An update on endangered species shows how climate change is a threat multiplier

A quarter of the world’s freshwater fish are threatened with extinction, according to the first comprehensive assessment of these animals by the world’s leading scientific authority on species status.

The findings, published on Monday by the International Union for Conservation of Nature at the UN climate summit in Dubai, United Arab Emirates, are part of the organization’s latest update to its Red List of endangered species. They came as a slew of scientists, advocates and ministers attending the negotiations urged countries to tackle the global biodiversity crisis along with global warming.

Healthy ecosystems store planet-warming carbon while nourishing wildlife, plants and fungi, delivering a double win for the climate and biodiversity. When nature reserves are destroyed, losses are incurred on both fronts.

As climate change increases, it will impact wildlife that is already experiencing staggering declines.

The assessment found that the biggest threat to freshwater fish was pollution, affecting 57 percent of the threatened species in the group. The pollution comes from fertilizers and pesticides running off the fields, from sediment that clogs rivers and streams after the land is cleared, and from human sewage and industrial waste.

Dams and water extraction came in second, threatening 45 percent of endangered freshwater fish. Overfishing, invasive species and diseases are also taking their toll.

“Climate change brings all the other threats together,” says Catherine Sayer, who leads the group’s freshwater biodiversity program.

The update included assessments of 1,640 species of freshwater fish that had never been assessed before, bringing the total to 14,898. That met the threshold of 80 percent of known species in the group, the point at which the IUCN believes a group of species should be assessed comprehensively.

Atlantic salmon, which begin and end their lives in the rivers and streams of North America and Europe, have gone from being a species of least concern to being classified as near threatened. New evidence suggests their global population fell by 23 percent between 2006 and 2020, with climate change affecting them at all stages of life. Dams cut them off from spawning and feeding areas. Pollution from agriculture and logging kills their young.

Gilded catfish, a commercially important species that migrates thousands of kilometers from the mouths of the Amazon and Orinoco rivers to the foothills of the Andes and back, and which previously fell in the category of least concern, are now classified as vulnerable. Hydroelectric dams planned for the Madeira River basin in Brazil and Bolivia are expected to cause a population decline of at least 37 percent within the next 20 years.

And a small, orange and blue iridescent species of killifish from Mozambique, assessed for the first time, was classified as endangered, threatened by agricultural expansion and graphite mining.

The assessment of freshwater fish contributes to a grim trend for biodiversity worldwide. While public attention has long focused on charismatic mammals and birds, there is increasing scientific awareness of alarming declines in a variety of groups. Amphibians appear to be the most endangered vertebrates 40 percent are threatened with extinction, and their status is deteriorating worldwide. For reptiles this is 20 percent. Invertebrates are even more difficult to assess and protect.

Then there are the plants. While a global tree assessment is underway, Current data shows that a third of all tree species are endangered.

Monday’s Red List announcement included an update on the status of bigleaf mahogany, which has long been valued for its fine wood. Threatened by illegal logging throughout its native range, from Mexico south to Brazil and Bolivia, it moved from the vulnerable category to the more critically endangered category.

“Trees are not seen as a finite resource,” said Megan Barstow, who worked on the assessment from her position at Botanic Gardens Conservation International, an umbrella group that aims to prevent plant extinction. “People do not regard wood products as a natural product.”

Scientists emphasize that good conservation works. Two of the species in Monday’s update are even success stories. The scimitar-horned oryx, an antelope whose horns live up to its name, went from extinct in the wild to endangered after efforts to reintroduce the species to Chad. The saiga, an antelope with a cartoonish profile found in Kazakhstan, Mongolia, Russia and Uzbekistan, went from critically endangered to near threatened.

The successes were thanks to strong collaboration between governments, non-profit organizations, scientific experts and local communities, said David Mallon, co-chair of the IUCN Antelope Specialist Group.

A year ago, countries around the world agreed to a series of commitments to halt biodiversity loss, including protecting 30 percent of the Earth’s land, fresh water and oceans by 2030. This month, officials from the United Nations is expected to release information about what countries have done. far.

On Saturday in Dubai, the country leading the current climate negotiations, the United Arab Emirates, and the country leading last year’s biodiversity talks, China, called on countries to integrate their plans to curb climate change and biodiversity loss and align.