Greening of grey and murky harbours: enhancing biodiversity and ecosystem functioning on artificial shorelines

Shoreline armouring in coastal cities can cause habitat degradation and biodiversity loss, often exacerbated by common anthropogenic stressors. Boulders are used as riprap to create revetments walls; but the homogenous surface and absence of shelter reduces intertidal biodiversity and ecosystem functioning. Eco-engineering can mitigate habitat loss through the addition of water retention and other microhabitats. We deployed four eco-engineered designs in a degraded harbour riprap for 18 months. Two units with site-specific designs combined multiple microhabitat types, attracting the highest species diversity. All four designs generally increased within-site β diversity and fish diversity compared to nearby unmanipulated ripraps. Suspension-feeding species and more species within key functional groups colonised eco-engineered units at patch and site scale. Tailored, site-specific eco-engineering shows great potential to rehabilitate degraded ripraps into functional, novel ecosystems. Combining eco-engineering with anthropogenic stress reduction to enable recovery can enhance biodiversity and ecosystem functioning in coastal cities.