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One quarter of freshwater fish species face extinction

The International Union for Conservation of Nature (IUCN) has raised an alarm about the risk of extinction facing a significant number of freshwater fish species. 

In a report presented at the United Nations climate conference in Dubai (COP28) on Monday, the IUCN’s assessment of nearly 15,000 species revealed that about 25 percent are on the brink of extinction, with climate change affecting at least 17 percent of these threatened species. 

Contributing factors

Rising sea levels are pushing seawater into rivers, exacerbating the threat to freshwater species. Additionally, these species are endangered by factors such as pollution, overfishing, invasive species, diseases, dams, and water extraction. According to the IUCN, pollution affects 57 percent of the at-risk freshwater fish species.

Freshwater ecosystems 

Kathy Hughes, co-chair of the IUCN freshwater fish specialist group, highlighted the critical role of these species in ecosystems, noting their importance to billions of people dependent on freshwater ecosystems and the millions who rely on fisheries for their livelihood. 

“Ensuring freshwater ecosystems are well managed, remain free-flowing with sufficient water, and good water quality is essential to stop species declines and maintain food security, livelihoods, and economies in a climate resilient world,” said Hughes.

Atlantic salmon 

In 2021, the World Wildlife Fund reported that at least 200 million people globally depend on freshwater fish as their primary protein source. The IUCN assessment also pointed to a decline in the global population of Atlantic salmon, classified as near threatened, with a 23 percent decrease from 2006 to 2020. 

Atlantic salmon, which inhabit both freshwater and saltwater, are adversely affected by climate change across their life cycle, including developmental challenges, reduced prey availability, and the expansion of invasive species. Additionally, human-made barriers like dams hinder their access to vital spawning and feeding grounds, while pollution and sedimentation from activities like logging and agriculture increase young salmon mortality.

Climate change

The threat is not limited to freshwater species alone. The IUCN’s updated Red List of Threatened Species now includes 157,190 species, with 44,016 facing the threat of extinction. “Climate change is menacing the diversity of life our planet harbors, and undermining nature’s capacity to meet basic human needs,” said IUCN Director General Dr. Grethel Aguilar.

Climate change poses several significant threats to freshwater species through various mechanisms. Protecting freshwater species from these threats requires global efforts to mitigate climate change and local conservation actions to preserve and restore freshwater habitats.

Temperature changes 

Increasing water temperatures can disrupt the life cycles and breeding patterns of many species. Some species will not survive if the water becomes too warm for their physiological processes.

Altered water levels

Climate change causes changes in precipitation patterns, resulting in altered river flows, lake levels, and wetland areas. This can destroy or reduce habitats for many freshwater species.

Increased pollution

Higher temperatures can exacerbate pollution issues by increasing the concentration of pollutants and reducing the water’s capacity to dissolve oxygen, leading to hypoxic conditions.

Changes in seasonality

The timing of seasonal events, like spring thaw or seasonal rains, is shifting due to climate change. This can affect breeding and migration patterns of aquatic species.

Invasive species and diseases

Warmer temperatures may allow invasive species and new pathogens to thrive in areas where they were previously unable to survive, outcompeting or infecting native species.

Ocean acidification

While primarily an issue for marine ecosystems, the increasing acidity of oceans can affect freshwater systems as well, especially in coastal and estuarine areas.

Habitat fragmentation

Extreme weather events like droughts and floods, which are becoming more frequent due to climate change, can lead to habitat fragmentation, isolating populations and reducing genetic diversity.

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