What is it about?

Our study demonstrated that mega-dams were mainly responsible for the high forest mortality in the upper Madeira River basin after the 2014 extreme flood, with forest loss rates at least five times higher when compared to the losses resulting from rainfall extremes. In addition, the results also showed, in an unprecedented way, that the extreme rainfall anomalies, probably triggered by global warming and intensified in the last decades, also represent a key driver of forest mortality in the Amazon, even in areas not affected by dams, as observed for the Beni, Guaporé, Madre de Dios and Mamoré River basins. Finally, the interaction between extreme rainfall events, and the installation of mega-dams has negative consequences of extensive magnitude for the Amazon rich biodiversity.

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Why is it important?

We showed that the mega-dams were the main driver of tree mortality in Madeira basin forests after the 2014 extreme flood. The proliferation of dams and the increase of uncertainties about climatic anomalies place at risk different ecosystems in the Amazon basin, threatening their rich biodiversity with more drastic effects on floodplain forests. Furthermore, the interaction between the new flood pulse, as controlled by the hydroelectric dams, and the new scenario of global climate uncertainties increases the difficulty of forecasting the long-term environmental impacts of mega-dams in the Amazon.


Environmental impact studies required for environmental licensing of mega-dams by governmental agencies should consider the increasing trend of climatic anomalies and the high vulnerability of different habitats to minimize the serious impacts of dams on Amazonian biodiversity and carbon stocks. We highlight the importance of a new licensing approach that considers the interactions between ongoing climate changes and the construction of mega-dams in the Amazon, and its associated impacts on their biodiversity.

Marcelo Medeiros
Brazilian Agricultural Research Corporation - Embrapa

Read the Original

This page is a summary of: Mega-dams and extreme rainfall: Disentangling the drivers of extensive impacts of a large flooding event on Amazon Forests, PLoS ONE, February 2021, PLOS,
DOI: 10.1371/journal.pone.0245991.
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