Roger Hanlon

Megadamania The global desire to develop energyhungry industries and Western lifestyles, combined with the necessity to do so without further increasing the use of fossil fuels, has led to a massive spree of dam building around the world. A recent assessment by Christiane Zarfl from the Leibniz Institute of Freshwater Ecology and Inland Fisheries at Berlin, Germany, and colleagues estimates that 3,700 major dams with more than one MW hydroelectric generating capacity are currently under construction or in planning. On completion, these would nearly double the existing capacity, raising it to 1,700 GW (Aquat. Sci. (2015), 77, 161–170). The assumption that enormous hydroelectric plants are climatefriendly because they are based on a renewable kind of energy, namely the hydrological cycle, still has to be tested in detail. If methane emissions from reservoirs are as bad as some studies predict them to be, large hydroelectric plants in the tropics may be no better than fossil fuels in climate terms. The megalomania of investors, including the World Bank and various development funds, may turn out to be part of the problem. It is in line with the wider phenomenon that Bill Laurance from the James Cook University in Cairns, Australia, has described as an “infrastructure tsunami”, which will also lead to a doubling of road capacity and an unsustainable expansion of motor traffi c still largely powered by fossil fuels (Curr. Biol. (2016) 26, R307–R310). If, instead of megadams, they put their money into decentralised solutions that serve the people of developing regions, this may also be better for the planet. If, however, they have to invest into structures they can see from space, they may want to support some science fi rst, to make sure that those dams don’t end up contributing to climate change.