provide society with diagnostic capabilities of the changes that terrestrial and aquatic ecosystems are already undergoing.

Publication Date

11-12-2021

Publication Title

Amazon Assessment Report 2021 (ISBN: 978-1-7348080-0-1)

Publisher

UN Sustainable Development Solutions Network (SDSN)

Creative Commons License

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.

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Digital Object Identifier (DOI)

https://doi.org/10.55161/IKRT9380