Finding 85 groups of wasps on just 10 intensive farms has been a big surprise, writes Michael Viney
Parasitic wasps can be beautiful, in metallic green and blues - that is when they're big enough to see. The smallest of all, called "fairy flies" can be smaller than a pin-head, and none comes near the size of the big yellow-and-black social wasps soon heading for our jam-jars.
The parasites' lifestyle is also a bit down-market: they attack the eggs, larvae and pupae of other insects, often using them as a living larder for their own young. They act as a control on many insect populations - by, for example, killing millions of caterpillars, among them many pests of agriculture.
It's no surprise that Ireland has a lot of different kinds of these wasps - they belong to the largest family of insects, and the 1,500 or so species known in these islands have left plenty more to be discovered. Even so, finding 85 different groups of these wasps, few of them ever recorded in Ireland, on the grassland of just 10 intensive farms, has been a huge surprise. It vindicates the choice of these insects, by the universities' Ag-Biota project, as a key to monitoring the impact of Irish farming on the biodiversity of our countryside.
Is 85 groups of the wasps a lot to be found in fields of heavily-fertilised ryegrass? We don't know. Perhaps a similar search of 10 "unimproved" meadows, with their undisturbed diversity of native plant species, would find 850 groups of the wasps preying on 10 times the variety of insects. What Ag-Biota has produced is a baseline and a sensitive research tool with which to monitor change. The real surprise is how little we seem to have known about this branch of Ireland's insect life. For years, Dr Martin Speight, chief insect expert of the National Parks and Wildlife Service, has deplored the lack of attention to creatures which, as he puts it, are "the glue that holds the biosphere together."
His special area of expertise is the Syrphidae - the 350 or so hoverflies that dart about to pollinate crops and wild flowers - and his database has already been used to show how intensifying land use, with a loss of hedges, scrub and wetland, can cut hoverfly species by half.
Along with diversity of birds and beetles, trees and shrubs, Ag-Biota has also concerned itself with the survival of earthworms, essential to good soil structure and recycling of nutrients for new plant growth. In one study by its team, on land mechanically cultivated for potatoes, the number of earthworms was reduced from more than 1,100 to 54 per square metre after a single season, and to a scant four worms per square metre the following year. At the same time, the number of species fell from nine to one.
Another disturbing finding from Ag-Biota's early work is that while farms that have joined the Rural Environment Protection Scheme have cut back on stocking rates and fertiliser use, the biodiversity of plants and insects has scarcely improved. This may be because the cattle or sheep are still being grazed intensively within fenced-off strips.