Between the tides and the city’s sprawl, Mumbai’s mangroves stand as silent sentinels shielding its shores from storms, filtering its waters, and anchoring life along its creeks. Yet beneath their dense roots, an unseen crisis is unfolding.
A recent study has uncovered alarming levels of microplastics, fragments smaller than a grain of sand, trapped within their muddy soils. Carried by sewage, runoff, and urban waste, these pollutants are seeping into the very ecosystems that protect the city. What was once a landscape of resilience is turning into a reservoir of toxins. As Mumbai grows, its mangroves bear the weight of its waste reminding us that the cost of neglect often lies buried, just below the surface.
Mangroves are unique coastal plants including trees, shrubs, ferns, and palms that live where land meets the sea. Their roots breathe saltwater, trap silt and sediment, and create nurseries for fish, crabs, and countless other species. They filter pollutants, store carbon, and protect freshwater aquifers from seawater intrusion. Mangrove forests are more than just coastal greenery. They are resilient, resourceful, and lifelines for both nature and people. They thrive in the zone between high and low tides, and they are regularly soaked in seawater and then exposed to air as the tides shift.
Mangroves protect coastlines, nurturing biodiversity, and sustaining communities.
Their tangled roots and rich soils provide perfect nurseries for crabs, prawns, molluscs, fish, birds, reptiles, and mammals.
They provide valuable local resources such as firewood, timber, cattle feed, honey, and traditional medicines.
Mangroves help keep freshwater aquifers safe from seawater intrusion and filter out toxic heavy metals from coastal pollution.
They act as natural buffers and reduce the impact of tsunamis, storms, and floods, saving lives and infrastructure.
Mangrove ecosystems provide services worth over $1.6 billion every year globally, supporting food security and livelihoods for millions.
The total mangrove cover of the country is 4,991.68 km2 , which accounts for 0.15 percent of the country’s total geographical area. Among this, Very Dense Mangrove comprises 1,463.97 km2 (29.33 %) of the total Mangrove cover, Moderately Dense Mangrove is 1,500.84 km2 (30.07%) while Open Mangroves constitute an area of 2,026.87 km2 (40.60%).
Of the 32,000 square kilometres of mangroves that dot Maharashtra’ s 720 kilometre coastline, a third are in the metropolitan city of Mumbai and its suburbs. While the Forest Survey of India, reports a growth in mangroves across the state, Mumbai’s suburban regions show a decline of 1.08 km² of mangrove cover. The mangroves in Mumbai are located in one of the world’s most industrialised and densely populated areas, and include four creeks: Malad, Mahim, Manori, and Mahul, which play a crucial role in supporting mangrove development.
A detailed analysis of the state of Mumbai’s mangroves in a recent study titled ‘’Assessment of secondary microplastics trapped in mangrove ecosystem of a highly populated tropical megacity, India” in the Journal of Hazardous Material Advances however reveals a startling truth. The muddy roots of Mumbai’s mangrove forests are hiding an invisible crisis. On average, 6,730 microplastic particles were found in just one kilogram of dry mangrove sediment. That’s not just pollution—it’s an ecological collapse in slow-motion.
Microplastics are tiny fragments of plastic, often smaller than a grain of sand. They come from broken-down packaging, synthetic clothes, industrial waste, and untreated sewage. Mumbai dumps 2,200 million litres of untreated sewage into the sea every day. During monsoons, this toxic cocktail floods into mangrove creeks, carrying microplastics with it. These particles do not just sit in the mud. They get eaten by crabs, fish, and birds. They carry toxic chemicals that climb up the food chain—right up to us.
The study investigated depth-wise presence and characteristics of MPs in the mangrove sediments of Mumbai to understand the contribution of urbanisation and tidal dynamics on MP distribution in this unique ecosystem.
Researchers selected six mangrove sites - three urban influenced regions namely Gorai, Versova, Bandstand and three less urbanised areas namely Sewri, Vikhroli, and Elephanta Island. The map below shows the location of these mangrove sites.
They found that:
Versova had the highest microplastic levels.
Fibres (like threads from clothes) were the most common type.
Types of microplastics
Most particles were smaller than 100 microns—tiny enough to be swallowed by marine life.
Black and translucent plastics dominated, which were possibly derived from packaging and textiles.
Colour composition
The distribution and abundance of microplastics (MPs) in mangrove sediments varied significantly across different shore types in the Mumbai region, including rocky (Bandra), sandy (Gorai), and muddy shores (Versova and Sewri). Muddy areas trapped more microplastics than sandy or rocky ones, but local pollution levels played a more important role in determining MP concentrations.
Microplastics smaller than 100 μm made up nearly 40 percent of all particles, making them the most prevalent size class across regions. These tiny particles are especially concerning due to their ability to penetrate biological tissues and evade filtration systems.
This is because the dense, tangled root systems of mangroves can trap fine sediments and microplastics. Microbial activity and organic matter in the soil surrounding the mangrove roots also retains particles smaller than 100 μm. Tidal flows, wave action, and sediment movement constantly churn this plastic debris which breaks down further into smaller particles due to UV exposure and abrasion against roots and sediments.
The microplastics trapped in the mangrove roots and soil may be consumed and accumulate in the bodies of animals and plants living at the bottom of the mangrove sediment layers such as crabs, molluscs, and detritivores threatening their health as well as that of humans consuming them.
Mangroves can act as both sinks and sources retaining particles but also releasing them during storm surges or erosion events. Microfibers - tiny threads that slip through wastewater treatment can also settle deep into ecosystems threatening survival of animals living in the muddy waters, disturb the food chain, and harm humans who consume animals such as crabs, molluscs, fish living in and near the mangroves.
This isn’t just a mangrove problem, but also a problem of how waste is managed in the city. It needs urgent actions such as:
Treating sewage before it reaches the sea
Monitoring fish and birds for plastic ingestion
Exploring new technologies like magnetic nanoparticles to remove plastics from water
Reducing plastic waste at the source like homes, industries, and packaging
Mangroves are not just patches of greenery. They are the city’s lungs, filters, and first line of defence. Their roots hold not just soil, but the stories of a coast that has long absorbed the costs of progress.
Mumbai’s mangroves are sounding an alarm, one that doesn’t roar like a cyclone or rise like a tide, but rustles quietly through the plastic-strewn mud. The question is whether we will listen before it’s too late.