Rivers inspire plenty of poetic moments and a plethora of singalong songs, but they don’t always get the attention they deserve in terms of climate and biodiversity – or restoration.
Their flows make up a tiny proportion – just 0.0002 percent – of all the water on the planet, but they supply most of the water that we use. They also sustain wetlands, which provide homes and breeding grounds for about 40 percent of all known plant and animal species.
But rivers and lakes are also the most degraded ecosystems in the world, facing major threats from pollution, dams and barriers, and excessive water consumption.
As a result, biodiversity is declining twice as quickly in freshwater as in oceans and forests: nearly a third of all freshwater fish species are now at risk of extinction.
Rivers as carbon cyclers
Rivers also play a central role in the carbon cycle – one that has been largely overlooked, say the co-authors of a recent review article that provides a global-scale assessment of river ecosystem metabolism.
“Rivers are not just ‘pipelines’ to the ocean,” says co-author Judith Rosentreter, a senior research fellow at Southern Cross University, in the study’s press release. “They are ‘biogeochemical reactors’ that break down organic carbon that they receive from the land and emit some of this as greenhouse gases to the atmosphere.”
Rivers also serve as an important climate solution by storing carbon in their sediments, the authors say. As such, when a river is degraded, it could experience a shift in its carbon balance, which could further affect both climate and biodiversity.
“River flow is important for the overall carbon balance in rivers,” says Rosentreter. “Changes in water level and flow greatly affect river metabolism and greenhouse gas emissions.”
To this end, the authors are calling for the establishment of a new worldwide river observation system to help track and predict these impacts.
“We need to understand how global climate change and human impacts will change the sinks and sources of carbon in rivers in the future,” says Rosentreter.
‘Rewiggling’ and other remedies for rivers
As the importance of rivers – and their vulnerabilities – become increasingly clear, many landscape actors are turning to nature-based management, with some inspiring results.
Last year, Australia’s Wollombi Brook, which flows into the Hunter Valley in New South Wales, survived one of its largest floods on record without suffering major erosion or sediment movement.
This was largely thanks to efforts by the local community to rehabilitate it over the past 20 years using nature-based approaches like continuous streamside vegetation, according to a press release for a new study tracking the country’s progress in this arena.
Wollombi Brook, say the authors, “encapsulates the sort of changes we need to make to meet river health goals set by the United Nations in its ‘Decade on Ecosystem Restoration to 2030’.”
In a similar vein, a community in the U.K. has found success with a recent ‘rewiggling’ project for the Swindale Beck river.
About 200 years ago, the meandering waterway in Cumbria had been straightened to create more space for farmland on either side. But the new course flowed much faster, meaning that many of its fish couldn’t spawn, and more sediment was uplifted, clouding its once-clear water.
So in 2016, the Royal Society for the Protection of Birds (RSPB) and its partners set about turning back the clock. They worked out where the river used to flow and brought in diggers to carve back that channel.
The biodiversity response was rapid, said Lee Schofield, a senior site manager at the RSPB. “About three months after the diggers left, we had salmon and trout spawning in the river again,” he told the BBC.
From voices to action
While these success stories show some of the ways we can rehabilitate our rivers, they can still be challenging to manage. Rivers have often proven a prickly issue for environmental governance because they frequently flow across multiple landowners, states and countries, so it can be difficult to agree on what should be done with them – and who should pay for it.
In Chile’s arid Petorca province, for instance, privatized water ownership rights allow vast avocado farms to run wells and rivers dry, with disastrous impacts for communities downstream.
In New Zealand, Indigenous Māori are fusing ancestral concepts and modern law to develop more holistic models of river management. In 2017, the Whanganui River was given the status of ‘legal personhood,’ which means its rights can be defended in court – a move that proponents hope will help protect its intrinsic value.
Since then, other rivers – such as the Atrato in Colombia and the Magpie in Canada – have attained the same, though there’s still a lot of debate over how far those rights extend.
For instance, a significant proportion of the Whanganui’s flow continues to be diverted to power a hydroelectric plant, and the river remains cloudier and more contaminated than it should be due to agricultural pollution from nearby farms.
This highlights a central concern. New and old ways of tracking and conceptualizing rivers are certainly important, but it’s what we do with that knowledge that will make the difference for riverine health – and thus for people, biodiversity and the climate.
As Howard Hyland, a waka ama (traditional Māori canoe) coach and paddler on the Whanganui River, contemplated in an interview with The Guardian: “If you give the river a voice, are you going to listen?”