Earlier this month, I had the pleasure of visiting New York and experiencing the dynamism and vibrancy of the Big Apple. I am also in regular touch with our World Expo counterparts in Shanghai as we gear up for participation in the Shanghai Expo.

In New York, Shanghai and Hong Kong, there is growing emphasis on our open spaces and how to make the best use of them.

Here in Hong Kong, about 46% of the land is country parks, or protected space. Less than a quarter of Hong Kong is regarded as "built up". That's partly because the rocky terrain that makes construction difficult and expensive, but it also in some way reflects our love of nature.

Despite the limited land supply, our population has soared from 4 million in the 1970s to 7 million today. And our census and statistics projects that by 2036, we will reach 8.6 million people.

To cope with the population growth, our planners, architects and engineers have been looking for new - and often higher - solutions.

At the same time, there is increasing environmental awareness and growing demand for high-quality living and more balanced development. This covers not only cleaner air and water, but also better recycling facilities and waste disposal facilities. It is also about preserving our built heritage and enhancing the character of our city.

Here, the Government has an important part to play in terms of planning and regulations.

Under the Hong Kong Planning Standards and Guidelines, building height and density regulations are assessed together with the provision of public facilities, such as transport, utilities and social infrastructure.

In particular, where appropriate building height is to be lowered to preserve views to ridgelines. To mitigate the urban heat island effect, developers are also required to take account of air ventilation in urban areas.

Each of our cities count the waterfront area as an invaluable public asset. It is rightly so.  To preserve and enhance the Hong Kong waterfront, we encourage the preservation of our harbourfront for current and future generations to enjoy.  In this particular area, the notion of "vertical city" happily gives way to horizontal corridors of green lawns, public amenities and personal leisure.

We already have a number of beautiful waterfront promenades and parks on both sides of the Victoria Harbour. I hope you will get a chance to visit some of these areas and enjoy a slow stroll along Victoria Harbour or simply admire the picture-postcard views. You will also see that we are having a major face-lift on both sides of our harbour, which in a few years' time will bring our world-renowned harbourfront to the next higher level.

But these days it is not enough to simply supply homes with great views, good facilities and convenient locations. The United Nations Environment Programme has estimated that buildings alone contribute to over one third of global energy use and carbon emissions.

The Hong Kong Government has made it a priority to promote more energy-efficient buildings. We are encouraging our residents and building owners to find energy-saving solutions to reduce emissions and save money.

We also want architects and engineers to incorporate more environment-friendly designs and energy-saving devices into new buildings in order to help combat climate change.

Last year, we established the Green Building Council as a platform for our community, professional bodies and Government to set standards and best practices in green building. The Council will also be involved in public education and research into green buildings to help achieve a sustainable built environment.

My final point today is about heritage conservation. Whether you are relaxing in Central Park in New York, strolling along the Bund in Shanghai or dining on the Peak here in Hong Kong it is easy to see why people love to live in the city.

Each of our cities has our own characteristics which make it vibrant and unique places to visit and, more important, to live.

We are placing more emphasis on preserving and revitalising old buildings and entire precincts that have historic and cultural significance. One such area is our iconic business and financial district of Central where thousands of people work during the day and socialise in the evening.

Our strategy includes transforming the old Victorian-style police station into a new hub for arts, culture and tourism right in the heart of our city. As well as preserving the best of "old Hong Kong" we will also be generating economic activity and enhancing the experience for those who live and work in this area or who want to enjoy our world-famous nightlife.

According to the United Nations, over half of the world's population currently live in cities. This ratio is expected to increase to two-thirds by 2050, with developing economies leading the urbanisation trend.

As three of the largest, most successful and dynamic vertical cities on the planet, New York, Shanghai and Hong Kong can all lead by example in providing a green, clean and vibrant city living environment for our future generations.

Chief Secretary Henry Tang gave this address at the Pre-Expo Forum for the 100-day Shanghai Expo countdown.