Amazon forests failing to keep up with climate change

An environmental scientist from the University of Plymouth has contributed to major new research assessing the impact of global warming on thousands of tree species across the Amazon.

The study, led by University of Leeds in collaboration with more than 30 institutions around the world, sought to discover the winners and losers from 30 years of climate change.

A team of more than 100 researchers, including Lecturer in Environmental Science Dr Sophie Fauset, used long-term records from the Amazon Forest Inventory Network (RAINFOR) to track the lives of individual trees across the Amazon region.

Their results showed that since the 1980s, the effects of global environmental change – stronger droughts, increased temperatures and higher levels of carbon dioxide in the atmosphere – have slowly impacted specific tree species’ growth and mortality. 

In particular, the study found the most moisture-loving tree species are dying more frequently than other species and those suited to drier climates were unable to replace them. 

Lead author Dr Adriane Esquivel Muelbert, from the School of Geography at Leeds, said: 

“The ecosystem’s response is lagging behind the rate of climate change. The data showed us that the droughts that hit the Amazon basin in the last few decades had serious consequences for the make-up of the forest, with higher mortality in tree species most vulnerable to droughts and not enough compensatory growth in species better equipped to survive drier conditions.”

Dr Fauset, formerly a Research Fellow at Leeds, contributed data to the research collected in forests in a remote area of French Guiana. She said:

“Because tropical forest trees have such long lifespans – decades if not hundreds of years – it takes a very long time for species composition to respond to environmental changes. The results suggest species composition in the Amazon is responding to increasingly intense dry seasons, but not as fast as the climate is changing.”

Through their research, the team also found that bigger trees – predominantly canopy species in the upper levels of the forests – are outcompeting smaller plants.

Their observations confirms the belief that canopy species would be climate change 'winners' as they benefit from increased carbon dioxide, which can allow them to grow more quickly.

This further suggests that higher carbon dioxide concentrations also have a direct impact on rainforest composition and forest dynamics – the way forests grow, die and change.

In addition, the study shows that pioneer trees – trees that quickly spring up and grow in gaps left behind when trees die – are benefiting from the acceleration of forest dynamics.

Study co-author Oliver Phillips, Professor of Tropical Ecology at Leeds and founder of the RAINFOR network, said:

“The increase in some pioneer trees, such as the extremely fast growing Cecropia, is consistent with the observed changes in forest dynamics, which may also ultimately be driven by increased carbon dioxide levels.”

Co-author Dr Kyle Dexter, from the University of Edinburgh, added:

“The impact of climate change on forest communities has important consequences for rainforest biodiversity. The species most vulnerable to droughts are doubly at risk, as they are typically the ones restricted to fewer locations in the heart of the Amazon, which make them more likely to be extinct if this process continues. Our findings highlight the need for strict measures to protect existing intact rainforests. Deforestation for agriculture and livestock is known to intensify the droughts in this region, which is exacerbating the effects already being caused by global climate change.”

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