Lure of the albizia woods

Ho Hua Chew, Straits Times 5 Jun 08;

THE Straits Times reported recently that some Singaporeans have taken a stand against the destruction of an albizia woodland at South Buona Vista. These people deserve our applause.

The albizia (Paraserianthes falcataria), one of the world's fastest-growing tree species, has proliferated in underdeveloped areas all over Singapore since it was introduced from Indonesia. Unfortunately, it has become an anathema to park managers, who are wary of its fragility. It has also upset botanical purists, who want to uproot the aliens no matter how long they have been established here.

It is also heartening to learn that National Parks has shown great sensitivity to the appeal by the Zehnder Road residents, by cutting down only 15 trees identified as likely to pose a hazard. Human safety and prevention of property destruction cannot be ignored.

However, care needs to be exercised in removing these trees, because a pair of the spotted wood owls, a nationally rare and endangered species, have been known to haunt the woodland. The tree-culling should proceed in ways that will not deprive these spectacular owls of a roosting or a hunting ground.

Despite its foreign origin, the albizia tree has become an indispensable habitat for many species of birdlife in our suburbs and countryside. When they grow into mature woodlands, these trees provide a sort of replacement habitat for the original forest that was destroyed.

The variety of birdlfe is amazing - as attested by the Zehnder Road residents. I have observed at least 40 species, migratory and resident, that have benefited from the albizias. Prominent examples include the common goldenback woodpeckers that sidle along the branches picking up ants; the long-tailed parakeets that screech softly as they rest in big flocks on the upper branches; the handsome dollarbirds that sit stolidly on the highest twigs in between sallies for aerial insects; and the hill mynas that use holes in the trunks for their nests.

Importantly, the white-bellied sea eagle, the changeable hawk eagle and the grey-headed fish eagle also depend on these trees for nesting sites outside forest nature reserves. The latter two are nationally endangered.

The white-bellied sea eagle favours the albizias nearer the sea, where it usually hunts for fish at places such as Pulau Ubin and Punggol, while the grey-headed fish eagle favours those at the edge of our rivers and reservoirs, like at Khatib Bongsu and Seletar Airbase. The changeable hawk eagle prefers the denser albizia woodlands, for example those at Khatib Bongsu and Ulu Pandan.

Why are albizias favoured? Outside forest nature reserves, mature albizias are the only trees that are sufficiently high and open at the canopy to be used as perches and nesting sites. The eagles have to find a towering perch to consume their prey in peace and build their nests of twigs beyond the reach of human predators.

In providing our eagles with nesting sites as well as perching and roosting places outside the very limited forests of the nature reserves, the albizias play an important ecological role in the Singapore countryside. They should not simply be dismissed as ecological undesirables.

It has been suggested that the albizias should be slowly replaced with indigenous species. This is a better policy, but a systematic and costly scheme of tree-removal and tree-planting is unnecessary. The existing albizias should be allowed to stand. But the natural process of plant succession that will enable native species to make a comeback should also be allowed.

Given time, the albizias will likely be overwhelmed by native species that are more adaptable to local conditions. Such a change will be gradual and non-disruptive, allowing the birds and other wildlife that they harbour to have time to adapt to the re-emerging native habitat.

The albizias have beautified the Singapore landscape immensely. Without them, it would be monotonous. Our country is flat as a result of the flattening of most of our hills. The mature albizias, massive and towering with their widespreading open canopies, strike the eyes from a great distance, lending an aura of green enchantment. Whether they are present in a cluster or as a woodland, their green foliage softens the landscape. Looking upwards into the canopy, the fine lacy pattern of the foliage is delightful.

I hope that that the relevant authorities will take heed of the ecological, aesthetic and psychological value of these woodlands. They contribute to making our lives satisfying beyond the obsession with material security.

The writer is the chairman of the Conservation Committee of the Nature Society (Singapore). The views expressed here are his own.