The effect on coastal vegetation of trampling on a parabolic dune Patrick Hesp a, * , Phillip Schmutz a , M.L. (Marisa) Martinez b , Luke Driskell a , Ryan Orgera a , Katherine Renken a , Natalia Alejandra Rodriguez Revelo b , Oscar Alberto Jimenez Orocio b a Department of Geography and Anthropology, Louisiana State University, 227 Howe/Russell/Kniffen Geoscience Complex, Baton Rouge, LA 70803, USA b Instituto de Ecología, A.C., Km 2.5 Antigua Carretera a Coatepec, Xalapa, Veracruz, Mexico article info Article history: Received 28 October 2009 Revised 16 March 2010 Accepted 17 March 2010 Keywords: Coastal dune Trampling Species richness Dune slopes abstract This paper examines the effect of trampling activity and intensity on the vegetation growing up the cen- tral axis of a tropical coastal parabolic dune at La Mancha, Veracruz State, Mexico. A trampling path was established across the dune with slopes varying from 1° to 34°, and the vegetation cover and richness was sampled after 0, 10, 30, 50, 70 and 100 tramplings. There was a significant decline in relative cover over time as the trampling intensity increased, and rare species disappeared after only 10 tramplings. As the slope increased the rate of decline of relative cover of the dominant species also increased. Within the steeper slope segments of the path (21–25, >25, crest, and relic slipface down-slope segments) between 40% and 80% of the number of species disappear from the survey transect by 100 cumulative tramplings, whereas, only 13–30% of the number of species disappeared from the survey transect within the low/ moderate slope segments by 100 cumulative tramplings. Within the 21–25° slope segment, a staircase morphology was gradually created, while at higher slopes, shearing occurred and linear debris slopes were formed. There was a greater decrease in richness values on steep slopes compared to low/moderate slope angles, independent of trampling intensity. Apart from the 21–25° slope, the creation of bare sur- face area does not appear to be related to slope angle as trampling increases. Published by Elsevier B.V. 1. Introduction Increased tourism in recent years has had severe effects on coastal ecosystems contributing to their destruction and reduction of natural and recreational values (Crawford and Liddle, 1977; Anderson, 1994; Lemauviel and Rozé, 2003; Marion and reid, 2007). The attractive ecological diversity and the distinctive land–water interface of the coastal zone make beaches and their adjacent dune landscapes popular areas for tourism and recreation (Williams et al., 1997). Excessive visitor pressure, however, can physically damage dunes leading to the degradation of this diver- sity (Anderson, 1994; Carter, 1988). Lemauviel and Rozé (2003) ar- gue that human trampling represents the major ecological disturbance of dune ecosystems; and the subsequent monitoring of the resultant ecological change is of noteworthy value as the ef- fects of human trampling are poorly understood and little mea- sured (Liddle, 1975a; Slatter, 1975; Williams et al., 1997; Kutiel et al., 2000; Kerbiriou et al., 2008). In a comparison of the effects of trampling in different environments, Andersen (1995) stated that natural dunes were the most vulnerable to human trampling (cf. Burden and Randerson, 1972). Several researchers have studied the relationships between trampling by humans and changes in vegetation and other charac- teristics (Bayfield, 1973; Slatter, 1975; Crawford and Liddle, 1977; Hylgaard, 1980; Hylgaard and Liddle, 1981; McDonnell, 1981; Sun and Liddle, 1993; Anderson, 1994; Williams et al., 1997; Lemauviel and Rozé, 2003). In general, as trampling intensity increases, spe- cies diversity decreases (e.g. McAtee and Drawe, 1980; Ikeda, 2003), plant cover, biomass, height, and top and root weights is re- duced (e.g. Liddle, 1975b, 1991; Liddle and Grieg-Smith, 1975; McAtee and Drawe, 1980), shoot production is reduced (Bowles and Maun, 1982), the proportion of different species changes (e.g. Westoff, 1971), successional trends are altered (McAtee and Drawe, 1980), some effects are long lasting (Leney, 1974) and spe- cies may be eliminated (e.g. Schofield, 1967), evaporation and soil bulk density is higher (Liddle and Grieg-Smith, 1975; McAtee and Drawe, 1981), soil surface stability and threshold friction velocities are lower (Belnap et al., 2007), and the fauna is affected (e.g. Baccus, 1977; Liddle, 1991). The majority of these studies, however, relate vegetation distur- bance strictly to the intensity of human trampling (i.e., the number of trampling passes). Although vegetation disturbance depends a great deal on the intensity of trampling, Bayfield (1973) and Hylgaard and Liddle (1981) suggest that the effects of trampling are also dependent upon the topography of the path. Williams et al. (1997) indicates that the mechanical forces applied to the 1875-9637/$ - see front matter Published by Elsevier B.V. doi:10.1016/j.aeolia.2010.03.001 * Corresponding author. E-mail address: pahesp@lsu.edu (P. Hesp). Aeolian Research 2 (2010) 105–111 Contents lists available at ScienceDirect Aeolian Research journal homepage: www.elsevier.com/locate/aeolia