Evie Ward

Background: Evie is a Project Officer at the Plan Vivo Foundation who has a particular interest in marine conservation. This blog reflects some of her research that she completed during her masters degree in this area.

  

 

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Blue carbon has been getting a lot of attention recently, and rightly so. Amongst the most productive environments on the planet, there is increasing evidence to show that many coastal and marine ecosystems store carbon at a greater rate than their terrestrial counterparts. This makes them a key tool in the mitigation of climate change and the transition to a net-zero economy. It will come as no surprise to those who have worked or studied alongside me that mangrove forests are my favourite of all biomes, and so I am increasingly excited by the growing interest in blue carbon projects in the voluntary carbon market. However, when much of the focus is on their physical and chemical properties, it is easy to overlook the other myriad of benefits that these ecosystems provide. Whilst I am always impressed by the capacity of mangrove forests to accrete sediment over time, storing huge amounts of carbon, it is not their climate change mitigating abilities that initially drew me to these unique ecosystems.

Intertwined in the tangled root systems below the water’s surface, and up in the trees’ canopy, is a huge amount of life. At the margin between land and sea, mangroves are highly dynamic ecosystems and are important for maintaining the high biodiversity of the tropics. A recent study found that 13% of all marine megafauna use coastal vegetated wetlands, including mangroves, at different points in their lives. Mangroves act as nurseries for juvenile marine animals, with species such as the near-threatened bull shark and lemon shark, and the critically endangered smalltooth sawfish, seeking more sheltered waters during their vulnerable early life stages. Meanwhile, turtles, manatees, dolphins and more all enter the nutrient-rich waters of mangroves to forage and graze on the variety of molluscs, crustaceans and plants that inhabit the areas. They are also important for terrestrial biodiversity, and it was found that almost 500 different terrestrial mammal, reptile and amphibian species use mangroves around the world.  

 

An aerial shot of the Tahiry Honko project’s mangrove forests

 

However, there is more to mangrove-associated biodiversity than the charismatic megafauna mentioned above. Mangroves are also the cornerstone of many of the world’s fisheries, as numerous fish and invertebrate species use mangroves as breeding grounds and as a refuge from predation when young before heading out into the open ocean or nearby reefs. A global analysis found that each year, current mangrove cover adds more than 1,000 trillion fish and invertebrates to coastal waters around the world. Whilst acting as incredibly productive, fish-generating systems, the narrow channels and dense root growth make it difficult for large scale, commercial fishing activities to take place. This means that mangroves are ideal fishing grounds for local, artisanal fishers who rely on their catch as their main livelihoods or source of protein. Given that coastal fishing communities are amongst those hardest hit by climate change, it is vital for food security that healthy fish stocks and their habitats are maintained. 

Yet, despite their importance to both human and non-human life, estimates suggest that 20 – 35% of global mangrove cover has been lost between 1980 and the early 21st century. Whilst this rate of destruction has since slowed, anthropogenic causes such as land-use change still account for almost 2/3 of global mangrove loss. This is leading to a decrease in the biodiversity of mangrove ecosystems and a growing need to conserve existing mangroves and restore those that have already been lost. Alongside climate change, biodiversity loss is one of the biggest issues faced by humanity and our planet today, and one that is not as often talked about. We are amid a rapid and continued decline in species and estimates show that 1 million species are threatened with extinction, many of which rely on the existence of unique and specific habitats such as mangroves. 

Whilst the conservation of already established mangroves should maintain a priority, modelled predictions have found that ecosystem restoration can help to reverse the current downward trajectory. By restoring just 15% of degraded landscapes and wetlands in priority areas, it is estimated that over 60% of these expected species extinctions could be avoided. However, tree planting alone is often insufficient in restoring mangroves to their natural state, and many restoration efforts have historically failed. It is valuable to focus on ecologically restored mangroves, designed with optimum species habitat in mind to facilitate the return of fauna. Importantly, many animals that live in mangroves also help contribute to the growth and survival of the trees, and so biodiversity should not be an afterthought. Migratory birds, for example, connect habitats and bring in nutrients to sustain growth, whilst nectar-feeding bats can be important pollinators. By focusing on the restoration of ecologically functioning mangroves, it is possible to meet the trifecta of climate, biodiversity, and livelihood benefits that underpins the Plan Vivo approach.