Rivers Must Flow
If a river's flow is our planet’s heartbeat, then we humans are the heart disease
A World Water Day Special
A version of this article originally appeared online in Al Jazeera.
Rivers act as the planet’s circulatory system. Like our body’s circulation system, the planetary one doesn’t work very well when it’s clogged. If a river's flow is its heartbeat, then we humans are the heart disease. We’ve blocked most major rivers with dams, bled them dry with water diversions, and given up all too many once-great rivers for dead once we’ve used them up.
More than 50,000 large dams now choke about two-thirds of the world’s largest rivers. The consequences of this massive engineering program have been devastating. Large dams have wiped out species; flooded huge areas of wetlands, forests, and farmlands; displaced tens of millions of people, and affected close to half a billion people living downstream. Large dams hold back not just water but silts and nutrients that replenish farmlands and build protective wetlands and beaches. Dams change the very riverness of our waterways, in ways we can’t always see but that the earth can certainly feel.
Of all the complex and interconnected environmental disruptions that dams inflict on the landscape, the most obvious is the permanent inundation of forests, wetlands and wildlife. Reservoirs have flooded vast areas — at last count, the world’s dams had flooded an area bigger than the United Kingdom. Equally important is the quality of these lost lands: river and floodplain habitats are some of the world's most diverse ecosystems. Plants and animals that are closely adapted to valley habitats often cannot survive along the edge of a reservoir. Dams also are usually built in remote areas that are the last refuge for species displaced by development elsewhere. In large measure due to dams, freshwater ecosystems are losing species and habitats faster than any other type of ecosystem.
Large dams also fragment the riverine ecosystem, isolating populations of species living up and downstream of the dam and cutting off migrations and other movements. Because almost all dams reduce normal flooding, they also fragment ecosystems by isolating the river from its floodplain. The elimination of the benefits provided by natural flooding may be the single most ecologically damaging impact of a dam.
Rivers That Capture Carbon
A newly significant environmental impact of dams is how they might eliminate a source of carbon capture in some watersheds. Scientists have discovered that major rivers play a surprisingly large role in helping tropical oceans absorb carbon. The vast flow of major river basins delivers phosphorus, iron and other nutrients far offshore, where it is consumed by certain forms of sea life such as phytoplankton. These microorganisms “fix” carbon by taking it out of the atmosphere. The organisms eventually sink, taking carbon with them to the deep seafloor. Dams could change the delicate workings of this ecosystem service by holding back the river-borne sediment that feeds this cycle.
At least two major river basins slated for damming – the Amazon and the Congo – are important planetary sources of nutrient flows. A 2009 study of Africa’s biggest proposed hydropower project, the Grand Inga Complex on the Congo, says that “plans to divert, store or otherwise intervene in Lower Congo River dynamics are truly alarming” and “ignore the river’s significant influence on the equatorial Atlantic, which, in turn, is central to many climate change models.”
Scientists predict that damming the Amazon, the Congo, the Mekong, and other high flow rivers in warm-ocean areas could reduce their ability to mitigate climate change. Research on other rivers’ carbon-sink capacity is underway.
Photo by Ian Umeda
What can be done?
Free-flowing rivers are now such a rarity that they would be classified as an endangered species if they were considered living things rather than merely support systems for all living things. Yet we can take small comfort from the fact that rivers have a natural ability to self-heal. Over time, all of the efforts to engineer dynamic, powerful and unpredictable rivers will inevitably fail, and the river will have a chance to restore itself. As renowned river explorer Richard Bangs wrote in his book River Gods: “Wild rivers are earth’s renegades, defying gravity, dancing to their own tunes, resisting the authority of humans, always chipping away, and eventually always winning.” We all win when rivers are allowed to flow freely.
But we can’t just wait for rivers to chip away at the dams that clog them. First, we need to protect remaining free-flowing rivers while we still have some to protect. A growing movement of citizen activists in countries where damming is on the rise is working to get their governments to pass laws that would protect free-flowing rivers. A number of countries have devised legislative tools that are useful models for such efforts; the US Wild and Scenic Rivers Act is just one effective model.
Where entire rivers cannot be protected, we must prioritize the protection of areas of great ecological integrity. This “landscape approach” requires that a network of regional-scale ecosystems be protected; that sufficient levels of each ecosystem are included to make protected areas ecologically viable and to maintain the integrity of populations, species and communities, and that the protected areas encompass variability of habitat within ecosystems. The biggest challenge is not the science of evaluating what to save, but the political will needed to maintain the protections.
When rivers are dammed, we must insist on naturalistic flows to support the basic ecosystem functions of dammed rivers. So-called “environmental flows” are planned releases intended to support the basic ecosystem functions of dammed rivers. Such systems can be complex to devise and maintain, and many dams around the world currently lack the mechanisms needed to control water discharge. Therefore, as with medicine, the best approach is to “first, do no harm”— no dams unless there are no better options (and there almost always are). But once a dam is inevitable, it is imperative that the river be maintained with as natural a flow as possible. As water expert Sandra Postel has written: “an ethic of stewardship toward fresh water and its dependent species requires that we err on the side of allocating too much water to ecosystems rather than too little.”
And finally, we must remove the worst dams to restore flows that support habitats, fisheries and other natural services lost to poorly planned dams. A growing movement to remove dams and restore rivers in the United States is a global inspiration. American Rivers estimates that more than 925 dams have been removed over the past 100 years in the US.
We must also undertake a greater study of the world’s river-dependent biodiversity, much of which still remains unknown to us. As Pulitzer-prize-winning biologist E.O. Wilson has said, “In reality, we don’t know 90 percent of what we’re losing, because we’ve only discovered about 10 percent of the planet’s species. When we're trying to stabilize the environment – trying to stop ecosystems from collapsing in the face of global warming or big dams or whatever – we really need to know what's in each of these habitats. We need then to move ecology way ahead of where it is today, really make it a much bigger priority.”
Because most new dams are being built in the global south, we must move more quickly to help the developing world adopt clean energy and water supply systems that preserve riverine lifelines. Large dams are an ineffective approach for solving the water and energy needs of the poor majority. Small projects take less time to build, are more easily phased, and are more adaptable to a changing climate. Breakthroughs in clean energy technologies and water-efficiency methods are not only better suited to strengthen energy and water access for the poor, they will also strengthen our resilience to climate change. They do however require greater investment in research, development and deployment. The world's wealthiest countries should assist the world’s poorest in developing a cleaner, more efficient energy path and water-secure future rather than in destructive mega-projects that repeat the mistakes of the past.
The final piece of the puzzle is personal. Protecting our rivers now is the health insurance policy we all need for a climate-challenged future. Find ways to become an advocate for a river near you.