Predicting trends of invasive plants richness using local socio-economic data: An application in North Portugal $ Ma ´ rio Santos a,n , Raul Freitas b , Anto ´ nio L. Crespı ´ b , Samantha Jane Hughes c , Jo ~ ao Alexandre Cabral a a Laboratory of Applied Ecology, CITAB—Centre for the Research and Technology of Agro-Environment and Biological Sciences, University of Tra ´s-os-Montes e Alto Douro, 5000-911 Vila Real, Portugal b Herbarium, UTAD Botanical Garden, CITAB—Centre for the Research and Technology of Agro-Environment and Biological Sciences, University of Tra ´s-os-Montes e Alto Douro, 5000-911 Vila Real, Portugal c Department of Forest and Landscape, CITAB—Centre for the Research and Technology of Agro-Environment and Biological Sciences, University of Tra ´s-os-Montes e Alto Douro, 5000-911 Vila Real, Portugal article info Available online 16 April 2011 Keywords: Stochastic dynamic methodology Invasive plant richness Geophysical parameters Socio-economic trends Disturbance ecology abstract This study assesses the potential of an integrated methodology for predicting local trends in invasive exotic plant species (invasive richness) using indirect, regional information on human disturbance. The distribution of invasive plants was assessed in North Portugal using herbarium collections and local environmental, geophysical and socio-economic characteristics. Invasive richness response to anthro- pogenic disturbance was predicted using a dynamic model based on a sequential modeling process (stochastic dynamic methodology—StDM). Derived scenarios showed that invasive richness trends were clearly associated with ongoing socio-economic change. Simulations including scenarios of growing urbanization showed an increase in invasive richness while simulations in municipalities with decreasing populations showed stable or decreasing levels of invasive richness. The model simulations demonstrate the interest and feasibility of using this methodology in disturbance ecology. & 2011 Elsevier Inc. All rights reserved. 1. Introduction The invasion of habitats by non-native species is a major cause of ecosystem homogenization and biodiversity loss, with serious deleterious consequences for economic and social systems (Mooney, 2005; Hobbs et al., 2006; Keller et al., 2006; Cuneo et al., 2009). Although the major drivers of invasibility are well known, studies tend to give inconsistent results on the influence of the number of propagules entering a ‘‘new’’ environment, the characteristics of exotic species and the susceptibility of the environment to invasion (e.g. Davis et al., 2000; Stohlgren et al., 2002; Meiners et al., 2008). The cross-scale interactions that characterise invasions present a challenge in understanding system behavior and effects at scales that differ from those where information was obtained (Doren et al., 2009a). Some studies demonstrate that a few selected characteristics appear to deter- mine the success of invasion in disturbed systems and that in undisturbed areas invasive species are absent or within tolerable critical limits for their ecological integrity (Alpert et al., 2000; Lake and Leishman, 2004). As human activities increase, alteration and degradation of autochthonous ecosystems creates new opportunities for invasive species coupled with the massive transport of propagules between regions, resulting in many new introductions of species in natural, semi-natural and artificial ecosystems (Pino et al., 2005; Chyron et al., 2009). Although many colonisations fail for stochastic reasons (Alpert et al., 2000; Taylor and Irwin, 2004; Chyron et al., 2009), increasing levels of accidental or premeditated introductions have amplified oppor- tunities for successful colonisations and play a major role in the growing numbers of successful species (Williamson, 1996; Are ´ valo et al., 2005; Leprier et al., 2008). Species invasions are regarded as enormously complex pro- cesses (e.g. Alpert et al., 2000; Vil  a and Pujadas, 2001; Richardson et al., 2005; Chytry ´ et al., 2005; Meiners et al., 2008; Doren et al., 2009b). A test for using invasive plants as indicators of ecosystem disturbances is to increase the ability to predict the invasiveness of species and the invasibility of habitats and landscapes (Peterson, 2003; Crossman et al., 2011). The most popular tools for assessing ecosystem disturbance to date are biological indices, which reduce the dimensionality of complex ecological data sets to a single univariate statistic or 2 to 3 dimensional ordination plots (Santos, 2009). None of these methods adequately express temporal patterns of structural change when habitat conditions are also substantially changing (Cabral et al., 2007). This lacuna can be overcome by creating dynamic models that capture both structural and composition patterns in systems affected by Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/envres Environmental Research 0013-9351/$ - see front matter & 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.envres.2011.03.014 $ No funding supported the present manuscript. n Corresponding author. Fax: þ351 259 350 480. E-mail addresses: mgsantoss@gmail.com (M. Santos), raulfreitas@portugalmail.com (R. Freitas), aluis.crespi@gmail.com (A.L. Crespı ´), shughes@utad.pt (S.J. Hughes), jcabral@utad.pt (J.A. Cabral). Environmental Research 111 (2011) 960–966