As coastal cities become increasingly urbanized, the surrounding waters are littered with a plethora of artificial structures. An “artificial structure” can be anything from seawalls and breakwaters to an abandoned garden statue, like this eagle (right) in South Seattle, which ended it’s long terrestrial journey at the bottom of the ocean. Though colonized by a colorful variety of organisms, artificial structures are rarely added to underwater landscapes with clear, coordinated, and ecologically-oriented goals in mind. The undersides of coastal cities can therefore become ecosystems of happenstance, a chaotic patchwork of opportunistic marine species that may or may not promote the conservation agenda of urban residents or the ecosystems services upon which urban residents rely.
But does it have to be this way? This was the question posed by Dr. Katherine Dafforn and colleagues in a recent publication in Frontiers in Ecology and the Environment (link). Using a series of case studies, they explore how artificial structures might instead be designed, or engineered, to meet specific ecological goals. For instance, to combat pollution, artificial structures could be “seeded” with seaweeds that absorb contaminants, and bivalves that filter organic pollutants. If we want to promote local biota, we could design artificial structures to mimic natural conditions, and restore natural coastal barriers, like wetlands and other shoreline features. (Here’s one such example documented by other UW biologists at the Olympic Sculpture Park in downtown Seattle. The video below shows the kelp forest ecosystem that formed at the site after old artificial structures were rebuilt with more natural materials.)
Though ecological engineering is not a new idea, Dafforn et al. are among the first to emphasize how the approach could help us realize the “multifunctional potential” of artificial structures in urban marine environments. Indeed, anyone who spends time observing marine life in cities is aware of the diversity of life these structures support and the benefits they could offer, both ecologically, and for people, if developed intentionally and with clear objectives in mind. As Dafforn and colleagues explain, these objectives do not need to be singular, as a multifaceted coastal management plan that incorporates a variety of ecological engineering projects and techniques could provide many benefits simultaneously. Perhaps it’s not too grandiose to conjecture that forward-thinking design initiatives could even realign the trajectories of humans and marine ecosystems in coastal cities so that they converge onto a single, more sustainable path forward.