Freshwater fauna faces an uncertain future

Pacific salmon is one of Canada's iconic creatures. Each summer, they complete an average four to five year life cycle by returning from their rich ocean feeding grounds to the creeks and streams where they were born. Here, in the footsteps of their parents, they will lay, die and give birth to the next generation of salmon.

This pbadage from freshwater to the sea and back is sometimes several thousand kilometers long. It can also be dangerous: fish must navigate steep rapids and avoid voracious predators.

But the trek is made more difficult by unnatural challenges. Humans continue to impede and pollute rivers, to fish in excess and to introduce invasive plants and animals. And this is just the tip of the iceberg when it comes to how humans are reshaping freshwater in Canada and around the world.

As part of our research on the migration and conservation of Pacific salmon, we examined the evolution of freshwater ecosystems – lakes, rivers, streams and wetlands – around the world. Society has the finger on the pulse of the oceans, but what about our fresh waters too often forgotten?

Lakes and rivers in crisis

Although freshwater is only a fraction (0.01%) of all the world's waters, it is home to almost 10% of the planet's known animal species, including one-third of all vertebrates (all has a spine). There are even more fish species in freshwater ecosystems than in the ocean.

Unfortunately, this image changes quickly. The World Wide Fund for Nature (WWF) recently released the "Report on the Living Planet 2018", which shows that the loss of freshwater species is more serious than the decline of species on land or in the ocean.

Alarmingly, freshwater species populations have declined on average by more than 80% in 50 years, while land-based and ocean-dwelling creatures populations have declined by less than half.

It is clear that freshwater is in crisis and that trends have worsened over the past decade. But why?

Threats: the dirty dozen

Scientists know that dams, pollution, overfishing and the introduction of new species alter the "aquatic landscapes" of the world and hinder the survival of animals such as Pacific salmon. We have known these threats to freshwater biodiversity for at least a dozen years.

But many things can change in 12 years – and it has happened. With an international team made up of the world 's greatest scientists in freshwater, our new study documents a dozen threats – some new, some growing – freshwater species:

1. A rapidly changing climate
2. Online trade in wildlife and invasive species
3. Infectious disease
4. Proliferation of toxic algae
5. Hydroelectric dam and fragmentation of half of the world's rivers
6. Emerging contaminants, such as hormones
7. Nanomaterials for engineering
8. Microplastic pollution
9. Light and sound interference
10. Coastal freshwater more salty due to the rise in sea level
11. Calcium levels lower than the needs of some freshwater organisms
12. The additive – and possibly synergistic – effects of these threats

Our team is concerned that fresh waters will continue to be neglected. These growing threats and the rapid loss of species are taking place under the surface of the water – as far as the eye can see.

"It's an invisible and silent tragedy that is causing far too little interest," said Steve Ormerod, freshwater ecologist at Cardiff University, Wales. , in the UK, and one of our team members.

We hope to change this story by drawing attention to these 12 critical threats.

We must act now against these threats.

Hope on the horizon?

It's a lot to take. One may have the impression that there is no solution that will change the trajectory of freshwater species. Fortunately, this is not the case and we are highlighting opportunities for conservation gains.

New scientific tools are changing the way we monitor freshwater populations. Environmental DNA, for example, may soon allow us to use a single water sample to identify all fish from a watershed – without ever seeing the species.

Other approaches, including the use of "environmental flows" (electronic flows) to manage the flow of water under a dam, the removal of the dam as well as fish pbades allow to fish like Pacific salmon to get around some of the obstacles we have created.

But the solution does not rely solely on technological advances to reverse the mistakes of the past. We must meet the freshwater needs of people and nature by changing our treatment of freshwater, for example, through our daily actions, by joining or supporting the Alliance for Freshwater Life and by encouraging our governments to join the world. effort to preserve fresh water.

Explore further:
Species of Mediterranean freshwater fish susceptible to climate change