How to make a really good wildlife pond: an update

In April 2009 I made some suggestions about how to make a good wildlife pond:

– Clean water

– Plenty of shallows

– Focus on the edges: they’re the place where most things live.

Since then, looking at the ponds in my garden and at ponds in Abingdon more widely, I’d add a couple of further observations.

It looks like one of the hardest things to get right is the water plants. It’s not easy to get a variety of native aquatics growing in new garden ponds – which is perhaps why retailers have focused so much on selling us non-natives like Curly Waterweed (Lagarosiphon major, often called ‘Elodea crispa’) which seem to take quickly and easily more or less wherever they are put.

In fact, in most of the garden ponds I’ve looked at there have been hardly any native water plants – with the exception of duckweeds. Unlike the animals, the water plants really are a bit of a disaster area in most gardens.

Our detailed surveys of Abingdon garden ponds also confirm that the best ponds do indeed have the cleanest water. But there are sometimes exceptions: some low conductivity – pretty clean – ponds have poor wildlife communities – look at the bottom left of the graph below.

The graph shows how as conductivity increases (usually a sign of increased pollution) the number of animal species found in the pond goes down. There is an interesting apparent exception.

In the Abingdon survey there was also another pond which, at first sight, appeared to be an exception to the general rule. This pond – on the upper right of the graph (with a circle around it) had a high conductivity and a high number of species.

But this pond is actually a reminder of the limitations of conductivity as a measure of pollution: conductivity is a cheap, quick and accurate way of measuring the total amount of chemicals dissolved in the water, both those present naturally and those added as a result of human activity. It’s often high where water is polluted, so can give us clues about the presence of pollutants but it doesn’t tell us exactly what is dissolved in the water.

In this case, despite the high conductivity, more detailed measurements of the pond water chemistry showed that this pond had pretty good water quality with near-natural nutrient levels. In this case the high conductivity was caused by there being more calcium in the water than in most other ponds in Abingdon.

Added to that the pond had a completely natural base – being dug into wet peaty soil with no liner – so had better margins than most other ponds. It was also the second largest pond in the survey.

So although it appears to contradict the general trend at first, actually it fits the predictions pretty well.

It really does seem to be important to have clean water.


One Response to “How to make a really good wildlife pond: an update”

  1. Elaine Kneller Says:

    Having just created a new wildlife pond last week, we are eager to read everything and learn new tips. It is so exciting to have a small pond in our garden now.

    Looking forward to the arrival of inhabitants.

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