Abstract
Dune spits of the island of Sylt (North Sea) persisted through millennia by mobile dunes transferring sand from exposed to sheltered shores. However, 150 years of systematic planting on washovers, blowouts and migrant dunes have almost completely stopped this sand conveyor belt. Spits lost sand until sand replenishments to the exposed side compensated for losses during the last three decades. Based on maps since 1878, aerial images from the 1930s onward as well as botanical ground surveys, we document a long-term shift from loose grass cover to dense heather dominated vegetation. Bare sand areas almost vanished and high shrubs proliferated. Only three dunes continue migrating with about 3 m a-1 since 1936. Mainly artificial dune stabilizations and introduced plants have facilitated succession to an almost complete plant cover. Thus, revitalization of aeolian dynamics would be desirable, and pilot projects may acquire the appropriate knowledge. For a 1.7 × 2.5-km corridor across the island spit, we therefor discuss two suggested experiments: (1) intensify sand nourishments to the eroding beach and stop stabilization measures to allow excess sand blown inland and washovers entering deflation plains, and (2) examine the potential of tunnels for roads to let mobile dunes passing over. Such experiments may not only contribute to dune biodiversity but also to long-ranging adaptations of crowded barrier islands to accelerating sea level rise.
Highlights
More than two thirds of coastal beaches are eroding (Bird 1987), and this will exacerbate with global warming (Zhang et al 2004)
During the last 150 years, dune dynamics have rapidly faded on the island on Sylt
We attribute the long-term increase of heather and other shrub vegetation typical for aging dunes at the expense of bare sand and marram grass areas typical for dune mobility on a barrier island in NW-Europe to dune stabilization measures aggravated by introduced plants
Summary
More than two thirds of coastal beaches are eroding (Bird 1987), and this will exacerbate with global warming (Zhang et al 2004). Transgressive dune fields often develop (Hesp 2013). Since the nineteenth century more and more of these dunes became stable. Dune stabilization programs intended to prevent damage to and burial of arable land, hous-. A paradigm shift in coastal dune management is discussed (Arens et al 2013; de Groot et al 2017b; Martínez et al 2013; Oost et al 2012; Psuty and Silveira 2013). Restoring former morphodynamics should both reverse decreasing dune biodiversity and increase their adaptive capacity to adjust to an accelerating sea level rise in the future. At coasts with high real estate prices, a return to coastal dynamics constitutes a challenge (Döring and Ratter 2018; Hofstede and Stock 2018; Oost et al 2012)
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