It is of little comfort to be told that the city's sweltering 'heat-island effect' is unlikely to get any worse. Canadian expert Tim Oke said this week that the temperature differences between urban areas and the countryside were already extremely pronounced by any world standards and he did not expect to see them going much higher. This amounts to differences of 2 to 10 degrees in air temperature and 5 to 12 degrees on the surface. On an average winter night, a person may need a sweater in Tak Kwu Ling but only a shirt in the middle of Mong Kok. Hong Kong has all the characteristics that create these heat traps, including densely packed buildings that block air flow and prevent sea breezes from the harbour to clear the air. Our buildings have very little vegetation; few have rooftop gardens. And they rarely use heat-absorbing materials. New buildings should incorporate these environmentally friendly features. Although the government means well by imposing building-height restrictions in Tsim Sha Tsui and the Mid-Levels, the result may be bulky buildings that expand sideways instead of going up as developers find new ways to maximise saleable floor areas. This may make matters worse. We are not only sacrificing our quality of life but jeopardising our health. Heat traps and air pollution go hand in hand, and exacerbate a variety of health problems. Unless we summon our collective will to improve urban planning, the situation will not improve. Clearly, we can no longer afford to over-build, as we have in the past. To this end, future zoning must take into account the effects of walled-in pollution and trapped heat when any development application is made. There should be criteria for approving or rejecting an application that take these factors into account. Where it is safe, people should be encouraged to introduce more vegetation and greenery to their buildings. It is an encouraging sign that green groups and residents are becoming increasingly vocal about developments that might raise concerns about the wall effect, visual impact and quality of life in their neighbourhoods. Developers need to be made aware there has been a shift in the public mood. People want livable space with room for air to flow, not shoe-boxes for homes and oversized buildings for offices.