Photograph of ocean and riprap at dusk
Big Ideas, Ecosystem Services, Recent Research

Climate change and the proliferation of shoreline armoring

Louise Firth and colleagues recently published this article in Environmental Science Processes & Impacts: Climate change and adaptational impacts in coastal systems: the case of sea defences. It provides a brief exploration of shoreline armoring in the face of climate change. The general idea is this: as sea levels rise, coastal cities and developments are requiring increases in coastal defense structures (breakwaters, riprap, etc). These structures carry negative and potentially positive impacts for marine ecosystems. Why not construct them with these impacts in mind?

Photo of coastline with riprap and seawall

(c) Nigel Chadwick

“There is no doubt,” Firth and colleagues state in their paper, “that [armoring structures] modify the natural environment and can have deleterious impacts…” They cite research that has demonstrated how armoring structures act as stepping stones for species undergoing range expansions and how they have facilitated biological invasions. However, they may have potentially beneficial impacts as well, by supporting species of conservation importance and increasing habitat heterogeneity, as Firth et al. (2013) note.

So what does this mean for the construction of coastal defense structures? If the objective is to enhance intertidal biodiversity, Firth et al. (2013) provide these guidelines:

  • ”Build structure lower in the intertidal zone.”  Areas that are submerged for longer tend to support a greater number of species. Would this alter habitat that would otherwise be unaltered? That’s a discussion for another day I suppose.
  • Avoid smooth rocky material“, as these types of surfaces tend to be to be colonized by fewer species.  Specifically, they suggest a mixture of hard and soft rock to create greater surface roughness.
  • Create rock pools,” which should provide refuges for some species at low tide and support greater diversity.
  • Create pits” and crevices.  These provide hiding places and habitat heterogeneity.
  • Deploy precast habitat enhancement units.” Firth et al. (2013) note that a variety of such units are currently being tested around the world at the moment.  More on this soon in future posts!