Research shows that Bengal receives less transboundary pollution compared to other Indian states

The West Bengal Pollution Control Board (WBPCB)’s decision to set up a bio-shield — a wall of mega plantations — along its western fringe for stopping air pollutants from entering the state has raised questions.

The Board’s rationale is that pollution from other states is responsible for close to half of West Bengal’s pollution load.

The detailed project report is yet to be finalised. But it is expected that the project will cover around 800 kilometres (km) across the Purulia, Birbhum, Paschim Bardhaman and Jhargram districts.

All four districts are part of the Rarh region and lie on Bengal’s border with Bihar, Jharkhand and Odisha. The West Bengal Biodiversity Board has been entrusted to execute the project.

“WBPCB has come up with a unique plan of putting up a bio-shield, a massive plantation, along the borders of our state to prevent the incoming air pollutants. We have already cleared the proposal that may take a few years to give dividends as the trees will take some time to attain maturity,” West Bengal’s Environment Minister Manas Bhuiya told this reporter recently.

“We have planned the bio-shield to curb the inflow of transboundary air pollution in Bengal, which is about 50 per cent of our overall load, from adjoining states. We also receive sizable air pollution from Bangladesh,” WBPCB chairman Kalyan Rudra said.

Experts disagree

Several experts across India, with whom this reporter spoke, have pointed out that WBPCB’s ‘unique’ plan, the execution of which may run into several crores and take years, may not serve its purpose.

Gufran Beig, an air pollution expert and director of the System of Air Quality Forecasting and Research (SAFAR) network set up by the Government of India, said the green wall is not likely to have any direct role in countering the flow of transboundary pollution.

He told this reporter December 22, 2022:

The transboundary pollution flows in between 500 metres and 2 km beyond the boundary of inversion layer with local pollutants based on the season and climatic condition; and hence bio-shield or green wall has no direct relation in countering any pollution flowing within Bengal from beyond its border. 

“I do not know exactly what the WBPCB has planned but our research findings show that transboundary air pollutants, especially the most toxic PM 2.5, normally moves at least 500 metres above the surface during winter,” Abhijit Chatterjee, an air pollution scientist associated with the Bose Institute, said.

Transboundary pollutants were thus unlikely to be arrested by bio-shield which will be at a much low height, Chatterjee said.

“Transboundary movement of pollution can be curbed only with a regional clean action strategy to cut emissions from a large number of pollution sources spread across the region. Green walling with plantations can only filter dust to some extent and that too if it is hugely extensive,” Anumita Roy Chowdhury, executive director, research and advocacy, Centre for Science and Environment (CSE), New Delhi, told this reporter.

However, both Beig and Chatterjee accepted that massive plantations may play a limited role in arresting the pollutants which mix with local pollutants once they land; or to address locally generated pollutants.

“You may expect a 10-20 per cent reduction,” added Beig.

“Rather than having a bioshield, perhaps West Bengal requires a treaty and coordinated programme with adjoining states and places like Bangladesh to minimise the impact,” said SN Triphathi, an air pollution expert from the Indian Institute of Technology, Kanpur.

Tripathi told this reporter he is not aware when asked whether there was any instance in the country or even internationally where transboundary pollution has been attempted to be stopped through green-walling.

West Bengal receives less transboundary pollution at a proportional scale, compared to many states, research shows.

CSE has referred to a research paper in a recent report which points out that transboundary pollution sources contribute about 46 per cent of West Bengal’s total pollution load, a statistic comparable to the national average.

The paper, titled Cross-state air pollution transport calls for more centralization in India’s environmental federalism, was written by Xinming Du of Columbia University in the United States and other scientists. It was published in the journal Atmospheric Pollution Research.

Telangana receives the maximum amount of transboundary pollution — 68 per cent — among Indian states and Union territories, according to the paper.

It is followed by Chandigarh with 65 per cent and Odisha with 62 per cent. Of 22 states considered for the study; 13 receive a higher proportion of transboundary pollution compared to West Bengal.

The green wall will cost many crores, according to tree plantation experts.

“Even if we consider trees to be planted at a distance of two metres from one another, we are looking at a possibility of planting 400,000 trees for 800 km in one row,” said wildlife expert Biswajit Roy Choudhury, who heads a non-profit that has planted millions of trees in West Bengal and elsewhere in the country.

Roy Choudhury estimated the total cost of the project was likely to be Rs 12 crore considering the mortality and maintenance of planted trees over the period.

“If multiple rows of plants are erected; the cost will increase manifold,” he added.

“We are not against tree plantation. But we would like to know the scientific evidence on the basis of which WBPCB has made such a costly decision. If it is so useful, why are regions like Delhi and the National Capital Region, which are so much affected by transboundary pollution, not doing the same? We feel that it will lead to nothing but a waste of money,” said an environmentalist associated with the environment platform Sabuj Mancha.

“We do not have any evidence (that such an initiative will succeed); you may say we are building up the evidence,” said a senior WBPCB official while responding to the point raised by environmentalists.

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