Urban ponds and biodiversity

Interviewer: Andy Tootell (Ideas Lab)
Guest:  Ian Thornhill
Recorded: 20/06/2012
Broadcast: 25/06/2012

Intro VO: Welcome to the Ideas Lab Predictor Podcast from the University of Birmingham. In each edition we hear from an expert in a different field, who gives us insider information on key trends, upcoming events, and what they think the near future holds.

Andy: Hello, today I’m with Ian Thornhill who’s a Doctoral Researcher in the field of Urban Ecology at the University of Birmingham’s School of Geography, Earth and Environmental Sciences. Hello Ian.

Ian: Hi there. 

Andy: So do you want to tell me a little bit about what you do?

Ian:  My personal interest is in the ecology of urban areas and my specific research is looking at small water bodies, ponds, within urban areas. 

Andy: Now today we’re going to be talking about urban ponds and biodiversity. You’ve been looking at ponds for around three and a half years now for your research. Why are ponds important?

Ian: Well, urbanisation is a growing trend. Figures from the UN indicate that over 50% of the world’s population now live in urban areas and as such it’s very important that we consider the impacts that this can have on wildlife. My main focus is on the ecological communities of ponds in urban areas. Ponds are generally defined as standing water bodies between 1m² and 2 hectares in area. This is up to about two and a half football pitches in size.  Despite their relatively small size they have been found to contribute significantly to the regional species pool when compared against rivers and streams. They support a huge diversity of life, including dragonflies, aquatic beetles, mayflies, caddisflies and other endangered amphibians such as the great crested newt. However, numbers of ponds in the UK have declined dramatically at quite an alarmingly fast rate. To break it down a little bit for you, in Cheshire there's an estimated 61% loss in pond numbers and that’s between 1870 and 1993 so over quite a short amount of time. 

Andy: Yeah. 

Ian: And results from my own study of Birmingham have suggested that over a similar period, 1902 to 2009, there’s actually been a greater than 80% loss in numbers. 

Andy: So like you say it’s a relatively short amount of time. What’s been going on for these ponds to disappear?

Ian: Well there’s a number of factors that have contributed to pond loss. A main contributing factor in the rural landscape is changes in farming practice, so a number of these ponds were created from the extraction of marl which used to be used as fertilizer on the land or for the watering of livestock. You have urban equivalents to this as well, for example mill ponds which have since become derelict for their initial use.  Consequently a lot of these ponds have become infilled, whether it’s been to make way for development or from natural succession. Moreover, the creation of ponds by natural processes has been inhibited by our use of the land so although many ponds are of manmade origins, they act as surrogates for natural ones that may otherwise ordinarily have occurred. 

Andy: So why does it matter that these ponds are disappearing?  Obviously they’re nice to have but what are the consequences?

Ian: Well this loss in pond numbers causes fragmentation of the habitat across the landscape and lower connectivity and by this I mean increasing isolation of these individual habitat patches and fewer potentially smaller patches across the landscape as a whole. So if you imagine that you’ve got one of your local ponds and there’s been a pollution incident in that pond, if it was more isolated there are fewer neighbours that are close enough to replenish its ecological communities. 

Andy: Right. 

Ian: So there’s far fewer sites that could quickly bring that back to a good quality site. If it was well connected then it would recover a lot quicker. This in time can reduce overall biodiversity. The isolation of ponds in urban areas might also be exaggerated by the landscape in between sites. So if you imagine you’re flying along and you’re a happy mayfly that’s recently come out of the pond then you’re confronted in urban areas by such obstacles as buildings or roads and obviously this is more costly and quite possibly more difficult to disperse across than if you were going across a nice natural environment. 

Andy: A nice open field somewhere. 

Ian:  Indeed. 

Andy: So what other pressures are urban ponds facing apart from this habitat loss which obviously sounds quite dramatic?

Ian:  Well due to their small size, ponds have a limited capacity to buffer against pollution incidents. So if you imagine a river receives a pollution incident, it has quite a lot of water flowing through it that can cleanse it essentially. 

Andy: So flush it out. 

Ian:  Flush it out, yeah.  Whereas ponds are quite vulnerable in that sense.  They also have relatively small catchments such that small changes in their catchments in terms of land use can have considerable effects upon the water quality in the ponds themselves. Now ponds in rural areas have been frequently found to be affected by nutrient excess because of surrounding agricultural landscapes and I’m finding a similar scenario within my study of urban ponds though perhaps not quite for the same reasons. What I’ve found is that nutrient excess is linked to increasing amounts of impermeable surface within quite a small proximity to the site. It’s also affected by increasing amounts of tree cover – not only directly over the site but also again in close proximity.  What this means in terms of the nutrient input into the sites is that as you have more tree cover you have more leaf litter. As this goes into the sites it gets broken down and as it gets broken down you get more phosphates.  More phosphates means more nutrient enrichment and then more algal growth and consequentially from that you get depleted oxygen conditions and you often get a reduced amount of habitat complexity. So there's far less niches for different animals to exploit, so you get a much reduced diversity on site of animals.  Increasing amounts of impermeable surface may also indicate a reduction in the amount of vegetation available to intercept run-off from the surrounding land use before reaching the pond.  It’s currently my task now to try and establish to what extent the connectivity and fragmentation of the landscape and the more local scale impacts in terms of the local land use and the insight habitat, which of those two groups of factors affects the biodiversity of insight. How then can we improve that situation?

Andy: So what’s the impact on us, because we’ve talked about things in an environmental sense but what are the impacts on us?

Ian: Well as I’ve been doing my research in the field I’ve encountered many stakeholders, the general public, land owners and the overwhelming feeling is that people really care about these sites and one of the main things that make people care is the way they feel when they’re within that environment. Now this is where I see a lot of the conservation interests coming from in the future. It’s going to stem from the interests we have to our own well-being. For example, colleagues at the University of Queensland where I recently visited are soon to begin a study into the effects of reduced exposure to biodiversity in urban areas and its effect upon human health and well-being. 

Andy: So basically if we’re deprived of access to the kind of life that ponds spawn or host, we’re all the worse for it. 

Ian:  Yes, absolutely, and I’m sure upcoming research is going to show this all the more and it’s not just the ponds themselves, it’s the associated green space and the other wild areas that we have in diminishing returns within urban areas.  

Andy: So is there anything coming up in the future that has an impact on this area of research?

Ian: Yes, absolutely.  For example there is the Water Framework Directive. This is a European level piece of legislation which requires all surface water bodies to achieve an ecological ‘good status’ by 2015. Now unfortunately ponds, due to their size, may fall underneath the regular monitoring that this Directive is going to require. There's also Pond Conservation in the UK, a UK charity, that are creating over half a million ponds ideally over the next fifty years called the Million Ponds Project

Andy: That sounds like a huge project. 

Ian: Yeah, certainly. And that’s with the idea to replenish these many ponds that have been lost in the landscape. And the other thing is the very thing that makes them vulnerable makes them manageable. They are small sites with small catchments and particularly in urban areas we can do something small with insight within their catchment to make a big difference to them, so there is hope certainly. 

Andy: It seems very much that this is something that everyone should be dealing with, not just the academics and the scientists. These are environments that are obviously important to us and beneficial to us by all accounts. What can we be doing?

Ian: Well, it can start in our gardens, for one.  In urban areas as we’ve got this loss of ponds in the – or the larger ponds – in the wider environment, there are increasing houses and garden ponds associated with these houses.  If we consider our garden as part of a wider network, if we’re part of a community group or a friends of group, consider that pond to be part of a wider environment, a wider pond network, then that would help greatly and particularly if council members can maybe coordinate action at a landscape level between different stakeholders, be they householders or ‘friends of’ groups, community groups, then we can see great improvements. 

Andy: Ian Thornhill, thank you very much for joining me today.

Ian:  Thanks very much for having me. 

Outro VO: This podcast and others in the series are available on the Ideas Lab website: www.ideaslabuk.com. On the website, you can find out how to e-mail us with comments, questions or suggestions for future topics for the podcast. There's also information on the free support Ideas Lab has to offer to TV and radio producers, new media producers and journalists. The interviewer and producer for the Ideas Lab Predictor Podcast was Andy Tootell.