Last month I wrote about the 86% decline in populations of migratory fish since 1970. Turns out that was just a trailer for the feature film.
In September, WWF released its Living Planet Report, which includes the grim statistic that essentially all vertebrate species that depend on freshwater ecosystems are following the same precipitous plunge as migratory fish.
How the world developed its energy systems, particularly hydropower dams that fragmented rivers, is one of the primary reasons for this dramatically dropping trendline.
How the world designs, builds and operates its future energy systems will be key to halting, and ultimately reversing that trendline.
The current decline in freshwater populations is tracked by the “Living Planet Index” (LPI), which provides insights into the health of global wildlife, much like an index fund provides insights into the health of financial markets. And just as an index fund reflects the prices of hundreds or thousands of individual stocks, the LPI is composed of abundance data for more than 21,000 distinct populations of approximately 4,000 species of vertebrates (mammals, birds, fish, reptiles and amphibians) across the world.
The LPI for all tracked vertebrate populations has declined by 68% since 1970 while the LPI for freshwater species has dropped by 84% over the same time (see below). To make these numbers more real, imagine a tourist visiting a national park. If, in 1970, she had a chance to see 100 river dolphins swimming in a stretch of river in that park, today her daughter could only hope to see 16. If you had the good fortune to fish in a river with a run of 20,000 salmon in 1970, today you’d be casting toward a greatly diminished population of 3,200 fish. Now repeat that thought experiment for storks, giant otters, frogs, freshwater turtles, sturgeons, and on and on, across the whole planet.
We are losing our neighbors – particularly those with watery addresses.
Of course, some populations haven’t declined, while some have dropped even further, and even disappeared. But, on average, populations of freshwater species are 84% smaller than they were when I was born.
Multiple scientific reviews have pegged water infrastructure, such as dams and levees, as among the leading causes of the decline of freshwater species. This infrastructure is so problematic for freshwater species because its primary function is to fragment and disconnect rivers – keep this side wet and make sure this side stays dry, hold a large amount of water here behind this wall to prevent it from going downstream and then release a portion of it into this canal toward a powerhouse as electricity demand rises.
Infrastructure is intended to create orderly boundaries in both space and time. But freshwater ecosystems are neither orderly nor bounded. They are rambunctious and dynamic. It’s in their nature to be fluid – but they can’t be fluid if they’re fragmented.
Only 1/3 of long rivers remain free-flowing and connected across the world, and hydropower dams are the leading cause of this fragmentation.
The fragmentation of large rivers by hydropower dams began about a century ago and a trendline tracking the global number of free-flowing rivers since then looks about the same as the freshwater LPI – a steady decline (67% in 100 years).
When the direction of an indicator is steady and consistent for 50 years (the LPI) or 100 (the number of free-flowing rivers), it’s easy to assume that the trend is inexorable and that plans for halting loss and restoring ecosystems, such as the Emergency Recovery Plan for freshwater biodiversity published earlier this year, are well-intentioned clarion calls for more of the same failed strategies.
And that may be the case if those strategies are aimed at stopping inexorable trends. For most of this century, the continued steady expansion of hydropower, and accompanying loss of free-flowing rivers, did in fact seem like one of those inexorable trends.
But then something happened. After more than a decade of rapid growth—a 400% increase in annual capacity growth since the start of the century, with projections for a further global doubling of capacity by 2050—hydropower investment peaked in 2013 and then began its own dramatic decline (see below). Annual investment in hydropower for 2019 was about 1/3 of its high point six years earlier and most indicators suggest the trend is not about to reverse.
This pattern is part of a broader decoupling of trends for energy growth and environmental degradation.
For nearly all of humanity’s existence, achieving positive growth in indicators for energy necessitated negative growth in indicators for environmental health. When wood was energy, increasing energy for people and economies required massive clearing of forests. Then coal fueled growth and greenhouse gases surged. Hydropower projects brought power to poor regions of the US and then countries around the world, but came at the cost of flooded valleys and the displacement of 80 million people, along with the loss of free-flowing rivers and migratory fish.
There are numerous explanations for the recent decline of hydropower, but no doubt the dramatic drop in cost of wind and solar PV has contributed. The cost of solar PV has dropped over 80% and the cost of wind projects has dropped by about half just since 2010. As a result, investment in these technologies has surged and wind and solar together represented two-thirds of all new global generation capacity added in 2019. The cost of lithium-ion batteries have declined 83% since 2010. These dramatic declines in cost are major drivers of the renewable revolution and are supported by advances in other technologies and tools for integrating a steadily rising proportion of variable generation sources into grids.
So, given the fifty-year downward trend for freshwater populations, why is it realistic to think that we can “bend the curve” of freshwater biodiversity loss? One reason for optimism is that a set of previously steady trends driving biodiversity loss have themselves bent and reversed, while a new set of trends—those tracking the renewable revolution—have taken their place. And rather than struggling upstream against energy trends, river conservation efforts can now swim with the steady currents of energy trends flowing in the same direction. (Here I should acknowledge that land-use and social impacts from renewable energy technologies will still require careful management, but research suggests the world has more than sufficient land area where wind and solar can be sited with minimal social and environmental conflicts).
The challenges facing rivers and freshwater biodiversity are diverse, and the protection of free-flowing rivers (and their restoration through dam removal and other interventions) are only part of the solution. But the decoupling of energy trends from those that track the degradation of both the climate and rivers is an important step toward halting and then reversing the half century of decline of freshwater wildlife.