March 15 (UPI) – While some of the effects of climate change have a balancing effect, working to slow warming patterns, many others appear to fuel feedback loops that accelerate warming.
Now, an international team of researchers led by researchers at the University of Leeds has found another one. According to the analysis, the loss of alpine glaciers has made mountain rivers more fungus-friendly, accelerating plant decay and carbon emissions.
Researchers described the feedback loop in a new paper, published Monday in the journal Nature Climate Change.
With alpine glaciers at their lowest level for thousands of years, mountain rivers are getting warmer. They have also become so susceptible to the variability of water flow and sediment movement, allowing fungi to thrive.
When fungi dig up grass, leaves and pieces of wood, they produce CO2, much of which pushes out of the river and into the atmosphere.
To better understand this process, scientists measured the growth of fungi and the rate of decomposition of organic matter in 57 rivers flowing through six different mountains – including rivers in Austria, Ecuador, France, New Zealand, Norway and the United States.
“We have found an increase in the rate of decomposition of organic matter in mountain rivers, which can then be expected to release more carbon into the atmosphere,” lead author Sarah Fell said in a press release.
“This is a kind of feedback from climate, where warming leads to the loss of glaciers, which quickly recycle carbon in rivers before it is returned to the atmosphere,” said Fell, an expert on alpine river ecosystems and a doctoral researcher at Leeds.
Many studies have documented the acceleration of mountain glaciers worldwide, but the impact of glacial erosion on freshwater carbon cycles is less well understood.
For the study, researchers developed a cotton canvas designed to mimic the organic matter, leaves and grass, that accumulate in rivers.
Scientists left the clothing strips in dozens of rivers for a month. Once assembled, researchers measured how easily the strips could be torn.
Studies have shown that the strips from rivers receiving the glacial meltwater showed the highest levels of fungal colonization, and were the most susceptible.
“Our discovery of cellulose-like patterns at sites around the world is very encouraging as it shows that there could be a universal rule for how these river ecosystems develop as mountains continue to lose ice, “said study co – author Lee Brown.
“If so, we will be in a much better position to make predictions about how river ecosystems will change in the future,” said Brown, professor of water science at Leeds.
Instead of measuring the diversity and abundance of different fungal species on each strip, researchers measure the activity of the specific gene that is responsible for the synthesis of the cellulose-degrading enzyme called Cellobiohydrolase I, or CBH1.
Strips with higher levels of CBH1-related gene activity were more likely to be bilateral and easily torn.
With increasing fungal activity in alpine rivers, scientists suspect that less organic matter is making its way downstream to forests, which are dependent on a constant supply of leaf litter.
Reduced flow variability can encourage the growth of streamside trees, grasses and shrubs – vegetation that may have been washed away for centuries.