Key Points

◆Panel data analysis identified key factors that influence mangrove gross gains in Southeast Asia.
◆Mangrove areas have recovered and expanded due to increased human interventions, including afforestation and reforestation.
◆Expansion of conservation areas and protected zones contributed to mangrove gains.
◆Community involvement in policymaking led to positive mangrove restoration projects.
◆Increased drought intensity constrains mangrove forest area expansion.
◆Time-series effects derived from climate change, such as rising minimum temperature and sea level rise, remain limited in magnitude.

Summary

　Mangrove forests are ecologically and economically important habitats that provide a wide range of ecosystem services. These include supporting fisheries and tourism industries, regulating climate, protecting coastlines, and, most notably, contributing to climate change mitigation through their exceptional carbon sequestration capacity.

　Recent global assessments suggest that more than half of the world's mangrove ecosystems could face collapse by 2050, underscoring the urgent need for conservation at the international level. In contrast, remote-sensing data show that mangrove forest areas are expanding in some regions, with about 82% of this growth attributed to natural regeneration. While many studies have investigated mangrove loss and its driving factors, much less is known about the mechanisms behind mangrove expansion. This gap highlights the need for more rigorous quantitative assessments to better understand ecosystem dynamics.

　In this study, we applied a causal inference framework using fixed effects panel data analysis to control for confounding variables and examine how changes in forest area (derived from satellite data) relate to changes in potential driving factors over time. The analysis identified three key contributors to mangrove forest gains:

1. Reforestation efforts to maintain and expand planted mangrove forests (p = 0.014);
2. Expansion of protected areas, including Other Effective Area-based Conservation Measures (OECMs) (p = 0.019); and
3. Increased public engagement in policymaking (p = 0.085).

　Conversely, higher drought intensity negatively affected mangrove gains (p = 0.026). Natural factors linked to climate change, such as minimum temperature and sea level changes, did not show statistically significant time-series effects, suggesting that their influence is more geographically dependent than temporally dynamic (Fig. 1).

　Overall, our findings indicate that recent recovery of mangrove forests in Southeast Asia, which hosts over 30% of the world's mangrove forests, has largely resulted from deliberate human-driven restoration rather than spontaneous natural regeneration. This highlights the critical role of active afforestation and conservation efforts, and the need for policies that further strengthen these initiatives.

　Moreover, our study demonstrates the value of integrating diverse time-series datasets to uncover causal structures underlying mangrove ecosystem dynamics. This approach offers a more precise understanding of the relative contributions of natural regeneration and human intervention during the ecosystem recovery.

Fig. 1. Key factors influencing gross gains in mangrove forest area across Southeast Asia
This study was supported by JSPS KAKENHI (JP22H03852, JP23H01584, JP23H03605), the JST Program for Co-creation in Knowledge Integration (JPMJPF2110), and the Environment Research and Technology Development Fund (JPMEERF20241M03) of the Environmental Restoration and Conservation Agency, provided by the Ministry of the Environment, Japan.

Authors

Kizashi Koga, Master’s Program Student
Laboratory of Forest Landscape Planning and Design, Graduate School of Agricultural and Life Sciences, The University of Tokyo

Chihiro Kayo, Professor
Forest Management and Policy Laboratory, Institute of Agriculture, Tokyo University of Agriculture and Technology

Jay Mar D. Quevedo, Research Fellow
Asia Research Institute, National University of Singapore

Ryo Kohsaka, Professor
Laboratory of Forest Landscape Planning and Design, Graduate School of Agricultural and Life Sciences, The University of Tokyo

Paper Information

Journal:　Forest Ecology and Management
Title:　What drives mangrove forest gains? Evidence from six Southeast Asian countries using fixed effects panel data models
Authors:　Kizashi Koga, Chihiro Kayo, Jay Mar D. Quevedo, Ryo Kohsaka* (*corresponding author)
DOI:　https://doi.org/10.1016/j.foreco.2025.123330
URL:　https://www.sciencedirect.com/science/article/pii/S0378112725008382

Contact

The Laboratory of Forest Landscape Planning and Design, Department of Forest Science,
Graduate School of Agricultural and Life Sciences, The University of Tokyo
Tel:03-5841-5218
E-mail: kohsaka.lab[at]gmail.com
(Please replace [at] with @ when contacting.)

Collaborator　Organization

Forest Management and Policy Laboratory, Tokyo University of Agriculture and Technology
https://sites.google.com/go.tuat.ac.jp/rinkei/