The Mangroves of Mumbai: An Asset for Cultivating Coastal Resilience

The Mumbai metropolitan region, with more than 20 million people, is one of the densest urban centres where the majority of the population lives in low-elevation coastal zones. As such, Mumbaikars are especially vulnerable to the effects of climate change including sea level rise (SLR), increased storm events and coastal flooding. However, Mumbai is partially protected by 60 km2 of mangrove forests lining its coastline: an invaluable but underappreciated asset to the city’s long-term resilience.

Mangrove wetlands are set to play a very crucial role in climate change since they are at the front line of SLR in tropical regions. Mangroves are a community of trees, shrubs and other plant species that grow in brackish to saline tidal waters of tropical coastlines (Mitsch & Gosselink, 2015). They are highly productive habitats for coastal organisms and provide critical ecosystem services that provide stability to shorelines against erosion and protect inland areas from hurricane or tidal wave damage (Mitsch & Gosselink, 2015: 311; Odum and Heald, 1972; Gedan et al. 2011). Hence, they have to be preserved as an integral element of any coastal protection system. Mumbai’s mangroves are only a remnant of what was lost to urban development since its founding as a city. However, the remnants of this protective system are further threatened by infrastructural interventions and visions that overlook – and outright destroy – the potential of these landscapes to protect the city’s increasingly vulnerable coastline.

The city of Mumbai was built by the British over decades by ‘reclaiming’ the land between the original seven islands. ‘Reclamation’ is an odd-term that privileges the claim of the ‘land’ over the ‘water’. In practice, this has meant the production of new land from culturally undervalued tidal flats, estuaries and coastal mangroves (Mathur and da Cunha, 2009).

Thus, the destruction of Mumbai’s mangrove systems began with the radical practice of reclamation in the 1700s in the south and eventually crept northwards to follow the trajectory of urban development.

After centuries of urbanisation replaced tidal, soft land with concretised, dry land, water finally made its claim in a most brutal manner. On July 26th 2005, Mumbai experienced unprecedented flooding, causing 500 fatalities and direct economic damages estimated at almost US$ 2 billion. Around 20% of the city’s area was affected, with flood waters to a depth of 0.5 to 1.5 m in low-lying areas (Gupta, 2007) bringing Mumbai to a standstill. It is no coincidence that the worst affected areas overlapped those that were historically reclaimed. The worst flooding occurred around the Mithi River – a former bayland estuary that has been transformed into a concretised channel (Refer to Image 1).

In response to this tragedy, more than US$ 600 million was mobilised towards flood mitigation strategies. The entire sum focused solely on hard infrastructure – upgrading the storm water infrastructure, adding pumping stations and building walls along the Mithi River. In some places, the walls were built to disconnect the mangroves from natural tidal influxes, effectively killing off the floodplain wetlands. Even within upstream sections of the rivers where the soft edges could provide a natural solution for flood mitigation, walls were erected to maintain the river as a channel (Refer to Image 2). 

By doing so, engineers have effectively increased the city’s risk to flooding since there are no floodplains or wetlands to slow down water flow during extreme rain events.

This is in stark contrast to an approach that leverages the inherent resilience of natural systems. In 1972, the US Army Corp of Engineers deemed floodplain wetlands so effective for flood controls that it purchased them rather than build expensive flood control structures to protect Boston. They demonstrated that if wetlands in the Charles River basin were drained and walled off from the river, flood damages would increase by US$ 17 million per year (Mitsch and Gosselink, 539). Rather than embracing some of the more contemporary approaches to infrastructure that work with ecological systems and make room for dynamic water flows, Indian cities continue to invest in overly engineered solutions that many Western cities are spending billions to undo. While the Mithi River project removed any potential for riverbank wetlands and compromised the health of mangroves at the mouth of the river, another project on the boards threatens to compromise the health of coastal mangrove systems along the western coast of the city.

The Coastal Road is a 30 km long highway that seeks to facilitate north-south flows along the western edge. It is beyond the scope of this article to go into how building more highways does little to ease congestion or the non-egalitarian nature of a project that will spend US$ 1.8 billion on a car-centric project for a city where only 4-8% of the population uses private transport to commute. The severe ecological impact of this project proposal is yet another symptom of an approach that seeks technocratic shortcuts that demand immense resources but compromises the city’s long-term resilience.

The western coast of Mumbai is rich in structural as well as ecological diversity with at least five different mangrove ecosystems, four sandy beaches and the mouth of three river systems (Refer to Image 3). There are a number of rocky outcrops, estuaries and tidal mudflats, which become important habitats, nutritional sources and sinks.

The livelihoods of many fishing communities along the coast depend upon the biodiversity this morphology affords. The technical committee report on the Coastal Road views these geomorphic features simply as “...’sharp kinks’ in the coastline that must be replaced through reclamation into ‘gentle curves’ to smoothen traffic flow.” (Indorewala and Wagh, 2015).

The report recognises the ecological impact of the project but minimises it by recommending ‘compensatory mangrove plantation’ to address environmental costs (Indorewala and Wagh, 2015). Mangrove restoration depends on getting the hydrology right – ensured by the right physiographic conditions and the drainage of water, sediments and nutrients from natural creeks and tides. The coastal road appears to disrupt these conditions entirely, so they are unlikely to succeed in its restoration.

A visual survey of the coastal road drawings of specific interchanges reinforces the assumption that no ecologist or environmental engineer played a role in its design! The road indiscriminately runs over mangroves or between the coastal interface of mangroves and the sea, both of which will decimate the health of the ecosystem (Refer to Image 3). In many places, land reclamation seeks to modify the coastline to ease the alignment of the road completely ignoring the ecological value of the ruggedness of coastal edges as habitat.

The Coastal Road has been fiscally evaluated in terms of its construction costs, but it does not consider the huge maintenance liability of hard infrastructure getting battered by the forces of tides, waves and storm surges. While natural systems like mangroves grow more complex and strengthen over time, man-made structures simply decay against the forces of nature over time without constant maintenance. In the face of climate change, Mumbai’s vulnerable coast needs immense investment to prepare for chronic stresses like seasonal flooding and long-term risks like SLR. Rather than wasting resources on a white elephant project that disrupts the city’s relationship to the coast and severs all land-water linkages sustaining mangroves, Mumbai’s planners and engineers need to work together to protect and strengthen all natural systems.

Metropolitan resilience has to be cultivated through strategic efforts to expand the ecological buffers along the coast and restore inland rivers and creeks to their natural form. Mangroves need to be given room to grow as they are squeezed by rampant urbanisation on one end and rising sea levels on the other. 

Principles from wetland science, landscape ecology and urban ecology have to inform a collaborative effort between engineers, planners, designers and citizens to achieve this goal within a highly populated estuary. The city’s citizenry successfully banded together to stall the felling of trees in Aarey Forest for the metroshed. Mumbai’s mangrove forest is in need of a similar citizen-led effort to shelve the Coastal Road project and focus on a nature-based strategy to improve our coast.

REFERENCES:
• DaCunha, Dilip and Mathur, Anuradha. 2009. ‘Soak: Mumbai in an Estuary.’ Rupa Publications
• Gedan KB, Kirwan ML, Wolanski E, Barbier EB, Silliman BR. 2011. ‘The present and future role of coastal wetland vegetation in protecting shorelines: answering recent challenges to the paradigm.’ Clim Change 106:7–29. doi: 10.1007/s10584-010-0003-7
• Gupta K. 2007. ‘Urban flood resilience planning and management and lessons for the future: a case of study in Mumbai, India.’ Urban Water J 4(3):183–194
• Inderwala, Hussain and Wagh, Shweta. 2015. ‘Mumbai’s coastal road plan is a welfare scheme for the well-to-do.’ Scroll.in April 02, 2015. Web. http://scroll.in/article/713403/mumbais-coastal-road-plan-is-a-welfare-scheme-for-the-well-to-do. Accessed: 2 March 2018
• Mitsch, William & Gosselink, James. 2015. ‘Wetlands Fifth Edition.’ John Wiley & Co.: New Jersey
• Odum, W.E., and E.J. Heald. 1972. ‘Trophic analyses of an estuarine mangrove community.’ Bulletin of Marine Science 22: 671 - 738