England’s Rivers See Biodiversity Boost Thanks to Reduced Metal Pollution
A significant improvement in freshwater biodiversity in England’s rivers has been directly linked to declining levels of zinc and copper pollution, primarily resulting from the decrease in coal burning and heavy industry, according to new research.
The Rise and Plateau of River Biodiversity
Invertebrates, crucial indicators of a river’s ecological health and biodiversity, experienced a widespread and significant increase in species richness across England during the 1990s and early 2000s. Data from the Environment Agency confirms this positive trend. However, since then, further significant improvements have largely stalled.
To understand this plateau, a team of scientists, led by the UK Centre for Ecology & Hydrology (UKCEH), conducted a comprehensive investigation. They employed statistical modeling to analyze a wide array of chemical and physical factors, including temperature, river flow, and landscape characteristics.
Uncovering the Key Culprit: Zinc and Copper
Researchers meticulously examined an extensive dataset from the Environment Agency, encompassing 65,000 individual observations. This data included pollutant measurements and invertebrate data collected from 1,457 sites between 1989 and 2018.
The study, published in the journal *Environmental Science & Technology* and funded by the Natural Environment Research Council, revealed a compelling finding. While ammonia and organic matter (often associated with sewage effluent) influenced invertebrate diversity, the strongest correlation was observed with zinc and copper concentrations.
Why the Decline in Zinc and Copper?
The researchers attribute the reduction in zinc and copper entering rivers after the 1980s to several key factors:
- Decline in Coal Burning: Coal burning is a significant source of atmospheric metal pollution, which ultimately reaches rivers through acid rain.
- Reduction in Heavy Industry: Heavy industries release metals into the atmosphere and discharge sewage containing pollutants, both of which contribute to river contamination.
- Decrease of Zinc/Copper Domestic ProductsLess metal pollution entered the sewage system.
Expert Insight: Focusing on Metal Reduction
“There is a widespread desire by the public to improve water quality and biodiversity in our rivers,” explains Professor Andrew Johnson, an environmental research scientist at UKCEH and lead author of the study. “But the problem for policymakers is what steps would be most likely to achieve results.”
Professor Johnson emphasizes, “Our study provides strong evidence that concentrations of zinc and copper have the biggest influence on invertebrate species richness, so future attempts to increase freshwater biodiversity are unlikely to bear fruit without further reductions in these metals.”
The Lingering Impact of Abandoned Mines
The highest metal concentrations are still found downstream of abandoned mines, continuing to negatively impact biodiversity. The Department for Environment, Food and Rural Affairs (Defra) has set a target of halving the length of rivers affected by this type of pollution by 2038, as outlined in its Environmental Improvement Plan.
A New Approach to Understanding River Health
Beyond metal reduction, improvements to wastewater treatment processes have also played a role. The Urban Wastewater Treatment Directive has led to better removal of organic matter and ammonia from effluent, further contributing to increased river biodiversity.
It’s important to note that the Environment Agency doesn’t measure every single contaminant. However, the researchers’ statistical analysis incorporated wastewater exposure (linked to organic pollutants and pharmaceuticals) and arable land cover (a proxy for pesticide use). This approach provides a broader perspective on potential stressors.
Instead of only using lab experiments, Professor Johnson stated using statistical methods to look at real world long term data “allows the wildlife themselves to speak to us directly.”
Looking Ahead: Sustaining River Recovery
This research provides crucial insights for future river management strategies. While progress has been made, continued efforts to reduce metal pollution, particularly from abandoned mines, are essential to sustain and enhance the biodiversity of England’s rivers. The findings underscore the importance of addressing specific pollutants and employing data-driven approaches to effectively protect and restore freshwater ecosystems.
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