Coastal squeeze reduces diversity of dune habitats, but not their heterogeneity - Scripts & Data

Authors: Eva M. Lansu,  Max Rietkerk,  Martin Wassen, Tjisse van der Heide, Valérie Reijers

Abstract

Coastal ecosystems 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 – called coastal squeeze – is particularly pressing for sandy coasts and their coastal dunes systems. About one-third of the world's shoreline is defined by sandy coasts with developed dune ecosystems. Yet, it remains unknown how coastal width affects habitat diversity (i.e. the total number of distinct habitats in a landscape) and habitat heterogeneity (i.e. the number of habitats per surface area) in coastal dunes. Using a recently developed high-resolution habitat map of the Dutch coastal dunes, we sampled habitat diversity and heterogeneity along 306 cross-shore transects. We find that wider coastal dune systems accommodate higher habitat diversity, but they do not show a greater habitat heterogeneity. Next, using a dataset of in-field observations of plant species diversity in the coastal dunes, we explore how plant diversity is influenced by coastal width, habitat diversity and heterogeneity. Regression analyses show that both coastal width and habitat diversity steer plant diversity, while habitat heterogeneity has no effect. Our results therefore suggest that both alleviating coastal squeeze and enhancing habitat diversity help to maintain dune plant diversity. In addition, as we find no indication of a relation between habitat heterogeneity and plant diversity, our analyses suggest that management should not strive at enhancing small-scale heterogeneity, but better be targeted at increasing the number of habitats on the landscape scale.

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Methods

The analyses rely on a freely accessible coastal habitat map:

https://liquid-optics-366616.projects.earthengine.app/view/coastal-habitats 

In the deposited folder, you find two main MATLAB scripts to run and accompanying datasets to load. With the first script "M1_create_paper_figures.m" the figures, as presented in our study, can be created. With the second script "M2_regression_analysis.m", the regression analyses can be performed. When running the script, the accompanying MATLAB datasets (data_underlying_figures.mat & data_underlying_regressions.mat ) and CSV files are loaded. 

A readme file is included, which further explains the scripts and datasets.

Source data file

In the data file Source_Data.xlsx, each sheet contains the data for one figure or table of the manuscript.