Perhaps it’s one of nature’s little jokes: the way that fire can set off a chemical chain reaction that pollutes nearby water precisely when it’s needed most. But every year it proves to be no laughing matter for people around the world when vital reservoirs are placed under threat due to algal blooms in the wake of wildfires and soil erosion.
Thanks to the research of a specialist team at Plymouth University, however, land and water management authorities across Australia, Europe and the UK are beginning to understand the process and take preventative measures.
Researchers in the Consolidated Radioisotope Facility, located within the School of Geography, Earth and Environmental Sciences, have amassed more than a decade’s worth of study into soil erosion caused by changes in its hydrology following wildfire.
“In normal conditions, when rain falls in a forested area you expect the rainwater to soak into the soil because it has lots of holes, lots of organic matter,” says Dr Will Blake, Director of the facility. “But in a fire, that organic matter is burned and the resulting ash blocks up those holes, making it less permeable. There’s also a chemical process that takes effect, a complex response to fire, where natural oils from trees are released, effectively coating the soil and making it water repellent. Fire can enhance or destroy this depending on temperatures reached. The critical thing is that the burned layer and ash contains nutrients such as phosphorus. When it rains, that layer gets washed into streams and rivers, creating nutrient pollution and risk of toxic algal blooms.