Amazon failing to keep up with climate change

Scientists have assessed the impact of global warming on thousands of tree species across the Amazon.

The effects of climate change are altering the rainforest’s composition of tree species, but not quickly enough to keep up with the changing environment, their analysis found.

The team of more than 100 researchers, led by the University of Leeds in collaboration with more than 30 institutions including Edinburgh, used long-term records from more than 100 plots to track the lives of individual trees across the Amazon region.

Species growth

Their results found 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 most moisture-loving tree species are dying more frequently than other species and those suited to drier climates were unable to replace them.

Height advantage

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

The team’s observations confirm the belief that canopy species would 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 – those that quickly spring up and grow in gaps left behind when trees die – are benefiting from the acceleration of forest dynamics.

The study is published in Global Change Biology.

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 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 Adriane Esquivel MuelbertSchool of Geography, University of Leeds

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.

Dr Kyle DexterSchool of GeoSciences, University of Edinburgh

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Image credit: Dr Adriane Esquivel Muelbert