January 7th, 2021
Midterm Question: To what extent do dams negatively impact the surrounding wildlife/animal habitats?
In the article “The potential impact of new Andean dams on Amazon fluvial ecosystems”, written by Bruce Forsberg, John Melack, Thomas Dunne, Ronaldo Barthem, Michael Goulding, and Rodrigo Paiva, published by the Public Library of Science, the authors conclude that building six new dams in the Andes will have detrimental impacts on the natural resources and fluvial ecosystems of the Amazon River basin. These impacts range from reducing the yield of fish and the supply of nutrients and sediments, creating more greenhouse gas emissions than an oil-fired power plant, and an increase in mercury levels in reservoir fish that get eaten by human communities.
This article was found in the Gale: Opposing Viewpoints database, using the search terms "dam(s)" and "wildlife". Key terms that were new to me were fluvial, downstream versus upstream impacts, sediments, anoxic, reservoirs, and inundation.
Eight different potential impacts were investigated in this article, all resulting in interesting findings. The first results were the impact of downstream sediment and nutrient supply. 93% of the sediment in the Amazon basin comes from the Andes mountains¹, which means that constructing these six dams would ultimately reduce the sediment supply to the basin by more than half. Since sediments are necessary nutrients that enrich the soil, making it more fertile and farmable, a reduction in sediments could lead to less crop yield from the Amazon. These dams would also retain the nutrients phosphorus and nitrogen, dropping the total supplies to the basin by 10% and 28% respectively¹. Less sediment transportation would also result in a reduction of plant diversity and inundation¹, which is “likely to promote agricultural development with accompanying increases in deforestation”. Other impacts are on downstream and upstream fish production. If the dams are built, this would result in less flooding downstream. Flooding is a necessity for the fish species P. nigricans as flooded forests increase their rate of survival by providing more areas of refuge from large predators¹. This fish species is very important to the Loreto fishery in the Amazon, and if the dams were built therefore preventing flooding, these fish would produce less and lead to a smaller yield of fish for the fishery. Upstream fish production is much less impacted since they’ll still have nutrients sustaining them, therefore upstream fish yield could compensate for the decrease in downstream fish yield¹. Another impact that was investigated was the reservoir sedimentation. The construction of dams would impede the flow of sediments, leading to it building up in the reservoir which can then “affect dam operation, the quality of benthic habitats and the pattern of human occupation and activities in the reservoir”. The reservoir could reach the point where it's so full of sediment that it begins to enter the turbines, and there are also environmental impacts like the creation of wetlands that can act as sources for more greenhouse gases and mercury methylation¹. Mercury itself is a problem, as the anoxic (without oxygen) conditions created by the dams and their reservoirs promote bioaccumulation of mercury¹. This mercury is then found in the fish that human communities will eat, which is a health risk for humans.
My focus for this midterm revolves around researching to what extent dams negatively impact their surrounding wildlife and animal habitats. The results of the investigation all pointed to the fact that constructing these large reservoirs of water that would generate electricity in the Andes would have detrimental impacts both geographically and biologically. These findings were then published with the intent to dissuade the general audience from believing that the dams would just have the positive impact of creating energy in a renewable way. The investigation proved this to be not true, as there were other environmental impacts perhaps more detrimental than global warming in certain aspects. Although this article didn’t solely focus on the wildlife impact, it touched upon the impact it’d have on the surrounding habitat as well as on the fish population. I think it's important to make note of the fact that although it appears that there are more downstream impacts than upstream ones, the buildup of mercury occurred in both locations. Also, although the loss in fish yield downstream could be made up by the fish yield upstream, I believe that this could potentially not be the case due to the eventual building up of sedimentation. If the sediments can fill the reservoir to the point where they enter the turbines, I’m sure it could also eventually take up more space from the fish. In general, it’s hard to believe that the ecosystem of the fish upstream would remain unchanged with the construction of the dam. Also, the buildup of mercury and methyl could have unknown effects on certain populations of fish, possibly causing the death of some species. I think for the next article, I’m going to analyze the impact on wildlife more specifically since this article was more heavily focused on sediments and fluvial impacts.
Bibliography:
Forsberg, Bruce R., John M. Melack, Thomas Dunne, Ronaldo B. Barthem, Michael Goulding, Rodrigo C. D. Paiva, Mino V. Sorribas, Urbano L. Silva, and Sabine Weisser. "The potential impact of new Andean dams on Amazon fluvial ecosystems." PLoS ONE 12, no. 8 (2017): e0182254. Gale In Context: Opposing Viewpoints (accessed January 7, 2021). https://link.gale.com/apps/doc/A501665590/OVIC?u=nysl_ca_guild&sid=OVIC&xid=2ae2aadc.