Temporal and spatial changes in plant dune diversity in urban resorts Ana Faggi & José Dadon Received: 12 August 2010 / Revised: 20 January 2011 / Accepted: 21 January 2011 / Published online: 1 February 2011 # Springer Science+Business Media B.V. 2011 Abstract We investigated the temporal and spatial changes in the floristic composition and abundance in sand dunes along a coastal strip in the province of Buenos Aires (Argentina). Firstly, we analysed changes over a span of 70 years, comparing 41 of our own inventories carried out in 14 beach resorts in 2005–2006 with 18 inventories made in the first half of the XXth century (1930–1940) in the same study area. We grouped sampled plots into four categories for comparison, taking into account the time period (1930–1940 or 2005–2006) and location at each end of the surveyed coastal strip in the northern or southern ‘tourist’ sectors. Secondly, we analysed the effect of afforestation with exotic trees on extant sand dune vegetation for the period 2005–2006. A total of 74 plant inventories were carried out in afforested and natural dunes at the same resorts. In both comparisons we contrasted plant richness, percentage plant cover, similarity and diversity. A cluster analysis was used to classify categories taking into account plant abundance and composition. Significant differences in total diversity were observed between sampling years, suggesting an increase in diversity at the present time due to urbanization and recreation related activities. Nevertheless, no single exotic plant species was clearly dominant across the sampled sites, suggesting that these coastal areas are, up to now, resistant to alien invasion. Diversity indexes discriminated by plant groups indicating different habitat conditions and exotics were shown to be more sensitive to existing changes than to total richness and cover. Keywords Vegetation cover . Afforestation . Urbanization . Atlantic coast . Argentina Introduction Natural dunes are much appreciated and in demand as ideal landscapes for recreation and tourism and, consequently, a series of conflicts between the sustainability of economic activities and the conservation of coastal resources have been on the increase since the latter decades of the XXth century. Residential uses, sea-and-sand tourism, and recre- ation activities set great pressures on the natural processes that shape the landscape. The most noticeable impacts of human activities on the sedimentary cycle and vegetation dynamics can easily be detected. The principal driving forces behind biodiversity change at beach resorts are usually recognised as being changes in land use resulting from urbanization, afforestation and activities associated with tourism (Lemauviel et al. 2005; Van der Maarel and Usher 1997). As dune landscapes are highly dynamic and complex (Rust and Illenberg 1996), land use, watershed processes and biodiversity are often intricately linked to each other and are affected by several inputs. For centuries coastal san dunes have been considered to be fragile systems. To prevent sand drift and to help stabilize the dunes, planting of trees (mostly exotic) have been carried out (Doody 2005). The existence of dunes is greatly imperilled when activities such as sand extraction, dune reshaping, beach cleaning or off-road vehicle riding and A. Faggi (*) CONICET, Museo Argentino de Ciencias Naturales, A.Gallardo 470, Buenos Aires, Argentina e-mail: afaggi@macn.gov.ar J. Dadon CONICET, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina e-mail: dadon@ege.fcen.uba.ar J Coast Conserv (2011) 15:585–594 DOI 10.1007/s11852-011-0148-1