Shyam Chainani has lost the battle to give Mumbai its version of New York's Central Park, a breathing space the densely packed Indian metropolis so desperately needs.

Now, he has another struggle coming up: getting the 19 million inhabitants of Mumbai and its suburbs access to the eastern waterfront.

Chainani is one of India's leading crusaders on issues related to environment and heritage. The fight he lost in 2006 was about getting some public space freed up from the 600 acres of prime commercial land occupied by Mumbai's defunct textile mills, relics from the city's industrial past.

Most of that land is slowly coming on the market for construction of glitzy, glass-and-chrome office towers and high-end shopping centres and restaurants along narrow roads; very little is going to the civic authorities.

The other debate, which is yet to be resolved, involves a land area that's three times bigger, and Chainani's adversary is the Mumbai Port Trust, a government agency that's sitting on 1,800 acres of land along a sea-facing strip that starts in the south in the city's main business and financial precinct of Ballard Estate.

Home to docks, warehouses and ship-breaking yards, the strip covers the entire harbour-side shore of the island-city of Mumbai. To the north, it ends in swampland where - unbelievably for a city boasting some of the world's most-expensive real estate - there still are salt pans. "The Port Trust must return the unutilised and underutilised land," says Chainani. "Back in 1988, the Environment Ministry asked them to gradually reduce traffic and make available surplus land for greening and recreation."

Chainani has a point.

The "new" Jawaharlal Nehru Port (it's 18 years old now) was built on the mainland across the harbour, precisely to enable the "old" Mumbai port to wind down operations.

To be sure, India's economic landscape has changed. As a fast-growing economy that's also rapidly integrating with the world, India does need more port capacity. So it's not altogether surprising that rather than scaling back its use, the old port is going ahead with an expansion plan that includes building an offshore container terminal.

But it's possible to create that capacity elsewhere. A few miles southeast of the Mumbai harbour, Reliance Industries, India's largest non-state-owned company, is proposing to build what it says will be the country's deepest-draft port.

It's also possible to build a very large, supremely efficient port using a fraction of the land that the Mumbai Port Trust currently has in its possession. And when the land in question is extremely valuable - for instance in building a new financial centre, a national priority - then why delay handing it over?

The Ministry of Shipping, which supervises the Port Trust, says the calculation of surplus land by the Mumbai-based Urban Design Research Institute has used "old data" and made "incorrect assumptions".

A new bargain is required to balance the various needs.

Shortchanged

Otherwise, Mumbai will once again find the interests of its majority shortchanged, which is just what happened in the case of the mill lands. The original conditions under which the state government allowed mill owners - including the federal government - to sell their land envisaged two-thirds of it going back to the civic and urban development authorities.

The idea was that one-third of the land should be freed up for public housing and a similar amount should be used to create boulevards and recreational facilities, including one large park, or several smaller ones.

The mill owners were to be compensated with building rights elsewhere in the metropolis - or a higher floor-space index on the part retained by them - in lieu of returning badly needed public spaces in the inner city. This plan had the support of Chainani and even a large section of the former mill workers.

It was also upheld by the Bombay High Court, which blamed the diminishing open spaces for the drop in the city's capacity to absorb rainwater. That inadequacy saw Mumbai pay a heavy price during the freak floods of July 2005.

However, the Supreme Court wasn't convinced and it overturned the decision, a saga Chainani narrates at some length in his 2007 book, titled Heritage and Environment: An Indian Diary.

Today, some of the trendiest, and most expensive, real-estate projects in Mumbai are coming up on mill land. That isn't surprising.

Recently, there have been some signs of cooling in Mumbai's property market. In general, though, quality office space in Mumbai remains badly undersupplied.

But so does clean air. The battle for getting Mumbai its own Central Park has ended. And both Chainani and the city as a whole have lost.

Sure, some of the mill land is still supposed to revert to the civic and the urban-development authorities. But it's a pittance. The resolution of the port-land debate, unless carefully handled, may meet the same fate.

Navroz Mody, a founding member of the Bombay Environment Action Group with Chainani, says private businesses are quietly moving into the docklands, in anticipation of a real-estate windfall.

Once again, private wealth may come at the cost of collective welfare.