Growth in diversity of river life over 30 years signals "continuing recovery" researchers find

Growth in the variety of water creature populations in English and Welsh rivers has revealed “continuing biological recovery from organic pollution, consistent with national scale trends in water quality,” over the 30 years to 2019 according to recent research findings.

The researchers from Cardiff and Swansea Universities and the Environment Agency reported: “Our results are consistent with biological recovery of English and Welsh rivers continuing over 30 years.” The study focused on macroscopic invertebrates – creatures without backbones that can be seen without a microscope such as insect larvae, snails ands worms – at 4,000 sites in England and Wales.

The researchers said, over the study period, "macro invertebrate communities indicated quality improvements," and went on to say the richness in the variety of species "increased in the 1990s, with weaker evidence for a post-2015 gain."

They reported that “recovery was greatest within urban rivers, where improvements in sanitary water quality and [animal and plant life] have been well documented, but improvements were also observed in rural catchments.”

Among other findings reported in an academic paper published in Science of the Total Environment the researchers documented a shift favouring pollution-sensitive life forms over the 30-year period. And they reported a growing prevalence in traits that were in line with better water quality including preference for fast flowing water and feeding by shredding or scraping.

The researchers predicted that “increases in richness and the prevalence of sensitive [categories of living things] will be greater and continue for longer within more heavily urbanised catchments, as they have been more polluted historically leading to greater scope for recovery.”

They warned that it was it was “likely” that the national trends presented in their paper might “disguise local declines” in the variety of categories life forms: “Whilst this national-scale picture is broadly positive, we highlight the need to investigate more local variations or pollutants that depart from this aggregate picture.