Micro, meso, and macroplastics are significant by-products of human activities that have entered our oceans, creating a pressing global issue. These particles pose a serious threat to marine life and lead to alarming consequences for the delicate balance of underwater ecosystems. Among the most vulnerable habitats affected are mangroves, which play a crucial role in providing biodiversity and regulating climate stability.
Mangroves are remarkable ecosystems composed of trees, plants, microbes, and animals that live at the interface between land and sea. They offer coastal protection, support vital natural processes, and serve as dynamic centers of biodiversity, as well as sources of economically valuable resources. Furthermore, mangroves demonstrate the principles of circular economy by efficiently utilizing resources that enhance sustainability and resilience in coastal environments. Safeguarding these areas is vital, not only for preserving habitats but also for ensuring the planet's health and humanity's well-being.
Mangroves’ Ecological Role
Mangroves provide a wide range of ecological functions and ecosystem services. Around 75% of commercially caught fish and prawns, along with numerous species of crabs, mollusks, birds, reptiles, mammals, amphibians, and insects, rely on mangrove habitats, which serve as spawning, nursery, and feeding grounds.
Vegetated coastal habitats have powerful processes that positively contribute to climate change mitigation, such as CO2 sinks, and adaptation, such as shoreline protection. MaMangrove soils contain three to four times the mass of carbon commonly found in boreal, temperate, or tropical forests. Their remarkable capacity to sequester and accumulate large stocks of carbon in their sediments at millenary time scales allows them to bury a similar amount of organic carbon to terrestrial forests annually, despite the extent of coastal marine vegetation being less than 3% of that of forests. Furthermore, the complex network of roots, along with the dense layer of coastal vegetation, helps to protect soil carbon reserves from erosion. Nonetheless, it has been observed that the removal of mangroves and salt marshes can destabilize soil carbon stores, exposing the soils to the atmosphere—these bare habitats then release CO2 and CH4 into the air. Ultimately, vegetated coastal areas can shield the coastline from the impacts of climate change events like waves, storm surges, and tsunamis by causing wave energy to dissipate through flow separation.
Researchers estimate the monetary value of the benefits, or “ecosystem services,” such as filtering runoff, carbon stock, trapping and stabilizing sediments, nutrient cycling, and shore protection provided by mangroves at $194,000 per hectare annually. Multiplied by their global extent, the world’s remaining mangroves provide around $2.7 trillion in services annually.
Threats to Mangrove Ecosystems
Regardless of their significant role, mangrove ecosystems are susceptible and currently face threats from various pollutants. The majority of the waste contaminating the mangroves consists of plastic, textiles, glass, wood, and more. Plastics account for approximately 70% of all marine debris related to the mangroves. Although they are durable, plastics break down into different sizes of fragments, including microplastics (<5 mm), mesoplastics (5–25 mm), and macroplastics (>25 mm), posing risks to living organisms. Additionally, the increased anthropogenic activities carried out in both coastal and nearer mangrove areas might introduce many sorts of contaminants into these mangrove ecosystems by improper waste management practices, affecting microorganisms' health.
With plastic production increasing every year and the unresponsible human behavior in coastal regions, mangrove sediments have served as plastic sinks. Because of their complex aerial root systems, mangrove forests have a high structural complexity, creating a high trapping potential for marine debris. The retention of particles occurs when plants’ shoots, roots, and pneumatophores interact with the top layers of the water column, where microplastics are typically found. A study conducted in the Red Sea and the Arabian Gulf shows that despite the low rate of microplastics in the surface waters, these two areas are actually sequestrating and settling in the seafloor. These plastics remain undegraded in sediments for decades.
Moreover, microplastics can be easily confused with food and are consumed by numerous marine species across nearly all trophic levels, such as invertebrates, turtles, seabirds, fish, and large marine mammals. This results in the absorption of harmful chemicals that frequently become part of the human food supply, posing a risk to the entire food chain. Microplastics can enter and accumulate in various organisms associated with mangroves, such as mollusks and fish, causing adverse impacts such as weight loss, slow reproductive growth, and fecundity rates. Additionally, it has been observed that a rise in the proportion of surface area occupied by litter within a mangrove forest was significantly linked to a reduction in the number of active crab burrows, and there were also sightings of crabs burying plastic.
Circular Economy and Mangroves
Mangrove ecosystem services are connected to the principles of the circular economy in multiple aspects. They sequester substantial quantities of carbon in their underground structures, comprising a mix of old and new roots. Additionally, they efficiently utilize nutrients when possible and reduce energy expenditure, which enhances their evolutionary resilience. This symbiotic relationship within the mangrove ecosystem exemplifies the circular economy’s focus on interconnectedness and resource efficiency, where waste from one species becomes an input for another, minimizing waste.
Despite mangrove's effectiveness at capturing "blue carbon’’ and storing it, the majority of the algae population does not aid in carbon sequestration. Nevertheless, it can play a role in alleviating climate change if it is utilized to produce biofuels. This innovative approach involves creating what are known as "blue fuels," which offer even more significant benefits compared to conventional green biofuels and have the potential to create multiple positive environmental and social effects.
Strategies to reduce plastic waste
Reducing waste at its origin is essential for stopping plastic pollution from affecting fragile environments like mangroves. According to the circular economy model, minimizing plastic waste involves creating products and systems that decrease dependency on new plastics and decrease environmental discharge. This can be accomplished through methods such as substituting materials, enhancing product design for durability, and establishing circular supply chains. Furthermore, implementing strategies to prolong the lifespan of plastic items by repurposing them for various uses diminishes the necessity for new plastic production and alleviates waste buildup.
Thanks to new technological advancements, it is now more feasible to address plastic pollution at its origin, such as by adopting biodegradable plastic alternatives. The term ‘bioplastic’ describes plastic made from renewable biomass resources. The application of bioplastics offers various environmental benefits, including improved resource efficiency by utilizing biomass as a raw material, conserving fossil fuel resources, decreasing greenhouse gas emissions and the carbon footprint, and lowering the overall manufacturing costs of products. Industries that are increasingly seeking bioplastics include single-use bag production, the manufacturing of household items (primarily for bathroom use), and the use of bioplastics for agricultural quilting. Nevertheless, it’s important to note that not all biodegradable materials meet the necessary technical standards for safety in marine environments, as some only break down under particular temperatures and industrial settings.
One of the main routes of environmental pollution through microplastics is the wastewater treatment plants. Techniques that prevent plastic from reaching coastal ecosystems may ensure the removal of micropollutants and may reduce their concentrations before discharging them into open water sources. However, microplastics removed from wastewater during treatment processes are often washed away with the sludge, which is commonly used as organic fertilizer ending in the fields.
Another waste stream comes from the fishing industry. Fishing nets, floats, fish boxes, crates, traps, barriers, weirs, line gears, and packaging materials are used during fishing operations. When improperly disposed of in marine or coastal environments, they break down and release microplastics, which can be toxic. Ensuring proper disposal practices is crucial.
Almost all microplastics' emergence into the environment arises from anthropogenic or human activities. Our daily-use products, such as textiles, teabags, paper cups, food containers, personal care products (PPCPs), and face masks, are some of the main sources of microplastics. Therefore, educating the public is the primary and essential action that should be taken to reduce the sources of microplastics and lessen their release by human activities.
Ultimately, enhancing collaboration among scientists, environmental advocates, governments, NGOs, communities, and industries is necessary for creating innovative, scalable solutions for plastic management that safeguard mangroves. To tackle this issue, a holistic strategy is essential, which should involve more efficient waste management, policy implementation, education, and raising public awareness. For example, tourists' involvement in conservation initiatives can be increased through campaigns aimed at minimizing single-use plastics, like the "No Plastic Straw" and "No Plastic Bags" initiatives. Moreover, stakeholder meetings like the upcoming INC Fifth Conference, scheduled to take place from November 24 to December 1 in Busan, Korea, are poised to advance these collaborative efforts significantly. This conference aims to facilitate the development of an international legally binding agreement addressing plastic pollution, with a particular emphasis on safeguarding the marine environment. By incorporating the initiatives and commitments from the INC Fifth Conference into both local and global plans, there is an increased opportunity to achieve significant reductions in plastic waste, ultimately leading to the protection and restoration of mangrove ecosystems around the world.
Mangroves exemplify how natural systems can contribute to sustainable development by capturing carbon, nurturing biodiversity, enhancing water quality, and shielding our coastlines. With the right combination of research, policy instruments, and sustainable practices, we have the power to protect these vital ecosystems and continue to thrive from the fundamental services they offer. But the journey doesn’t end here-it’s time for all of us to take action. Imagine a world where every piece of plastic is reused, recycled, or thoughtfully disposed of, ensuring our mangrove guardians remain pristine and resilient. The health of our mangroves—and, indeed, our planet—depends on the choices we make today. Together, we can turn the tide on plastic pollution and secure a greener, healthier future for generations to come.