Post-tsunami mangrove planting, Sri Lanka: zero survival at 54% of planting attempts nationwide

PRECONDITIONS

• Planting confined to the intertidal window with suitable depth, duration and frequency of inundation; positions above it caused drought and irradiance stress, positions below it prolonged submergence [1]
• Species selection matched to the composition of natural reference forests nearby, not to propagule handling convenience [1]
• Topographic survey combined with hydrologic characterization of reference sites across wet and dry seasons before any planting [1]
• Undisturbed natural sedimentation and water movement at the site; the national guidelines now require verifying both before restoration, and prescribe soil assessment [2]
• Funded multi-year post-planting care: removal of flotsam, debris and barnacles, up-righting fallen seedlings, secure fencing against cattle, replacement of dead plants, frequent site visits [1]
• Specialist technical guidance following ecological mangrove restoration principles; survival was significantly associated with its presence [1]
• A coordination and approval authority; the surveyed wave proceeded without one, and agencies were unaware of plantings recorded in their own names [1]
• Realistic coastline screening: mangroves can grow along less than one third of the Sri Lankan coastline, per the coastal vulnerability study cited by the evaluation [1]

FAILURE ANALYSIS

The failure is technical: planted seedlings died of siting and species selection errors, compounded by absent aftercare. Documented mechanisms: (1) Sites selected by tsunami damage, not ecological suitability. Planting concentrated where the tsunami hit hardest: 20 of 23 sites lay in severely affected coastline sectors, where 700 to 800 ha replanted yielded 40 to 50 ha surviving, against 150 to 200 ha surviving from 300 to 400 ha in less-affected sectors; two thirds of the 36 zero-survival attempts (21) occurred in the dry and arid zones, and all three sites with survival above 50% lie in less-affected sectors [1]. (2) Planting outside the intertidal window. Seedlings placed at the high intertidal and beyond, in abandoned swamps and meadows (Komari, Palandi, Halawa, Panakala), suffered drought and midday irradiance around 79,500 lux in the dry and arid zones; low intertidal positions (Rekawa, Medilla, Meegama, Ittapana) brought prolonged submergence under wet-zone rains; the evaluation identifies inappropriate depth, duration and frequency of inundation as the key factor [1]. (3) Species-site mismatch. 97% of stock was Rhizophora spp., selected for large, easily handled propagules and nursery convenience; agencies did not survey which species occurred naturally and did not use nearby forests as references, producing monospecific stands in open lagoon water, and planted unsuitable Bruguiera spp. and Sonneratia caseolaris at Meegama, Maggona and Kaluwamodara against the composition of adjacent reference forests [1]. (4) No aftercare. Post-planting care was absent at most sites and only 10 of 23 sites showed any monitoring process; survival correlated significantly with post-care (p=0.0009); cattle trampling and browsing occurred at essentially all sites, insect attacks at 95% and algal smothering at 77% [1]. (5) Delivery pressure over ecology. Post-tsunami projects were donor-driven with a mandate to plant a green belt rapidly; signboards marked initiatives with no surviving plants behind them [1]. (6) Governance vacuum. No approval or coordination mechanism existed; the Forest Department and Coastal Conservation Department did not coordinate, and interviewed officials were unaware of planting efforts recorded in their own agencies' names [1]. The counterfactual inside the data: the initiatives that followed technical guidelines, the University of Ruhuna at Galle and SFFL at Pambala and Kalpitiya, achieved the country's only high survival (up to 78%), and survival correlated with technical guidance (p=0.0148); where technique was right, the same species in the same country established, while a guided site without maintenance (Rekawa) still failed [1].

Stated in the evaluation and later enacted in part by the Government of Sri Lanka. Kodikara et al. [1]: establish a national authority that grants approval and provides technical guidance and leadership for mangrove planting; formulate Sri Lankan planting guidelines adapted from ecological mangrove restoration methodology; drop immediate direct planting as the default in favor of promoting site conditions, including hydrologic restoration such as breaching dikes of abandoned aquaculture ponds, so that natural regeneration establishes mixed stands; plant only where hydrography remains conducive and find alternative protection for the roughly two thirds of the coastline where mangroves cannot grow; couple any planting with proper post-planting care. The operator side responded: a national mangrove policy was adopted in early 2020, and the Ministry of Environment's Biodiversity Secretariat published National Guidelines for the Restoration of Mangrove Ecosystems in 2021, prepared by a National Expert Committee and a restoration Task Force and launched on 15 June 2022; the guidelines cite the evaluation, accept that invested funds had not restored or expanded mangrove cover for want of scientific guidance, require verification of hydrology and sedimentation before restoration, prescribe soil assessment, mandate reporting of every restoration project to the Biodiversity Secretariat on standard data forms, and require Forest Department or Department of Wildlife Conservation approval inside protected areas [2][3]. National practice shifted from mass planting to assisted natural regeneration, with a stated goal of 10,000 ha restored by 2030 [4].

POLITICAL TEST

The planting wave was a one-off reaction to the December 2004 tsunami, financed largely by donors, and it lapsed with its donor mandates rather than persisting as a program through any political transition. The evaluation found no political support for mangrove planting, while conversion of mangrove land to shrimp farming proceeded under political patronage [1]. The documented failure later acquired political consequence in the opposite direction: Sri Lanka adopted a national mangrove policy in early 2020, published national restoration guidelines in 2021 that cite the evaluation and mandate site verification, approvals and reporting [2][3], and reoriented national practice from mass planting toward assisted natural regeneration, recognized as a UN World Restoration Flagship in February 2024 with a goal of 10,000 ha restored by 2030 [4]. The record is classified failed_technical because the planted seedlings died of biophysical causes, siting outside the intertidal window and species-site mismatch; support was not withdrawn mid-program and communities did not reject a functioning intervention.