Quantitative Analysis of Methodological and Environmental Influences on Survival of Planted Mangroves in Restoration and Afforestation

Abstract

Mangrove planting has been employed for decades to achieve aims associated with restoration and afforestation. Often, survival of planted mangroves is low. Improving survival might be aided by augmenting the understanding of which planting methods and environmental variables most influence plant survival across a range of contexts. The aim of this study was to provide a global synthesis of the influence of planting methods and background environment on mangrove survival. This was achieved through a global meta-analysis, which compiled published survival rates for the period 1979–2021 and analyzed the influence of decisions about minimum spacing and which life stage to plant, and environmental contexts such as climate, tidal range and coastal setting on the reported survival of planted individuals, classified by species and root morphology. Generalized Additive Mixed Modeling (GAMM) revealed that planting larger mangrove saplings was associated with increased survival for pencil-rooted species such as Avicennia spp. and Sonneratia spp. (17% increase cf. seedlings), while greater plant spacing was associated with higher survival of stilt-rooted species in the family Rhizophoraceae (39% increase when doubling plant spacing from 1.5 to 3.0 m). Tidal range showed a nonlinear positive correlation with survival for pencil-rooted species, and the coastal environmental setting was associated with significant variation in survival for both pencil- and stilt-rooted species. The results suggest that improving decisions about which species to plant in different contexts, and intensive care after planting, is likely to improve the survival of planted mangroves.

Combining Traditional Ecological Knowledge and Scientific Observations to Support Mangrove Restoration in Madagascar

“…Our results showed that the density of planted mangroves is positively correlated with the survival rate. Even though greater plant spacing was associated with high survival of stilt-rooted species in the family Rhizophoraceae [24,51], we found that it is important to consider the reference forest in the vicinity to ensure that the restored site has achieved an adequate stem density. Although the density of the plantation surpassed the highest density recorded within the mangrove forests in the bay [39], with the average survival rate (82.5 ± 1.8%), we expected that the density of mature stands within the restored forests can reach 3816 ± 278 stem/ha −1 which closely aligned with the undisturbed forests in the bay.…”

“…The survival rate in 2017 was very high, the season of the plantation may explain this given that climate was correlated with the survival of planted both stilt-and knee-rooted species [51]. The climate of the west coast of Madagascar is dependent on the Inter-Tropical Zone of Convergence movement.…”