One of the aims of PondNet is to monitor change in pond condition across England and Wales. We aim to survey 150 ponds in the wider countryside (ponds which are randomly selected) and a minimum of 60 high priority ponds (ponds within protected sites).
High priority ponds:
Twenty-five years ago, when Freshwater Habitats Trust was in its infancy, we undertook the first national survey of ponds in Britain. We collected plants and invertebrate data from over 150 ponds in some of the UK’s most beautiful places – everywhere from shallow serpentine pools on the Lizard to the wildwood lochans of Abernethy Forest in Scotland.
In 2015, our Technical Director, Penny Williams who surveyed the plants in our original survey, returned to 29 survey sites as a volunteer for our HLF funded People, Ponds & Water project. It is was an important piece of information gathering because there are incredibly few long-term data sets for freshwater habitats, and none look at biodiversity changes in our highest quality ponds in National Nature Reserves, SSSIs and National Parks.
The survey results showed that some ponds had retained or increased their richness over the last 25 years – like the wonderful pools in Castor Hanglands NNR near Peterborough and Brown Moss in Shropshire. Unfortunately, this wasn’t typical. Most ponds had lost a significant number of plant species, with the average a worrying 19% decline: from 26 species per pond in the 1990s, to 21 in the same ponds today. Submerged aquatic plants like water-milfoils were particularly vulnerable and declined significantly by over 30%. Uncommon and rare species were also badly hit with many ponds losing their most uncommon plants like Water Violet, Frogbit and Tubular Water-dropwort.
We haven’t yet completed analysis of the data – but provisional results suggests that ponds fared best if they were located in extensive semi-natural landscapes – like moorland grassland, particularly if there were many other ponds and wetlands nearby. The worst hit were small ponds and pools on heathlands that were once grazed, but have now become tree covered and shaded.
The results from these high quality ponds in protected areas closely mirror findings from our previous work with CEH in the wider landscape, which showed that the number of plants in typical lowland countryside dropped by 20% between 1996 and 2008.
Penny will continue the survey work on high quality ponds in 2016 and will be giving PondNet volunteers the opportunity to join her on these survey visits.
Wider Countryside Ponds:
Volunteers from across England and Wales surveyed the first tranche of ponds in 2015. A total of 43 ponds were surveyed for both wetland plants and invertebrate families. We then used PSYM, the Predictive SYstem for Multimetrics, (pronounced sim) to analyse the results. The PSYM method has been developed to provide a method for assessing the biological quality of still waters. The method uses a number of aquatic plant and invertebrate measures (known as metrics), which are combined together to give a single value which represents the waterbody’s overall quality status. Comparing the pond’s real PSYM score with what would be expected in a pristine pond, indicates how degraded the survey pond is. Ponds are then given a quality ranking based on the PSYM score (good, moderate, poor, very poor). PSYM measures also give an indication of possible causes of any damage (e.g. Trophic Ranking Score which can be used to indicate problems with water enrichment).
So far the results indicate that only 10% of the ponds we surveyed in 2015 were in the ‘good’ category. In other words only 4 ponds in the survey were found to be free from degradation. This is a sad but not unexpected result. Countryside Survey results in 2007 showed a similar picture – only 10% of ponds were found to be in good condition, and 80% of ponds were poor or very poor.
We’ve only surveyed a third of the PondNet sites this year, so it’s too early to start drawing conclusions about change in pond condition over the last 10 years. We’d also like to know what sort of landscapes are still supporting good quality ponds and what factors are causing high quality ponds to decline. By the end of 2016 we should be able to begin to answer some of these questions.