Bulletin

Issue: November/December 2007

News

Saving insects Down on the farm

Many people have been conditioned to think of insects as pests. They have neither appreciated the beneficial roles native insects and other invertebrates play – in soil ecology as pollinators and consumers of pests – nor the dire economic consequences should these roles fail.

Now, a book by Professor of Zoology, Tim New, seeks to help farmers improve their understanding of the diverse range of insects in agricultural ecosystems, a key arena for invertebrate conservation.

‘For example,’ says Professor New, ‘mass loss of pollinating insects already means some crop managers have to hire humans to do the job of bees.’

After decades of conservation effort, work by entomologists like Professor New and market pressure against insecticide residues in produce, many farmers are now sympathetic to more ecologically sensitive crop protection.

His book, Invertebrate Conservation and Agricultural Ecosystems, publishedby Cambridge University Press, buildson this understanding. The book hastwo purposes: to introduce principlesof crop management to invertebrateconservation biologists, and theneed and rationale of invertebrateconservation to agricultural producers.

It analyses research into such practices as leaving unsprayed field margins, conservation of hedgerow trees, ‘withinfield habitats’ for natural enemies of crop pests, planting density, and biological control methods.

The last of these, says Professor New, is particularly controversial, as it may involve releasing insects from overseas and concerns that these may spread and invade more natural ecosystem. The pros and cons of pesticides are presented, with the emphasis on balance rather than controversy.

‘There has been a tradition of antagonism between agriculture and conservation,’ Professor New says. ‘In this book I explore the common aims of both. Now when I talk to farmers’ groups, I have an audience largely sympathetic to landscape management that incorporates measures for invertebrate conservation.’

With some 36 per cent of the world’s land area devoted to agriculture, there has been great loss of biodiversity through alienation of more natural ecosystems. Many insects and other organisms occur only in tiny isolated fragments of their former wide range.

Invertebrate Conservation and Agricultural Ecosystems puts the case forconservation rather than the continuedneglect of insect diversity and otheranimals that interact with crop production.As an entomologist, Professor New is athis most passionate advocating on behalfof these less conspicuous species.

‘For example, an entire “decomposer community”, unknown to most people, inhabits the top few centimetres of soil: snails, slugs, nematodes, millipedes, slaters, woodlice, mites, springtails and worms, to name a few. Arthropods -insects, mites, springtails – are particularly important. Some are called the “webmasters of ecosystems” for their role in releasing nutrients from leaf litter.

‘Parallels occur in many other ecological processes. Most of the important organisms involved in these are almost entirely unknown, other than to a handful of specialists.

‘Many cannot be identified. Even when identification guides exist, many are out-of-date. Reflecting the vast diversity of insects, most entomologists focus on one order (or, even, family) of insects. Many insect orders contain more species than all the vertebrate groups put together – and the chances of a beetle specialist identifying small flies or tiny wasps is remote.’

While fragmentation of habitat through land clearance has had a major impact on many insects, Professor New says other threats include pollution, pesticides and the introduction of exotic species – ‘and conservation measures must heed future changes such as in climate’.

The book, one of nearly 30 by Professor New, was recently reviewed in BioScience and Bulletin of the British Ecological Society, which commend it for taking on the importance of invertebrates and their conservation in the ‘ecological deserts’ we call farms.