Environmental Science Popularization丨44016 species are endangered, why?

At a time when the world is concerned about climate change and its impact on the environment and the future of humanity, the International Union for Conservation of Nature (IUCN) recently updated the Red List of Threatened Species, which now includes 157,190 species, of which 44,016 species are threatened with extinction.

The IUCN Red List update coincides with the just-concluded 28th Conference of the Parties (COP28) to the United Nations Framework Convention on Climate Change (UNFCCC), with two "firsts" worth noting: the publication of the first comprehensive assessment of the world's freshwater fish species, and the first large-scale evidence of climate change adversely affecting species.

Climate change and biodiversity are now an important issue. To this end, this reporter interviewed Zhang Yan, director of the China Representative Office of the International Union for Conservation of Nature (IUCN), and Jiang Zhigang, former executive deputy director of the National Scientific Committee on Endangered Species and researcher at the Institute of Zoology of the Chinese Academy of Sciences.

Completion of the first comprehensive assessment of the world's freshwater fish species

"The biggest highlight of this update to the IUCN Red List is that the 10-year assessment of freshwater fish has been completed and announced at the time of the update. Zhang Yan said that the assessment of aquatic species is more difficult than that of terrestrial assessment, and the global assessment of freshwater fish species is a very milestone work.

The assessment shows that 25 per cent of freshwater fish species (3 086 out of 14 898 assessed species) are at risk of extinction and at least 17 per cent of threatened freshwater fish species are affected by climate change.

In addition, pollution (which threatens 57% of endangered freshwater fish), dams and water withdrawals (45%), overfishing (25%), invasive species and diseases (33%), these threats have a significant impact and harm to endangered freshwater fish species.

Jiang Zhigang said that freshwater fish are an important source of protein for humans. Seventeen percent of threatened freshwater fish species on the updated IUCN Red List of Threatened Species are affected by climate change, including falling freshwater levels, rising sea levels and the flow of seawater upstream to rivers. This means that we have a deep and comprehensive understanding of the state of freshwater fish worldwide, and this is the first comprehensive assessment of freshwater fish stocks, which can help governments, conservation organizations and citizens take action to focus on freshwater fish and conserve and sustainably use freshwater fish stocks.

The phenomenon of changing the threat level of species is worthy of attention

Species are classified into two categories: assessed and unassessed, and the IUCN Red List assesses seven levels of threat: extinct, extinct in the wild, critically endangered, endangered, vulnerable, near threatened, least threatened, and one category for lack of data. The level of threatened species is adjusted as conditions such as population size and habitat change.

This time, the IUCN Red List has adjusted the endangerment status of some common fish. For example, the threat level of Atlantic salmon was adjusted from Least Concern to Near Threat.

"Because the global Atlantic salmon population declined by 23% between 2006 and 2020. The migration of Atlantic salmon between freshwater and marine habitats is threatened by a variety of factors, including climate change, and Atlantic salmon spawn in fewer rivers in northern Europe and North America than they lived a century ago. Climate change also affects the development of juvenile Atlantic salmon, reducing their food and leading to the invasion of alien species. Jiang Zhigang explained.

In addition, the Steller's sea eagle, an economically important freshwater fish species in Kenya, has gone from being Least Concern to being Vulnerable due to declining populations due to overfishing, habitat degradation due to climate change, and dams reducing freshwater access to the lake.

Jiang Zhigang said that climate change is also a growing threat to green sea turtles, with high temperatures reducing the success rate of green turtle hatching, rising sea levels that may inundate the beaches where green turtles lay their eggs, and ocean warming and currents caused by extreme weather also affecting the growth of seagrass that green turtles feed.

According to the updated IUCN Red List, green sea turtle populations in the central and eastern South Pacific are endangered and vulnerable, respectively.

In addition, bigleaf mahogany is one of the most commercially popular timber species in the world, having been changed from vulnerable to endangered on the IUCN Red List. Models suggest that climate change is expected to make some large-leaved mahogany no longer suitable for growth in their current habitats.

However, there are also some species that have been "downgraded" because of their strong protection.

Scimitaris has gone from being wild extinct to endangered on the IUCN Red List, and saiga has improved from critically endangered to near threatened.

"Thanks to the concerted efforts of the host governments, conservation organizations and local communities, populations of the once-extinct scimitar-horned antelope and the critically endangered saiga in Central Asia have gradually recovered, marking the success of the species conservation project. Jiang Zhigang said.

However, our analysis of the causes of species decline suggests that there is a link between climate change.

Scimitar antelope was once common in Africa's Sahel region, but increasing poaching, combined with extreme drought every decade, caused them to disappear from the wild in the late 90s of the 20th century.

The high mortality rate in the 2015 mass mortality event was triggered by unusually high temperatures and humidity, and this is expected to occur more frequently as climate change intensifies.

In part, this reflects the fact that climate change could still threaten the future of species.

Emphasizing that climate and the biodiversity crisis are inextricably linked

"In the 60s, it was recognized that climate change could have an impact on species, but this is the first time that the IUCN Red List has been assessed on a large scale to prove that climate change is not just catastrophic to a single species or a single species, but has significant adverse effects on a wide range of species on a global scale. Zhang Yan emphasized.

"Climate change is threatening the diversity of life on Earth and undermining nature's ability to meet basic human needs," said IUCN Director-General Grett Aguila. This update to the IUCN Red List highlights the strong link between climate and the biodiversity crisis. Species decline is an example of the havoc caused by climate change, and we have the capacity to take urgent, ambitious action to keep temperature rise below 1.5 degrees Celsius. ”

Although the IUCN Red List update is an update and supplement of some species, it has aroused people's attention to global climate change, and will urge people in all countries to pay attention to the impact of climate change on biodiversity and take concrete actions to implement the Kunming-Montreal Global Biodiversity Framework. Zhang Yan said that from a global perspective, the IUCN Red List is like a Xinhua dictionary in the field of threatened species, which serves as an important reference book to support the Aichi Targets and the Kunmeng Framework.

"The IUCN Red List of Threatened Species provides an early warning of the endangered status of species globally and provides big data for global biodiversity research, while the National List of Threatened Species identifies the threatened status of species in the country and fills the knowledge gap of the Global Red List of Threatened Species. Jiang Zhigang added.

From Atlantic salmon to green sea turtles, from the common freshwater fish in Kenya to the saiga in Central Asia, global climate change is already affecting global biodiversity and the environment in which people live. Climate change has proven to be threatening the survival of more and more species, and it is urgent to address climate change.

Source: China Environment