The Trust have been concerned for some time about the declining numbers of certain types of visitors, so with the help of the volunteers they have created a water feature in a wild pleasure – garden setting. This is to attract a select group of visitors to the Centre with sustainable conservation in mind – it’s for the little creatures known as invertebrates which start off the food chain, and which are being lost at an alarming rate.
Where have all the insects gone?
We can probably remember not so long ago when the car windscreen would be covered in dead insects after a trip, but not any more. Then there were the clouds of white fly in the greenhouse, also covering the brassicas on the allotment along with those pesky black fly on the broad beans. What about the greenfly sucking the life out of the roses? These are past events unlikely to return unless Governments are prepared to recognise a problem. Gardeners might be pleased with such a turn of events but the wildlife who depend upon the invertebrates would not be!
In the latest edition of Science there is one such attempt to get the politicians and the public to raise their game. Entomologists have been assessing diversity and abundance across western Germany and have found that between 1989 and 2013 the biomass of invertebrates caught, had fallen by nearly 80%.
This information gives the lie to our obsession with biodiversity – because the international lists of species of conservation concern, known as red lists, do not pick up on alarming losses within relatively common species. So there is a degree of comfort in looking at those lists – but they can deflect attention from the real problem, which is a loss not so much of biodiversity but a loss of bioabundance.
Our preoccupation with killing any insect which comes into view is not helping the situation. Habitats are all very well but we need invertebrates to colonise them. The widespread use of weed-killers and insecticides is devastating the numbers of our most common species. Our arable fields are but sterile savannahs. The whole ecosystem is now so out of kilter that it is only a matter of time before it starts to seriously impact on humans. Some say it’s all down to evolution – now evolution has given rise to a specie with a profound impact on everything, us!
However we cannot blame the loss of bioabundance solely on the lowland farmers, for in upland Wales there are huge areas similarly devoid of insects, which have never been sprayed with chemicals.
There is something we don’t know, or we are not being told – the causes of the loss must be identified. The culprit is undoubtedly airborne, and is routinely present in sufficient concentrations to cause species to fail to breed. The prime suspect is low-level ozone – that is a known toxin affecting plants, animals and humans. It is produced by the interaction of pollutants such as volatile hydrocarbons – unburnt fossil fuel from internal combustion engines – with bright sunlight.
Anyway, the water feature has been in place now for nearly two years and this passion project is being maintained by the volunteers. It might seem to be just a drop in the ocean for restoration, but it’s a start – Ashridge have around thirty ponds requiring an upgrade, but that’s another story. Let’s hope that the new arrivals in Emily’s garden like the conditions and multiply big time!
thanks for the contribution from Hugh Warwick.
I read this post from Hugh Warwick with particular interest. It is drawn from an article he wrote for The Guardian on 13th May. That article refers to a piece written by Gretchen Vogel in the 10th May edition of the prestigious journal Science. Vogel rightly draws attention to shocking declines in insect abundance and describes supporting data collected in Germany over a 30-year period. She laments the lack of standardised long-term data on insects but draws attention to the best data there are – those of the Rothamsted Insect Survey, based at Rothamsted Research in Harpenden (www.rothamsted.ac.uk/insect-survey). The group has been operating two national networks of traps for more than 50 years. Suction-traps, basically 12-metre tall inverted vacuum cleaners, are designed for monitoring agricultural pests, especially aphids, but suck in everything unfortunate enough to fly over the tube. All the samples are stored and thus it has been possible to track changes in abundance and seasonality of a range of insects, and also to weigh the whole lot to get an idea of overall biomass. Light traps, operated by volunteers, monitor moths. The key thing about both networks is that the methodology has changed very little over the half century and thus records are directly comparable across that period. Whilst there are exceptions, a general rule has emerged. Insects that we don’t want, in other words pests, are holding up pretty well whilst insects that we do want are not – a double whammy. Why might this be? The theory that the Rothamsted team proffers is that the characteristics that make insects pests, for example high mobility and high fecundity, also make them highly adaptable to habitat fragmentation and to other environmental changes. Less mobile and less fecund insects have more trouble blasting their way through an increasingly fragmented habitat, and more trouble making up for losses should they be lucky enough to find a new home.
Why my particular interest? Until I retired (two years ago today as it happens), I headed the Rothamsted Insect Survey. I spent the whole of my 36-year career there, working particularly on aphids, from a fundamental understanding of what makes their populations go up and down in time and space, through to practical advice for growers. Should enough volunteers be interested, I’d be happy to give a talk on the group’s work one day.
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