Читать книгу Nature Conservation - Peter Marren - Страница 9

About 30 years ago, when I was just setting out into the nature conservation world, we used to be slightly apologetic about British wildlife. Almost anything we had, other European countries had better, we thought. Britain has few endemic species worth mentioning, apart from Primula scotica (the Scottish primrose) and the good old red grouse (which, ornithologists insisted, was the same species as the bigger, better-looking continental willow grouse), nor much of world importance, apart from the grey seal (which we were then culling by the hundred) and maybe the gannet. Since then, Britain’s stock has risen considerably. We have places such as the New Forest, St Kilda and the Cairngorms, which are important after all, and more old trees than anywhere north of the Alps. Our marine life, estuaries and Atlantic oak woods are pretty special, and Britain is right at the top of the European liverwort league. I was slightly staggered to hear we have 40 per cent of Europe’s wrens. If Britain sank beneath the waves, quite a lot of species would be sorry.

Britain’s wildlife is important in another way. Natural history is very popular – we have 4,000 RSPB members for every species of breeding bird – and we are very good at it. (Who wrote The Origin of Species? Who lived at Selborne?) Britain probably has the best documented wildlife in the world – all right, we might tie with the Dutch and the Japanese. Our 60-odd butterflies are nothing on the world stage, but the expertise acquired in studying them has been exported worldwide. British bittern experts are in demand internationally, though we have only a handful of bitterns. We might not be much good at protecting wildlife, but we certainly know a lot about it. How well, in fact, are our wild animals and plants faring at the start of the new millennium?

There are some grounds for optimism. The loss of wild habitats with which we are sadly so familiar can now be seen in a historical context – as a feature of the domination of intensive agriculture (including forestry) between 1940 and 1990. The statistics of habitat loss put together by the NCC in 1980 have been much repeated, and certainly paint a grim picture. I will not march through them all again, since statistics tend to have a numbing effect on our jaded twenty-first century minds, and they are meaningless without context. For example, what does the loss of 95 per cent of ‘neutral grassland’ mean? It does not tell us whether all the lost ground was of importance for wildlife, nor whether what remains is of the same value as it was. It does, however, imply that something pretty far-reaching has happened to the landscape, and that perhaps only one unimproved meadow in 20 has survived. Meadows are the biggest losers of the habitat loss stakes, but we have lost almost as much wet peatland and ‘acid grassland’, mainly on former commons and village greens, and about half the chalk downs and natural woods that existed before 1939.

The red grouse, Britain’s most celebrated endemic animal, adapted for life on heather moors. (Derek Ratcliffe)

The official nature conservation agencies publish annual estimates of habitat loss and damage in their annual reports. The loss is ongoing, and although it has fallen since the peak in the agricultural high noon of the 1970s, there is now less habitat to damage. The problem with the figures is that, however they are defined, damage assessment is relative. Some types of ecological damage, such as eutrophication, need a trained eye, while others, such as surface disturbance, may look like damage, but may be harmless or even beneficial. Moreover, the agencies have a bad habit of changing their method of calculation from year to year, and since devolution it has become maddeningly difficult to compare what is happening in England with Scotland or Wales or vice versa. All the same, the losses indicate that statutory protection of wild habitats has not been as effective as many had hoped.

The decline of lowland heath in six parts of England over two centuries. (From Nature Conservation in Great Britain, NCC 1984)

The concensus at the turn of the millennium is that loss and damage has slowed considerably and for some habitats may have halted. SSSIs have acquired a greater land value because of the grants they now attract, and SSSI protection is also more effective than formerly. Also more of them are owned or managed by conservation bodies or benign private owners. For at least one well-documented habitat, hedges, removal is now offset in terms of length by newly planted or repaired hedges (quality is not assessed). Hedgerow removal peaked between 1955 and 1965, when many of the open barley prairies of eastern England were created. The process went on in lower gear, with about 2,000 miles (3,200 kilometres) of hedges removed per year, mainly by arable farmers, but also for urban development, roadworks and reservoirs. The Government’s Countryside Survey found virtually no overall decline in hedges between 1990 and 1998, except in neglected ‘remnant hedges’: about 10,000 kilometres (2 per cent) of hedges were removed, and a similar amount planted. But the survey found evidence for some loss of plant diversity, especially tall grasses and ‘herbs’. The reason why hedges have stabilised is because government no longer pays the farmer to pull them up, but pays him to plant them. Stewardship and other agri-environmental schemes are the main reason why hedges are still planted.

We have lost a lot of wildlife habitat, but conservation bodies saved many of the best places, and the story is by no means all doom and gloom. Today’s problem, which I will turn to in the last chapter especially, is the reduction in habitat quality and diversity, which is all the more insidious because it is hard to measure precisely. When we turn to species, the overall picture is the same. Many species – possibly most species – have declined over the past half-century, but relatively few have become nationally extinct. Some once believed extinct have since reappeared, or have been reintroduced in biodiversity schemes. The best-known victim of the past half-century, the large blue butterfly, has been reintroduced from Swedish stock, which closely resembles the lost British race. Thanks to thorough research and ground preparation by Jeremy Thomas and David Simcox, the project has been a resounding success, and several introduction sites are now open to the public. But there is a very large disparity between the small number of recorded extinctions and the much larger number that seem to be approaching extinction. For example, the JNCC considers that about 20 native wild flowers are extinct (though my own tally makes it nearer ten), but some 200 face extinction in the short or medium term. Similarly, some 29 lichens are considered extinct, but 148 are ‘endangered’ or ‘vulnerable’. The implication is that conservationists are good at saving species at the last ditch, but bad at preventing them from getting that far.

The status of plants and fungi in Britain (based on details from the JNCC’s website)

Invertebrates are often ‘finely tuned’ to their environment and are more vulnerable to change than birds or many wild plants. Their fortunes have varied from group to group. Ladybirds and dragonflies are not doing too badly – ladybirds like gardens, dragonflies like flooded gravel pits – but things are currently looking grim for wood ants, and some bumblebees and butterflies. In a recent review I learned that some 200 species of flies (Diptera) are considered endangered and another 200 or so vulnerable (Stubbs 2001). Granted that flies are mysterious things with rather limited appeal, one wonders what the implications of 400 nose-diving flies could be. If 400 subtle, specialised ways of living are under threat, the environment must be quietly losing variety, losing tiny facets of meaning, like a little-read but irreplaceable book being nibbled away bit by bit by bookworms. Interestingly the author of this review blamed some of the losses on conservationists – ‘inappropriate decisions by amenity and conservation organisations’ – as much as farmers and developers. Tidying up is bad for flies.

Not all species are fated to decline. In a detailed assessment of Britain’s breeding birds by Chris Mead (Mead 2000), the accounts are surprisingly well balanced: some 118 species are doing well and 86 are doing badly. However, the fortunes of different species fluctuate, reflecting the lack of stability in the modern countryside. Some once rare birds, such as Dartford warbler, red kite and hobby, are among those that Mead awards a smiling face, meaning that they are doing well – stupendously well in the case of the kite. Among other smiling faces are gulls, geese, many water birds and seabirds and most raptors. Several species have colonised Britain naturally, notably little egret, Cetti’s warbler and Mediterranean gull, and others, such as spoonbill and black woodpecker, may be on the brink of doing so. The commonest bird in 2000 was the wren, which has benefited from the recent run of mild winters and thrives in suburban gardens. Conservation schemes have probably saved corncrake, cirl bunting, stone curlew, and perhaps woodlark, for now. Perhaps the best news of all is the recovery of the peregrine falcon from a dangerous low in 1963, following the ban on organochlorine pesticides, though it still faces persecution in parts of Britain. We are now quite an important world stronghold for peregrines.

About 14 per cent of our moss and liverwort flora is considered vulnerable, endangered or extinct. This is JNCC’s projection of their respective ‘threat status’. (JNCC)

The losers – Mead’s unhappy faces – include familiar farmland birds such as skylark, song thrush, linnet, grey partridge, lapwing and snipe. Even starling and house sparrow have declined markedly. The problem they all face is lack of food on today’s intensively managed, autumn-sown cereal fields. The red-backed shrike has ceased to breed, and the red light is showing for black grouse and capercaillie, which are finding life difficult in the overgrazed moors and upland woods (and no good just putting up deer fences: the capercaillie crashes straight into them). Interestingly, small birds are faring worse, on balance, than big ones. A birder of the 1960s would be shocked at what has happened to lapwings or golden plovers, but pleased and probably surprised at how well many comparatively rare species have adapted to a changing environment. Stranger things lie just ahead. Try imagining green parakeets stealing the food you left out for the disappearing starlings.

Like birds, some of the smaller mammals have declined more than the big ones. Some carnivores, such as polecat and pine marten, are more widespread today than they were in 1966. The grey seal is much more numerous, thanks entirely to the cessation of regular culling. Deer are also more numerous, though this is a mixed blessing. Though increasing, the red deer is threatened genetically by hybridisation with the increasing, introduced sika deer, and may soon be lost as a purebred species. Bats, as a class, have declined. The best counted species, the greater horseshoe bat, is believed to have declined by 90 per cent during the twentieth century. The present population is estimated to be only 4,000 adult individuals. Only 12 colonies produce over ten young per year (Harris 1993). Rabbits have made a slow recovery from myxomatosis, and are back to about 40 per cent of their original abundance, but occur more patchily than before. The otter has staged a slow recovery, aided by reintroductions, but may take another century to recover its former range across eastern Britain. The real losers are red squirrel and water vole, both victims of introduced mammals. Dormouse and harvest mouse are also declining, apparently because of changes in woodland and agricultural land that reduce food availability. Our rare ‘herpetiles’ (i.e. reptiles and amphibians), sand lizard, smooth snake and natterjack toad, have benefited from site-based conservation and a zealous British Herpetological Society. Most of our freshwater fish seem fairly resilient, but the burbot has been lost and our two migratory shads reduced to rarity status because of pollution and tidal barrages. The char, which likes clear, cold water, has disappeared from some former sites. The powan faces an uncertain future in Loch Lomond following the accidental introduction of a competitor, the ruffe, which eats its eggs. Its relative, the pollan of Lough Neagh, is now threatened by carp, casually introduced nearby to please a few anglers. In the sea, we, with the help of our European friends, have overfished herring, cod and 22 other species, and almost wiped out the skate.

We should not, however, judge the success of nature conservation measures solely by changes in the numbers of well-known animals. Birds are important, because everyone likes them, and because losses and gains among such well-recorded species are important clues to what is happening to their environment. In nature conservation, every bird is a miner’s canary. But birds are almost too popular. In the 1960s, many field naturalists specialised in relatively obscure orders, pond and shore life, and difficult insects, such as beetles or bugs. Today, an oft-heard complaint is that taxonomists are an ageing and diminishing band, and that the few professional ones are nowadays tied up in administrative tasks. The number of people who can identify protozoa, or diatoms, or worms is probably fewer now than a century ago. As a result, we have no idea what is happening to them. All too often, biodiversity has been lost from ignorance, even on nature reserves. Britain’s nature reserves are run by people who would know a hawk from a handsaw at a thousand paces, but to whom invertebrates are just wriggly things that live in bushes.