Association between Opuntia species invasion and changes in land‐cover in the Mediterranean region

Abstract

In Mediterranean regions, biological invasions pose a major threat to the conservation of native species and the integrity of ecosystems. In addition, changes in land-cover are a widespread phenomenon in Mediterranean regions, where an increase in urban areas and major changes from agricultural abandonment to shrub encroachment and afforestation are occurring. However, the link between biological invasions and changes in land-cover has scarcely been analyzed. We conducted a regional survey of the distribution of the two alien prickly-pear cacti Opuntia maxima and O. stricta in Cap de Creus (Catalonia, Spain) and related patterns of invasion to spatially explicit data on land-cover/change from 1973 to 1993 to test the hypotheses that the two Opuntia species invade areas that have experienced large land-cover transformations. We found that Opuntia invasion is particularly high in shrublands and woodlands located near urban areas. O. maxima are over-represented in the shrublands and O. stricta in the woodlands that were former crops. Crop coverage has dropped by 71% in this 20-year period. This study highlights the role of past land-cover in understanding the present distribution of plant invasions.

Altered water and nitrogen input shifts succession in a southern California coastal sage community

“…In many areas, native shrubs have encroached into grasslands, apparently due to increased livestock grazing and decreased fire frequency (Harrington 1991, Brown and Archer 1999, Van Auken 2000. In Californian drought-deciduous coastal sage scrub (CSS or ''soft chaparral'') and in other mediterranean-climate shrublands around the globe, the opposite trend is observed, with a frequent conversion of native shrublands to systems dominated by a few invasive species, such as conversion of CSS to nonnative Eurasian grasslands (Stylinski and Allen 1999, Cione et al 2002, Vila et al 2003, Gaertner et al 2009). In a 1998 study resampling the 1930s Vegetation Type Mapping (VTM) survey (Wieslander et al 1933), Minnich and Dezzani documented that 18% of the area once covered by CSS was converted to grasslands dominated by Eurasian species, including Bromus madritensis and Avena barbata (Minnich and Dezzani 1998).…”

“…Adjacent chaparral communities dominated by evergreen sclerophyllous shrubs at slightly higher elevations (''hard chaparral'') do not seem to be experiencing this conversion (Allen et al 2005). Coastal sage scrub and other mediterraneanclimate systems have been identified as biodiversity ''hotspots'' and have decreased in cover by direct land use changes for human activities, making vegetationtype conversions in remaining open space of critical concern (Kirkpatrick and Hutchinson 1980, Myers et al 2000, Vila et al 2003, Bonet 2004, Padilla et al 2009, Manuscript received 9 July 2013; 31 October 2013; accepted 18 December 2013. Corresponding Editor: E. A. Newell.…”

The role of land-use history in major invasions by woody plant species in the northeastern North American landscape

“…In highly altered landscapes, land-use history is arguably the dominant factor in disturbance regimes (De Blois et al 2002;Foster et al 1998), so we might expect that different patterns of land-use change will create distinct ''windows of opportunity'' for invasion (Hobbs 2000;, which should affect distributions of invasive plants. Indeed, several recent papers have pointed to the over-riding importance of land-use history in understanding and predicting the distribution and abundance of plant species in general (Bellemare et al 2002;Donohue et al 2000;Dupre and Ehrlen 2002;Verheyen et al 2003a, b;Vila et al 2003), and of individual invasive species (DeGasperis and Motzkin 2007). But to our knowledge, no comprehensive study has examined how variation in land-use patterns across a heterogeneous landscape influences the presence and abundance of a suite of important invasive species.…”

Weed biological control in the European Union: from serendipity to strategy

“…It has become invasive in Spain, particularly in areas of high disturbance, near urban areas and abandoned fields (Vilà et al 2003;Padrón et al 2011) but also in natural areas where it competes with native vegetation and severely modifies habitats and landscapes. One of its natural enemies, Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae), is a sap-sucking insect, commonly known as a cochineal.…”