Mangrove restoration without planting

Background

Mangrove planting is the most common method of restoring mangrove forests. However, this approach is not often successful, especially when the causes of mangrove degradation were not removed prior to planting new seedlings or propagules. A successful mangrove restoration project may not necessarily include a planting phase. When the stressors are removed and suitable environmental conditions are present, natural regeneration processes could recover mangroves from degradation.

Research goals & methods

This paper describes an approach to mangrove restoration applied to an exposed shoreline on the west coast of Peninsular Malaysia. A detached breakwater was erected seaward at the shoreline to shelter the restoration area from wave action, prevent the ongoing erosion and promote sediment deposition raising the elevation of the substrate to the target elevation. Early survival of Avicennia marina seedlings transplanted in the sheltered area was significantly reduced due to sediment burial (P < 0.05). However, about eight months after construction of the breakwater, the sedimentation rate decreased and the substrate became stable. Subsequently, natural recruits appeared on the site.

Conclusions & takeaways

The authors suggest that waterborne seeds or propagules were available from adjacent stands in the study area, but unsatisfactory conditions for establishment such as wave exposure and insufficient sediments reduced the possibility of natural recruitment. The breakwater provided more favorable conditions, facilitating reestablishment and natural recovery of the mangrove ecosystem without planting.