How Mapping Mangrove Species Can Help With Coastal Erosion Mitigation

Mark Altaweel

Updated:

Coastal erosion is on the rise due to climate change. Fortunately, mangroves offer a natural solution to help limit this erosion.

How mangroves limit coastal erosion

A type of tidal vegetation, Mangroves play a vital role in mitigating coastal erosion through their dense and complex root systems, which stabilize soil and sediments by binding them together and preventing them from being washed away.

Additionally, the roots and trunks of mangroves act as natural barriers that dissipate wave energy, reducing the impact on shorelines. Mangroves also trap sediments with their roots, facilitating sediment accumulation and elevating the land, which enhances the coastline’s resilience to erosion and storm surges.

Mangrove protection against coastal erosion varies by species

While most mangrove species provide some level of coastal protection, they differ in their ability to accumulate sediments and buffer storm surges.


Free weekly newsletter

Fill out your e-mail address to receive our newsletter!
Email:  

Red mangrove habitat, Everglades National Park. Photo: NPS
Red mangrove habitat, Everglades National Park. Photo: NPS, public domain.

To understand and enhance the protective role of mangroves, it’s crucial to develop a detailed map showing the distribution of different mangrove species. This map would allow for accurate modeling of mangrove growth and their potential to protect coastlines.

The Need for Species-Specific Mangrove Mapping

A new global dataset has been created by researchers from the University of Queensland that attempts to map mangrove distributions. The benefit is the data can enable coastal engineering to be better planned, provide more clarity for marine scientists and wetland ecologists, and sequester carbon.

Increased attention has been given recently to how mangroves can mitigate erosion and limit some of the worst damage from storms. However, to forecast this potential there needs to be a species distribution map, given variability in different mangrove species to protect coastlines.

Map created by Twomey and Lovelock (2024) of the frontal mangrove species/genera for each Marine Ecoregions of the World (MEOW).
Map created by Twomey and Lovelock (2024) of the frontal mangrove species/genera for each Marine Ecoregions of the World (MEOW).

Key Factors in Mangrove Protection

Key factors in mangroves include their variability that affects volume extent, depth of their growth, density, and root and branch architecture that affects soil accretion. Species that have large aboveground root systems are much better at attenuating high waves, with Rhizophora spp. having been demonstrate to attenuate waves up to 70%.

Hydrodynamic models are typically used to estimate the effects of mangroves on coastal erosion by modeling drag. However, given species-specific effects, models could be highly inaccurate without knowing what species is growing in coastlines modeled.

Nukuhou coastal wetland. A tidal wetland with grey mangroves (Avicennia marina) and salt marsh threatened by sea level rise. At Ohiwa Harbor, North Island, New Zealand.
Nukuhou coastal wetland is a tidal wetland with grey mangroves (Avicennia marina) and salt marsh threatened by sea level rise. Photo: Ohiwa Harbor, North Island, New Zealand, USGS.

Developing Zonation Diagrams and Species Distribution Profiles

Scientists have created zonation diagrams that qualitatively describe where given species exist as well as their distribution profiles. This is often based on factors such as intertidal environmental factors, salinity, soil-type, sedimentation available, and nutrient availability.[1] 

Although these data typically do not have coordinates, they can be used to help project and estimate where given mangrove species can be found given their detail. Using this, scientists projected mangrove species presence and discrete order of mangrove species in intertidal areas, ranging from seaward to landward locations. Marine ecoregions can be projected as well with given distributions based on the data as region-specific information is generally provided.[2]

Structured Search Approach for Mangrove Mapping

To create the map, a structured search approach using terms (country name, mangrove zonation, etc.) was used to find relevant diagrams for given regions. This was done for every country that has an ocean border (141 in total). From this, 195 studies and 510 zonation diagrams were found. Although for many zonation areas an exact coordinate location was not indicated, location names were generally found and this allowed a specific region to be projected with given mangrove profiles.

Spatial data with marine ecoregion information enabled projections of where specific mangrove species could grow as well as estimate their profile and zonation. Frontal species for different areas were selected based on the diagrams.

The most common species was used for areas that had multiple diagrams. If regions had multiple diagrams and different species’ patterns, multiple polygons were created to represent the region and its varied speciation. All validation of the final mapping results were checked using Google Earth.

Threats to Mangroves

The release of these data is very timely as recently there has also been news that many mangroves are under great threat, with potentially half of mangrove zones facing potential collapse by 2050.  The International Union for Conservation of Nature (IUCN) Red List of Ecosystems recently announced an update to threatened ecosystems.[3] 

Many global mangrove ecosystems have been classified as vulnerable, endangered, or critically endangered, with 20% assessed as high risk. Pollution, development, deforestation, and dam development are among human activities threatening various mangrove zones.

Although mangroves can help mitigate flooding, they are also threatened by overall sea level rise. About 33% of mangrove ecosystems recently observed show some stress from climate change. If these mangroves under threat are lost by 2050, this would potentially mean the loss of 1.8 billion tonnes of carbon stored (17% of all carbon stored in mangroves) and 2.1 million people would face more severe flooding threat.

The Critical Role of Mangroves in Protecting Coastal Communities

Some mangrove species have become vital in protecting coastal zones and providing important resources for communities. Their loss could be harmful to these communities; however, understanding this loss is not possible without better mapping data and improved modeling.

Now that we have an improved map of mangrove species and their distribution, we can better estimate where their loss could threaten communities the most. This information can be used to aid conservation efforts that not only protect specific mangrove zones but also help better target efforts and resources for protection measures as storm surges and coastal erosion become more common problems.

The Critical Role of Mangroves in Protecting Coastal Communities

Preserving mangroves and restoration are the best ways in which mangroves can be helped. Ecosystem integrity needs to be maintained to enable greater protection offered by some of these mangrove zones.[4]

Some mangrove species have become vital in protecting coastal zones as well as providing important resources for communities. Their loss could be harmful for these communities; however, understanding this loss is not possible without better mapping data and improved modeling. Now that we have an improved map of mangrove species and their distribution we can better estimate where their loss could threaten communities the most. This information can be used to aid conservation efforts that not only protects given mangrove zones but could help better target efforts and resources for protection measures as storm surges and coastal erosion increasingly become common problems. 

References

[1]    Factors influencing mangroves can be further explored here:  Ragavan, P. et al. Three decades of global mangrove conservation–An overview. Malayan Nature Journal 72, 551–576 (2020)..

[2]    For more on how the global mangrove ecosystem map was created, see:  Twomey, A., Lovelock, C. Global spatial dataset of mangrove genus distribution in seaward and riverine marginsSci Data 11, 306 (2024). DOI: /10.1038/s41597-024-03134-1.

[3]    The IUCN Red List.

[4]    The IUCN press release on threatened mangrove ecosystems.

Photo of author
About the author
Mark Altaweel
Mark Altaweel is a Reader in Near Eastern Archaeology at the Institute of Archaeology, University College London, having held previous appointments and joint appointments at the University of Chicago, University of Alaska, and Argonne National Laboratory. Mark has an undergraduate degree in Anthropology and Masters and PhD degrees from the University of Chicago’s Department of Near Eastern Languages and Civilizations.