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

Anna Lafratta,Daniel Gorman,Mathew A Vanderklift

doi:10.3390/f13030404

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.

Highlights

Mangrove forests are highly productive coastal ecosystems distributed worldwide in tropical and subtropical regions [1]
The aim of this study was to provide a global synthesis of influences on mangrove survival after planting, arising from (1) methods used and (2) environmental context
Most studies were performed for the purpose of restoration (80%), with fewer studies conducted for afforestation (20%), with the majority of these involving the use of Sonneratia spp. in places such as the Bay of Bengal

Summary

Introduction

Mangrove forests are highly productive coastal ecosystems distributed worldwide in tropical and subtropical regions [1]. They provide numerous ecosystem services such as coastal protection, enhanced biodiversity, fisheries support, nutrient cycling and climate change mitigation and adaptation by storing carbon [2,3], supporting human well-being and livelihoods [4,5]. Mangrove forests are one of the most threatened ecosystems on Earth due to climate change and human activities [6]. Forests have been extensively modified or cleared for aquaculture, food production and coastal development, which in many parts of the world continues up until the present [7–9]. Some estimates suggest that up to 35% of the world’s mangrove forests have been damaged or destroyed during the last 20 years [10,11]. Multiple efforts to halt and reserve this trend [12] have slowed the overall rates of loss (e.g., dropping to less than 2% per year in Asia [13])

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