As Mumbai expands its infrastructure to meet the demands of a growing population, the Mumbai Coastal Road Project (Phase 2) represents a major shift in the city’s mobility. However, from a climate perspective, this development involves a significant Read more
Mumbai Coastal Road Project's Impact on Mumbai's Mangroves Forest : Me
As Mumbai expands its infrastructure to meet the demands of a growing population, the Mumbai Coastal Road Project (Phase 2) represents a major shift in the city’s mobility. However, from a climate perspective, this development involves a significant exchange: the conversion of high-performing "Blue Carbon" ecosystems into concrete infrastructure. This report quantifies that exchange, focusing on the specific carbon sequestration potential of the 103 hectares of mangroves currently under diversion.
1. The Carbon Powerhouse: Why Mangroves Matter
Mangroves are not merely trees; they are complex carbon-capture systems. Unlike terrestrial forests, mangroves are "net sinks" that rarely reach saturation because they continuously bury carbon in deep, waterlogged soils where it cannot decompose.
Detailed Carbon Impact of the 103-Hectare Clearance
Based on recent studies by the Mangrove Cell of Maharashtra and global data, we can calculate the loss across two categories:
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Carbon Stock Release (Immediate Impact): Mangroves store an average of 937 to 1,023 tonnes of carbon per hectare. Clearing 103 hectares risks the oxidation of roughly 100,000 tonnes of stored carbon, equivalent to 367,000 tonnes of CO2.
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Annual Sequestration Loss (Ongoing Deficit): In tropical regions like Mumbai, mature mangroves sequester approximately 23.7 to 38.5 tonnes of $CO_2$ per hectare per year (when accounting for both above-ground biomass and below-ground sediment burial).
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Total Annual Loss: Removing 103 hectares removes the capacity to absorb ~3,200 tonnes of CO2 every year.
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2. Global Comparison: The Efficiency of Blue Carbon
To understand why mangrove loss is so impactful, we must compare it to the sequestration rates of other major forest biomes. Mangroves are widely considered the most carbon-dense forests in the tropics.
| Forest Type | Annual Sequestration Rate (tCO2/ha/yr) | Carbon Stock Density (tC/ha) | Primary Storage Location |
| Mangrove Forest | 24.0 – 38.0 | ~1,000 | Sediment/Soil (80-90%) |
| Tropical Rainforest | 11.0 – 20.0 | ~300 | Living Biomass (Wood) |
| Temperate Forest | 7.0 – 12.0 | ~150 | Living Biomass / Litter |
| Boreal Forest | 1.5 – 4.0 | ~80 | Soil Peat (Slow growth) |
Expert Insight: One hectare of Mumbai's mangroves provides the same annual climate benefit as roughly 2 to 3 hectares of a typical inland tropical forest, and nearly 10 hectares of boreal forest.
3. The Offset Challenge: From Saplings to Sinks
The government’s primary strategy is Compensatory Afforestation (CA)—planting 1.37 lakh saplings to replace the 9,000 cut and 36,000 impacted trees. While this is a necessary step, it faces three critical "sequestration gaps":
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The Maturity Gap: A young mangrove sapling has a negligible sequestration rate for its first 3–5 years. It takes approximately 15 to 20 years for a plantation to reach the sequestration efficiency of the mature forest currently being removed.
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The Soil Gap: Simply planting a tree does not immediately restore the "Blue Carbon" soil pool. Soil carbon burial is a process of centuries; excavating the Versova-Bhayandar mudflats destroys a "carbon vault" that a new plantation cannot replace in the short term.
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The Shadow Effect: For the 36,675 trees remaining under the road's shadow, research suggests their sequestration rate may drop by 20–40% due to reduced photosynthetically active radiation (PAR).
4. Strategic Recommendations for a "Net-Zero" Road
To improve the government’s plan, we recommend moving beyond a "tree count" metric toward a "carbon function" metric:
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Restoration of Abandoned Salt Pans: Rather than distant inland plantations (like Chandrapur), the government should focus on restoring abandoned salt pans in Mira-Bhayandar. Converting these hypersaline lands back to tidal wetlands offers the highest "Carbon Return on Investment."
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Advanced Sediment Management: During construction, silt curtains and specialized "tidal windows" should be used to ensure that the carbon-rich sediment in the "shadow zones" is not washed away, preserving the existing soil carbon stock.
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Blue Carbon Monitoring Stations: Establish 5 permanent carbon-flux towers along the Versova-Dahisar belt to measure actual $CO_2$ absorption. This provides the data needed to adjust mitigation strategies in real-time.
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Hydrological "Daylighting": Ensure that the piers do not just "allow" water but facilitate tidal flushing. Improving water flow to inland mangrove patches (currently choked by debris) can stimulate "compensatory growth" in existing forests, helping to offset the losses elsewhere.
References
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1. Core Scientific Papers (Blue Carbon Foundation)
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Alongi, D. M. (2014) – Carbon Cycling and Storage in Mangrove Forests
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Significance: This is the definitive review of how mangroves handle carbon. It establishes the "956 Mg C per hectare" global average.
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Donato, D. C., et al. (2011) – Mangroves among the most carbon-rich forests in the tropics
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Significance: The seminal paper in Nature Geoscience that first quantified that mangroves store up to 4x more carbon than tropical rainforests.
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2. Regional Maharashtra & Mumbai Specific Data
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Maharashtra Mangrove Cell & Foundation (2020-2030) – Thane Creek Flamingo Sanctuary Management Plan
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Significance: Provides localized data on the health, species (mostly Avicennia marina), and conservation strategies for the creek systems directly adjacent to the Coastal Road.
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Summary & Context via Urban Nature Atlas | https://mangroves.maharashtra.gov.in/
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CSTEP (2024) – Sea Level Rise Scenarios and Inundation Maps for Selected Indian Coastal Cities
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Significance: A critical July 2024 report highlighting that Mumbai's sea level is rising at 0.315 cm/year, making mangrove "bioshields" more valuable than ever.
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Systematic Study of Carbon Sequestration: Raigad & West Coast (2025/26)
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Significance: Recent empirical data from Maharashtra showing that Avicennia marina (the dominant Mumbai species) stores significantly more carbon below-ground than terrestrial zones.
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3. Global Policy & Climate Context
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IPCC (2019) – Special Report on the Ocean and Cryosphere (SROCC)
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Significance: Chapter 4 specifically discusses the "Limits to Adaptation" and the role of coastal ecosystems in protecting cities from extreme sea-level events.
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MDPI (2026) – Global Carbon Sequestration and the Roles of Tropical Forests
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Significance: A current (Feb 2026) perspective on the surplus of carbon emissions and the urgent need for "nature-based solutions" like mangrove restoration.
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FAQ
How many mangroves are actually being cut for Phase 2?
Out of nearly 60,000 trees surveyed, the government has received permission to impact 45,675 mangrove trees. However, a distinction is made between those physically removed and those "disturbed":
9,000 trees will be permanently cut to make room for bridge piers.?
9,000 trees will be permanently cut to make room for bridge piers.
36,675 trees will be in the "shadow area" (under the road), where the government aims to restore them after construction.?
36,675 trees will be in the "shadow area" (under the road), where the government aims to restore them after construction.
Will planting trees in Chandrapur (850 km away) really help Mumbai?
This is a major point of debate. Legally, the government is fulfilling "forest diversion" laws by planting 103 hectares in Chandrapur. However, ecologically, this does not compensate for Mumbai's local loss. To address this, the Bombay High Court has mandated additional mangrove-specific plantations in Palghar and Mira-Bhayandar, which are more ecologically relevant to our coastline.
How much travel time will the road actually save?
The road is designed to bridge the gap between Versova and Bhayandar. Current travel times of 120 minutes during peak hours are expected to drop to approximately 18 minutes. This 85% reduction in commute time is the primary driver behind the project’s "public interest" clearance.
Won’t removing mangroves increase the risk of flooding in suburbs like Charkop?
Mangroves are natural flood barriers. To mitigate this risk, the project includes an 8.5-meter-high seawall and specialized floodgates along certain stretches. However, experts argue that "grey infrastructure" (concrete) is less flexible than "green infrastructure" (mangroves) when dealing with unpredictable storm surges.
What is the "Shadow Zone" restoration plan?
For trees located under the elevated road, the BMC plans to use in-situ restoration. This involves ensuring that tidal water continues to flow under the bridge during and after construction. The government has also proposed setting up mangrove nurseries (10-15 hectares) along the alignment to supply saplings for densifying these areas.
Is there any independent monitoring of these environmental promises?
Yes. Under the December 2025 High Court order, the BMC is required to file comprehensive audit reports for 10 years regarding the survival and maintenance of the 1.37 lakh compensatory trees. These reports are intended to ensure that the "offset" isn't just on paper.
How does this project affect the local Koli fishing community?
The community faces two main challenges: the physical blockage of their navigation routes by bridge piers and the potential decline in fish/crab breeding grounds. The government is currently negotiating compensation and examining "navigational spans" (wider gaps between piers) to allow fishing boats to pass safely.
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