The Planning Department recently issued "Hong Kong 2030", its long-term planning vision and strategy. Every citizen should be aware of this important document, since its stated goal is "a long-term planning strategy to guide future development and provision of strategic infrastructure, and to help implement government policy targets in a spatial form".

The report was a long time in the making, principally because fundamental assumptions such as population growth had to be revised. Much effort was put into consulting the community and reflecting changing social aspirations. A genuine attempt was made to give due weight to the principles of sustainability. The effort and sincerity behind the report must be recognised.

There are, however, a number of serious misgivings. One of the most fundamental assumptions to be made in long-term planning is population growth. Original assumptions were far too aggressive, and had to be scaled down. Unfortunately, the revised assumptions still appear wholly unrealistic. The base case assumes that our population will rise from around 6.8 million today to 8.4 million in 2030. This assumption is important, because it is being used to justify infrastructure planning and growing urbanisation.

Hong Kong's birth rate is around 0.9 births per woman of child-bearing age. This is the lowest in the world, well below the "replacement rate" of 2.1. It means that the population is effectively halving every generation - a demographic catastrophe. How is it that the government is able to extrapolate from this birth rate (which is a fact) a population rising by 1.6 million by 2030?

The answer given by the Planning Department at a recent meeting of the Advisory Council of the Environment (of which I am a member) is that there are many mainland-born babies with right of abode in Hong Kong, and many Hong Kong ID card holders living abroad who have the right to return to live and work here. This is laughable. With our current birth rate, our population would, by a rough measure, halve by 2030 on an organic basis. We would need 4 million mainland-born babies just to take up the slack.

This brings me to a point that I have made before in these pages: with our low birth rate, any long-term projection of population essentially boils down to immigration policy. Since the Hong Kong government denies that there is any pressure from Beijing to open our doors to immigrants, we can effectively choose whether we want population growth at all. This issue is central to much of our policy, yet there seems to have been no public discussion of it.

On the basis of the 2030 report, the government is already calling for studies for three "New Development Areas" for 100,000 to 200,000 people. This is an insidious justification of further urbanisation and infrastructure development based on flawed population growth projections.

Another area of misgiving expressed by some council members is the unimaginative responses in the report to long-term planning issues. One of the report's major constraints is that it is a product of the Planning Department - which had no influence on other key policy areas such as transport - rather than a holistic, overarching long-term vision involving other important areas of policy.

One example: the base case in the report assumes that border traffic for private cars will grow from the current 8,200 per day to 96,400 per day in 2030; for goods vehicles from 14,800 to 39,400; and for container trucks from 12,800 to 39,900. It does not seem to have occurred to the report's producers that such dramatic increases are wholly undesirable. Container truck traffic already contributes hugely to air pollution. Must these projections be taken as given? Is there no alternative?

Several council members urged the government to "dare to dream" in its long-term vision. We should be planning a 21st-century city, not reapplying 20th-century solutions.