ISA HK/China --- Tree Planting to cool HK

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Dear Station Members,

The conversation by the Director of the HK Observatory Mr. Lam Chiu-ying yesterday to the media has given the HK people warning that we may lose the winter that we know of in 50 years' time, if we carry on the way we build our city. Some excerpts are given below for his comments:

1. 石屎森林 熱夜世紀末倍增http://hk.news.yahoo.com/070608/60/2951n.html

2. 50年後跟冬天說再見 樓宇日吸熱晚釋放 「熱夜」急增http://hk.news.yahoo.com/070608/12/294u7.html

There have been some talks on greening our roofs to cool the city recently. However, if we compare the surface area of the roof to absorb sunlight with the surface area of the vertical sides of any high rise building, greening roof alone is negligible in its cooling effect because :

1. The roof area is very small when compared to that of the vertical faces in any tall building.

2. The sun will shine from East to West everyday & will not stay vertically on the roof to be absorbed.

3. The vertical faces of a tall building will absorb, reflect & release heat as much as the roof, depending on the sun's angle.

Unless we green the vertical faces of our tall buildings as well, which is rather impractical, greening roofs alone would only be just another political show although better than doing nothing.

When Singapore became a country in the 1960's, their leaders have taken the foresight to cool their city by a massive Tree Planting Program. Singapore is situated at 3 degree North in Latitude & they have no winter. The sun is equally hard on them. Air conditioning in the 1960's was unpopular & expensive. Their political leaders then thought of planting trees to cover as much of the city area as possible to cool their interior. Urban planning & construction has taken Tree Planting as a priority, & trees have become an asset for the Singaporeans.

In Singapore's Greenery Program, Tree Planting is no doubt the backbone. Their designers have forsaken flowering as the most prominent factor in choosing species but rather go for canopy coverage. After all, flowering in most trees would stay on the perimeter of the canopy & maybe birds can see them better. On the other hand, the shade of the canopy will benefit the people below. The arrangement of shrubs & groundcovers would play only second fiddle in any Singapore landscape. Even so, Singapore has always been known internationally as the 'Garden City' in the past & now better known as a 'City in a Garden'. Singapore has achieved success indeed in their Greenery Program.

The Greenery Program in Singapore is led by the National Parks Board of the Singapore Govt (Nparks). Nparks has around 600 staff to look after their 1.3 million trees in the city, as compared to the around 730,000 trees by our LCSD of approx. 8,000 staff in HK, although not all LCSD staff are devoted to look after only trees like in Nparks. Nparks has been traditionally led by Foresters & now Arborists. They have now over 100 Certified Arborists working in their various Depts with only around 10 Landscape Architects to carry out design as a fact. Nparks also practises ISA arboriculture & their work can be browsed through in www.nparks.gov.sg .
If we are going to cool our city of HK to avoid losing winters, appropriate Tree Planting would seems to be a probable solution. We have seen our neighbours in Singapore who have more sun than ourselves done it with flying colours. Can we learn something from them & should we protect our environment by Tree Planting? If not, why are we different?

To look ahead a little further, should we set up an Arboricultural Office in our Govt to coordinate tree planting, maintenance & preservation? How & what kind of personnel should be leading it? Which international practices should we follow? What kind of qualified personnel should be allowed to do the Tree Inspection, Hazard Assessment, Structural Pruning, Felling Approval, Transplantation Assessment, Tree Climbing, Tree Selection & many others? What are their legal liabilities?

Should we respect & protect our trees in HK? Do we desire our trees to become an asset for HK rather than liabilities?

There are a lot of questions we can ask ourselves indeed.

best regards,

Sammy Au
Station Manager