1 Biological Conservation 100 (2001) Short note Land-use and socio-economic correlates of plant invasions in European and North African countries Montserrat Vila` *, Jordi Pujadas Centre de Recerca Ecològica i Ap
1 Biological Conservation 100 (2001) Short note Land-use and socio-economic correlates of plant invasions in European and North African countries Montserrat Vila` *, Jordi Pujadas Centre de Recerca Ecològica i Aplicacions Forestals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Catalonia, Spain Received 5 June 2000; received in revised form 28 December 2000; accepted 16 January Abstract Biological invasions are causing significant ecological impacts and economical costs world-wide. Human activities are the primary cause of this conservation and environmental problem. We conducted a stepwise regression analysis between several land-use and socio-economic parameters and the density of alien species in European and North African countries. We found that the parameters that best explained the density of alien plants were the Human Development Index and imports. The extent of terrestrial transport networks and the percentage of protected areas were the land-use variables that best accounted for the density of alien plants. If we are going to influence policies dealing with biological invasions, more emphasis should be placed on the analysis of land-use and socio-economic determinants at different spatial scales and their changes throughout time. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Alien plants; Developing countries; Drivers of invasion; Invasibility; Landscape 1. Introduction The introduction of alien species is a world-wide phenomenon with recognised negative effects on the conservation of the native biota and the integrity of ecosystems (Lodge, 1993). It also incurs important economic costs (Pimentel et al., 2000). Research on the characteristics of the recipient regions is essential to understand the process of invasion (Vermeij, 1996). The number of studies on the ecological and biogeographic factors that determine the naturalisation and invasion of aliens at the local and regional level is increasing (Sandlund et al., 1996; Starfinger et al., 1998). For alien plants, analysis at the regional level has demonstrated that disturbed and man-made areas are invaded more than pristine areas (Hobbs and Huenneke, 1992; Pysek, 1994). For example, ruderal areas, roadsides and agroecosystems harbour a great number of alien species. Biogeographic surveys have also found that the size of land area and coast perimeter for islands is positively correlated with the number of alien species (Lonsdale, 1999). * Corresponding author. Tel.: ; fax: address: (M. Vila` ). Species introductions and invasion are mainly due to human activities (Elton, 1958), for example, through gardening, horticulture and human traffic (Lonsdale and Lane, 1994; Hodkinson and Thompson, 1997). Changes in land use are important means by which aliens spread and increase. For example, agricultural intensification in the US has led to an increased abundance of aliens in adjacent habitats (Boutin and Jobin, 1998). Fragmentation is another factor enhancing plant invasions (Saunders et al., 1991; Brothers and Spingarn, 1992). However, the protection of natural areas does not guarantee the exclusion of aliens (Lonsdale, 1999). The percentage of alien species is correlated with the number of visitors to protected areas (Chaloupka and Domm, 1986). Likewise, transport networks (e.g. highways, railways, etc.) also enhance immigration rates of new species and the spread of already existing ones (Ernst, 1998). The presumption that trading increases the introduction of aliens is also largely accepted among ecologists and land managers (Jenkins, 1996, 1999; Baskin, 1998). However, the quantification of such associations has scarcely been explored. Overall, land-use and socio-economic factors directly influence the introduction and spread of alien species. There is a general perception that development and /01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S (01)
2 398 M. Vilà, J. Pujadas / Biological Conservation 100 (2001) progress increase the number of alien species (Jenkins, 1996). However, this underlying hypothesis has not been tested on a regional scale. At present, there are international initiatives that incorporate an interdisciplinary approach in developing a comprehensive strategy for addressing the problem of biological invasions. The Global Invasive Species Programme (GISP) is addressing this issue by including the economic impacts of biological invasions as well as the economic activities that are likely to promote them. In this context, a recent publication by Baiocchi and Dalmazzone (2000) has analysed the relative influence of several economic variables on the share of aliens. They have found that disturbances associated with human activities and gross domestic product per capita (GDP) are important determinants of a given country s vulnerability to invasions. In this paper we conduct a regression analysis between several land-use and socio-economic parameters and the density of alien plants in European and North African countries in order to explore th