Thousands of exotic trees face axe over winter

Government workers will axe thousands of trees in country parks across Hong Kong this winter - all in the name of biodiversity.

After years of tests and trials, the Agriculture, Fisheries and Conservation Department has embarked on a programme that will gradually phase out exotic tree species and replace them with local ones.

It is all part of a move towards greening focused on quality, rather than quantity, and aims to improve biodiversity in the long term.

Most exotic tree species are unable to provide suitable habitats and appropriate foods, such as berries and nuts, for a wide range of wildlife, from birds and bats to civet cats.

At 21 country park sites - from Tai Lam, Pok Fu Lam, Tai Tam, Ma On Shan and Lantau to Sai Kung - exotic tree species that were widely planted on barren land after the second world war will be removed to make way for a mix of local species.

The exotic trees, such as Taiwan acacia, paperbark and Brisbane box, were introduced in large numbers for their fast growth, tolerance to harsh growing conditions and ability to hold soils together.

However, their relatively short lifespan, about 20 to 30 years, means many are now ageing and in poor health.

Further aggravating the situation is that many of the trees were densely planted, leaving virtually no space and sunshine for other species to grow. The homogeneous forests also increase the risks of pests.

Thousands of the trees will be felled this winter, with new trees belonging to local species to be planted in spring.

The infant trees will be cared for intensively, with sufficient spacing between them to allow them to grow healthily.

'It is our goal to replace all exotic species with local ones in all the parks,' senior country park officer Ngar Yuen-ngor said.

'But it is going to be a lifetime work.'

Ngar said up to a half of the green coverage in country parks was dominated by exotic trees. However, the public should not worry about the natural deaths of those trees since most were in inaccessible areas.

Country parks officer Dr Samuel Lam Kin-san said the local species would be supplied by the department's nurseries, which could provide 60 different species such as sweet gum, camphor, thick-leaved oak and myrobalan.

Lam said such local species, with longer lifespan of up to 100 years, were versatile. For instance, sweet gum leaves could become as colourful as maple leaves in winter and its seeds could be used as herbal medicine to improve blood circulation.

'What is most important with these species is that they can attract wildlife, which can then help spread the tree's seeds to other areas and sustain forest growth,' he said.

Ngar said the project would not add to costs because resources would be diverted from existing greening programmes.

As a result, the number of new trees planted in country parks each year would be cut to about 700,000 from a peak of 900,000 in 2008. About half of the new trees planted recently have been local species.

Felled trees would be left to decompose in damp areas so that their nutrients could return to nature.

Signs will be erected at each of the 21 sites to inform visitors about the scheme, in an attempt to avoid misunderstandings.

Fresh roots

New tree plantings in country parks peaked at 900,000 in 2008.

They have fallen to about: 700,000