Quarter of Freshwater Species at Risk of Extinction

Photo: Alex Stulce

It shouldn’t be a secret to any angler that freshwater fish face significant challenges. Trout habitat is on the decline in many parts of the world, despite robust restoration efforts. Invasive carp threaten to upend entire ecosystems, and it seems that every year, we hear of hoot-owl restrictions earlier and earlier in the season.

This isn’t just anecdotal, or hand-wringing from a group of people who prefer the company of fish to most humans. In a recently released study in Nature, a large team of scientists reached the conclusion that a full quarter of freshwater species are at current risk of extinction.

“Freshwaters support over 10% of all known species, including approximately one-third of vertebrates and one-half of fishes, while only covering less than 1% of the surface of the earth,” the study reads.

That truly puts this problem into perspective, at least for me. I consider myself well-versed on conservation issues, but I didn’t know the numbers behind how much life freshwater supports, especially given its small volume overall.

So, the data says a quarter of freshwater species are at risk. What exactly put them in that position?

According to the study, the main problems are a reduction of wetland areas, pollution, and the loss of free-flowing rivers. The study stated that 35% of wetland area was lost between 1970 and 2015, which is a rate three times higher than that of lost forests.

“Of the remaining wetland habitats, 65% are under moderate-to-high levels of threat,” the study reads.

The issue that most anglers are likely familiar with has to do with dams. 37% of rivers over 1,000 kilometers in length are no longer free-flowing throughout their entire length. Dams interrupt the natural exchange of biological matter, especially between marine and freshwater environments. They also significantly impact water temperature, as we’ve seen in the Lower Snake River. Many freshwater species are highly temperature-sensitive.

One section of the study, in particular, deserves attention here:

“Pollution is also considered a key threat to fishes (59%), again with agricultural and forestry effluents (45%) as the key sources, followed by domestic and urban waste waters (29%), and industrial and military effluents (21%, including seepage from mining and oil exploration). Water management (including dams and water extraction) is considered another key threat to fishes (46%), with dams blocking migration routes and causing habitat degradation and loss (for example, by affecting downstream hydrology and flow regime, altering sediment flux and converting upstream riverine habitat to lentic impoundments). Fishes face the widest variety of threats, also being frequently affected by invasive species and disease.”

This study puts into words what many anglers and conservationists have said for years—that the freshwater world needs more help and attention than it currently receives.

The study’s authors point to an all-hands-on-deck effort to reverse course (something else anglers have long called for).

“Pollution, dams, and water extraction” are major threats to freshwater species, and addressing those problems won’t be simple.

“These primary threats are systemic in their effects and will require changes in water management practices…integration with the water sector and improved consideration of biodiversity in water development and governance…is, therefore, an essential component of tackling declines in freshwater species.”

As an example of what that sort of solution may look like, let’s give the Henry’s Fork Foundation some attention.

The Henry’s Fork has gone through documented declines in insect hatches over the past decade. One potential cause of that problem are the flows from Island Park Reservoir, which can impact silt load and water temperatures in the river. The Foundation has worked with the reservoir managers to tweak flows in a way that’s beneficial for both agriculture and anglers, and while conditions aren’t perfect, there’s improvement in aquatic insect populations numbers and river turbidity.

The simple fact that dam managers and anglers are working together to solve a problem as important as the Henry’s Fork both lays a foundation and gives hope that similar projects can happen across the world.