Eeek – don’t believe everything you read

It’s a familiar theme of mine that, when it comes to ponds, you don’t want to believe everything your read.

Here are a few myths and misconceptions about garden ponds which you might notice without digging very deep on the web. These are all packed into one paragraph of text from an apparently reputable source. The quote is in italics.

‘It’s an ecosystem in miniature….‘ – I’ve never quite known what to make of this old cliché: ponds are small by definition but they aren’t miniatures of something else. They are ponds! You might think I’m nit-picking but actually this viewpoint – usually put forward by people with a quite limited knowledge of ponds – implies that ponds are inferior versions of something bigger (like a nice big lake or a river). Actually, its taken roughly 100 years from the beginnings of freshwater biology to realise that ponds are not miniature versions of something else, but important in their own right.

‘……most pond plants and creatures prefer sun and warmer water; it [YOUR POND] should be away from excessive shade, something which will also help to avoid too many leaves falling in during autumn.’ – Two for the price of one here. As I’ve noted a few times, plenty of freshwater plants and animals are happy in shade. My Old Pond is in the shade for about half the year, is right next to 20 foot tall trees and shrubs and is in excellent condition (if a little over-loved by frogs this year). In mid-summer, around now, it gets the sun for about 4 of 5 hours  a day, on one side. The leaves, it goes without saying, are an important habitat and food resource – though if your pond is completely full of leaves it won’t be such a great place. This problem looks to be especially bad if you’ve got the traditional 2 foot or more deep sump in the centre of the pond which accumulates a lot of rotting leaves. And I’ve just been speaking at an international pond workshop where we’ve been discussing the fact that polluted ponds are affected by shade (it reduces the variety of plants) but unpolluted ponds are much less impacted. Indeed, clean shaded ponds are as likely to support a wide variety of plants and animals, including the most sensitive species, as open ponds.

‘The larger the better but even a small pond is of great value.’ One of the widely repeated older myths is that the ‘bigger the pond, the better’. This is actually a version of the ‘ponds are just inferior versions of  lakes’ idea: a small thing can’t be important so you want to make it as big as possible. We’ve known for a long time – nearly 20 years now – that many factors as well as size influence how many species you’ll find in a pond. And of course, there is some truth that bigger ponds have more things in – however, to roughly double the number of things in a pond you need to increase the area by 10 x and just as important is how polluted the pond is, how much habitat there is, it’s structure, it’s location and a number of other factors.

We also now have some evidence specifically for garden ponds: in Abingdon we can see that size has only a small influence on the number of invertebrate species found in ponds. Other factors are much more important (fish, pollution) and the two richest ponds were 3 m square and 20 m square.

Interestingly in the 2009 Big Pond Dip there was also a suggestion that Common Frogs bred most frequently in medium sized ponds (up to 5 x 5 m) and were less frequent in bigger ponds.

‘Depth needs to be 2ft (60cm) or more in the middle, giving the pond creatures an ice-free refuge in winter‘. I think we fairly comprehensively dispelled this idea last winter when the coldest winter for some time froze ponds to a depth of 2 or 3 inches. In our garden where the ponds are about 25 cm maximum depth there was no problem with freezing solid and we had no dead amphibians.