The effectiveness, costs and coastal protection benefits of natural and nature-based defences

This paper addresses two issues critical for designing restoration projects for coastal protection. It discusses the synthesis of the costs and benefits of projects designed for coastal protection (nature-based defences) and analyses of the effectiveness of coastal habitats (natural defences) in reducing wave heights and the biophysical parameters that influence this effectiveness.

The study analyses data from sixty-nine field measurements in coastal habitats globally and examines measures of effectiveness of mangroves, salt-marshes, coral reefs and seagrass/kelp beds for wave height reduction and synthesises the costs and coastal protection benefits of fifty-two nature-based defence projects. The study then estimates the benefits of each restoration project by combining information on restoration costs with data from nearby field measurements.

The analyses of field measurements show that coastal habitats have significant potential for reducing wave heights. In general, coral reefs and salt-marshes have the highest overall potential.

The comparison of costs of nature-based defence projects and engineering structures show that salt-marshes and mangroves can be two to five times cheaper than a submerged breakwater for wave heights up to half a metre and, within their limits, become more cost effective at greater depths. Nature-based defence projects also report benefits ranging from reductions in storm damage to reductions in coastal structure costs.

PLoS ONE 11(5): e0154735. doi:10.1371/ journal.pone.0154735. The document has been shared under a Creative Commons CC0 public domain dedication.