The historical role of agriculture and gardening in the introduction of alien plants in the western Mediterranean

Abstract

The aim of this study is to clarify the role of gardening and agriculture in the introduction of alien vascular plants to the western Mediterranean Basin during the last century. The main country in which this study is based is Spain. However, other countries in the Western Mediterranean Basin also form part of it. These are Portugal, France, Italy and Morocco. Three percentages were calculated. Firstly, the percentage of alien flora was calculated. Then, we calculated the percentages of species introduced as either a consequence of gardening or of agriculture. The figures were based on thirty-four floristic studies carried out in the western Mediterranean Basin between 1904 and 2006. A regression model, in which the explanatory variable is time and the dependent variables are the three percentages mentioned above, was drawn up with the data obtained. The results show the existence of positive correlation between time and the percentages of total exotic flora and the species introduced through gardening (R = 0.64 and 0.56, respectively) and the negative correlation between time and the percentage of alien species introduced through agriculture (R = -0.43). During the last century, the roles of agriculture and gardening as sources of the introduction of exotic flora to the western Mediterranean Basin were reversed. However, in the areas where the socioeconomic scene is more predominantly agrarian, the role of gardening is still limited.

Comparison of the invasive alien flora in continental islands: Sardinia (Italy) and Balearic Islands (Spain)

“…Increased invasiveness of coastal ecosystems is a result of strong tourist vocation of both territories and the Mediterranean in general, which promotes the degradation of these habitats and the development of gardening activities which act as efficient vectors in the introduction of alien species (Sanz Elorza et al 2009). Moreover, a great part of these taxa are favored due to the Mediterranean climate of their native regions, as A. saligna from Australia, or Carpobrotus sp.…”

Comparación de la flora exótica vascular en sistemas de islas continentales: Cerdeña (Italia) y Baleares (España)

“…Una mayor invasibilidad de los ecosistemas costeros es consecuencia de la fuerte vocación turística de ambos territorios y del Mediterráneo en general, que propicia la degradación de estos hábitats, así como el desarrollo en éstos de actividades como la jardinería que actúan como vectores eficientes en la introducción de especies exóticas (Sanz Elorza & al., 2009). Por otra parte, muchos de estos táxones se ven favorecidos porque vienen de regiones con clima mediterráneo, como A. saligna, procedente de Australia o Carpobrotus sp.…”

“…Su presencia es evidente sobre todo en las zonas donde la agricultura tradicional todavía persiste, en los bordes de los campos o en las antiguas tierras de cultivo. Por su parte, como ya han puesto de manifiesto algunos autores , los neófi-tos son táxones introducidos principalmente para usos ornamentales (Reichard & White, 2001;Mack, 2003;Sanz Elorza & al., 2009) que se han escapado de jardines o parques, llegando a naturalizarse en los há-bitats más antropizados, como los sinantrópicos, una tendencia común a otros territorios (Panetta, 1993;Mack & Erneberg, 2002;Pyšek & al., 2002;DehnenSchmutz & al., 2007aDehnenSchmutz & al., , 2007bMilbau & Stout, 2008).…”

Las invasiones vegetales en sistemas agrícolas. Retrospectiva de los últimos 40 años en Cataluña

“…En los hábitats agrícolas, las principales vías de introducción involuntaria de especies exóticas son la contaminación de lotes de semillas no certificados, la dispersión mediada por el manejo del propio cultivo (p.e. a través de la maquinaria agrícola) o la dispersión involuntaria de especies con interés ornamental o forrajero (Sanz-Elorza et al, 2009). Si una especie está presente de forma esporádica o casual, pero sin haberse establecido aún, se le denomina adventicia.…”