Amazonian Rainforest

Mar 9, 2011 (Last modified Feb 2, 2013)
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Possible dieback in 21st century

The tropical forests of the Amazon Basin are at risk not only from climate change, but also from interactions between deforestation and alterations in fire regimes. Deforestation in the Brazilian Amazon closely follows road construction due to the inaccessibility and remoteness of Amazon forests. Associated with deforestation is the human use of fire to clear or maintain pastures for crop production or grazing, with these fires frequently 'escaping' into pristine, non-fire adapted forests. The interactions between climate change, fire and deforestation are expected to provide a positive feedback that may increase the rate, and influence the spatial pattern, of Amazon forest dieback. The outcome of these processes on changes in Amazon forest cover and biomass were recently modeled using a dynamic global vegetation model (DGVM) to investigate the individual and combined effects of climate change, fire, and deforestation.

Dr. Ben Poulter (PIK) and colleagues found that by the year 2100, climate change and CO2 fertilization changes forest biomass by -16.6 Pg C to +33.1 Pg C. By the end of the century, deforestation (with no climate change or CO2 fertilization) reduces biomass by -30.8 to -13.8 Pg C, and that fire and deforestation interact to reduce biomass by an additional 1 Pg C. When all three processes are included together, forest biomass is reduced by -40.6 Pg C, but with some of the wetter climate projections and a strong CO2 fertilization effect increasing biomass by 12.1 PgC.

To carry out the research, Dr Poulter and colleagues used an ensemble of 9 IPCC-AR4 (4th Assessment) global climate model projections for the SRES A2 emissions storyline. The climate scenarios were included with two deforestation scenarios from the simAmazonia project, coordinated by the Woods Hole Research Center, Universidade Federal de Minas Gerais, and Instituto de Pesquisa Ambiental da Amazonia. The LPJ DGVM model was modified to include the effects of escaped fires by linking cropland expansion with simulated annual burned area. The use of an ensembles approach allows for a probabilistic assessment of the risk of Amazon forest dieback. The role of CO2 fertilization and grassland management are key uncertainties in representing the future of Amazonian carbon stocks.

Overall, the synergistic effects of climate, deforestation and fire, are important considerations in the rate, magnitude and spatial pattern of Amazon forest dieback. Quantifying the uncertainty of the impacts model projections is valuable for informing and prioritizing policy options related to mitigation and adaptation where long-term investments are required.

Dr Poulter has made all the published model results available in Data Basin in a gallery entitled: Aboveground biomass and tree cover dynamics for the Amazon Basin under 21st century deforestation, fire, and climate change scenarios.

Reference: Poulter, B, L Aragao, J Heinke, A Rammig, K Thonicke, F Langerwisch, U Heyder and W Cramer. 2010. Net biome production of the Amazon Basin in the 21st century. Global Change Biology 16(7):2062-2075. DOI: 10.1111/j.1365-2486.2009.02064.x.

Photo credit:  Alexander Torrenegra

Recommended by Brendan C. Ward
Citation
Dominique Bachelet. 2011. Amazonian Rainforest. In: Data Basin. [First published in Data Basin on Mar 9, 2011; Last Modified on Feb 2, 2013; Retrieved on Dec 19, 2018] <https://databasin.org/articles/37c3c7b74c434efaa50e75bc49a0058b>

About the Author

Dominique Bachelet
climate change scientist with Oregon State University

Dominique received her Master’s degree in 1978 in Lille (France) and her Ph.D. in 1983 from Colorado State University with a thesis focused on biogeochemical cycles in the shortgrass prairie. In 1984 she went to U.C. Riverside as a postdoc simulating nitrogen fixing shrubs in the Sonoran desert then...