Coastal squeeze threatens dune biodiversity - Scripts & Data

Authors: Eva M. Lansu, Hallie S. Fischman, Christine Angelini, Nadia Hijner, Luc Geelen, Dick Groenendijk, Solveig Höfer, Annemieke M. Kooijman, Max Rietkerk, Sten Tonkens, Sierd de Vries, Martin Wassen, Evaline van Weerlee, Daniël Wille, Valérie Reijers, Tjisse van der Heide

Abstract

Coastal dunes form valuable ecosystems that provide vital services to humanity including flood protection, clean drinking water and high biodiversity. Although their functioning critically depends on large-scale habitat zonation arising along sea-to-land gradients, infrastructure development and sea level rise progressively squeeze natural dune ecosystems into a narrow coastal strip. However, it remains unknown how much coastal width is required to support the diverse suite of habitat and species assemblages found in natural, undisturbed dune systems. Here, we investigate plant and habitat diversity in 614 plots along 47 sea-to-land transects in the southeastern USA and the Netherlands. We discover a strong linear relation between habitat diversity and species richness, indicating that diverse habitat assemblages are required for species-rich dunes. Moreover, we find that both plant and habitat diversity non-linearly depend on coastal width, with cumulative plant diversity reaching ~75% of its potential at 800 and 1800 m width in the USA and the Netherlands, respectively. Alarmingly, dunes are narrower than these width values along 79% and 66% of the USA and Dutch coastlines, respectively, highlighting that lack of space compromises the ecosystems’ potential biodiversity benefits along the majority of coastlines. Finally, analyses of management measures along the transects reveal that strategic interventions can, at least in part, mitigate biodiversity losses from coastal squeeze. As coastal squeeze is a global phenomenon, our results suggest that it may severely threaten biodiversity in dune areas worldwide. We argue that establishment or expansion of nature reserves may be vital for conserving wide dune systems, and that targeted management measures can help maintain biodiversity where coastal squeeze cannot be alleviated.

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Methods

The analyses rely on the following freely available datasets:

 Lansu et al. (2024) " A global analysis of how human infrastructure squeezes sandy coasts” Nature Communications 15.1 (2024): 432. https://www.nature.com/articles/s41467-023-44659-0

OpenStreetMap - shoreline: https://osmdata.openstreetmap.de/data/land-polygons.html

Protected areas: https://www.protectedplanet.net/en/thematic-areas/wdpa?tab=WDPA