Sea Change: Bay of Bengal’s Biodiversity is in Danger

The Bay of Bengal is at risk due to disgorging of urban sewage and global climate change, writes Ranjan K Panda.

Spotted-deer on the fringe of Sundarbans, the world’s largest mangrove forest along Bangladesh’s southwest coast. (Photo: Reuters)

In December 2014, when over 75,000 gallons of oil spilled out of a drowned tanker in the Sunderbans delta, pollution of the Bay of Bengal came under international limelight. The Bay of Bengal, occupying an area of about 2.2 million sq km, is one of the world’s largest marine ecosystems, replete with biological diversity such as coral reefs, estuaries, mangroves, fish spawning and nursery areas.

The Sunderbans, straddling Bangladesh and India, is an UNESCO-designated and protected World Heritage Site. It hosts the world’s largest tidal mangrove forest, hundreds of endangered Bengal tigers, and riverine Irrawaddy and Ganges dolphins.

Urbanisation Trend

A fourth of the world’s population lives in countries bordering the Bay, at least half a billion people living in its low littoral are highly vulnerable to sea rise. Experts attribute population growth and climate change as two greatest threats to the Bay, whose health can be rightly considered as the lifeline of Asia’s economic resurgence. On World Oceans Day, I am worried about the trend of urbanisation, and a related unsustainable lifestyle-driven economy.

Representative picture. (Photo courtesy: Facebook page of Ranjan Panda)

Some of the largest and most important rivers that disgorge into the Bay of Bengal are now highly polluted. Among them are the Ganges and its distributaries such as Padma and Hooghly; the Brahmaputra and its distributaries such as Yamuna and Meghna; and rivers such as Irrawaddy, Godavari, Mahanadi, Krishna and Kaveri have all recorded alarming rates of pollution.

In five years, the number of polluted rivers in India has more than doubled. According to the latest assessment by the Central Pollution Control Board (CPCB), the number of polluted rivers has gone up from 121 in 2009 to 275. The number of stretches of these rivers has also doubled from 150 in 2009 to 302. With India’s urban population growth rate outstripping the rural growth rate, the bulk of the pollution load that our rivers receive is from urban centres.

Polluted River Stretches

The CPCB report says that the sewage generated from 650 cities and towns situated along the 302 polluted river stretches has also increased from 38,000 million litres per day (MLD) in 2009 to 62,000 MLD today. Environment Minister Prakash Javadekar recently said that effective treatment of sewerage in our cities is about 15 to 17% only. All the waste travels down to the sea.

A heavily polluted Mahanadi. (Photo Courtesy: Facebook page of Ranjan Panda)

My studies of the Mahanadi basin, one of the major river systems that empties into the Bay of Bengal, shows that waste water, including sewerage load discharge of Odisha’s major cities, alone has increased by about 300% over the last two decades.

The UN has warned that land-based sources (such as agricultural run-off, discharge of nutrients and pesticides and untreated sewage including plastic) account for approximately 80% of marine pollution, globally. Our pollution monitoring systems are currently discounting the pollution by industrial and mining affluent.

Fossil Fuel-Driven Growth

However, ground realities show that coal mining and thermal power plants have emerged as the greatest threat to the basin as well as the Bay of Bengal. Even in the Sunderbans, protests against the Rampal power plant plan show how urban lifestyle fuelled by fossil fuel and unsustainable industrial growth-based development is polluting the Bay of Bengal to an irrecoverable extent.

Immersion going on in the Bay of Bengal. (Photo: Reuters)

Assessing the role of pollution by urbanisation alone, researchers from Monash University, Australia, have projected a gloomy future for the Bay of Bengal. Expecting that 50% of the Bay’s adjacent population would be urban by 2050 — in countries like Bangladesh, India and Myanmar — they project a considerable increase in nutrient levels in rivers from sewage and other sources that would lead to harmful algal bloom in coastal waters of about 95 % of the Bay’s total drainage.

Other data, however, suggests the urban feat may be achieved much earlier, by 2035. The doom is coming faster.

Fossil fuel driven growth has another bearing on the Bay of Bengal. The rise in sea surface temperature (SST) is largely driven by global temperature rise due to increased CO2 in the atmosphere. According to scientists, rise in SST is a major cause of increased intensity of cyclones that ravage the Bay of Bengal from time to time.

Worrisome also is the fact that mangrove forests, the richest among which are found in this Bay, that act as a natural shield against cyclones are also shrinking fast due to “development.” To save the Bay of Bengal, we certainly need to look the way we are seeking ‘progress.’

(The writer is a water and climate change researcher).