More Frequent Droughts Alter Makeup Of Amazon Rainforest, But Ecosystem Cannot Match Speed Of Change

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Frequent droughts are changing the assortment of trees in Amazon basin ecosystems, with water-loving varieties slowly being replaced by more drought-resistant species. However, the forests are not adapting fast enough, and are failing to keep pace with the rate with which the basin’s climate is changing, according to a new study published in the journal Global Change Biology. Using data collected by a long-term international collaboration known as RAINFOR, Adriane Esquivel Muelbert, a tropical forest ecologist at the University of Leeds in Britain, and her team found that in the most drought-prone Amazon regions, water-loving plants are being replaced by those adapted to extreme dry weather.

RAINFOR is a network of international and local researchers from more than 30 countries who’ve maintained continuous monitoring of all trees in more than 300 one-hectare (2.5 acre) plots across the Amazon basin. Using data from 106 of the longest-monitored plots, researchers found that mortality has increased over the 30-year period among moisture loving tree genera such as Mezilaurus and Inga.

In Amazonian regions that have experienced the most intense droughts, new samplings of drought-tolerant genera such as Brosimum and Pseudolmedia have increased in abundance. In short, “the Amazon’s composition of species is becoming more drought-tolerant,” said Esquivel. The scientists also reported an increase in the prevalence of large-statured tree genera such as Mora and Eschweilera, whose larger crowns and more extensive root systems offer a competitive advantage which may help them via the photosynthesis-boosting effects of elevated CO2 levels in the atmosphere.

Importantly, the team reports that the rate of change in tree composition lags by two orders of magnitude behind the change in climate, suggesting that the Amazon basin may struggle to keep up with predicted ongoing and escalating climatic upheaval.

Ed. - emphasis added.

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https://news.mongabay.com/2018/12/amazon-forests-not-changing-fast-enough-to-keep-up-with-climate-change-study/