The current biodiversity crisis
We are in the middle of a catastrophic biodiversity crisis.
Even here in Britain, a wealthy, developed country with wide-ranging protective legislation, many animal and plant species are declining or have already disappeared.
Britain has already lost several species that were fairly widespread, if not common, within the last century.
Sadly, on current trends, further local extinctions seem almost inevitable -- even in one of the richest countries of the world -- so prospects elsewhere must be grim.
Numerous possible causes for declines
A major problem for conservationists trying to understand, arrest or reverse declines in wildlife is the wide range of possible causes. There are far too many factors to list them all here, but some are
- Habitat loss, for example, hedgerow removal, which was actively encouraged by government policy in the past.
- Degradation of existing habitats. This may be happening in the Raynhams area in Norfolk (UK) as habitats often look promising but seem relatively species-poor.
- Increased risks along migration routes. Long-distance summer migrants, such as shrikes, flycatchers etc, may now be unsustainably depleted by trapping and shooting on their routes southwards. Mist-nets and guns may be easier to obtain now.
- Side-effects of pesticides. For example, though originally claimed to be harmless to vertebrate wildlife, DDT eventually proved to have devastating effects on raptors in the 1960s. Currently neonicotenoids are under strong suspicion.
- Numerous alien introductions, such as red-eared terrapins, signal crayfish, mink etc, which may be incompatible with native species. On occasion 'animal-rights activists' have exacerbated problems of this kind.
- New diseases coming into the country. Ash die-back is an obvious example. The virulent strain of elm disease in the 1970s is thought to have come in from North America.
- Climate change may have been a factor in range expansion or contraction of some species. This may help to explain the increase of some species (heron allies such as great white and little egrets, spoonbills etc. have moved in, firecrests have increased). Briefly golden oriole may have benefitted from warmer summers but now seems to have disappeared again.
- The annual release of gamebirds in huge numbers must present a competition threat to wild birds and perhaps to some mammals too. (For example, a local shoot releases approx. 45000 birds each summer, into an estate of roughly 2300 hectares, implying a rough density of 20 birds per hectare).
- Unsustainable culling levels. Certain species are still, surprisingly, on the legal quarry list in Britain, even though these species are in decline. Frankly, why anyone should feel the need to be shooting black grouse, golden plover, snipe, woodcock and various other species is baffling. Anyone engaged in these activities should use their imagination and find something better to do with their time.
- Egg-collecting. Even today, egg-collecting remains an obsession (or an addiction) with a few individuals, despite the damage these people must know they are causing. When, in the (distant) past, the nightingale population was at a level of 10000 pairs, a few nests emptied by eggers probably had little effect on trends. However, with populations now so small, the damage can be terminal. Around five nests at one particular site in mid-Norfolk are thought to have been emptied in a single year quite recently, probably by just one person. Nightingales are no longer present as breeders at that site.
- Sometimes the factors causing decline are complex and unexpected. Research in south and west Gemany described by Werner Kunz indicates that, superficially, habitat for wrynecks is still present there, but has been degraded, accidentally, by conservation measures. Old orchards are still common, but they are mowed late in the season, and the grass is allowed to grow too long. It turns out that wrynecks, which eat ants, need very short vegetation or even bare ground to be able to find food successfully. (See Weisshaupt et al. 2011, Bird Study 58). Other birds that seem to require patches of bare ground include woodlark and turtle dove.