# Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?
## 1 Introduction  
In the last 70 years there have been extensive losses of coastal habitats and naturally functioning coastal dune systems globally [1; 2; 3; 4; 5; 6; 7]. This is due to dramatic population expansion and urban development along coastal plains, coupled with changes in land-use practices and climate-related changes in aeolian processes. [8; 9; 10]. Globally this has led to substantial increases in dune fixation (stabilization) and a significant loss of naturally mobile (shifting) dunes [11; 12; 13; 14; 15; 16]. Restoration strategies for coastal dune systems are complex because sandy dunes are exposed to multiple dynamic processes that operate on different temporal and spatial scales [17; 18]. Moreover, dune restoration methods are varied and sometimes conflicting. These range from re-establishment of vegetation, to removal of vegetation and eliminating exotics; the strategy usually depends on the management objectives (reviewed by [2; 19]). Many dune management regimes around the world have focused on promoting dune fixation through the introduction of (sometimes non-native) grasses and nourishment in orderto enhance flood protection and wave erosion defences. These activities have further added to the loss of dune mobility in coastal systems, and their associated specialist species [20; 21; 22; 23; 24; 25]. In this study we test the effect of vegetation removal to see whether it can be used as a tool to restore mobile dune biodiversity. Flora and fauna found on mobile dunes are often psummophilic, endemic species, highly adapted to harsh, seric sandy conditions, and often form unique assemblages [6; 26; 27; 28; 29; 30; 31]. Several researchers recognize that dune fixation, whether through succession or intentional re-establishment, can result in adverse consequences for mobile dune species [14; 24; 25; 32; 33]. In fact, a review of coastal management actions reported that dune fixation always had a negative impact on coastal species diversity, either through species loss or increase (e.g., invasive species), or changes in composition [19]. Most open habitats in Europe are semi-natural, including dry sandy grasslands and coastal dune systems, which have been traditionally maintained by anthropogenic activities for thousands of years [34]. Some argue that pastoral human activity simply replaced natural dynamic dune characteristics such as wind erosion, wildlife grazing and trampling, which had existed prior to the advancement of civilization [1; 35]. Contemporary coastal researchers now advocate actively restoring mobile dunes by removing vegetation and introducing disturbance, in order to reactivate sand mobility and imitate natural disturbances [4; 6; 7; 15; 33; 36; 37; 38; 39; 40; 41; 42; 43; 44]. A disturbance can generally be defined as any event that disrupts the assemblage or population structure, or changes the resource pool, substrate availability or physical environment [45; 46]. It can therefore refer to either natural or anthropogenic events. Three main types of disturbances are commonly recognized; i) pulse disturbances are short-term and sharply delineated in time (e.g., natural flood, wildfire, or deforestation); ii) press disturbances may arise sharply and then reach a constant level that is maintained (e.g., grazing, persistent pollution, or off-road vehicle use), and iii) accumulating ramp disturbances, which occur when the strength of the disturbance steadily increases over time (e.g., drought or build-up of toxic waste; [47; 48]. We investigate two pulse disturbances and one stress disturbance in this study. Mobile coastal dunes are naturally exposed to high degrees of press disturbance in the form of wind erosion and sand burial, as well as pulse disturbances, such as blow-outs and sea storms [15; 49; 50]. As dunes shift inland, weakening of these processes allows perennial species, such as _Artemisia monosperma_, to establish.