Why Delhi must convert Yamuna river into 22-km biodiversity stretch

Delhi must develop the Yamuna’s 22-km course through the city as a biodiversity stretch to mitigate the risk of lethal heatwaves that the capital and other Indian cities are likely to experience.

This was the topic of a video discussion on The Federal between CR Babu, founding director of Delhi University’s Centre for Environmental Management of Degraded Ecosystems (CEMDE), Yamini Gupt, DU Professor of Finance and Business Economics, and Vivek Chaudhary, CEMDE’s Scientist-in-charge of Tughlakabad Biodiversity Park in Delhi.

Babu said a network of biodiversity parks along the Yamuna would offer an array of much-needed ecological services. They would be heat and carbon dioxide (CO2) sinks. The multi-tier vegetation would scrub the air of dust and other particulate matter. By lowering ambient temperature, the jungles would enable the river water to absorb more oxygen, which in turn would promote the growth of microbes that purify sewage and heavy metal containing industrial waste water.

The parks, Babu said, would be a recreation of the vegetation that existed along the river before urbanisation destroyed it.

Life finds a way

When Babu began developing the 450-acre Yamuna Biodiversity Park in 2002, the wetlands had silted and the soil was alkaline. Salt-loving bushes and brambles thrived. Restoring the river’s ecosystem began with desilting the wetlands up to depths of three to seven meters and spreading the soil elsewhere on the floodplains of the river. Native grasses and legumes were planted to promote soil microbial activity. Fish fingerlings were introduced. Native plants, shrubs, and trees were brought in. Over time, nature took over. The city’s seven biodiversity parks now have about 3,000 species of plants and animals in 75 to 100 biological communities, representing about 15 ecological systems. They are home to migratory birds.

Also read: 1,200 metric tonnes of garbage removed from Yamuna, says Delhi L-G

Babu said the Yamuna is a complex ecosystem. Apart from the main water course (which has multiple channels) there are marshes, active and inactive flood plains, and the embarkment. Each of these have their unique flora and fauna. The biodiversity parks have trees at three or four different heights, and they are a tropic cascade with aquatic plants that feed microbes, grasses that are food to herbivores, which in turn are eaten by primary and secondary carnivores.

What trees do

Gupt said according to her estimation, the adult trees of Aravali Biodiversity Park in Delhi have stored about 9,000 tonnes of carbon dioxide equivalent in their trunks. In addition, they absorb about 1,250 tonnes of CO2 equivalent every year. The avoided runoff of rainwater is about 1,10,000 cubic feet or three million litres.

Gupt did the estimation using a software of the United States Department of Agriculture’s Forest Services division. She based it on a sample of 829 trees aged 15-18 years in 83 random blocks of 100 sq m each and projected the readings on to an estimated two lakh trees in the 500-acre forested area of the park. The carbon captured by grasses, plants, shrubs, young trees, and organic matter stored in soil is yet to be calculated.

However, carbon capture of 9,000 tonnes will hardly make a dent in Delhi’s annual release of pollutants, which an official study of 2014 had estimated at nearly 38 million tonnes. During the nine years since then, the pollution dumped into the air would have increased despite many countervailing measures, because of population increase. Delhi’s residents, the study said, accounted for lower emissions than residents of London, Beijing, and Tokyo, but their per-capita contribution was 1.5 times the national average.

Also read: Yamuna pollution in Mathura, Agra: NGT directs UP chief secretary to ensure remedial action

Why biodiversity parks are needed

This is the reason why biodiversity parks need to be scaled up. The 22-km stretch of the Yamuna in Delhi would make available about 7,000 hectares. If restored to the original vegetation, it could to a great extent help mitigate the effect of climate change, which is likely to be felt more acutely in the years to come. May, so far, has been unusually cool and wet in Delhi but this is an aberration. According to the Indian Meteorological Department, temperatures last summer were consistently 3° C to 8°C above normal, breaking many decadal and some all-time records in several parts of the country. This year is likely to be hotter, especially because of the likelihood of El Nino, a southern Pacific warm water phenomenon associated with droughts or deficient rainfall in South Asia.

A World Bank report on sustainable refrigeration and indoor cooling in November 2022 referred to the warning in the August 2021 report of the Intergovernmental Panel on Climate Change (IPCC) that the Indian subcontinent would suffer more frequent and intense heat waves over the coming decade. Quoting a 2019 paper of the International Labour Organisation, it said up to 75% of India’s workforce, or 380 million people, depend on heat-exposed labour, at times working in potentially life-threatening temperatures. With heat-exposed work contributing to nearly half of the country’s GDP, the country is extremely vulnerable to job losses. By 2030, it said, India may account for 34 million of the projected 80 million global job losses from heat stress associated productivity decline.

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Why Delhi must take the lead

Urban people are particularly vulnerable because cities are heat islands. Delhi should take the lead in converting the Yamuna into a biodiversity stretch. Chaudhary, who is developing the Tughlakabad biodiversity Park, said people have become more aware of the environment after the first two waves of the Covid pandemic. He said there are challenges of encroachments and finance, but these could be met if there was citizens’ pressure on the authorities to develop the biodiversity parks.

Chaudhary said the parks could also rehabilitate abandoned mines. He cited the example of Purnapani iron ore and limestone quarry, 40 km from Rourkela in Odisha, which was developed with financial support from the Steel Authority of India. This 200-acre quarry is now a vibrant ecosystem that provides livelihood to displaced tribals. They harvest tussar silk, lac, resin, honey, and other forest produce. The quarry has become a reservoir where the tribals fish for their own consumption and for sale.

Biodiversity parks along the Yamuna and the Ganga are not a novel idea. The National Green Tribunal had in its orders of July and August 2018 recommended setting these up.