Story at a glance

  • The fires in Australia have killed an estimated 1 billion animals on land, but experts say the environmental damages will also reach underwater ecosystems.
  • When rains come, the resulting runoff will be filled with ash and fine silt that can choke fish’s gills and smother aquatic plants.
  • Funds from the Australian government dedicated to environmental restoration are currently only focused on terrestrial life, which some environmentalists say is a mistake as life underwater has also been imperiled by the fires.

The unprecedented fires in Australia have killed an estimated 1 billion land animals, but the environmental destruction wrought by the flames will also extend to aquatic plants and animals, Hakai reports.

More than 17 million hectares have been reduced to ash since the fires ignited in September. These mountains of ash will eventually be washed into coastal lakes, estuaries and seagrass and seaweed beds by rain. Also, in many areas the vegetation, which would normally filter and slow this storm runoff, has been burnt up. The denuded landscape will also erode more quickly as water flows across it, meaning runoff will carry more silt and debris. 

The fine particles of ash and silt can clog fish gills and carpet seagrass and seaweed beds — blocking the sunlight they require for photosynthesis.

“It’s essentially like putting a shade cloth all over the entire system,” Leonardo Guida of the Australian Marine Conservation Society (AMCS), told Hakai. 

The glut of charred plant matter blended into the stormwater means it’s also high in nutrients, which may sound like a good thing, but an excess of nutrients can cause huge blooms of algae. 

Such blooms can completely overwhelm an ecosystem, proliferating until they’ve used up all the nutrients. Worse, when the algae run out of nutrients and die the bacteria that show up to feast on their remains can suck all the oxygen from the water — creating dead zones of little or no oxygen that can’t support fish. 

Many aquatic ecosystems in Australia are particularly adapted to surviving on low levels of nutrients, which makes them even more sensitive to the massive influxes anticipated in coming months.

Many commercial species, such as flathead, snapper, prawns and types of shellfish, begin their life cycles in coastal lakes and beds of seagrass or seaweed which are likely to be negatively affected by the slurry of ash and silt coming their way. The damage to these ecosystems could shrink populations of the species that depend on them, according to researchers. 

The areas of southern New South Wales, Victoria and Kangaroo Island are already reporting issues with fisheries and aquaculture operations as a result of the fires, Australia’s Department of the Environment and Energy (DEE) told Hakai.

When rains finally came to the Central Coast region of New South Wales, a local Aboriginal land council called the Darkinjung created barricades to prevent the silt and ash-laden runoff from entering the region’s waterways. Still, the group has reported dead fish in nearby rivers. 

The Australian government has dedicated $35 million to restoring and protecting ecosystems and wildlife damaged by the fires, but, according to the AMCS, the program and its funding don’t explicitly target marine or freshwater ecosystems. However, some of the work on land supported by the fund, such as erosion control, will help to mitigate the flow of ash and mud into aquatic ecosystems.

Though damage to underwater ecosystems is less visible than blackened forests and barbecued wildlife, the AMCS told Hakai that Australia’s waterways and coast are in trouble and need funding to help them recover.

Published on Jan 23, 2020