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

Abstract

This study investigated the effectiveness of mangrove planting initiatives in Sri Lanka. All the lagoons and estuaries in Sri Lanka were included in the study. We documented all agencies and locations, involved in mangrove planting efforts, along with the major drivers of these planting initiatives, their extents, and the possible causes of the success or failure of planting. An adapted three‐step framework and a field survey consisting of vegetation and soil surveys and questionnaires were used to evaluate the objectives. We found that about 1,000–1,200 ha of mangroves, representing 23 project sites with 67 planting efforts, have been under restoration with the participation of several governmental and nongovernmental organizations. However, about 200–220 ha showed successful mangrove restoration. Nine out of 23 project sites (i.e. 36/67 planting efforts) showed no surviving plants. The level of survival of the restoration project sites ranged from 0 to 78% and only three sites, that is, Kalpitiya, Pambala, and Negombo, showed a level of survival higher than 50%. Survival rates were significantly correlated with post‐care. Planting mangrove seedlings at the incorrect topography often entails inappropriate soil conditions for mangroves. Survival rates showed significant correlations with a range of soil parameters except soil pH. Disturbance and stress caused by cattle trampling, browsing, algal accumulation, and insect attacks, factors that may themselves relate to choosing sites with inappropriate topography and hydrology, were common to most sites. The findings are a stark illustration of the frequent mismatch between the purported aims of restoration initiatives and the realities on the ground.

Structural and functional responses of xylem in <em>Rhizophora mucronata</em> Lam. seedlings under drought and hypersaline conditions

“…Selection of incorrect tidal positioning in mangrove planting due to ignorance of the accepted technical guidelines such as EMR (Ecological Mangrove Restoration) methodology (Lewis 2005;Lewis and Brown 2014) and modified protocols (Bosire et al 2008), often leads to create stress conditions like drought (or negative soil water potential) and hypersaline conditions for planted seedlings (Kodikara et al 2017a). Mangrove seedlings have therefore no choice rather than facing to such stress conditions.…”

“…Rhizophora mucronata Lam. was selected for the study as the most commonly used mangrove species in planting programmes (~97%) in Sri Lanka (Kodikara et al 2017a). …”

“…Mangrove planting in Sri Lanka has received a higher attention particularly after realizing the unprecedented mangrove loss in previous decades (Polidoro et al 2010;Richards and Friess 2016) and safeguarding action of mangroves against the tsunami in 2004 (Dahdouh-Guebas et al 2005b;Lee et al 2014;Jayatissa et al 2016;Satyanarayana et al 2017). However, majority of the planting attempts showed higher failure rates (Ahmad 2012;Kodikara et al 2017a) as they were not supported by sound scientific knowledge. Among the relevant causes for the failures, improper site selection without studying site history and planting inappropriate species have been identified as two major causes for the failures (Primavera and Esteban 2008;Lewis 2009;Kathiresan 2011;Ahmad 2012;Kodikara et al 2017a).…”

“…However, majority of the planting attempts showed higher failure rates (Ahmad 2012;Kodikara et al 2017a) as they were not supported by sound scientific knowledge. Among the relevant causes for the failures, improper site selection without studying site history and planting inappropriate species have been identified as two major causes for the failures (Primavera and Esteban 2008;Lewis 2009;Kathiresan 2011;Ahmad 2012;Kodikara et al 2017a). In many cases, mangrove planting practitioners tend to establish mangrove plantations out of intertidal range (i.e.…”

The effects of salinity on growth and survival of mangrove seedlings changes with age

“…However, these planting initiatives have often not been supported by sound scientific data. Governments, international and national NGO's and coastal communities have shown great interest in mangroverestoration activities although many attempts in Sri Lanka suffer high failure rates (Kodikara et al 2017).…”