Dammed if you do, dammed if you don’t

The following is a guest post by Dr. Clinton Jenkins, an NC State biologist whose research focuses on conservation science. Jenkins is co-author of a new study in PLoS ONE about the possible impact of hydroelectric dams on the Andean Amazon. Dr. Matt Finer, a researcher affiliated with Save America’s Forests and the Center for International Environmental Law, is the study’s lead author. The entire study is available online at: http://dx.plos.org/10.1371/journal.pone.0035126

The Andean Amazon, arguably the most biologically diverse zone on Earth, has quickly emerged as a major frontier for construction of new hydroelectric dams. With a growing regional demand for electricity, governments in the region are prioritizing hydropower as the centerpiece of their long-term energy plans.

By and large, these projects lack strategic planning around the possible consequences of the disruption of the critical ecological link between the Andes Mountains and the Amazonian floodplain. This connection has existed for millions of years, and is critical to the survival of one of the most productive ecosystems on Earth.

The Andes supply the vast majority of the sediment, nutrients and organic matter to the Amazon floodplain. In addition, many important Amazonian fish species spawn only in Andean-fed rivers, including a number of long-distance migrants that must travel from the lowlands to the foothills.

Our new study is the first to analyze the full portfolio of planned dams across all six major river basins connecting the Andes to the Amazon, a geographic scope spanning five countries (Bolivia, Brazil, Colombia, Ecuador and Peru).

The study documents plans for more than 150 new dams, a potential 300 percent increase over the number of existing dams in the region. More than half would be large dams over 100 megawatts and 40 percent are already in advanced planning stages.

Most notably, 60 percent of the dams would cause the first major break in river connectivity between protected Andean headwaters and the lowland Amazon, threatening the current free-flowing nature of many Andean-Amazon rivers. More than 80 percent of proposed dams could also drive new deforestation due to new roads, transmission lines or direct flooding of land. Some of that potentially flooded land is already home to indigenous people, a recipe for more social conflicts in the region.

In order to measure the potential environmental impact of these dams, we looked at two major factors: first, the physical disruption of river connectivity by the dam itself; and second, the infrastructure necessary to build, maintain and transport energy from the dam, such as roads and transmission lines. Essentially, the bigger and more isolated a dam is from existing infrastructure, the worse its potential impact. We also rated the first dam on a river as having a higher impact, because it is the first to block the movement corridor.

Using these parameters, we found that nearly half of the proposed dams qualify as high impact, while just 19 percent were low impact.

Without better strategic assessment and planning for these regional projects, hydroelectric power – which has been touted as an inexpensive and clean energy source – may end up putting tropical rivers and forests at risk.