River fish populations are increasing amid environmental challenges

River fish populations are increasing amid environmental challenges

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Credit: Unsplash/CC0 public domain

Surprising trends in the abundance and richness of river fish species around the world have been revealed in a new study.

Until now, the prevailing scientific belief has been that increases in species richness and abundance in freshwater ecosystems were the result of recent improvements in water quality in historically industrialized areas.

The new research, led by academics at the University of Sheffield in collaboration with Illinois State University, the University of Tennessee and the University of Washington, has since found that the increase in river fish diversity is not a result of ecosystem restoration, as previously thought, but a result of the increasing dominance of non-native species.

The study published in Nature ecology and evolutionIt revealed an average increase in community abundance of 13% per decade and a 7% increase in species richness.

However, the study also revealed an average decrease of 30% in riverine fish community similarity per decade.

By exploring the impact of human activities on river ecosystems over time, the researchers found that areas experiencing environmental degradation experience faster shifts in river fish communities. The study highlights how the combination of land degradation and human introductions of non-native species is contributing to this accelerating change.

This trend becomes more evident in areas where human impacts have recently intensified. Initially, human actions damage habitats, causing a decline in the number and abundance of native species.

Over a longer period, these activities introduce non-native species, either intentionally or unintentionally, such as through fishing or aquaculture. These non-native species thrive in degraded ecosystems and can outcompete native species that are less adapted to such conditions.

Rivers, lakes and wetlands, which cover less than 1% of the Earth’s surface, are home to about 10% of known species, including a third of all vertebrates. Despite their ecological importance and contribution to essential resources such as food, water, and energy, freshwater systems face increasing threats from human activities.

“In the midst of the current human-induced biodiversity crisis, describing local changes in biodiversity around the world is essential to assess the level of ecosystem degradation,” said Alan Dannett, a postdoctoral research associate at the University of Sheffield and lead author of the study. To evaluate the effectiveness of environmental policy and take adequate conservation measures.

“We want to highlight how biodiversity is changing and why it is important to care about specific species found in different environments. Our research shows that although there has been an overall increase in the number of species over time, this is accompanied by rapid replacement of species. Many of these new species are not native and can adapt to different environments.” affected.

“Contrary to the idea that more species always means a healthier ecosystem, our findings suggest that reported increases may not be good news for ecosystems affected by human activities.”

more information:
Alan Danette et al., Past and recent human pressures are driving rapid changes in riverine fish communities, Nature ecology and evolution (2024). doi: 10.1038/s41559-023-02271-x

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