Research indicates most accurate picture yet of how the Amazon will respond to climate change

The Amazon may have longer and more intense dry seasons, but this will cause the rainforest to change gradually from a moist environment with diverse plant species into woodland-type ecosystems, academics predict. Fire, logging, and other disturbances caused by humans may further exacerbate this change to the ecosystem. But the study suggests, rather than a sudden tipping point, there will be many different continuous changes.

The study has found the sensitivity of tropical forests to changes in climate is dependent on the length of the dry season and soil type, and also how individual plants compete. These interactions between different plants and the environment result in Amazon rainforests that are more sensitive to climate change than previously thought.

Amazon forests store half of the tropical forest carbon and play a vital role in global water, energy, and carbon cycling.

The study, Ecosystem heterogeneity determines the ecological resilience of the Amazon to climate change, is published in the Proceedings of the National Academy of Sciences of the United States of America. Researchers used remote-sensing and ground-based observations to explore the sensitivity and ecological resilience of the Amazon to changes in climate.

Dr Ted Feldpausch, Lecturer in Physical Geography at the University of Exeter, who is one of the report’s authors, said: “it is particularly important to understand how changing climate will affect tropical forest regions because they store large amounts of carbon, and loss of forests has regional and global impacts. For example, during past droughts our ground-based measurements indicated that Amazon forests lost carbon. Looking forward, we need a better understanding of forest response to drying regional climate.

“As part of the current study, we combine different types of observations on Amazon forest dynamics with a state-of-the-art terrestrial ecosystem model. This allows us to show the sensitivity of tropical forests to changes in climate is dependent on the length of the dry season and soil type, but also, importantly, on the dynamics of individual-level competition within plant canopies.”

Paul Moorcroft, Professor of Organismic and Evolutionary Biology at Harvard University, and a senior author of the study, said: “Our analysis predicts that as the climate changes, the ecosystem will respond almost immediately, but those changes will be less drastic, so in some sense it says the ecosystem is both more vulnerable and more resilient."

The future of the Amazon is uncertain. Previous studies had predicted that the future of the forest would either be stable, or there would be catastrophic loss due to more severe water stress. The current study suggests that the Amazon rainforest may be more sensitive to changes in climate than previously predicted, but that the transition under changing climate may be graded and varied.

The study was led by academics at Harvard University, who also worked with colleagues from the Smithsonian Institution, Jardín Botánico de Missouri, Universidad Nacional de San Antonio Abad del Cusco, Instituto de Ciencias Naturales, University of Oxford, University of Southern California, University of Oklahoma, The Woods Hole Research Center, University of Leeds, University College London, Grupo de Investigación en Servicios Ecosistémicos y Cambio Climático and Instituto Nacional de Pesquisas da Amazônia.