Rivers are warming and losing oxygen faster than oceans, according to a Penn State-led study published today (Sept. 14) in the journal Nature Climate Change. The study shows that of nearly 800 rivers, warming occurred in 87% and oxygen loss occurred in 70%.
THREAT TO RIVER SYSTEMS AND AQUATIC DIVERSITY
The study also projects that within the next 70 years, river systems, especially in the American South, are likely to experience periods with such low levels of oxygen that the rivers could “induce acute death” for certain species of fish and threaten aquatic diversity at large.
UNEXPECTED FINDINGS RAISE CONCERNS
“This is a wake-up call,” said Li Li, Penn State’s Isett Professor of Civil and Environmental Engineering and corresponding author on the paper. “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.”
AI AND DEEP LEARNING UNCOVER TROUBLING TRENDS
The international research team used artificial intelligence and deep learning approaches to reconstruct historically sparse water quality data from nearly 800 rivers across the U.S. and central Europe. They found that rivers are warming up and deoxygenating faster than oceans, which could have serious implications for aquatic life — and the lives of humans.
IMPACT ON HUMAN LIFE AND WATER QUALITY
The National Oceanic and Atmospheric Administration estimates that most Americans reside within a mile of a river or stream, highlighting the significance of this issue for human populations.
“Riverine water temperature and dissolved oxygen levels are essential measures of water quality and ecosystem health,” said Wei Zhi, an assistant research professor in the Department of Civil and Environmental Engineering at Penn State and lead author of the study.
FUTURE PROJECTIONS AND ALARMING TRENDS
The research team developed novel deep learning approaches to reconstruct consistent data to enable systematic comparison across different rivers. Future deoxygenation rates were projected to be between 1.6 and 2.5 times higher than historical rates, indicating alarming trends.
The loss of oxygen in rivers not only endangers aquatic life but also drives the emission of greenhouse gases and the release of toxic metals. The model predicted that, within the next 70 years, certain species of fish could die out completely due to longer periods of low oxygen levels, which would threaten aquatic diversity broadly.
“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,” said Li. “This is our first real look at how rivers throughout the world are faring — and it’s disturbing.”