intertidal habitat loss which arises due to the high-water mark being fixed by a defence and the low water mark migrating landwards in response to sea level rise
This article complements the article 'Effects of global climate change on European marine biodiversity' by Lieven Therry with a shorth introduction to the impact of coastal squeeze on biodiversity.
A significant threat for coastal organisms is loss of habitat. This may be due to direct loss through coastal land claim. This often involves building structures to protect the land and/or infrastructure from erosion and sea defences to prevent erosion and/or flooding. These and other techniques effectivley 'fix' the coastline. This is particlularly important where it effects habitats and ecosystems that would normally move landward in response to erosive forces. Where there is a rise in sea level relative to the land a coastal squeeze takes place. This is exacerbated by global warming, which not only leads to higher sea levels, but also an increase of the storm frequency. Increased storminess results in coastal erosion including cliff erosion, retreat of beaches, loss of salt marsh and dune scarping with vegetation loss.
Effects on coastal organisms
Average sea level rise is predicted to be up to 90 cm by the year 2100 compared to 2000. This will not greatly affect the highly adaptable sandy-shore biota for beaches that follow sea level rise, according to the Bruun rule. Onshore migration is the natural ecosystem response to rising sea levels, but this is stopped by fixed sea defenses. Intertidal zones (e.g. beaches, mudflats, salt marshes) are trapped in a ‘coastal squeeze’ between the impacts of urbanization on the terrestrial side and manifestations of climate change at sea. While unconstrained, these intertidal zones are resilient, changing shape and extent naturally in response to storms and variations in wave climate and currents. However, human modifications of the coastal zone severely limit this flexibility. This raises a fundamental conflict between protecting socio-economic activity and sustaining the ecological functioning of the coastal zone in Europe under rising sea levels. It suggests a need for more soft protection (nourishment), managed retreat, and possibly accommodation strategies.  
The ecological consequences of hard engineering interventions on retreating beaches entails the loss of biodiversity, productivity, and critical habitats as well as modifications of the subtidal zone, which is an important recruitment zone for many sandy beach animals . Even beach nourishment is not free of negative ecological consequences, especially if the grainsize of the fill material does not correspond to the original beach sediment.
Solutions to coastal squeeze
Solutions to coastal squeeze are described in the article Climate adaptation measures for the coastal zone. Three types of measures are discussed:
- Seaward extension of the coast: see Foreland creation.
- Moving the flood defense inland: see Foreland restoration - managed realignment.
- Managed retreat: see Preparing for retreat.
- Shoreline management
- Sea level rise
- Bruun rule for shoreface adaptation to sea-level rise
- Effect of climate change on coastline evolution
- Climate adaptation measures for the coastal zone
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