Alien Plants And Their Influence On Vegetation

There is a high level of plant invasion in the Iberian Peninsula and Balearic Islands. Some of the contributing factors for this are the geographical, climatic and historical characteristics of these territories. The latest estimate of the number of naturalised alien taxa is 17.9% for Portugal and 11% for Spain. A list of 51 major invasive plants on the Iberian Peninsula and Balearic Islands with information about the main invaded habitats and the correspondence with the syntaxa is presented in this chapter. The number of invasions increases greatly every year, as a result of insufficient control measures from the respective authorities, a lack of commitment from the business sector involved and nearly nil public knowledge of the problem. The ecosystems globally most at risk of invasion are wetlands and coastal and riparian habitats. Coastal habitats house many endangered species and plant communities and numerous management strategies focus on them. Wetlands and rivers offer some of the most dramatic examples of displacement of native species and ecosystem disruption by, for example, Azolla filiculoides and Eichhornia crassipes, two of the main aquatic invasive species in the world. In order to highlight the importance of the control of invasive species in endangered habitats, we have chosen two study cases: Baccharis halimifolia, in the estuaries of northern Spain and Carpobrotus edulis in Mediterranean and Atlantic coastal communities.