Tuesday, March 11, 2008

Pond life


Every keen naturalist with a garden should have a pond. Do it right, says Steve Head of the Ponds Conservation Trust and you'll have a delightful oasis of diversity. Why ponds are importantImagine yourself in the Iron Age, 2,500 years ago, before the Romans, the agricultural revolution and modern intensive farming.
What would be the biggest differences? Apart from the howling of wolves at night and the serious absence of dental anaesthetics, one thing you would notice is how damp it was. At that time, at least a quarter of the British countryside was wetland and ponds, with a panoply of native species adapted to these conditions.
During the twentieth century alone, we lost more than a million ponds. Modern farming doesn't need ponds for draught animals or even for watering livestock, which now drink piped mains water from troughs. Many ponds have disappeared because of agricultural drainage and the redundancy of mill and forge ponds or have become seasonal by natural successional processes (most ponds fill with silt, peat and vegetation over time, and so unless new holes in the ground are continually created, pond numbers will slowly but inexorably decline).
Water bodiesOur research at the Ponds Conservation Trust has shown that networks of small ponds in the landscape may contain more biodiversity than stream and river habitats and yet have far less legal protection. Even the important EU Water Framework Directive, now being discussed, is likely to offer protection and monitoring only to water bodies larger than five hectares (about eight football pitches) - lakes rather than ponds.
Pond problemsThere are also worrying new threats for ponds. Like coral reefs, they are harmed by raised plant nutrient levels, the result of diffuse pollution from agriculture and road run-off. The consequence is domination by a few abundant species. Invasive exotic species, such as the American signal crayfish, Australian swamp stonecrop and parrot's feather, are spreading fast and ruining the ecological balance of ponds, ditches and streams. In the next 80 years, climate change will bring long, hot, dry summers, stressing the remaining ponds even more.
Even though they are small and usually too fertile, our garden ponds can be reservoirs for common animal and plant species and provide 'stepping stones' for species migrating through the country. There is evidence that 75 per cent of our frog population now lives in gardens.
Every keen naturalist with a garden should have a pond. Do it right, and you will have a delightful oasis of biodiversity.

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