Monitoring and conserving mangrove forests under climate change

ZSL is supporting efforts to conserve and restore mangrove ecosystems worldwide.

Summary of research

Mangroves are one of the most ecologically- and economically-important ecosystems in the world. Providing habitat for high levels of both terrestrial and aquatic biodiversity, containing high diversity of fish, birds, fungi, bacteria, zooplankton, invertebrates, molluscs, reptiles and mammals, and many threatened and endemic species. As well as their high biodiversity value, mangroves also deliver many valuable ecosystem services such as providing breeding and nursery habitat for economically-important fish species and preventing coastal erosion. They have been estimated to provide at least US $1.6 billion each year in ecosystem services, while their economic value is thought to be US $200,000–900,000 per km².

Mangroves are of particular significance in the context of climate change, affording among the largest per hectare global carbon stores and coastal protection from regular waves and frequent tropical storms. Growing global policy emphasis on both emissions reduction and climate impact mitigation in vulnerable countries places ever higher significance on the climate change mitigation and adaptation properties of mangroves.

A woman planting a mangrove seedling

Despite this, the relatively small area of global mangrove cover and their sensitivity to environmental changes means that they are one of the world’s most threatened biomes. Mangroves and the services they provide are disappearing globally due to processes of land conversion and climate change.

Today Mangrove forests are an urgent global conservation priority, and this has now been heralded by the recent creation of the IUCN SSC Mangrove Specialist Group. In order to mitigate the loss of these highly unique, biodiverse systems and the services that they provide, conservation projects such as ZSL’s Community-based Mangrove Rehabilitation Project in The Philippines aim to restore and rehabilitate degraded mangrove forests around the world, in order to promote regeneration of these ecosystems. However, there is currently little known about the effectiveness of such programmes in restoring mangrove ecosystem health and function, particularly in the face of processes of global environmental change – land-use and climate change.

Mangrove conservation and rehabilitation is an important Nature-based solution to tackle the global biodiversity crisis and enhance climate change mitigation and adaptation efforts in the tropics. ZSL continuously explores how remote sensing technology, such as satellite technology, can support the monitoring, conservation and restoration of mangroves, while helping to deepen the understanding of their ecological functioning and responses to global environmental change.

Mangrove forest at low tide, Philippines
Mangrove forest at low tide, Philippines

Why we are there

Coastal ecosystems, such as mangroves, provide key ecosystem services for climate change mitigation and adaptation. However, combined anthropogenic activities and climate change pose a severe threat to their global persistence, and to the continued delivery of these services. Mangrove conservation and restoration requires knowledge about their distribution, as well as a good understanding of mangrove vulnerability to global environmental change.

ZSL hosts the IUCN SSC Mangrove Specialist Group , which aims to support mangrove research and conservation projects by bringing together experts in the field to share their knowledge. Specifically, the group aims to; assess the conservation status of mangroves; identify, quantify and prioritise threats; and develop plans to conserve the most threatened species and habitats. ZSL moreover has a long-term interest in the use of remote sensing technologies to monitor wildlife and inform its conservation. Mangroves’ ecological distinctiveness make them particularly suitable for research aiming to further the role of remote sensing technology to assess ecosystems’ vulnerability to environmental change.

Practicum on mangrove outplanting

 

Impact

We introduced a novel, spatially explicit vulnerability framework able to generate assessments at the ecosystem scale and apply it to Mozambican forest mangroves, which are under growing pressures from climate change. Results showed that most of these ecosystems are currently highly vulnerable to sea level rise, while mangroves in the Zambezia and Nampula districts are highly vulnerable to both sea level rise and tropical storms. The introduced assessment framework was shown to have clear potential to inform conservation planning and management at various spatial scales, and help achieve adaptive management in the face of climatic uncertainties.

We then developed and implemented a novel multi-product (multispectral, microwave, derived-product) open-access satellite remote sensing approach to assess both coastal ecosystem sea level rise resilience and resistance capacity in multiple mangrove sites across the world, and landscape-level and anthropogenic factors driving these capacities. Our approach allows comparative ranking of resilience and resistance capacities across sites, based on relative observed ecosystem change (biomass, distribution) and in constraints to these two components of sea level rise vulnerability. Our work showed that site-specific resilience and resistance capacities and constraints can be highly incongruent, highlighting the importance of comprehensive sea level rise vulnerability monitoring for effective management. High within-site variation was also detected in resilience and resistance capacities and their constraints. This underlines the importance of spatially explicit monitoring at extensive spatial scales to inform decision making.

More recently, we investigated the robustness and adequacy of the current Red List of Ecosystem approach for risk assessments in such ecosystems, using a fringe mangrove ecosystem as a case study. Our work demonstrated how gaps in our appreciation and understanding of the structure and functioning of ecosystems are more likely to impede risk assessments of ecosystems characterised by a small number of foundation species (such as mangrove ecosystems), due to the low level of redundancy between candidate indicators available for their assessments. 
 

Project information