Environmental Conservation 30 (1): 52–60 © 2003 Foundation for Environmental Conservation DOI:10.1017/S0376892902000043 Recent historical land use change on the South Downs, United Kingdom NIALL G. BURNSIDE*, ROGER F. SMITH AND STEPHEN WAITE Biogeography and Ecology Research Group (BERG), School of the Environment, University of Brighton, Moulsecoomb, Brighton, BN2 4GJ, United Kingdom Date submitted: 19 December 2001 Date accepted: 25 September 2002 SUMMARY sity, identifies lowland calcareous grassland systems as among the most species rich and diverse habitats nationally. There is considerable interest in the fragmentation Agriculture is the principal land-use on the South Downs, and loss of natural and semi-natural habitats, but few and the sympathetic management of this activity is studies have examined the dynamics and mechanisms considered to be of primary importance for the maintenance of change. A temporal analysis of landscape change on of biodiversity (Hutchings & Booth 1996; Sussex Downs the South Downs in Sussex, UK, provides a clear Conservation Board 1996a; Muller et al. 1998; UK description of the process of change over the 20 years Biodiversity Group 1998). Since the Second World War, the 1971–1991. Transition probabilities were calculated landscape of the South Downs has been transformed by agri- from digital interpretations of an aerial photography cultural activities. The trend has been from the livestock time series of West Sussex. The analysis enabled quan- farming on unimproved grassland towards more profitable titative comparison of landscape mosaics within arable and high production grassland systems. Green (1990) different landscape ecoregions and under different records that between 1947 and 1981 large areas of permanent management regimes to be made. Past changes in downland, heathland and woodland nationally were ploughed land use have produced a fragmented downland land- and consequently the area of unimproved and semi-improved scape. The key land conversion sequences identified grassland decreased by around 40%. Due to economic press- show a substantial transition towards arable produc- ures, partly as a consequence of membership of the European tion, often at the expense of the internationally and Union, farming in southern England has moved progress- nationally important unimproved grassland systems. ively towards barley and wheat production (Green 1990). A geographical information system facilitated greater Significant tracts of downland have been ploughed and the understanding of the environmental and topograph- availability of inorganic fertilizers has meant that in some ical characteristics of land converted to arable and areas even thin nutrient-poor soils have been brought into other uses, and highlighted areas for protection and arable production. In many cases, the remaining grassland potential restoration. The patterns of land-use conver- fragments have been modified and have lost much of their sion observed in the study provide a landscape-scale diverse assemblages of flora and fauna (Fisher & Stocklin planning tool for assessing the potential impact of 1997; Brandon 1998). During this post-war boom, reductions agri-environmental policies, plans, and programmes in flock and herd sizes resulted in the abandonment by agri- in semi-natural grassland habitats. culture of some areas of steep lowland escarpments (Green Keywords: land-use change, geographical information 1990). Historically, because of the difficulty of mechanized systems, calcareous grassland, ecoregions access to steep north-facing escapement slopes of the South Downs, these areas had remained uncultivated. Yet, this withdrawal of management, in association with the decline in INTRODUCTION rabbit grazing following the arrival of the Myxoma virus, is Calcareous grasslands are of international conservation suggested by some workers to have led to the development of importance (Department of the Environment 1994; UK less floristically diverse grassland and scrub communities Biodiversity Group 1998), and recognized as species-rich (Sussex Wildlife Trust 1993; Hopkins 1996). plagio-climax communities, reliant upon appropriate grazing Under the current price support system operated within by wild or domesticated animals or cutting management the Common Agricultural Policy (CAP), the intensification (Smith 1980; Bacon 1990; Rodwell 1990; Schläpfer et al. of farming continues to pose a serious threat to natural and 1998). Without sympathetic management the current grass- semi-natural habitats (Blackwood & Tubbs 1970; Green land would change through successional processes to 1990; Brandon 1998; Burnside et al. 1998a). In the UK, deciduous scrub and ultimately mixed woodland. The UK organizations with responsibility for management and Biodiversity Action Plan (Department of the Environment conservation such as the Department of Environment, Food 1994), the UK’s initiative to maintain and enhance biodiver- and Rural Affairs (DEFRA) and the Sussex Downs Conservation Board (SDCB) are attempting to reconcile the conflicting interests of agriculture and nature conservation on * Correspondence: Dr Niall G. Burnside Tel: ϩ44 1273 642425 the downland by offering guidance to farmers and encour- Fax: ϩ44 1273 642285 e-mail: [email protected] aging ‘environmentally sensitive’ farming practices (Ministry Land-use change on the South Downs, UK 53 of Agriculture Fisheries and Food 1997) (Table 1). The METHODS South Downs is one of five areas of England awarded Stage 1 Temporal land-use and habitat data were used to estimate notification in 1987, via the Environmentally Sensitive Areas transitional probabilities and evaluate land-use and habitat (ESA) scheme (Ministry of Agriculture, Fisheries & Food change within a rural and agricultural landscape. Such an 1997). The ESA scheme in operation on the South Downs approach can provide a clear description of the texture and recommends that top-level protection (tier 1) be given to dynamics of the landscapes. This type of modelling approach grassland sites present on the scarp and in the dry valleys (the provides a means by which the different dynamics associated protection and management of existing features), whilst tier 3 with management options can be evaluated. (Buse 1992; prescriptions (reversion of arable land) are applied to other Poudevigne & Alard 1997) areas of arable cultivation on the southern dip slope and The main data source was aerial photographs completed inter-fluves and designed to encourage the reversion of arable and interpreted into the relevant land classes and ground land to chalk grassland or permanent pasture. Despite this truthed by West Sussex County Council (West Sussex designation and management prescription it appears that the County Council & English Nature 1996). The aerial images semi-improved and unimproved grassland areas in the region were rasterized to produce a uniform and consistent coverage remain under threat (Burnside et al. 1998b; Belden 2000; detailing 15 land-use classes on a 100-m grid basis over an Burnside 2000). area of 47 338 ha. A geographical information system (GIS) The objectives of the analysis undertaken were to establish database was established containing land-use data, which the extent and effects of recent human intervention and made possible comparisons of land conversion on the South management on unimproved grasslands on the South Downs among periods 1971, 1981 and 1991. The original Downs, UK. The time period investigated encompassed the classification was aggregated for the purpose of this study immediate aftermath of the agricultural intensification, which into seven classes, namely arable (arable and improved grass- occurred in the 1960s and 1970s, and the initial implemen- land), developed (urban areas and farmsteads), plantation tation of subsequent planning and management policies (woodland plantation areas), grassland (unimproved grass- aimed at protecting and enhancing the nationally and inter- land, c. 75% of which is calcareous grassland), scrub (scrub nationally important calcareous grassland resource. Thus, the habitats), wooded (deciduous and coniferous woodland) and study allowed the effects of market driven and policy driven ‘other’ (orchards, surface-water, marshes, quarries and changes on the landscape between 1971 and 1991 to be heathland) (Table 2). This reclassification was undertaken to quantified. Within the study area distinct ‘ecoregions’ char- reflect the major patterns of land-use change. acterized by management, topography and habitat The South Downs landscape may be divided into various characteristics were identified and used in the analysis and ‘ecoregions’. Bailey (1983) defined ecoregions as large description of the region. Although particular emphasis was geographical regions that include multiple ecosystems, which placed upon the biologically important unimproved grassland are often similar in ecological function. Analysis of the land- systems, other land-use categories fundamental to the land- scape on an ecoregion basis made possible the identification scape mosaic were also considered. Landscape fragmentation of differences in the sequences of conversion for land-use and conversion between different land classes and uses are classes (Table 3) within distinct landscape areas. important characteristics of the landscape mosaic. The study The Sussex Downs Conservation Board (1996b) recognize aimed to quantify spatial and temporal patterns of fragmen- 15 ecoregions or landscape character areas within the South tation.