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Species under tropical forest canopies are vulnerable to climate change, says study co-authored in Cambridge





The assumption that tropical forest canopies offer protection from the effects of climate change is unfounded, says a researcher from the University of Cambridge.

Tropical forests - crucial strongholds for biodiversity - are under threat as temperatures rise in the world’s most diverse terrestrial ecosystems, the new study published this week in the journal Nature Climate Change reveals.

Aerial view of Amazon rainforest
Aerial view of Amazon rainforest

Conventional wisdom holds that the forest subcanopy and understorey – where direct sunlight is reduced – would be insulated from the worst climate change impacts by the shielding effect of the forest canopy.

However, in the study - which used a microclimate model to examine temperatures beneath the rainforest canopy across the global tropics between 2005 and 2019 - most of the world’s undisturbed tropical forests experienced climate conditions at least partially outside the range of historic conditions.

Prof David Edwards, Professor of Plant Ecology at the University of Cambridge's Department of Plant Sciences and head of the Tropical Ecology and Conservation group, on fieldwork in Borneo. Picture: University of Cambridge
Prof David Edwards, Professor of Plant Ecology at the University of Cambridge's Department of Plant Sciences and head of the Tropical Ecology and Conservation group, on fieldwork in Borneo. Picture: University of Cambridge

Temperatures beneath the canopy in rainforests had previously remained relatively stable, but wildlife evolution taking place within this narrow range of temperatures left species poorly adapted to deal with temperatures outside this range. However, recent studies in largely undisturbed or primary lowland tropical forests have found changes in species composition and significant declines in animal, insect, and plant populations. These changes are attributed to warming temperatures and are consistent with the findings of the new research, which is titled ‘Novel temperatures are already widespread beneath the world’s tropical forest canopies’.

Deforestation in the Amazon - detail of an area.
Deforestation in the Amazon - detail of an area.

“Tropical forests are the true powerhouses of global biodiversity, and the complex networks of species they contain underpin vast carbon stocks that help to mitigate climate change," said Professor David Edwards at the University of Cambridge’s Department of Plant Sciences, and a co-author of the study.

“A severe risk is that species are no longer able to survive within tropical forests as climate change intensifies, further exacerbating the global extinction crisis and degrading rainforest carbon stocks.”

Dr Alexander Lees, Reader in Biodiversity at Manchester Metropolitan University and a fellow co-author, added: “Our study challenges the prevailing notion that tropical forest canopies will mitigate climate change impacts and it helps us understand how to prioritise conservation of these key areas of biodiversity effectively.

Orangutan spotted in the rainforest jumping from tree to tree.
Orangutan spotted in the rainforest jumping from tree to tree.

“It is paramount that distant, wealth-related drivers of deforestation and degradation are addressed and that the future of those forests acting as climate refuges is secured by effecting legal protection, and by empowering indigenous communities.”

Lead author of the study, Dr Brittany Trew, conservation scientist for the Royal Society for the Protection of Birds, concluded: “Our research shows that climate change is already impacting vast areas of pristine tropical forest globally.

Deforestation in the Amazon rainforest can not be blamed on Brazil alone.
Deforestation in the Amazon rainforest can not be blamed on Brazil alone.

“To provide species with the best chance to adapt to these changes, these forests must be protected from additional human-induced threats.”

The study was made possible through a global collaboration that included researchers at Mountains of the Moon University, Uganda; Universidade Federal do Pará, Brazil; the Brazilian Agricultural Research Corporation and Universidad Nacional de San Antonio Abad del Cusco, Perú. It was funded by the National Science Foundation (NSF).



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