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Make clean ponds to save freshwater biodiversity

With freshwaters under pressure like no time before, and showing little sign of improving, important good news has come recently from a perhaps unexpected quarter. Jeremy Biggs, Freshwater Habitats Trust, gives details of the lessons learned from the Water Friendly Farming Project and urges us to protect ponds as a critical habitat.

June 2020

With freshwaters under pressure like no time before, and showing little sign of improving, important good news has come recently from a perhaps unexpected quarter.

New research, published in April 2020, has provided striking evidence of the benefits of making new clean water ponds (CWPs) for reversing catchment-wide declines in freshwater biodiversity. In short, making clean ponds led to a remarkably large, landscape-wide, increase in freshwater biodiversity, much more than we normally expect from catchment projects. Making clean ponds – not just any ponds (and that’s important) increased by 25% the number of wetland plant species found in the whole landscape – the total species pool, in all freshwaters, streams ponds and ditches. The number of locally rare wetland species was increased 3 fold. That’s a massive increase given that, so far, most projects have made little or no difference to catchment scale freshwater biodiversity.

The work is part of the Water Friendly Farming project which is a decade long collaborative project of Freshwater Habitats Trust, Game & Wildlife Conservation Trust, University of York and the Environment Agency.
The work has a surprising number of lessons for all of us involved in water management. We’ve picked out five main issues covered in more detail in the policy briefing about the work available on the Freshwater Habitats Trust website.

First, it’s a reminder that ponds - the least protected, and richest, of freshwater habitats - are a linchpin habitat within the water environment. Deliberately excluding virtually all ponds and small lakes from the WFD was a significant mistake by the previous generation of freshwater policy makers. Now there is a chance to change this.

Second, wetland plant biodiversity - in the absence of any practical interventions - declined in the landscape during the course of the 9 year study at the rather fast rate of 1% species lost per annum. We believe this is a typical result as the study area is representative of a large part of lowland England, and is probably occurring all over the farmed lowlands.

Third, ponds with multiple-uses (e.g. intercepting polluted water, and storing water), had only a modest effect on biodiversity, much less effect than the clean ponds. It’s not surprising that adding some more polluted habitats to the landscape didn’t do much for biodiversity. Of course, polluted waterbodies are not lifeless but making more of them is a bit of a pyrrhic victory: our towns and countryside already have plenty of dirty water.

Fourth, ponds were a critical habitat that drove catchment trends – they supported the most freshwater species and most rare species of all the freshwater habitats in the project area. Rather than being a minor part of the freshwater system, they were a critical part. Catchment-scale biodiversity – whether increasing or decreasing – was largely determined by what was happening to the ponds.

Finally, and perhaps most surprising, this is the first study of biodiversity change across all waterbody types in the countryside; most other studies consider only one waterbody type (usually rivers, sometimes lakes) and often over-emphasises the significance of small changes This has important downsides for policy makers who end up promoting work which causes little change even if those changes are ‘statistically significant’.

Fortunately, these new results on clean water ponds have come just in time to influence the revised Blueprint for Water. Hopefully, this means they will go on to have an even wider impact.

The research was published in the journal Biological Conservation and has important practical implications for the management of freshwater biodiversity generally. It also supports and extends the results support many other observations of the exceptional value and impact of ponds.

Jeremy Biggs, Director at Freshwater Habitats Trust

Follow @PondRiverStream and @jeremybiggs

The opinions expressed in this blog are the author's and not necessarily those of the wider Link membership.