Does Hong Kong really need 470,000 flats over the next 10 years?

In the scramble to provide more housing, Chief Executive Leung Chun-ying has proposed to increase building densities across the city. According to a paper submitted by the Development Bureau to the Legislative Council at the end of January, development densities will rise by 20 per cent, except in the already extremely crowded parts of northern Hong Kong Island and Kowloon.

This means that permitted plot ratios - the total built area of a development divided by the total site area - may rise from 5 to 6 times in moderately dense areas like Ho Man Tin; and from 3 to 3.6 times in suburbs like Pok Fu Lam. Similar increases are planned for new towns. Even the Kai Tak new development, originally planned to have to a lower density to provide an "urban oasis", has been targeted.

Amazingly, not that long ago, policymakers were concerned about building densities. After the 2003 severe acute respiratory syndrome epidemic, public health experts warned that urban density and poor ventilation may aid the spread of disease. Only a few years ago, environmentalists campaigned against walled buildings, excessively large podiums, and the heat island effect.

The government developed guidelines to assess air ventilation and asked the Council for Sustainable Development to come up with recommendations on sustainable building. Now the policy paradigm - along with the property market - has swung in the opposite direction.

To be fair, taller buildings are not necessarily bad for the environment, if planned intelligently to preserve green spaces and allow for the free flow of air, and if the infrastructure can handle the additional population. The Development Bureau's paper does say that it would increase density only where the transport infrastructure could bear it, but its language concerning other environmental impacts is worryingly vague.

Besides, we need to ask whether Leung's plan to build 470,000 flats over the next 10 years is necessary or realistic.