Study

Have mangrove restoration projects worked? An in-depth study in Sri Lanka

  • Published source details Kodikara K.A.S., Mukherjee N., Jayatissa L.P., Dahdouh-Guebas F. & Koedam N. (2017) Have mangrove restoration projects worked? An in-depth study in Sri Lanka. Restoration Ecology, 25, 705-716

Actions

This study is summarised as evidence for the following.

Action Category

Produce guidance for marsh or swamp conservation

Action Link
Marsh and Swamp Conservation

Introduce tree/shrub seeds or propagules: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation

Directly plant trees/shrubs: brackish/saline wetlands

Action Link
Marsh and Swamp Conservation
  1. Produce guidance for marsh or swamp conservation

    A study in 2012–2014 of 23 coastal sites in Sri Lanka (Kodikara et al. 2017) found that the average survival rate of planted mangrove propagules/seedlings was higher in sites where technical guidance was used (46%) than in sites where it was not used (0%). Methods: Between 2012 and 2014, the number of surviving, healthy mangrove trees was counted or estimated in 23 coastal sites around Sri Lanka. Mangrove propagules and seedlings (97% of which were Rhizophora spp.) had been planted between 1996 and 2009, with multiple planting attempts in all sites. Six sites used published technical guidance to direct planting towards sites thought to be ecologically, socially and/or politically suitable. The other 17 sites did not refer to technical guidance. Note that all of the sites that used guidance also carried out post-planting care (e.g. removing debris and righting fallen seedlings), whereas 13 of the 17 sites that did not use guidance did not carry out post-planting care.

    (Summarised by: Nigel Taylor)

  2. Introduce tree/shrub seeds or propagules: brackish/saline wetlands

    A replicated study in 2012–2014 of 23 coastal sites in Sri Lanka (Kodikara et al. 2017) reported 0–78% survival of planted mangrove propagules and seedlings after ≥5 years, and that only 17–20% the area planted with mangroves was forested after 8–10 years. In 9 of the 23 sites, no mangrove trees were alive five or more years after planting. In 7 of the 14 sites with some surviving trees, survival rates were <10%. Only three sites supported >50% survival. Average survival rates were higher in sites where technical guidance was used (46%) than where it was not used (0%), and in sites with post-planting care of seedlings (13%) than without (0%). The study suggests that mangroves were planted into unsuitable environments in many sites. Finally, the study reports that of 1,000–1,200 ha of mangrove forest planted in these sites since 2004, only 200–220 ha was present 8–10 years later. Methods: Between 2012 and 2014, the number of surviving, healthy mangrove trees was counted or estimated in 23 coastal sites around Sri Lanka. In eight sites, the tidal influence was “negligible”. Mangrove propagules and seedlings (97% of which were Rhizophora spp.) were planted between 1996 and 2009, with multiple planting attempts in all sites. In 10 sites, mangroves were cared for after planting. The study does not distinguish between the effects of planting propagules and seedlings.

     

    (Summarised by: Nigel Taylor)

  3. Directly plant trees/shrubs: brackish/saline wetlands

    A replicated study in 2012–2014 of 23 coastal sites in Sri Lanka (Kodikara et al. 2017) reported 0–78% survival of planted mangrove seedlings and propagules after ≥5 years, and that only 18–20% the area planted with mangroves was forested after 8–10 years. In 9 of the 23 sites, no mangrove trees were alive five or more years after planting. In 7 of the 14 sites with some surviving trees, survival rates were <10%. Only three sites supported >50% survival. Average survival rates were higher in sites where technical guidance was used (46%) than where it was not used (0%), and in sites with post-planting care of seedlings (13%) than without (0%). The study suggests that mangroves were planted into unsuitable environments in many sites. Finally, the study reports that of 1,000–1,200 ha of mangrove forest planted in these sites since 2004, only 200–220 ha was present 8–10 years later. Methods: Between 2012 and 2014, the number of surviving, healthy mangrove trees was counted or estimated in 23 coastal sites around Sri Lanka. In eight sites, the tidal influence was “negligible”. Mangrove propagules and seedlings (97% of which were Rhizophora spp.) were planted between 1996 and 2009, with multiple planting attempts in all sites. In 10 sites, mangroves were cared for after planting. The study does not distinguish between the effects of planting seedlings and propagules.

    (Summarised by: Nigel Taylor)

Output references

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