Imagine your survival was dependent on a healthy free-flowing river – how would you feel if that river dried up? This is the reality that millions of people are already facing: mighty rivers, such as the Colorado, the Indus, the Murray, or the Yellow River, now frequently run dry before reaching the sea. In the UK, the source of the River Thames recently dried up for the first time in living memory, and major rivers all over Europe are currently drying up in the climate-driven drought.
The world’s rivers are suffering. Not only are they facing more intense climate-crisis induced droughts, but they are also being destroyed, dammed, overexploited, and polluted. The scale of this destruction has led to freshwater species disappearing at a much faster rate than terrestrial or marine species. Despite this, freshwater ecosystems are routinely ignored: too often, those responsible for prioritising conservation action, allocating environmental funding or developing infrastructure overlook the life-sustaining and vital role of healthy freshwater habitats.
This lack of attention for our rivers has wider implications: by failing to prioritise freshwater conservation, we are also ignoring a critical ally in the fight to reduce the impacts of the climate crisis.
Locking away carbon
When we talk about ‘nature-based solutions’ to the climate crisis, we often tend to focus on trees and forests. One great and powerful ally that we often forget about and undervalue is Earth’s rivers.
As rivers meander through valleys, plains, and forests, they pick up organic matter, such as decomposed plants and soil, which they transport from source to sea. On reaching the ocean, this organic matter sinks to the ocean floor where it is locked away until it surfaces several million years later in the form of rocks. This phenomenon forms ‘river plumes’ that can extend tens of kilometres into the ocean. Examples include the Amazon River plume and the Congo River plume, both of which are recognised to form carbon sinks of global importance.
An aerial photo of a river plume in Paraiba do Sul river delta in Brazil. Image: NASA
In 2015, researchers estimated for the very first time that globally rivers transport 200 million tonnes of carbon to the ocean every year. While this only represents 0.2 per cent of atmospheric carbon, over 1,000 years, that adds up to 20 per cent of total atmospheric carbon. Rivers alone will not be able to lock away enough carbon in time to reverse the climate crisis, but they play a vital part in the global carbon cycle and are powerful allies in mitigating the impacts of the climate crisis. Additionally, rivers feed and sustain wetland ecosystems, such as peatlands, and these are known to store twice as much carbon as all the world’s forests combined.
Southeast Pahang peat swamp, Pahang, Malaysia. Image: Global Environment Centre