The heather, the most characteristic plant of our treeless high hills and mountains, the mountain hare, ground-nesting birds like the golden plover and the hen harrier are among those species suffering from high densities of sheep.
``They are literally nibbling away the wildlife value of the uplands and leaving farmers with a long-term problem,'' said botanist and environmentalist David Bellamy, president of the nation's network of wildlife trusts.
``Hills and moors that used to be a blaze of purple heather in late August are now a uniform green colour - much like a suburban lawn. They are just a shadow of their former glory.''
A report from the trusts, Crisis in the Hills, points out that the number of sheep in the UK has risen by more than a third in the last 20 years to 44 million - which means four sheep for every five human inhabitants. Wales, northern England and parts of Greece have the highest stocking densities for sheep in the European Union.
It cites government research which shows at least half of the country's moorland heather is in a poor or suppressed condition, liable to further reductions and damage by sheep grazing.
There are about 60,000 farmers working the uplands. They mostly earn far less than their lowland, crop-growing counterparts but they have the bulk of Britain's grazing animals.
Their land is designated by government as a "less favoured area" because of the harsh climate and poor soil, and this entitles them to subsidy for each sheep and head of cattle they keep. This amounts to about pounds 30 per annum for each breeding ewe; the subsidies totalled pounds 655m last year.
This payment per head has encouraged the overstocking. While the more fragile upland habitats can tolerate fewer than two ewes per hectare without deterioration, in some areas there are more than seven.
Over the years more and more sheep have been spending the entire year on the hills, rather than only the summers, with farmers giving them supplementary feed through the long winters. This has sharply exacerbated the grazing and erosion damage.
In 1994, the subsidies were reformed with incentives to encourage lower stocking densities, but the wildlife trusts - which have 260,000 supporters and 2,000 nature reserves between them - say the changes did not go nearly far enough.
The report calls for several further changes - the most fundamental of which is to scrap subsidies based on the number of animals and replace them with payments based only on the area of land a farmer manages.
A spokesman for the Ministry of Agriculture said: "We are trying to strike a balance between environmental issues and maintaining viable farming, and this balance has shifted towards the environment."
Voluntary premium payments were available for farmers who reduced the density of sheep in sensitive areas. Furthermore, the Government had powers to withdraw subsidies when areas became severely overgrazed and it had occasionally threatened to use them. "But we prefer to work on a voluntary, goodwill basis when there is a problem," the spokesman added.Reuse content