Impacts of “Coastal Squeezing” from Infrastructure Development

Coastal ecosystems provide many vital services to us, including flood defence, carbon storage, biodiversity, recreation, and water storage.

However, infrastructure development can damage or disrupt this service by squeezing the space between the shore and the built environment, a phenomenon called “coastal squeezing”, for example, by limiting the space of beaches and dunes because the presence of infrastructure hinders their ability to protect us from sea level rise.

The study, “A global analysis of how human infrastructure squeezes sandy coasts”, published in Nature Communications, measures the coastal squeeze worldwide and examines their impacts. According to researchers, while shoreline retreat has been studied extensively, attention given to coastal congestion from infrastructure development still needs to be quantified.

Researchers calculated the distance between the sea and the nearest human-made structure (paved road or structure) at 1 km intervals, yielding 235,469 transects worldwide, representing 29% of the world’s ice-free shoreline.

Their measurements show that infrastructure occurs at a median distance of 392 meters from sandy shorelines. They find that 33% of sandy shores have less than 100 meters of infrastructure-free space and project that 23 to 30% of this area will likely be lost due to rising sea levels by 2100.

The study finds that in densely populated areas, infrastructure is generally closer to the shores. Countries with tight coastal regions include Japan, South Korea, Lebanon, Syria, Turkey, Italy, France, Spain, and the United States of America.

All these countries rank in the top 20 of the most severely squeezed countries in the world. On the continental level, Europe is most severely squeezed at 131 meters, followed by Asia at 151 meters, North America at 402 meters, and South America. Meanwhile, Africa’s sandy coasts at 1.6 meters and Oceania at 2.8 kilometres are less confined.

Impacts of Coastal Squeezing

Researchers expect coastal squeezing to increase worldwide. Rising sea levels will further narrow the space between the built environment and the sea. Without infrastructure, rising sea levels will tend to push these beaches and dunes inland. Their presence, however, will result in 30% of the beaches and dunes being washed up or drowned by 2100, threatening ecosystem services such as natural flood protection, freshwater storage, and biodiversity.

For beaches and dunes to fulfil these vital functions, the study notes that “sufficiently wide coastal zones are vital for preserving natural succession-disturbance dynamics that generate high habitat diversity, which supports a diverse assembly of unique plant and animal species. In addition, lack of space also threatens natural coastal defence functions.”

Citing previous studies, researchers say that beaches must be over 300 meters wide to “effectively reduce erosion and support natural dune development, but 46% of the world’s sandy shores currently have less than 300 metres of infrastructure-free space, implying that such areas could be at risk for erosion.

Consequently, ecosystem services such as biodiversity, carbon storage, recreation, freshwater supply, and flood defence are all under threat.”