Freshwater fish going extinct? Study reveals shocking changes in world’s rivers

UNIVERSITY PARK, Pa. — Scientists warn that freshwater fishing could become a thing of the past within the next 70 years due to rapidly warming rivers and declining oxygen levels. A team at Penn State says these environmental changes pose a serious threat to fish species and aquatic diversity worldwide.

The comprehensive research analyzed nearly 800 rivers and found that 87 percent have experienced warming, while 70 percent are losing oxygen. Both factors are essential for aquatic life, and the research reveals that we could see periods of dangerously low oxygen levels that could cause “acute death” for certain fish species.

“This is a wake-up call,” says corresponding author Li Li, a professor of Civil and Environmental Engineering at Penn State, in a university release. “We know that a warming climate has led to warming and oxygen loss in oceans, but did not expect this to happen in flowing, shallow rivers. This is the first study to take a comprehensive look at temperature change and deoxygenation rates in rivers — and what we found has significant implications for water quality and the health of aquatic ecosystems worldwide.”

The researchers utilized artificial intelligence and deep learning techniques to reconstruct water quality data from rivers across Europe and the United States. This study is groundbreaking because it helps to understand the changes in river environments, which are difficult to monitor due to inconsistent data and numerous variables that affect oxygen levels.

“Riverine water temperature and dissolved oxygen levels are essential measures of water quality and ecosystem health. Yet they are poorly understood because they are hard to quantify due to the lack of consistent data across different rivers and the myriad of variables involved that can change oxygen levels in each watershed,” says Wei Zhi, an assistant research professor at Penn State and the study’s lead author.

image of man fly fishing on river at daytime
Photo by Chris Sarsgard on Unsplash

The alarming results show that rivers are facing ecological changes at a pace even faster than oceans. Such rapid transformations could lead to the extinction of certain fish species and disrupt aquatic ecosystems.

Not only are fish at risk, but the deoxygenation process also increases the release of greenhouse gases and toxic metals into the environment, exacerbating climate change and pollution.

The study revealed that urban rivers are warming the fastest, while agricultural rivers are losing oxygen the quickest. Based on the trends identified, the team also projected that future rates of oxygen loss in rivers could be up to 2.5 times higher than what has been observed historically.

“That was really alarming, because if the oxygen levels get low enough, it becomes dangerous for aquatic life,” notes Prof Li. “Rivers are essential for the survival of many species, including our own, but they have historically been overlooked as a mechanism for understanding our changing climate. This is our first real look at how rivers throughout the world are faring — and it’s disturbing.”

The research serves as a crucial alert for environmental policymakers and conservationists, underlining the need for immediate action to preserve our rivers and the life they sustain.

The study is published in the journal Nature Climate Change.

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South West News Service writer Stephen Beech contributed to this report.

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