Twenty-five years ago, snorkeling among the submerged roots of mangrove trees for the first time, I had an epiphany.
As I floated just below the surface of the water, I realized that this mesmerizing ecosystem would be much more than just a key research interest in my career as a marine ecologist or the muse in my endeavors as a photographer. I was struck by the realization that it would also become a symbol of resilience and opportunity in light of worsening climate change.
I have been on many research expeditions to Latin American countries to observe, study, and photograph mangroves. In Mexico, my home country, I have studied and photographed them in all their glory: hosting migratory birds after long flights; acting as nurseries for juvenile fish that eventually sustain commercial fisheries and liven up coral reefs; buffering coastlines against powerful storms; and Iโve also photographed their mud and complex systems of roots and stems, where they store the carbon dioxide they absorb from the atmosphere.
The locations and conditions of my interactions with mangroves change, but I always walk away filled with wonder, mesmerized by these altruistic trees.
Diversity of species
Experiencing a mangrove forest can be a surreal experience.
The smell is thick and inescapable, a blend of rotten cabbage and seawater. The air wraps around you like a damp blanket, heavy with the moisture characteristic of the tropics. A single egret looks out sharply from a tree perch, its white feathers arranged like a cloak. The branches quiver as a spider monkey forages for fruit. You hear a distant hum: bees tirelessly tending to their hive. The canopy is dense, but sunlight filters through the leaves and makes the brackish water glisten with the gentle ripples of the incoming tide. Long-legged spoonbills wade forward as they swing their heads from left to right, sifting through the mud with their wide bills. Something green skims across the water with hardly a splash: a basilisk lizard. Underwater, small herring dash by in unison. A pair of uneasy eyes like black marbles reveals a grouper hiding down low, patiently waiting for its chance to feed. A juvenile lemon shark retreats to the safety of the mussel-encrusted mangrove roots as a pair of crabs scrambles furtively, trying to avoid detection. At night, attracted by the scent of mangrove flowers, orange nectar bats fly speedily toward their next drink.
A high number of species find in mangroves what they need to fulfill basic needs: food, water, shelter, and mates. Indeed, mangroves are critical to coastal ecosystems, they provide a nursery for many freshwater and marine species. Their tangled roots offer refuge to young fish, crustaceans, and mollusks that represent the next generation, and ultimate survival, of their own species and thousands of others.
But what many people donโt know is that mangroves also protect people. They are the first line of defense for our coastlines and coastal communities.
The skin of our coasts
I call mangroves the skin of our coasts. This is because healthy and intact mangrove forests perform a job similar to that of our own skin: they protect us. These coastal forests are highly effective at managing the energy exchange between land and sea, which means they can absorb the energy of waves and wind; this is especially important during storms and extreme weather events. They can also help prevent erosion and reduce flooding by retaining soil and water. Mangroves also trap pollutants and sediment and therefore increase the quality of the surrounding waters, acting as a natural filtration system. One surprising benefit of mangrove forests is that they can accumulate fresh water in lagoons, creating extensive reservoirs capable of supporting the water needs of cities with as many as 50,000 people. Without a doubt, the benefits to humans โ referred to as โecosystem servicesโ โ are varied and numerous when it comes to mangroves.
Yet it can be easy to underestimate the vital need for ecosystem services, especially when they appear only as facts on a page. But these services are intrinsically linked to real places โ to real people. I have witnessed these relationships countless times in different places throughout my career as a marine ecologist, such as when I visited La Encrucijada Biosphere Reserve, a mangrove ecosystem in Chiapas, Mexico that is home to some of the tallest mangroves in the world, giants that can reach heights of more than 70 feet (22 meters).
As with most coastal regions in Mexico, the towns surrounding La Encrucijada were founded on small-scale fishing and farming, but as these communities grew, so did the pressure on the mangroves. Consequently, a few years back, the communities of La Encrucijada realized how much their well-being depends on the well-being of the mangroves and they decided to more actively protect and manage the forests by adjusting their day-to-day living. For example, the local fishing cooperatives decided to establish five fish recovery zones, which initially meant less fish being landed. Local people also updated and modified their logging methods, learning to manage the mangroves more sustainably.
For instance, local fishers are working hard to repopulate the endangered American crocodile. Families look after nesting females and juveniles, a community-led approach that can be effective at increasing the likelihood of recovery for the species while raising the ecological knowledge of local people.
La Encrucijada is a wonderful example of people developing respect for mangrove ecosystems and translating their understanding of complex ecosystems into action, fostering the protection of this reserve. And though it may seem counterintuitive at first, prioritizing the health and growth of mangroves now is likely to pay off many times over in the future.
Economic significance
Back in 2008, I came up with the idea of studying the monetary value of mangroves in relation to fisheries. Maybe, I thought, knowledge of this value would inspire people who benefit from mangroves both directly and indirectly to protect them. I organized an expedition to northwest Mexico with a few other researchers who, like me, were determined to find answers about the contribution of mangroves to the economy.
Our findings were informative and amazing. We established that just one hectare of mangrove forest โ about the size of a professional football field โ generates approximately 37,000 dollarsโ worth of fish and blue crab. And this doesnโt include other species such as shrimp or oysters, so that number could certainly be higher. Our study showed that the more mangrove trees there are, the more catches or โlandingsโ of fish that are likely to occur.
Since then, hoping to foster appreciation for mangroves, I have used different approaches to highlight economic gains from protecting areas of mangroves, economic gains that can extend beyond their specific location. This is particularly urgent now, as the world grapples with worsening climate change and nations strive to carry out commitments agreed to on the 2016 Paris Climate Agreement, and to do so without significantly hindering their economies. To be successful, this requires meaningful and committed international cooperation.
In just one example of how healthy mangrove forests translate to economic gains that transcend national borders, we can look at the mangrove forests and coastal lagoons of Mexico. In an effort to foster transnational interest in the protection of Mexican mangroves, I became interested in uncovering the relationship between the abundance of migratory waterfowl and revenues from the hunting industry beyond Mexican borders. I partnered with other researchers to investigate.
Hunting may be a polarizing topic โ but sometimes we ecologists need to get creative and focus on the bigger picture: the protection of critically endangered ecosystems. We discovered that one square kilometer of mangrove forest or coastal lagoon in northwest Mexico can be worth as much as $1,640 in duck-hunting revenue in the US alone. This is because mangroves provide habitat to these waterfowl during the harsh US winters. We also estimated that Mexican wetlands generate between three and six million dollars of extra revenue for waterfowl hunters each year.
Mangroves have a far-reaching impact, and their loss would lead to serious economic losses and a catastrophic chain of events.
Carbon sponges
Mangroves are incredibly valuable in other ways, too: the carbon potential of mangroves concerns the entire world.
Ever since my first exploration of mangroves, their least well-known benefitโor in any case their least visible โ has attracted my attention. While a decarbonization of our economies (i.e., shifting away from fossil fuels towards clean, renewable energy sources) is the major action we need, mangroves can be a powerful ally to help mitigate the climate crisis, due to their remarkable ability to capture carbon dioxide and store it in their biomass and the sediment below their roots. In other words, mangroves are highly efficient โcarbon sponges,โ storing more carbon than any other type of tropical forest. In fact, research has shown that they absorb more than four times the amount of carbon dioxide that rainforests do. Most of this carbon, also known as โblue carbon,โ is stored for a long, long time โ Iโm talking thousands of years โ in deep layers of rich mud and peat. In some mangrove forests, peat has been found stretching down ten meters and dating back more than 10,000 years.
The environmental and ecological importance of mangrovesโ carbon absorption qualities cannot be overstated. It is a critical link within the complex systems that help maintain balance on the planet. But unfortunately, mangroves are suffering rates of deforestation and degradation of about one two percent per year. That may not sound like much, but then we must remember that the loss rate of mangroves reached 35% in the last 30 years and some regions lost as much as 80% of their mangroves. This is exceptionally worrying because a loss of mangroves not only means a loss of carbon sequestration and other benefits, it also means a release of the carbon theyโve stored in the soil for hundreds or thousands of years, which then contributes to rising carbon emissions and worsens climate change.
For better or worse, just ten countries contain almost 70% of the worldโs mangroves: Indonesia, Brazil, Australia, Mexico, Nigeria, Malaysia, Myanmar, Papua New Guinea, Bangladesh, and India. However, until very recently, most international policies surrounding conservation were failing to respond to calls from scientists to include mangrove protections and consider blue carbon in light of climate change.
Mexico alone contains 700,000 hectares of mangroves, the fifth largest area of mangroves in the world. But at the current rate of deforestation, half of mangrove forests in my home country will be lost in the next 25 years, and with them, their carbon stocks would be released into our atmosphere. If youโre wondering how much carbon that would be, well, we had the exact same question.
Carbon is stored in four carbon pools: above ground biomass, below ground biomass, soil carbon, and litter fall. Soil carbon is the largest pool and contains three times the mass of carbon stored per hectare compared to other forests. On average, one hectare of mangrove stores around 500 tons of carbon and has an estimated value ranging from $63,000 to $92,500. It has been estimated that it could take almost 200 years to accumulate all this carbon. So it is quite a significant amount.
During one of our studies, my colleagues and I evaluated the carbon stocks for each of Mexicoโs 174 coastal municipalities and identified the deforestation rate to estimate the amount of carbon that will be released by continued habitat destruction in these areas over the next quarter of a century. Based on our results, we were able to estimate the damages from climate impacts that could be avoided by safeguarding mangroves in the area.
Once again, shifting our energy needs away from fossil fuels and toward clean, renewable sources is the best way to address the rising carbon emissions that are driving climate change. Coastal wetlands like mangroves โ in Mexico and across the world โ will be incredible allies and part of the solution.
Building momentum
Together, all the benefits of mangroves โ support for fisheries, coastal protection, climate change mitigation โ are worth an estimated $100,000 per hectare annually, anywhere in the world. Despite this, we continue to destroy these forests in favor of industrial enterprises such as oil palm plantations, shrimp farms, and coastal development.
The value of mangroves is immense, yet it remains little known and poorly understood in many countries. Long considered nothing more than swampy forests standing in the way of lucrative coastal real estate, we are now able to better understand all that they provide to us.
The tide is beginning to turn. My studies, as well as many others concerning the valuation of mangrove ecosystem services have received unanticipated interest and concern by Mexican and international media. Using my images of mangroves, I have helped communicate their value, their intrinsic beauty, the species they support, and the threats they face. Using the power of a photograph backed by science, I have been able to prove that when a mangrove lagoon is dredged and transformed, valuable ecological services and the economic potential of a healthy mangrove forest are lost. This is creating a palpable shift in the attitudes of governments towards mangroves and in the communities fighting to protect them.
Finally, it seems, mangroves are gaining the appreciation they deserve. In fact, a recent report commissioned by the High Level Panel for a Sustainable Ocean Economy concluded that, over the next 30 years, investing between $2 trillion and $3.7 trillion globally across several sustainable ocean-based policy interventions would generate a net benefit of US 8.2 trillion to 22.8 trillion dollars. Can you guess what one of the four recommended major investment areas is? Yep, maintaining mangrove ecosystems.
We must ensure this momentum is not lost. Now more than ever, we need the skin of our coasts.
