Up to 43 MILLION tonnes of carbon from fires is absorbed by rivers every year and flushed out to sea where it can be stored for thousands of years
- Carbon tumbles into rivers as ash and charcoal or is dissolved into the waterway
- Rivers carry around 17 per cent of all carbon left on the ground by fires to oceans
- Scientists made the find by measuring carbon in 78 rivers across the world
As much as 43 million tonnes of carbon from fires is carried into the sea by rivers every year where it can be stored for millennia.
The carbon tumbles into waterways as ash and charcoal or dissolves from the air, before it is carried out to the oceans – which already store around 34 billion tonnes.
Once there, it takes ten times longer to break down into harmful carbon dioxide than the carbon left on land.
Rivers take away around 17 per cent of the 250 million tonnes of carbon released by fires, with a further two billion tonnes being emitted into the atmosphere.
Rivers can carry away around 17 per cent of the 250 million tonnes of carbon left on the ground by fires every year. Pictured is destruction of forests lining Xingu river, Amazon
For the study, published in Nature Communications, researchers measured the amount of carbon flowing through 78 rivers on every continent in the world except Antarctica.
Their results were then upscaled to estimate how much is transported into the oceans every year.
‘Rivers are the conveyor belts that shift carbon from the land to the oceans,’ said lead researcher from the University of East Anglia, Dr Matthew Jones.
‘They determine how long it takes for burned carbon to break down.’
When it reaches the oceans the element takes ten times longer to turn into harmful carbon dioxide than the carbon that is left on land. Pictured: Rain in the Amazon after fire
The scientists found around 12 per cent of all carbon flowing through rivers came from burned vegetation.
Around a third of this was long-lived ‘black carbon’, a potent pollutant.
‘With wildfires anticipated to increase in the future because of climate change, we can expect more burned carbon to be flushed out by rivers and locked up in the ocean,’ said Dr Jones.
‘It’s a natural quirk of the Earth system – a moderating “negative feedback” of the warming climate that could trap some extra carbon in a more fire-prone world.’
The amount captured by rivers is less than three per cent of that thought to be emitted by melting permafrost every year, and 0.1 per cent of the amount produced by humans annually.
However, it does suggest that oceans may offer a useful long-term storage solution for carbon released by burning vegetation as a result of wildfires and deforestation.