Oct 20 2017
An innovative study performed at the University of Stirling has proposed that the effect of hydropower production on the environment in the Amazon might be more than that speculated earlier.
Dr Isabel Jones led the study, which found the environmental impact of Amazonian hydropower is “significantly underestimated.” Credit: University of Stirling
The research indicates that approximated losses in carbon and biodiversity related to tropical hydropower might be greater than the speculated values because they do not take into account the total effect of forest fragmentation.
The study was headed by Dr Isabel Jones from the Biological and Environmental Sciences, and investigated lianas, long-stemmed woody vines also famously known as Tarzan’s preferred mode of transport, in the Balbina hydroelectric dam in Brazil.
Lianas might prevent the growth of trees or even kill them because they both strive to obtain essential resources such as light and water. In specific areas, lianas dominate trees, resulting in the formation of low biomass liana-dominated forests. This in turn leads to alterations or complete disappearance of food sources for animals, and the forest’s potential to ingest and store carbon, which is key in maintaining the worldwide carbon balance, is decreased.
Fragmentation
The ratio of the woody vines to trees leans always in favor of lianas if tropical forests are perturbed (e.g. due to fragmentation of continuous forest into smaller pieces for agricultural purposes or other land uses). This is because lianas are well-habituated for such environmental conditions.
Another reason for fragmentation is hydropower production in Amazonia, where large areas of forests are flooded upon closing dams, altering earlier hilltops into islands.
Although it is known that biomass in forest islands is reduced when the habitat area is decreased, for the first time, this innovative research has demonstrated that a dam-influenced landscape may lead to the tree population being outnumbered by lianas, as seen in other perturbed tropical forest systems.
According to Dr Jones, “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.”
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.
Dr Isabel Jones, Biological and Environmental Sciences, University of Stirling
Significance
Dr Jones and his colleagues carried out field surveys of trees and lianas, covering 89 forest plots from 36 islands of varying sizes and in continuous forests enclosing the reservoir.
The Researchers, 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, discovered that a larger number of lianas are beginning to grow when compared to trees in the most perturbed islands.
They also found that lianas continue to be compositionally unharmed irrespective of whether they grow in a disturbed island or on a forest. According to the researchers, this vigor in a dam-influenced environment is specifically important because trees get quickly degenerated in such a habitat.
“At present, islands are not included in environmental impact assessments, which causes a significant underestimation of the negative impacts of tropical dams,” added Dr Jones.
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.
Dr Isabel Jones, Biological and Environmental Sciences, University of Stirling
She further stated, “Our research highlights yet another way that tropical dams can result in long-term carbon emissions and damage to globally important ecosystems.”
The research titled “Woody lianas increase in dominance and maintain compositional integrity across an Amazonian dam-induced fragmented landscape” was partially funded by a research grant from the Carnegie Trust and has been published in the journal PLOS ONE.