Dead wood is an extremely important habitat for insects.
Many insects and other invertebrates are declining in areas where they used to flourish. Our insect conservation section explains why we need to be very concerned about this problem, which is mainly due to the fact that we humans are increasingly destroying habitats. The main solution is therefore to conserve habitats but this is easier said than done, since the destruction is the result of our quest for food, housing and prosperity. If we try to leave somewhere for insects to live, there may be a price to pay. This might, for example, be a reduced agricultural yield, or the extra cost of diverting a new road around a valuable wildlife site. On the other hand, insects are so vital to our own existence that we will all have a much greater price to pay if we fail to conserve their habitats. Also, there are plenty of things that we can do at little or no real cost, and some of these are mentioned below.
Insects were thriving perfectly well without humans as long as 400 million years ago. Why do we need to conserve their habitats now?
The problem is that we humans are now very numerous (approx. 6.5 billion) and so we are competing as never before with the species that share the planet with us. Also, a great many people are poor and have yet to take their fair share of the world's resources. You may think that habitat loss is nothing new and should not be portrayed as a new crisis. It's true that our ancient ancestors destroyed some kinds of habitat when they started to cut down forests and to till the soil, but the landscape still contained a diverse and plentiful range of habitats. It is only in the last few decades that modern technology has allowed people to create changes on a scale that now makes conservation so vital.
We already have nature reserves and other areas, which are protected for wildlife. Isn't this enough?
It's not enough if we want to conserve all the species which currently exist. The idea of creating reserves is based on the reasoning that we need most of the Earth's resources for ourselves but that we need to set aside a small proportion as wildlife reserves. In theory, if reserves and other protected areas could represent all the kinds of habitat within a particular region, they might be able to support all the species of that region. Unfortunately, however, it is usually impracticable to set up a fully representative range of reserves.
Even if protected sites could be fully representative, they would not be very successful as 'Noah's Arks'. This is because habitats do not last unchanged for ever in the same locality. Changes in vegetation, for example, can make a locality unsuitable for insect species which previously flourished there. Even from one year to the next, fluctuations in weather can make conditions temporarily unsuitable for a particular species, even if the habitat remains otherwise excellent. When adverse changes affect a locality, the species could become extinct within the general area unless another suitable locality is near enough to be reached by dispersing individuals. A large reserve might contain a number of suitable localities near each other, but a small reserve far from other suitable sites will tend to lose species over a number of years. Even a large reserve will lose species if it is not managed for diversity. The answer is to conserve habitat not only in protected areas, but also wherever we can, within the everyday landscape of farms, forest, towns and so-on. This will help to maintain the network of shifting populations of each species (known as metapopulations).
Can't we manage protected areas, so as to provide better habitats?
The answer is "yes", but no amount of good management in protected areas will remove the need to conserve habitats throughout the landscape. If we know the exact habitat requirements of a particular insect species, we can maintain or create the right conditions for that species by 'gardening' its habitat. The trouble is that we know the detailed requirements only for a very small minority of species. Also, there is a more fundamental problem: 'gardening' for the benefit of a few species, or perhaps only one, may harm others or even drive them to local extinction.
A good basis for managing a nature reserve is to know as much as possible about the main kinds of lifestyle of the species which it supports or has previously supported. Even though the precise requirements of only a few individual species may be known, we can still recognise key habitat features, which are needed by a range of species with similar requirements. For example, research has shown that some grassland insects need a mosaic of short and tall vegetation at different stages of their life cycles. This is almost certainly essential for many other species that have not been studied in such detail. If we were to manage a site only for the few which seem to need only short vegetation (or tall vegetation), this could cause others to die out.
Habitats are often managed in protected areas which are not nature reserves, but are managed for other purposes. In the UK, these include Sites of Special Scientific Interest (SSSI), where farming, forestry or other economic uses are allowed, subject to regulations which are intended to protect the biological or other value of the sites. These sites go some way towards maintaining metapopulations of insect species, but it is also vitally important to conserve habitats in the surrounding land.
What kinds of work need to be done to conserve habitats?
Habitats are being damaged all over the world, and so there are many different situations that need to be tackled. Where natural ecosystems, such as tropical rainforests, still exist, it is important to leave as much of them intact as possible. This often seems a forlorn hope, but the richer countries of the world could do more to help poorer countries to be able to afford to halt or slow down the rate of destruction.
Although there are probably many insect species which depend on natural ecosystems, there are many other species can co-exist with us on land that we use for growing crops, or around our houses, along roadsides and on industrial sites. These include all the species that occur nowadays in countries like the UK, where virtually all the land surface has been managed in some way. Many of these species are now declining because they are being deprived of habitats which developed or persisted alongside our ancestors. Here is a list of some (by no means all) of the things that can be done to conserve the habitats of insects and other invertebrates in the UK and other 'developed' countries:
- Do not destroy hedgerows or dry stone walls so as to amalgamate fields unless this is really necessary.
- Do not cut both sides of a hedge in the same year; this will help the long-term survival of the many invertebrates which live around arable fields.
- Avoid using pesticides and fertilisers around the edges and corners of fields and near hedgerows (follow guidelines for the management of 'conservation headlands'.
- If arable fields are already very large, create uncultivated strips ('beetle banks') across them, so as to restore habitats and to encourage natural enemies of pest species.
- Maximise the habitat potential of set-aside land (PDF, 43K); for example, by providing a wide range of insect food plants and by using herbicides as discriminately as possible.
- Retain unimproved grassland wherever possible.
- If controlling scrub on a conservation grassland, allow a proportion of the woody plants to survive, even if only by leaving the stumps untreated by herbicide.
- If grassland has been re-seeded and fertilised, try to restore a herb-rich sward if possible.
- Control grazing so as to create a mosaic of different sward heights; avoid both over-grazing and under-grazing. (The use of traditional breeds of livestock, suited to local conditions, may help in this kind of management.)
- If economically feasible, try to reduce or stop the use of artificial fertilisers and try to convert 'improved' pasture to a more herb-rich condition.
- If a grassland contains ancient trees (as in a pasture woodland), protect as much of the trees' rooting area as possible from trampling by livestock.
- Try to avoid or restrict the use of veterinary drugs, such as avermectins, which make the dung of livestock toxic to dung-feeding invertebrates.
Woodland and deadwood habitats
- Leave a proportion of trees to age and decay naturally, rather than harvesting them all.
- Keep woodland rides open and sunny, edged by a shrub layer.
- Create glades by periodic coppicing, but not in areas where neglected coppice has become valuable for insects which depend on deadwood or sap-runs.
- Protect ancient and 'veteran' trees (many of which occur in pasture woodland, rather than high forest) and try to ensure that younger trees will eventually take their place.
- Never leave firewood piles in areas (e.g. ancient woodlands or wood pastures) where they would act as 'decoys' for rare deadwood invertebrates.
- In farm woodland schemes, avoid planting areas where there are good habitats for wetland or grassland invertebrates.
Heath, moorland and mountains
- Maintain stands of heather by the periodic cutting or burning of small areas but never burn large areas.
- If open areas are turning into scrub or woodland, cut down some of the trees or scrub so as to protect the open habitat, but always leave some for shelter and for habitat diversity. Retain larger-diameter cut stems for deadwood habitat.
- Make sure that patches or strips of bare ground are always present throughout the area (e.g. avoid the improvement of paths, where this would seriously reduce the amount of bare ground habitat).
Aquatic and water margin habitats
- Do not deepen or straighten streams and rivers; try to support schemes to reverse such changes if they have already taken place.
- If a water body has been artificially deepened, restore gently shelving edges if possible.
- Support projects to protect or restore natural processes such as the dynamic formation of banks of shingle and sand in river beds.
- Maintain open vegetation, such as reedbeds, in marshy areas, but retain some of the woody plants (e.g. willows and alder) for the habitats which they uniquely provide.
- Do not remove fallen timber ('Coarse Woody Debris') from watercourses unless it poses a significant risk to people or property as a result of potential flooding.
- Restore ponds and ditches that are seriously silted up, but never 'all in one go'; always do the work in stages, so that the flora and fauna can recover.
- Avoid building anything in flood plains, where this would involve destroying habitats due to a need for flood defences.
Parks and gardens
- Provide some 'wild' areas. If a formal and tidy appearance is required, it can be achieved by maintaining neat lawns and flowerbeds only in certain areas (e.g. next to paths).
- Keep a compost heap, rather than getting rid of garden 'waste'.
- Use plants which provide habitats for a wide range of insects; not just nectar sources.
- If space allows, create water habitats and deadwood habitats (if any tree has to be cut down for safety reasons, keep a tall stump).
- Try to resist the development of domestic gardens for 'infill' housing.
Brownfield sites (e.g. derelict industrial land)
- As brownfield sites can have as much biodiversity as ancient woodland, try to dispel the myth that it is always better to re-develop them than to build on greenfield land.
- If brownfield land has to be developed for new housing or industry etc, try to ensure that the plans provide for areas of habitat to be retained and then properly managed after the development.
Can anything be done, apart from habitat conservation, to conserve insects?
It's possible to rescue endangered species from extinction by breeding them in captivity and releasing them back into the wild, but this kind of work can succeed only if habitats are conserved. Any project involving the release of specimens should be properly planned so as to avoid doing more harm than good.
Another thing that has been done increasingly in recent years is to impose legal restrictions on collecting. As mentioned in our insect conservation section, this may be a useful precaution in the few cases where a proper risk assessment shows that it might help to save certain insect species from extinction. On the other hand, unnecessary prohibition discourages entomological studies, which are essential for conservation.
Amateurs can help also by telling non-entomologists how important it is to conserve insects and insect habitats throughout the landscape. Becoming active in a local wildlife trust is one of the best ways of doing this. Such organisations welcome people who can lead entomological field meetings or give talks on insects. A lot of help for speakers can be found in the sets of educational invertebrate conservation slide packs which have been published jointly by the AES and Natural England (was English Nature).