A new study published in the Wiley Journal of Global Ecology and Biogeography has determined that both human pressures, when coupled with erosion, drought, and sea-level changes (i.e. certain effects of climate change), are the main culprits behind the diminishing mangrove forests in the Western Indian Ocean region.
Globally, mangroves provide goods and services estimated to be worth billions per year, including 65 billion USD in shoreline protection alone. But for many communities, including those in the Western Indian Ocean region, they are worth much more. Coastal residents eat or sell the fish who live around the mangroves, while others use their wood as building material and fuel to use themselves or sell—underscoring the importance of mangroves to both economic and food security. Mangroves also have important cultural and recreational value for adjacent communities. Yet the region has lost 20-33% of its mangroves in the past 25 years alone, a trend that—if left unchecked—is only likely to accelerate with rapid increases in population and coastal development.
These and other causes of mangrove degradation, including human pressures (logging, land-use conversion, etc.) and the effects of climate change (i.e. sea-level rise, cyclones including related wind and flood impacts, erosion, ocean climate, etc.), are well-known. “However, not all mangroves suffer equally from these drivers of deforestation,” noted Dr. Joseph Maina of Macquarie University (Australia), lead author of the study. “To create tailored responses to address mangrove degradation in different regions and increase their resilience to climate change, it is necessary to understand how mangroves are affected locally by these factors.”
This study, supported by the Nairobi Convention’s WIOSAP project, WIOMSA and Macquarie University, examines the level of exposure to threats to mangroves in Kenya, Madagascar, Mozambique, and Tanzania, applying the recently developed Western Indian Ocean Climate Change Vulnerability Assessment Toolkit. It finds that human pressure, erosion, drought, and sea-level changes are the main drivers of changes in mangrove cover in these four countries.
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