Abstract
The Intergovernmental Panel on Climate Change predicts that sea levels will rise by up to 0.82 m in the next 100 years. In natural systems, coastlines would migrate landwards, but because most of the world’s human population occupies the coast, anthropogenic structures (such as sea walls or buildings) have been constructed to defend the shore and prevent loss of property. This can result in a net reduction in beach area, a phenomenon known as “coastal squeeze”, which will reduce beach availability for species such as marine turtles. As of yet, no global assessment of potential future coastal squeeze risk at marine turtle nesting beaches has been conducted. We used Google Earth satellite imagery to enumerate the proportion of beaches over the global nesting range of marine turtles that are backed by hard anthropogenic coastal development (HACD). Mediterranean and North American nesting beaches had the most HACD, while the Australian and African beaches had the least. Loggerhead and Kemp’s ridley turtle nesting beaches had the most HACD, and flatback and green turtles the least. Future management approaches should prioritise the conservation of beaches with low HACD to mitigate future coastal squeeze.
Highlights
Coastal regions are dynamic and productive, and have high biodiversity [1]
We considered that hard anthropogenic coastal development (HACD) was any man-made hard structure that would prevent the landward retreat of beaches under future sea level rise scenarios
Natural barriers, such as embankments or vegetation, were not considered a barrier to beach recession as they would naturally recede over time, and roads were not counted as hard anthropogenic structures because they are usually flat and do not strictly prevent marine turtles accessing the beach behind them
Summary
Coastal regions are dynamic and productive, and have high biodiversity [1] They host human coastal populations at densities three times higher than the global average [2]. Coastlines would migrate landwards with sea level rise, but highly developed areas (e.g., coastal towns or cities) at risk may invest in sea walls, groynes, and coastal armouring to protect property and to offset economic and social costs of land loss [5]. This can result in a net reduction in beach area, a phenomenon known as “coastal squeeze”. Natural habitats provide billions of dollars’ worth of shoreline protection for human populations [12] and can be more cost effective against sea level rise, storms, and flooding than hard anthropogenic structures [4,13,14]
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