Habitat richness, not patchiness, drives plant diversity in coastal dunes - Scripts & Data

Abstract About one-third of the world's shoreline is defined by sandy coasts that provide vital services to humanity. Nevertheless, these ecosystems are under increasing pressure, as they are squeezed between rising sea levels and encroaching infrastructure. This spatial confinement, known as coastal squeeze, has been linked to species loss in dune systems. Yet the mechanism behind this species loss remains unclear: does narrowing primarily reduce species richness through declines in habitat richness (the number of distinct habitats within a landscape), or through changes in habitat patchiness (the density of habitat transitions)? Using a recently developed high-resolution habitat map of the Dutch coastal dunes, we quantified habitat richness and patchiness along 306 cross-shore transects. We show that dune systems lose habitat richness when their width is reduced to less than 1.4 km, whereas habitat patchiness is independent of dune width. In addition, analyses of in-field vegetation data reveal that habitat richness increases plant species richness, while habitat patchiness has no detectable effect. Our findings indicate that large-scale habitat richness, rather than fine-scale patchiness, underpins plant species richness in coastal dunes. We therefore suggest that dune management, aimed at enhancing species richness, should not focus on local patchiness but rather strive to increase the number of distinct habitats at the landscape level. Methods The analyses build on a freely accessible coastal habitat map: https://liquid-optics-366616.projects.earthengine.app/view/coastal-habitats This deposit contains two main MATLAB scripts and their accompanying datasets: M1_create_paper_figures.m reproduces the figures presented in the study. M2_regression_analysis.m performs the regression analyses. When executed, the scripts automatically load the accompanying MATLAB datasets (data_underlying_figures.mat and data_underlying_regressions.mat) and CSV files. A README file is included with further details on the scripts and datasets. Source data The file Source_Data.xlsx contains the data presented in each figure and table, organized as separate sheets.