In Hong Kong’s climate, forest is the natural vegetation everywhere. It can be suppressed by regular cutting or burning, but the harvesting of biomass for fuel ended decades ago and fires, although still common, are less often started and more rapidly controlled near urban areas than next to rural villages. An increase in the area of forest is therefore an inevitable, if paradoxical, consequence of the increasing urbanisation of the New Territories. Hong Kong Island, where the last grassland is disappearing under a tidal wave of shrubs and trees, illustrates the future for the whole territory. Within fifty years, forest will cover most of Hong Kong.

Good news for native biodiversity, surely? Well…yes… partly. It is true that many of our most diverse inland sites are in forest, but these are areas that have had continuous tree cover for centuries, as a result of inaccessibility or the protection of feng shui. The much larger areas of young secondary forest are a lot less diverse. Even at the best sites, the diversity is in the plants and invertebrates – organisms that can persist in the tiniest of forest patches. Vertebrates do not survive in such situations so Hong Kong has lost most species that require forest. The new forests are therefore empty in comparison with the larger, older forest areas in Guangdong, and even more so if compared with what must have been here a thousand years ago. There are no reliable records for Hong Kong from before the nineteenth century, when the vertebrate fauna was already impoverished. To get an idea of what has been lost, we must therefore extrapolate from recent and historical records for the South China region. These records suggest the local extinction, by the nineteenth century, of at least the following families of forest vertebrates: monkeys, gibbons, elephants, rhinoceroses, squirrels, flying squirrels, bamboo rats, pheasants, woodpeckers and trogons (Corlett, 2002). A species list would be much longer, since several major vertebrate groups, such as the babblers, cats, mustelids and rodents, are represented by just a few survivors of the original diversity.

But Hong Kong today does have squirrels and monkeys, and babbler list increases year by year. Doesn’t this suggest that forest vertebrate diversity will recover of its own accord? Unfortunately, the presence of these species is as much bad news as good. Almost all the increase in diversity over the past century was the result of the deliberate release of captive animals: the first monkeys in 1913, the squirrels around 1970, and most babblers within the last 20 years. Motivations have varied but few, if any, of the releasers have been concerned with the ecological consequences of their actions. The released species have been a random selection from those imported into Hong Kong, usually for sale as pets. Our monkeys are a hybrid mix, our squirrels are from Thailand and Shanghai, and while some of our new babblers were probably present in the region before deforestation, others are from Southwest China (Carey et al., 2001). A few bird species have made it to Hong Kong of their own accord, but the non-forest areas north of the border are an impenetrable barrier to most forest specialists.

Neither letting the new forests remain empty, nor filling them with exotic species released by kind-hearted Buddhists, makes any ecological sense. Only a program of planned reintroductions of species that used to be here in the past can restore a diverse, functioning forest ecosystem (see p.16). Such a program would have multiple benefits: it would restore ecological processes, such as seed dispersal, that have been truncated by local extinctions; it would enhance public awareness and support for conservation; and it would increase the security of the species concerned, by providing additional wild populations. Reintroduction of ecologically appropriate species would also reduce the risk that invasive exotics will fill the many vacant niches in our empty forests.

Bibliography

Carey, G. J., Chalmers, M. L., Diskin, D. A., Kennerley, P. R., Leader, P. J., Leven, M. R., Lewthwaite, R. W., Melville, D. S., Turnbull, M. & Young, L. (2001) The Avifauna of Hong Kong, Hong Kong Bird Watching Society, Hong Kong.

Corlett, R.T. (2002) Reintroduction of "missing" vertebrates to Hong Kong: benefits, problems and prospects. In: Hodgkiss, J. (ed.) Challenges of Nature Conservation in the Face of Development Pressure. Proceedings of the 2001 IUCN World Commission on Protected Areas, East Asia Conference, Agriculture, Fisheries and Conservation Department, Hong Kong, pp. 175-180.

Richard Corlett

P.1

See also : "Reintroduction: setting the ball rolling...." & "PORC! "