Wednesday, July 18, 2007

ISA HK/China --- Tree Planting to cool HK Pt. 2

*** Station Mail is for the information of Station Members only, but Station Mail has given up copyright & can be freely circulated. For administrative reasons, comments from outsiders are usually not entertained & may be circulated within our system locally & overseas.***

Dear Station Members,

Further to our station Mail a little while ago on the benefit of Tree Planting to cool our over-developed city, another warning came from the Director of HK Observatory Mr. CY Lam, on 14.7.07 that HK may lose its winter in a mere 40 years, instead of the initially estimated 50 years mentioned by him in less than a month ago.

His comments in Chinese can be visited at: .

HK is indeed getting hotter & hotter year by year. The Station Manager has noticed that it was 37C outside his office in Sheung Shui at 2 pm on July 16 & it was an alarming 39C at ETF during his visit at 2 pm on July 15. While the trees were so chosen to tolerate this temperature by selection at ETF, it was not so for the poor workers there working under sun. They could simply only recess & ETF was losing productivity.

Singapore has taken a measured foresight to cool their city by massive Tree Planting since the 1960's & they have preferred canopy coverage for practical reason instead of going blindly for flowering. After all, flowers on trees are really meant for attracting insects & birds for reproductive reason. We human just so happen to enjoy them as uninvited guests. On the other hand, how long a period would any flowering last for most of our trees anyway? Maximum for a month? How useful would these trees really be after flowering, to meet our desperate need of cooling our city, if they would really flower according to design (Flowering actually require many physiological criteria) ?? Maybe the answer can be obtained by counting the number of people strolling our city parks during high noon in summer. Many, or just a few ? Why ? Is it too hot to stay ??

If our 'flowering' trees do not have adequate canopy coverage to trap sun's ray, it will then be our concrete & other hard surfaces to absorb & release the heat to us day & night. In our current city texture, they are apparently the winners.

Then would anyone still insist to select our trees for 'flowering' only & whose money are being spent? Is that money really justified for individual compassion?

Some research papers published recently on the Cooling Effects of Trees have over-emphasized the reflectivity (albedo) of trees & have actually ignored the total energy absorption of Photosynthesis in its simplest form:

6CO2 + 6H2O ---> C6H12O6 + 6O2
Carbon Dioxide + Water ---> Carbohydrate + Oxygen

During Photosynthesis, the sun's energy is absorbed, turned & stored in the form of chemical energy in carbohydrate, which is then transformed through physiological processes with other compounds (partly from fertilizers) to form plant tissues, the predominant of which is Wood. If this wood is not immediately used as a an energy source by primarily combustion, it can be stored or compressed through time to be turned into fossil fuels, which during burning, will give us the energy so trapped by the sun. Therefore, trees are storing the sun's energy in an efficient & environmentally friendly manner, besides their many other social & psychological benefits to us. Just look at how human & animals stow under trees to get cooled in the tropics.

However, if we are going to plant trees to trap sun's energy & cool ourselves, we shall need to understand how to select, plant, maintain & inspect these eventually massive structures so that they will not become our liabilities. Mature trees can fall to kill people & damage properties, in storm & in tranquillity. Hence Western countries require Arborists to look after their trees, so does Singapore. Arborists are Tree Doctors & Tree Detectives, & tree care is their subject.

It is a practice that in Western countries, Arboriculture is a Practitioner Trade & Arborists need to touch trees, not only books & computers. ISA was inaugurated in 1924 when a lot of other Greenery Institutes were not even conceived. ISA was established out of a social need, not as a hobby.

If HK is going to select, plant, maintain & inspect our trees properly so that trees can become our asset instead of liability like in Singapore, it is only logical that we need Arborists to look after our trees. The Station Manager has always compared Horticulturist as Veterinary Surgeon to Arborist as Human Doctor. Each specializes in their own field. What organization can then supply & maintain qualified Arborists to international standard in HK/China at present? Perhaps only ISA HK/China with our growing 390 Station Members & international connection, because we are the biggest currently & very much alive.

Our Station will no doubt participate more & more into the HK society, if HK would demand quality trees to become our asset. Taiwan & China will be next.

If not, may be we shall need to turn on our air-con higher, & higher, & ...

best regards,

Sammy Au
Station Manager

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