Tuesday, 16 May 2017

aliens in my garden - and the need for 'a plan for nature'

News from Western Germany that the biomass of invertebrates as measured between 1989 and 2013 has fallen by nearly 80% comes as no surprise. This, of course knocks further dominoes over in the food chain explaining in part why our skies are empty of summers' glories - martins, swallows and swifts. Without air borne invertebrates these lovely birds starve.

Change in land use and the use of insecticides are at the heart of the problem. There is much science too about the effects on our native species of alien species. The World Conservation Union, states that the impacts of alien invasive species are 'immense, insidious, and usually irreversible'. I have yet to hear any of the main political parties putting this calamitous fact anywhere near the heart of their manifestoes.

We battle with the effects of alien species at Cordwood.

One of the dominating horse chestnuts in the Woodland Garden was removed in the winter.  Horse chestnut has four associated insect species. Now, the opened canopy illuminates hazels and maples in burgundies and lime greens growing on the woodland floor among a froth of sky-blue Forget-me-nots and foaming pink tiarellas. In the clearing created by the removal of the large horse chestnut, a common pippistele now paddles through the night sky.
The dry weather over these past six weeks has been an opportunity to clear the thousands of sycamore seedlings and other weeds. Sycamores are among my least favourite introduced species and their profligacy only sharpens my antagonism. Sycamores (like horse chestnuts) block light and moisture from the woodland floor, reducing the diversity of plants growing there. Sycamores have 15 associated insect species compared with 334 invertebrates associated with our native silver birch. My remarkable dad (89) isn't the man he was but he loves hoeing. And so together we hoe. When I stop him to rest he hoes from a seated position. Most of the woodland garden is now sycamore seedling free. This morning the dry spell abated with the day beginning with a shower.  Freshness of May foliage combined with the crispness brought about by recent weeding - stunning.

Our attempts to create a haven for wildlife face many challenges, not-the-least being the pernicious effects of other aliens.
Pheasants aren't native but have naturalised across the country. Our numbers are artificially inflated by birds escaping the guns on the surrounding fields. Millions of the hapless birds are released across the UK each year. The birds reaching safe haven here scavenge beneath the bird feeders and peck anything growing. Their impact on ground invertebrates must be immense.
Although native mallard ducks are on the red list of UK birds of most conservation concern, we have no concerns at Cordwood. There are up to seven - probably escapees from the neighbouring shoot where they are released - fouling the ponds. Invertebrate and amphibian life stands little chance under their onslaught. The garden is subjected to the 'gang rape' aspect of their 'courtship' too. Three males chase a luckless female and crash about among the plants in the Vegetable Garden. The male mallard is one of the few birds with a penis - apparently making his ardent advances more difficult for the females to resist. Recent studies have shown, however, that mallard ducks may have developed a cunning method of fighting back: their bodies can reject the sperm of unwonted advances.
Infernal American grey squirrels are here too, occupying nest box sites intended for native birds, eating wildfood that our native birds and mammals depend upon, damaging trees and destroying bird feeders: an unstoppable tide. The squirrel pox they carry kills the UK's native red squirrels. My lame airgun occasionally makes a popping noise through a gap in the kitchen window sufficient to halt mastication of sunflower seeds for a brief period before it begins again.
Lately feral greylag geese have discovered us. An expeditionary party of six honked over the pond before three landed. I chased them away as the occupants of the annex reached for another handful of slices from their loaf.

On Thursday we join other volunteers working with Nottinghamshire's Biodiversity Action Group. Britain's waters are now plagued by introduced American signal crayfish. Literally plagued. The plague they carry kills our native white-clawed crayfish. The larger signals also out-compete our natives - there's no happy co-existence. Nottingham's own river, the Leen, has sections that are still signal crayfish free and where our white-clawed survive. We will work in fishing ponds in Bulwell catching the signals and thereby trying to help the white-clawed crayfish facing seemingly irreversible decline. It's a difficult task as no areas in the UK have ever been successfully cleared of signal crayfish.

Depressing? My gosh it is. It is time for a consensus for wildlife in Britain. A plan similar in scope to the Marshall Plan that came to our aid after the World War II is required. A plan for nature, agreed by all parties that will halt the terrible declines in wildlife that we are witnessing. It can be done.

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