Helping Recovery of Damaged Marine Ecosystems

80% of European rivers are affected by water pollution, water removal for hydropower and irrigation, structural alterations and the impact of dams, with 12% suffering from impacts of all four. There is no doubt that human activities have harmed marine environments, however there are a number of conservation success stories where ecosystems have recovered from serious degradation. What isn’t always clear is how long recoveries took, how much of the damage was repaired and what factors helped drive the recovery.

A study, partly funded by the EU THESEUS project has identified five strategies for successful recoveries: raising public and political awareness, legal action and enforcing management plans, reducing human impacts, protecting or restoring biodiversity and complex ecosystems, and long term planning, as recoveries can take many decades.

The researchers found that between 10 to 50% of marine species and ecosystems showed some sign of recovery, although rarely to former levels of abundance. Recoveries tended to take longer for longer-lived species and for more complex ecosystems. For instance, many finfish and invertebrate stocks take three to 30 years to recover after depletion and slower-growing corals and sponges can take up to eight years to recover after bottom-trawling has ceased, compared to less than one year for faster-growing polychaete worms. Recovery can also take much longer if a species or ecosystem had been completely lost from an area, and sometimes depends on managed reintroductions to be successful.

Source: Lotze, H. K., Coll, M., Magera, A. M., Ward-Paige, C., & Airoldi, L. (2011). Recovery of marine animal populations and ecosystems. Trends in Ecology and Evolution. 26(11): 595-605.