Some of the themes I wrote about in recent blogs came together in the latest edition of BBC Radio 4’s Costing the Earth , which unpacked the issue of river water quality and, in particular, the pernicious effects of nitrogen and phosphorus on aquatic ecosystems. Overall, I thought that the program did a good job of explaining a complicated issue but it also served as a case study of the issues I wrote about in “Wide Sargassum Sea …”: algae are forever portrayed in the media as if they were A Bad Thing. Paul Knight, Chief Executive of Salmon and Trout Conservation UK, interviewed during the program, described algae in the River Itchen as “… a brown sort of claggy stuff …” and then went on to explain that excessive nutrients “… speed up the growth of algae and the wrong sort of weed”. From which I infer that there is a right sort of weed, but that all algae are universally bad? Pedantic? Maybe …
However, a few minutes later we hear John Slader, also associated with Salmon and Trout Conservation UK, bemoaning the lack of invertebrate life in the River Itchen: “You’ve got to recognise that this is part of a food chain and if these insects aren’t there, what would happen to your swallows, your martins, your wagtails …” The same subtle (or careless) omission: the food chain, of course, extends down to the algae as well as upwards to fish and birds. Successful restoration of chalk streams needs to be based on an understanding of the right sort of algae, as these ultimately create the habitat within which the insects and fish will thrive.
Later in the same programme, Mike Bowes of the Centre for Ecology and Hydrology was interviewed and he pointed out some of the practical problems associated with reducing nutrient concentrations to levels that would reduce the quantities of algae, based on the fine research he has performed over many years in southern England. He then went on to echo some of the points I made in my previous post, “An embarrassment of riches …”: it is possible to reduce the quantities of algae not just by reducing nutrients but also by planting bankside trees in order to create more shade. This would, incidentally, have bonus effects for wildlife and aquatic diversity, and would undoubtedly be much cheaper than removing nutrients. We should, however, remember that this may reduce the risk of eutrophication although the hazard that the nutrients presented would remain.
The program did a good job of presenting the complexity of river pollution and therein lies the challenge: if a problem is complex, there will not be straightforward cause-effect relationships. It should not, perhaps, surprise us that the interviewees representing the pressure group were the ones that simplified the story to a cause-effect relationship (“high nutrients = bad fishing and fewer birds”) whilst the independent academic scientist offered a more nuanced view. And it is perhaps inevitable that algae, the most diverse component of the river ecology story (see “The sum of things …”) are overlooked except when the narrative demands a convenient villain.
Bowes, M.J., Ings, N.L., McCall, S.J., Warwick, A.,Barrett, C., Wickham, H.D., Harman, S.A., Armstrong, L.K., Scarlett, P.M., Roberts, C., Lehmann, K., Singer, A.C. (2012). Nutrient and light limitation of periphyton in the River Thames: implications for catchment management. Science of the Total Environment 434: 201-212.