Land-use change in the coastal zone has led to worldwide degradation of marine coastal ecosystems and a loss of the goods and services they provide. Restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed and is critical for habitats where natural recovery is hindered. Uncertainties about restoration cost and feasibility can impede decisions on whether, what, how, where, and how much to restore. Here, we perform a synthesis of 235 studies with 954 observations from restoration or rehabilitation projects of coral reefs, seagrass, mangroves, saltmarshes, and oyster reefs worldwide, and evaluate cost, survival of restored organisms, project duration, area, and techniques applied. Findings showed that while the median and average reported costs for restoration of one hectare of marine coastal habitat were around US$80 000 (2010) and US$1 600 000 (2010), respectively, the real total costs (median) are likely to be two to four times higher. Coral reefs and seagrass were among the most expensive ecosystems to restore. Mangrove restoration projects were typically the largest and the least expensive per hectare. Most marine coastal restoration projects were conducted in Australia, Europe, and USA, while total restoration costs were significantly (up to 30 times) cheaper in countries with developing economies. Community- or volunteer-based marine restoration projects usually have lower costs. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, was highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%). However, success rates reported in the scientific literature could be biased towards publishing successes rather than failures. The majority of restoration projects were short-lived and seldom reported monitoring costs. Restoration success depended primarily on the ecosystem, site selection, and techniques applied rather than on money spent. We need enhanced investment in both improving restoration practices and large-scale restoration.

Database on cost and feasibility of marine coastal restorationThis database represents the core part of the synthesis review "The cost and feasibility of marine coastal restoration". It contains information on cost and feasibility of restoration projects worldwide. The database is divided into five sections according to each investigated ecosystem: coral reefs, seagrass, mangroves, saltmarshes, and oyster reefs. Each ecosystem-specific database section contains the full reference, general information about the publication and project, the restoration action undertaken, species involved, location, a description on the type of cost reported, information on funding sources, project duration (in years), the area restored in hectare (ha), the converted restoration cost in 2010 US$ ha-1, feasibility information (including reasons for success or failure), and restoration success in terms of % survival of restored organisms. For coral reefs, we also accounted for pre-transplant (i.e. survival of coral spat/larvae in culture before rearing them in nursery or out-planting), transplant (i.e. survival of coral fragments during nursery period), post-transplant (i.e. survival of coral fragments after out-planting to the reef) survival as well as for the overall survival averaged over the former three categories. See ‘Approach’ of the publication for a detailed database description and Table A1-A5 in Appendix A for a detailed summary of the database information.Restoration_database.zip