A global analysis of how human infrastructure squeezes sandy coasts

Abstract

Coastal ecosystems provide vital services, but human disturbance causes massive losses. Remaining ecosystems are squeezed between rising seas and human infrastructure development. While shoreline retreat is intensively studied, coastal congestion through infrastructure remains unquantified. Here we analyse 235,469 transects worldwide to show that infrastructure occurs at a median distance of 392 meter from sandy shorelines. Moreover, we find that 33% of sandy shores harbour less than 100 m of infrastructure-free space, and that 23–30% of this space may be lost by 2100 due to rising sea levels. Further analyses show that population density and gross domestic product explain 35–39% of observed squeeze variation, emphasizing the intensifying pressure imposed as countries develop and populations grow. Encouragingly, we find that nature reserves relieve squeezing by 4–7 times. Yet, at present only 16% of world’s sandy shores have a protected status. We therefore advocate the incorporation of nature protection into spatial planning policies.

Urbanisation on the coastline of the most populous and developed state of Brazil: the extent of coastal hardening and occupations in low-elevation zones

“…Here we adopted an elevation up to 5 m above sea level to provide a more conservative scenario in consideration of estimative errors in Google Earth elevation data (average error = 0.51 m, accuracy = 1.85 m; El-Ashmawy 2016). Likewise, the 100 m inland horizontal delimitation considers conservative projections of shoreline retreat (Vousdoukas et al 2020;Lansu et al 2024). Moreover, lowland coastal areas in SP are under eminent risk hazards of, and already facing, flooding and erosion (e.g., Marengo et al 2017; dos Santos and Serrao-Neumann 2018; Nunes et al 2019).…”

“…This figure represents more than half of the extent of sandy beaches, reaching 74 and 81% in the north and central regions, respectively (Table 2). These alarming results reveal a process of coastal squeeze far intense than the global pattern, where 33% of sandy shores harbour less than 100 m of infrastructure-free space (Lansu et al 2024). Extensive occupation of areas near sandy beaches reflects strong real estate speculation upon these highly valued territories, much of it driven by second-home market (Supplementary Material, Fig.…”