Stepping-stones for diversity: ponds and landscape conservation
For many people, ponds can be familiar and everyday freshwater habitats; small patches of water – both natural and man-made – found in gardens, parks, nature reserves and even dense urban areas.
Ponds aren’t just places to feed the ducks or sail toy boats, however, as an growing body of scientific research shows that they are valuable habitats for biodiversity, often for rare and endemic species, and particularly in ecologically-poor urban and agricultural landscapes.
Ponds help generate a range of ecosystem services. They can help buffer flood waters through storing excess rainfall, and similarly retain nutrients and sediments that might be washed away by flood water runoff. Vegetation growth – most notably of reed beds – can provide local-scale storage of carbon, and help cool urban heat island effects.
However, despite their role as beacons for freshwater biodiversity in highly-altered landscapes, ponds are often overlooked by conservation and policy initiatives. The EU Water Framework Directive – which requires European member states to improve water quality to ‘good status’) only covers lakes larger than 50ha (roughly 60 football fields in size – in other words ‘big lakes’). Similarly, only a small number of pond habitats (e.g. Mediterranean temporary ponds) and freshwater species (e.g. the Great Crested Newt, Triturus cristatus) are designated for protection under the EU Habitats Directive.
As a result, ponds are often overlooked and poorly conserved; regularly drained and filled in during building work, or used as dumping grounds for waste, pollutants and invasive species (such as unwanted pets).
However, there is an increasing movement within freshwater ecology and conservation circles to better document and protect pond habitats. In the UK, the Freshwater Habitats Trust has placed pond conservation at the centre of its work, most notably through the ongoing People, Ponds and Water project. For the Trust, pond conservation is an participatory process, involving local communities to document, champion and even create new pond ecosystems. We covered their report on small water bodies on the blog in 2014.
Freshwater scientists are increasingly turning their attention to diversity and importance of pond ecosystems, too, with a burgeoning number of journal papers published over the last decade or so. In an influential 2014 paper in Hydrobiologia, Régis Céréghino and colleagues report on discussions within the European Pond Conservation Network, to suggest that ponds are likely to become ever more important in creating connected landscapes in a changing climate, “Beyond the contribution of individual ponds to the aquatic and terrestrial life, connected networks of ponds are vital as a response to global climate change, by allowing the northward and/or upward movements of species.”
A new paper published in Biological Conservation by Matthew Hill and colleagues studying macroinvertebrate (or aquatic insect) diversity in rural and urban ponds provides more evidence to this growing knowledge base. Hill and colleagues sampled 91 lowland ponds in the English Midlands, across 3 land use types: floodplain meadows, arable and urban ponds, finding over 200 different macroinvertebrate species.
Whilst floodplain ponds supported the greatest macroinvertebrate diversity, those in arable and urban landscapes also held rich insect life, including species of high conservation value. A key finding of this study, therefore, is that ponds are important micro-habitats for biodiversity at a landscape scale. What this means is that whilst floodplain ponds are (perhaps as expected) the most diverse of the three habitats, all the ponds together generate cumulative, connected species diversity in otherwise ecologically-poor landscapes.
Conservationists across the world are increasingly focusing their attentions on conservation within the ‘landscape matrix’. This is an approach that doesn’t only focus on sites of high biodiversity or rare species inside protected areas, but instead seeks to understand, value and protect (often micro-) habitats such as ponds which provide refuges or ‘stopping-off points’ for biodiversity in highly altered landscapes.
As the Freshwater Habitats Trust have demonstrated, the presence of ponds in many people’s everyday landscapes mean that they have a valuable role in potentially connecting the public to issues of freshwater health and conservation.
As yet though, their small size and visibility means that ponds are continuing to ‘slip through the net’ of freshwater policy and conservation initiatives. The new study by Hill and colleagues concludes with a call for a renewed focus on ponds within environmental legislation, and a suggestion that such a ‘landscape approach’ to understanding their value in ecologically-poor environments may be the most appropriate way to help ensure their conservation (and creation) in the future.
So, perhaps next time you pass by your local pond, why not stop and look a little longer: the diversity of life you see might surprise you.