Impact of amazonian hydropower is 'significantly underestimated'

October 19, 2017, University of Stirling
Impact of amazonian hydropower is “significantly underestimated”
Credit: University of Stirling

The environmental impact of hydropower generation in the Amazon may be greater than predicted, according to new University of Stirling research.

The study suggests that estimates of biodiversity and carbon losses associated with tropical hydropower may be higher than estimated as they fail to consider the full impact of fragmentation.

Led by Dr Isabel Jones, of Biological and Environmental Sciences, the research studied – long-stemmed woody vines, enshrined in popular culture as Tarzan's favourite mode of transport – within the Balbina hydroelectric dam in Brazil.

Lianas can kill or prevent them from growing as they both compete for vital resources such as water and light. In some areas, lianas outnumber trees - causing the growth of low biomass liana-dominated forests. Such a transformation results in sources of food for animals to change or disappear completely, while the ability of the forest to uptake and store carbon – vital for maintaining the global carbon balance – is reduced.

Fragmentation

The liana to tree ratio is tipped in favour of the woody vines when are disturbed – for example, by fragmentation where continuous forest is split into smaller pieces for agriculture or other land uses – because lianas are well-adapted for those environmental conditions.

Hydropower generation in Amazonia is another cause of fragmentation with large swathes of forests left flooded when dams are closed, transforming former hilltops into .

It is known that forest islands lose biomass due to reduced habitat area, however, the new study reveals for the first time that a dam-induced landscape can result in lianas dominating the tree population, as witnessed in other disturbed tropical forest systems.

Dr Jones said: "If lianas are being favoured in this dam-induced landscape, then the biodiversity and carbon losses associated with tropical hydropower could be greater than expected. This is due to the potential increased loss of tree biomass, due to liana-tree competition, as lianas have lower biomass relative to trees.

Lianas - long-stemmed woody vines - compete with trees for vital resources, such as water and light. Credit: University of Stirling
"Therefore, a shift towards liana-dominated forest on tropical reservoir islands may result in even more biodiversity and carbon losses for already controversial tropical dams.

"These issues identified in this study should be accounted for in the carbon cost and benefit decision-making process of whether to construct new dams in Amazonia."

Significance

Dr Jones' team conducted field surveys of lianas and trees, surveying a total of 89 forest plots across 36 islands of different sizes and in continuous forests surrounding the reservoir.

The scientists – including experts from the University of East Anglia in Norwich, Universidade Estadual de Santa Cruz in Brazil and the Smithsonian Tropical Research Institute in Panama - found that a greater number of lianas are starting to grow than trees in the most disturbed islands.

In addition, they discovered that liana communities remain compositionally intact regardless of whether they are in a forest or on a disturbed island. This robustness in a dam-induced habitat is particularly significant as trees rapidly degrade in such an environment, they said.

"At present, islands are not included in environmental impact assessments, which causes a significant underestimation of the negative impacts of tropical dams," Dr Jones continued.

"Given that Brazil alone has plans for several new mega-dams, which will flood vast areas of highly diverse tropical forests, it is important that the total area of islands should be included in calculations considering the habitat impacted by dam creation."

She added: "Our research highlights yet another way that tropical dams can result in long-term emissions and damage to globally important ecosystems."

Explore further: Lianas stifle tree fruit and seed production in tropical forests

More information: Isabel L. Jones et al. Woody lianas increase in dominance and maintain compositional integrity across an Amazonian dam-induced fragmented landscape, PLOS ONE (2017). DOI: 10.1371/journal.pone.0185527

Related Stories

Ant bridges connect shy tropical tree crowns

November 16, 2016

Internet and phone connections are essential for effective communicators and for success in business. New results from the Smithsonian Tropical Research Institute (STRI) in Panama show that connections between trees may be ...

Recommended for you

Data from Kilauea suggests the eruption was unprecedented

December 14, 2018

A very large team of researchers from multiple institutions in the U.S. has concluded that the Kilauea volcanic eruption that occurred over this past summer represented an unprecedented volcanic event. In their paper published ...

Death near the shoreline, not life on land

December 13, 2018

Our understanding of when the very first animals started living on land is helped by identifying trace fossils—the tracks and trails left by ancient animals—in sedimentary rocks that were deposited on the continents.

The long dry: global water supplies are shrinking

December 13, 2018

A global study has found a paradox: our water supplies are shrinking at the same time as climate change is generating more intense rain. And the culprit is the drying of soils, say researchers, pointing to a world where drought-like ...

New climate model to be built from the ground up

December 13, 2018

Facing the certainty of a changing climate coupled with the uncertainty that remains in predictions of how it will change, scientists and engineers from across the country are teaming up to build a new type of climate model ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.