Natural Heritage Trends: Scotland 2001

Some 60% of rare and endemic vascular plant species examined during 1990-96 were stable or increasing, but the remaining 40% appeared to have fewer populations than were known to exist prior to 1990. Over 40% of native land mammals are thought to be in decline. The geographic ranges of most non-native plant species changed little between the 1950s and 1987-88. Nevertheless, of 58 plant species that increased their range significantly, 31 are thought to have a medium or high adverse impact on native species.

Although the ranges of 80% of butterfly species remained stable or increased between surveys in 1970-82 and 1995-99, widespread species have tended to increase, while scarce species have declined. The geographic ranges of about half of Scotland’s terrestrial and freshwater bird species showed little change between c.1970 and c.1990, but almost one third of species, including 60% of farmland birds, showed marked reductions in range size. A more recent breeding birds survey has shown that 16% of widespread species decreased significantly in abundance between 1994 and 1999. Nearly two-thirds of species given legal protection in Scotland were thought to be stable or increasing in 1997, with 36% in decline.

The majority of wintering waders and wildfowl increased markedly in abundance from the 1970s to the 1990s. Goose populations, in particular, have shown remarkable gains. Most seabird populations also increased between the 1970s and 1980s.

The relatively mild, wet climate of the western seaboard is particularly favourable to lower plants. Some 60% of Europe’s liverwort and moss species occur there. Being sensitive to air and water pollutants, many have their European stronghold along the Atlantic coast and Western Isles. The richness of bryophyte and other flora of the western Atlantic oak woods has been likened to that of a temperate rain forest. Also noteworthy are Caledonian pinewood remnants of the drier interior, relict arctic-alpine communities of the high mountain tops, expansive blanket mires and heather moorlands that dominate large parts of the uplands, and the varied coastal margins of high sea cliff and shingle shore, sand dune and machair grassland.

Chapter 4 summarises land cover trends from the late-1940s to the late-1980s, a period of rapid growth in farming and forestry, urban development and road building. Consequently, long-established and semi-natural habitats such as heather moorland, peatland, rough grassland and woodland, were reduced in extent. Between around 1947 and 1988 the area of semi-natural habitat in Scotland was reduced by an estimated 17%.

Chapter 5 reports on more recent trends on ‘broad habitats’. Between 1990 and 1998 the extent of fen, marsh and swamp increased by about 19%, pointing to reduced intensity of grassland management and land drainage, with more rushiness appearing in wet grassland. A 9% expansion of broadleaved and mixed woodland was another notable departure from previous trends, reflecting new planting and forest restructuring in the 1990s. There were some signs of a continued conversion of grassland to arable, particularly in the marginal uplands. Previous declines in peatland and acid grassland appeared to have been arrested.

Past rates of decline of heather moorland, or dwarf shrub heath, appeared to have continued in the 1990s, with weak statistical evidence of a 5% reduction in extent between 1990 and 1998. There was also some evidence of declines in the much less extensive neutral and calcareous grasslands. Although there was no clear evidence of change in overall hedgerow length, significant increases in relict hedges with trees and scrub suggested reduced hedgerow management. The length of fencing increased by around 4%.

Small changes in the botanical composition of habitats pointed to nutrient enrichment, favouring competitive species at the expense of plants that are naturally adapted to acidic or nutrient-poor environments.

Chapter 6 describes the development of the UK Biodiversity Action Plan (BAP), which quantifies the extent and nature of the problems facing each of a selection of habitats and species considered threatened in the UK. Action plans offer an approach to tackling these problems, and provide biological objectives and targets against which levels of success may be gauged. Some 41 BAP priority habitats and 261 priority species either occur in, or have recently been lost from Scotland. Among these, four habitats show signs of recovery, while five still appear to be declining. Of 186 BAP priority species recently assessed, 11 were showing signs of recovery, or were thought to have recovered. A further 47 species were thought to be declining. Sixteen species had been lost from Scotland, all prior to the BAP programme.

Trend data indicating progress towards achieving BAP targets are generally available only for priority bird species. Of 20 BAP priority bird species occurring in Scotland, at least 16 seem unlikely to achieve all of their UK plan targets.