Podcast: River pollution and its effects on birds
29 April 2014 by Richard Hollingham
This week in the Planet Earth podcast, Steve Ormerod of Cardiff University and John Clark of the RSPB explain why toxic chemicals banned long ago are still causing problems for Eurasian dippers and their chicks.
To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.
Richard Hollingham: This time in the Planet Earth podcast, how urban river pollution is affecting wild birds. I'm Richard Hollingham and I'm in Cardiff, just north of the city centre beside the River Taff which flows through Bute Park here, rather damp parkland behind me and in front a very full fast flowing river. I'm with Steve Ormerod, Professor of Ecology at Cardiff University and John Clark, Futurescapes Project Manager for the RSPB. Let's start with the birds, John, what sort of bird would we expect to find alongside this urban river?
John Clark: We're in one of these fantastic green fingers, we're in one of the many green areas that stretches throughout the city, but here on the Taff it is a real haven for wildlife and in particular river species, so birds we associate with these quite fast flowing rivers in fact. Now, I'm just actually looking at an assembly of goosander and we often get a range of goosanders here, particularly throughout the winter but really the bird that is a real star of this part of the river is the dipper and for such an urban environment, only really ten minutes from Cardiff City Centre, you can often hear dippers singing and that really rapid flight that they have up and down the river when they are foraging for those aquatic invertebrates that they feed on in these fast flowing rivers.
Richard Hollingham: I'm guessing the fact that it is called a dipper means it feeds off the river; it is dependent on the river?
John Clark: Absolutely. So crucially this species is really distributed along the west of the United Kingdom and particularly in upland areas, but they need these faster flowing river environments where you get highly oxygenated water which is where you get that abundance of these aquatic insects and other invertebrates within the actual streambed.
Richard Hollingham: Now, Steve, you are part of an international team studying the effect of water pollution on wild birds and particularly on dippers in this river. Before we get onto that, what did this river used to be like? It could almost be a rural scene this. We can't see any industry, we can't see any of Cardiff, we can just hear the river and see the trees.
Steve Ormerod: As John described it, it is a green finger going through the city but if you were to be here at 30, 40, 50 years ago something like 60% to 70% of all of these South Wales coalfield rivers were grossly polluted and they were polluted by a mix of colliery effluent, industrial effluent, poorly performing sewage treatment works, leaking trunk sewers and since then like many of Britain's urban rivers they have recovered really quite remarkably.
Richard Hollingham: But you've been studying pollution and the effects of pollution on these wild bird populations and you are still finding effects.
Steve Ormerod: So what's happened is the rivers have cleaned up - birds like the dipper that incidentally have declined, in other parts have started to recolonise these recovering urban rivers and paradoxically that we think is now exposing them to other particular kinds of urban pollutants that they acquire through their food.
Richard Hollingham: What sort of things then?
Steve Ormerod: Some of this is around legacy pollutants and things like PCBs that we've been interested in for quite a long time, using birds like dippers as an indicator of their distribution but also what we've increasingly detected is higher concentrations of things like PBDEs, these flame retardant chemicals, in dippers in South Wales, higher concentrations than anywhere else in songbirds anywhere in the world.
Richard Hollingham: How did you do this? How did you find out that these chemicals were being taken up by these birds?
Steve Ormerod: So there are two different bits to that. One is around using chemical measures, stable isotopes in the food of dippers that we can trace back to origins in waste water, waste water treatment, but of course also we can measure the pollutants directly in the eggs themselves, so we take very, very small samples of eggs and we measure, in fact CEH, Centre for Ecology & Hydrology can measure concentrations of things like PCBs, PBDEs and other chemicals.
Richard Hollingham: What effect is this having? That is the crucial question, because it wouldn't matter if it wasn't having an effect.
Steve Ormerod: So this is really where we are in this story at the present having shown that there are these elevated concentrations here. What we've come on recently to do is to start to monitor the performance of dippers and their chicks in nests and shown these really curious affects happening. So there is, for example, a dearth of female nestlings in nests in these urban rivers. The chicks are lighter for their size than their counterparts in rural areas, so in other words they have a lower weight, and also we're measuring reduced activity among various thyroid hormones and things that should be associated with normal nestling development.
Richard Hollingham: Do you think this is then similar to the effects scientists have seen on fish where you get these sex changes as a result of chemicals in waste water from sewage treatment plants, for example?
Steve Ormerod: The so called gender bending story. I think we're in a slightly different place. So this is around potential developmental effects, thyroid hormones regulate a whole set of different developmental aspects of the way young birds grow and develop and that's where there is this consistency with lower body weight, altered thyroid hormone even though food abundance here is enough to keep the birds going there is something else wrong.
Richard Hollingham: John, does this concern you? You were talking earlier about the health of this river and what's here.
John Clark: It's highlighting some of the specific urban diffuse population that we're experiencing. I mean if you just literally walk another five minutes up to Blackweir at Taff, I live about five minutes further. I come down here in my lunch break, on the way to and from work and regularly I will see a male dipper singing on a fish pass that has been installed underneath the footbridge and that I think is a really important image because it shows that we've done a lot to actually improve a river health, that river pass has put in, there's a water directive EU driver to improve our rivers and there's a whole range of other controls and pollution that has really meant that the rivers once ran black now have this wild life such as dippers, but actually in reaction to that these birds are being exposed to this background pollution and I think it harks back to the likes of Rachel Carson's 'Silent Spring', those stories about that bio concentration of pollutants within those top predators such as Peregrine Falcons, but even a dipper is actually showing us there is more insidious pollutants that are perhaps not as obvious within particularly the urban environment. I think that's why this story is really so important.
Richard Hollingham: And, Steve, PCBs, I mean they've been banned for decades and yet they are still turning up in these birds.
Steve Ormerod: An extremely persistent chemical of course and we are having a look at concentrations of PCBs in dippers for probably over 20 years now. The concentrations have barely declined at all. There is a little bit of change, but really not very much, so we are here dealing with a legacy of the past as well as these slightly more new novel pollutants that we think are having effects.
Richard Hollingham: What can you do about this, John?
John Clark: Well the RSPB works particularly in the upland catchments, we work a lot in partnership, sometimes with water utilities, with water companies and large upland estates trying to tackle those issues with water quality and river quality at source, but here in the urban environment and those urban catchment areas we also need to work in partnership, again with waste water treatment to ensure that you don't get that overtopping at storm events where you get that mixing of untreated water with river waters but crucially it is working in partnerships and it says that what Futurescape is about and that's the project I work on, where we're working at the landscape scale with multiple partners tackling not just wildlife issues but actually wider environmental management problems and challenges such as water quality.
Richard Hollingham: Steve, this is an example where the science can directly feed into the policy, but what would you like to see done?
Steve Ormerod: Well I think there are several science questions still to resolve here about how big the effects are on populations. I would to know far more about the roots through which these pollutants are arising because that tells us something about where we should be regulating more effectively, but also in the end if these birds are indicating environmental quality then we've got to look at just how far the quality effects reach when we're using dippers as indicators of problems of urban living, just how far, just which organisms are effected by those same kinds of pollutants.
Richard Hollingham: You've talked about this green finger, there's the parkland and this river, the trees, the birds here and yet there is still this underlying pollution, it is tackling that last bit of pollution that is the challenge.
Steve Ormerod: Particularly what is an area of South Wales which has an industry or legacy we are still hearing what is dominantly an urban landscape in South Wales in general and let's not forget that worldwide more people now live in urban areas than live in rural areas. We are becoming an urban species and we've got to understand the exposure that that brings in terms of pollutants to ourselves but also to the wildlife with which we share those environments.
John Clark: Well absolutely and remember birds are one of the key barometers on the general health of our environment, so maintaining these sorts of studies looking at, obviously, the physiology but also the ecology of these sorts of species is absolutely vital to answering key questions of how we can manage the environment better for the future.
Richard Hollingham: John Clark from the RSPB and Steve Ormerod from Cardiff University, thank you both, and if you don't believe us when we talk about how rural this scene looks we will put some pictures up on our Facebook page. That's the Planet Earth podcast from the Natural Environment Research Council. I'm Richard Hollingham from the River Taff in Cardiff, thanks for listening.