Climate change driving multiple species towards extinction at all stages of its lifecycle, assessment noted
Global population of Atlantic salmon (Salmo salar) dropped by 23% between 2006 and 2020, pushing the species from least concern category to near threatened. Photo: iStock About a quarter of the world’s freshwater fish species are at risk of extinction by climate change, a new International Union for Conservation of Nature (IUCN) Red List assessment revealed.
Out of the 14,898 species assessed, 3,086 are at risk of extinction, the IUCN report identified. At least 17 per cent of the threatened freshwater fish species are affected due to decreasing water levels, shifting seasons and rising sea levels pushing the seawater up the rivers, influenced by climate change.
The climatic change risks to fish compound threats from pollution that affects 57 per cent of the freshwater fish species, dams and water extraction that impact 45 per cent and overfishing that hurts 25 per cent, respectively, the IUCN said.
Disease and invasive species harm 33 per cent, the Red List further noted.
“For example, the large-toothed Lake Turkana robber (Brycinus ferox) – an economically important species in Kenya – has moved from least concern to vulnerable on the IUCN Red List due to overfishing, climate-change-driven habitat degradation and dams reducing freshwater entering the lake,” the assessment found.
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New evidence received by researchers showed that the global population of Atlantic salmon (Salmo salar) dropped by 23 per cent between 2006 and 2020, pushing the species from the least concern category to near threatened.
Atlantic salmon are now limited to a small portion of rivers across northern Europe and North America that were inhabited centuries ago. The population was reduced by multiple threats experienced during long-course migration between freshwater and marine habitats, the IUCN said in a statement.
Climate change has affected the entire life cycles of the species, influencing its development at a young age, reducing prey availability and restrictions due to invasive alien species. For example, the Pacific pink salmon has expanded its range towards northern Europe, among others. Further, anthropogenic disturbances such as dams and other barriers prevented access to spawning and feeding bases.
Water pollution and sedimentation, mainly from logging and agriculture, caused higher deaths among young salmon. The assessment also noted concerns and threats to farmed salmon and their lack of adaptability to climate change.
The Red List assessment also revealed that the Central South Pacific and East Pacific green turtle (Chelonia mydas) populations in the areas have moved from the categories of endangered and vulnerable to extinction.
The green turtles face threats from high temperatures that result in poor hatching success and increasing sea levels that threaten to flood their nests and drowning the young. The warming ocean temperatures and changes in currents due to climate change also affect the growth of seagrasses that the species consume, making them susceptible.
The assessment noted that one of the major reasons for green turtle mortality in the region is the incidental bycatch in industrial and artisanal fishing. “Numbers have also decreased as people harvest green turtles and their eggs for their own consumption or to sell at markets,” it pointed out.
The big leaf mahogany (Swietenia macrophylla) is another example, which is one of the world’s most commercially popular timber trees and moved from vulnerable to endangered on the Red List.
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New information received by the researchers revealed that the number of big leaf mahogany has reduced by 60 per cent over the past 180 years across Central and South America. It is the most sought-after timber across the United States, China, and Western Europe for producing veneers, musical instruments, decorative and ornamental features and high-quality furniture.
The drop in numbers has been attributed to unsustainable practices used to harvest the valuable timber from the wild and urban encroachment in tropical areas along with agriculture.
Illegal logging and trade continue to be a threat to the species, the assessment noted, despite having protection under national and international laws. Further, climate change threatens the habitat of the big leaf mahogany too.
In a press release shared by IUCN, Barney Long, environmental conservation organisation Re:wild’s senior director of conservation strategies, said:
It is shocking that one quarter of all freshwater fish are now threatened with extinction and that climate change is now recognised as a significant contributing factor to their extinction risk, which was also recently reported to be a serious emerging threat to amphibians.
It is imperative to safeguard our freshwater systems as they remain the sole home for precious, irreplaceable wildlife while offering humans with many services, he urged.
On a positive note, scimitar-horned oryx (Oryx dammah) is found to be upgraded from extinct in the wild category to endangered. The antelope reintroduced in Chad was once abundant in the Sahel region of Africa. However, its population had disappeared from the world by the 1990s. Increased intense poaching and extreme droughts every decade resulted in its demise by the 20th century.
“Following a long-term international project, the scimitar-horned oryx is now established in the wild, with at least 140 mature individuals ranging freely in the Ouadi Rimé-Ouadi Achim Faunal Reserve in Chad and 331 calves born there by 2021,” the assessment noted.
At present, an increase in poaching levels were observed mainly for dietary and survival needs to support poor population and address food insecurity.
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The Red List has also upgraded the status of Saiga antelope (Saiga tatarica) found in Kazakhstan, Uzbekistan, Russia and Mongolia. The species has moved from the critically endangered to the near threatened category.
The assessment found the population of Saigas in Kazakhstan increased from 1,100 per cent from 2015 to 2022, reaching to 1.3 million in May 2022. The population of the species declined due to poaching for its horns and meat, which was restored with strict anti-poaching measures, awareness and training of officials.
However, the species remains vulnerable to threats due to its susceptibility to disease outbreaks, which resulted in mass mortality in 2010, 2012, 2015 and 2016.
“The high death rate in 2015 is understood to have been triggered by abnormally high temperatures and humidity, conditions expected to become more frequent with climate change,” the statement said.
A statement issued by David Mallon, co-chair of the IUCN SSC Antelope Specialist Group, said:
The scimitar-horned oryx is the fourth large mammal to have been successfully reintroduced to the wild in the past 100 years. The success of this project and the dramatic recovery of the Saiga are the results of strategic vision, strong government commitment and investment, technical support from non-governmental organisations and scientific experts, and collaboration with local communities.
Grethel Aguilar, IUCN director-general, said, “Climate change is menacing the diversity of life our planet harbours and undermining nature’s capacity to meet basic human needs.”
Aguilar said the IUCN Red List update highlighted the strong links between the climate and biodiversity crises, which must be tackled jointly.
“Species declines are an example of the havoc being wreaked by climate change, which we have the power to stop with urgent, ambitious action to keep warming below 1.5 degrees Celsius,” she added.
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