Biology

Almost a quarter of all freshwater species are at risk of extinction

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Although freshwater ecosystems cover less than 1% of Earth’s surface, they are essential to life on this planet. A new study reveals that freshwater animals are at risk of extinction due to these environmental damages, with 24% of species at risk of extinction.

Thousands of fish, crab, and dragonfly species may become extinct in the coming decades, and many more are likely to become extinct.

A groundbreaking assessment of the health of around 24,000 freshwater species has found just under a quarter are at risk of extinction. Approximately 1,000 of these species are listed as endangered, and 200 of these may already be extinct.

These numbers may be just the tip of the iceberg, and scientists lack the information they need to properly understand the risk of extinction for thousands of species. Katherine Thayer, lead author of the study, said urgent action was needed to understand and protect these animals.

“A lack of data on freshwater biodiversity can no longer be used as an excuse for inaction,” she says. “Freshwater landscapes are home to 10% of Earth’s known species and are key to safe drinking water, livelihoods, flood control and climate change mitigation for billions of people, for both nature and people. must be protected.”

The research results were published in the journal Nature.

What challenges do freshwater habitats face?

Fresh, clean water is essential for all life on land, yet freshwater ecosystems are among the most threatened ecosystems on Earth. As demand for food, water and resources increases, freshwater environments are under pressure.

Wetlands, especially wetlands, mangroves, and salt marshes, bear the brunt of these losses. It is estimated that since 1700, we have lost an area of ​​wetland the size of India (a staggering 3.4 million square kilometers).

The loss of wetlands does far more harm than just the flora and fauna that live there, as it also limits our ability to combat climate change and stop flooding.

Freshwater sources also face various challenges. Increasing water withdrawals and river dams are reducing habitat for wildlife. Some rivers, like the Colorado River, don’t even reach the ocean.

Animals that survive in these reduced habitats are affected by sewage, industry, and plastic pollution. However, despite the increased risks to these species, freshwater environments are less well studied compared to oceans.

Study co-author Dr Topiltzin Contreras McBeath says this needs to change if freshwater species are to have the best chance of survival.

“To support healthy freshwater ecosystems, it is essential to proactively incorporate freshwater species data into conservation strategies and water use management,” says Dr McBeath. “Increased investment in measuring and monitoring freshwater species is needed to ensure that conservation actions and water use planning are based on the most up-to-date information.”

To what extent are various freshwater animals threatened?

About 10% of all species depend on freshwater, but this study focused on four groups that are particularly closely associated with freshwater: Decapoda, Odontata, Molluscs, and Fishes.

Decapods are a large group of crustaceans that include crabs, lobsters, crayfish, shrimp, shrimp, and more. Many species live in the ocean, but many others live in rivers and streams around the world, and about 30% are threatened with extinction.

The main threat to decapods is from pollution, especially agricultural runoff. Many pesticides used to kill insects harm crabs and shrimp when they enter waterways, especially when these animals molt. These chemicals are also a threat to fish and can affect their development, fertility, and behavior.

The order Trematoda is a group of insects that includes dragonflies and damselflies. Although these animals are best known as aerial predators, they spend most of their lives in freshwater as growing nymphs.

As a result, more than half of endangered species are affected by the conversion of wetlands to agricultural land, making them vulnerable to habitat loss. A similar proportion are affected by logging, resulting in the loss of the hunting grounds and shelter they relied on as adults.

Although conservation data for freshwater decapods, fish, and voles were readily available, the study was unable to include molluscs in the analysis due to a lack of information. This is a group that includes not only snails but also other invertebrates such as freshwater mussels and oysters.

Previous studies focusing on molluscs suggest that about a third are at risk of extinction, which increases the overall proportion of endangered freshwater species. Very likely.

Reversing these declines will be difficult because freshwater environments are vast and often interconnected. Cooperation between various stakeholders and countries is essential to give endangered crabs, dragonflies and other freshwater wildlife a fighting chance.

Further information: Catherine A. Sayer et al, “A quarter of freshwater animals at risk of extinction”, Nature (2025). DOI: 10.1038/s41586-024-08375-z

Provided by Natural History Museum

This story is republished with the kind permission of the Natural History Museum. Read the original story here.

Citation: Almost a quarter of all freshwater species are threatened with extinction (January 18, 2025) https://phys.org/news/2025-01-extinction-threatens-quarte-freshwater- Retrieved January 18, 2025 from species.html

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