Impacts of Dams on Biodiversity

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I recently wrote an article featuring news on hydropower dam development in Africa in the closing stages of 2015.

Now, I revisit the topic of hydropower to discuss a report in Science which investigates the impacts of dams on the biodiversity of the Amazon, Congo, and Mekong river basins.

The energy produced by these dams helps quality of life for the people people and the economies of the countries in which they are built, as power can be used in homes or to spur the construction of clinics and other amenities.

However, the ecological trade­offs have often been left ambiguous or understated.

The report points out that around one­-third of all species of freshwater fish globally can be found in the basins of these three rivers. The rivers have hundreds more dams that are either under construction or moving towards that stage, though that process can take a long time through international agreements and contracting.

Many species of fish have adapted for life in rapid water where dams are typically built. The dams not only affect diversity of fish species but also restrict their migrations and flood cycles, both of which are important for their life cycles.

The construction of dams also requires deforestation so that roads can reach the sites and often the displacement of people from their land.

Another reason for the ecological side of hydropower to be valued more heavily is that the predicted benefits of hydroelectric dam construction are often exaggerated well beyond what is truly produced, causing them to appear great enough to outweigh negative effects.

In fact, environmental impact reports can be ignored, completed after dam construction has already begun, or not conducted at all.

The Belo Monte dam in the Amazon was planned to produce the third most power of all dams in the world, which to some may excuse the extreme loss of endemic species and diversity there. However, the dam may actually produce much less power.

Fish diversity and dam locations in the Amazon, Congo, and Mekong basins.  From Winemiller et al, 2016.
Fish diversity and dam locations in the Amazon, Congo, and Mekong basins. From Winemiller et al, 2016.

The conclusion of the report hopes that more widely available spatial data will be used to analyze or monitor these projects more closely.

The authors of the report note skepticism that local communities that experience relocation, loss of livelihoods, and other direct effects are experiencing enough benefits of hydropower development to balance their losses.

Finally, the report recommends that environmental impact reports are conducted more thoroughly, at a larger scale, and taken more seriously: “common­sense adjustments”.

The report

Balancing Hydropower and Biodiversity in the Amazon, Congo, and Mekong by K. O. Winemiller et al. 2016. Science Vol. 351: Issue 6269, pages 128-129. doi:  10.1126/science.aac7082