With the Biodiversity Survey nearing completion, some clear generalisations are emerging. One of the most obvious is the differential impact of deforestation on Hong Kong's terrestrial flora and fauna. Hong Kong's forest flora has come through centuries of landscape degradation with a surprising - no, let's make that totally amazing - diversity. Hong Kong simply does not deserve to have 375 native tree species, for instance. With the forest fauna, however, it is a very different story. I cannot name a species which is completely dependent on forest which has survived, although I am sure there must be some among the invertebrates. Moths? Termites? Ants? Hong Kong's expanding secondary forests are dominated by habitat generalists, such as the Chinese Bulbul, which can make use of - and often prefer - non-forest habitats such as shrubland. This really should not be surprising: a tiny patch of forest can support several tree species for centuries but will lose forest-dependent animals in decades. The consequences for conservation management in Hong Kong, however, have not been clearly spelled out. Simply reforesting Hong Kong's barren hills will not necessarily increase faunal diversity. Indeed, where forest replaces species-rich shrubland, there may be a net decrease in diversity. This is not an argument against reforestation, which has many benefits and could, anyway, only be prevented by an unacceptable increase in fire frequency. It is an argument for reintroduction of the missing forest fauna.
Some species have arrived by themselves and others undoubtedly will. The Chestnut Bulbul population at Tai Po Kau is a good example. The expanding urban sprawl to the north of Hong Kong will, however, limit these self-introductions to the most mobile and tolerant of flying species. There have also been several, presumably accidental, human-assisted introductions of forest species already. The most successful are probably the Silver-eared Mesia and Pallas's Squirrel. These two animals are, respectively, outside their natural range and represented by the wrong two subspecies - but who is complaining? But it makes little sense to leave the choice of species to the bird and mammal trade, assisted by kind-hearted Buddhists. There has not been an ecological disaster yet but this does not mean that one is impossible. Reintroduction should be deliberate and should involve species which were probably here in the past and which will - again, probably - thrive under current conditions.
It would be easy if we had a list of recent extinctions to guide us but these are few: most of the forest fauna must have been extinct long before anyone cared enough to record what was there. The Red Fox, Vulpes vulpes, and Large Indian Civet, Viverra zibetha, have been lost within the last 50 years, and should obviously be high on any list of reintroductions, but for the most part we must rely on common sense. The Giant Flying Squirrel, Petaurista philippensis, for instance, has - or, at least, had until recently -a continuous distribution from Burma, Thailand and Vietnam, through southern China to Taiwan. It is conceivable that Hong Kong was always unsuitable in some way for flying squirrels but this seems unlikely. In any case, I can see no possible objection to an experimental reintroduction to Tai Po Kau or some other forest area. The smaller Hairy-footed Flying Squirrel, Trogopterus pearsonii, is another possibility, as is Striped Squirrel, Tamiops maritimus. Staying with rodents, one of the Bamboo Rats, Rhizomys spp., would be an interesting addition to our fauna, and perhaps the Long-Tailed Giant Rat, Leopoldamys edwardsi.
The Yellow-throated Marten, Martes flavigula (the one recent record of which is surely an escape?) and Siberian Weasel, Mustela sibirica, would both be well within their native ranges and unlikely to compete strongly with our existing carnivore fauna. The Hog Badger, Arctonyx collaris, and the Raccoon Dog, Nyctereutes procyonoides, are other missing species with distinct niches which do not appear to be currently occupied. Among the ungulates, the Sambar Deer, Cervus unicolor, ranged from Southeast Asia across South China to Taiwan in the recent past and would make a spectacular (re)addition to our fauna.
I could go on but, instead, I would like to throw this question open for suggestions to people working on other faunal groups. Why not, for instance, restore the full South China forest interior bird fauna to Tai Po Kau, instead of waiting for the bird trade to do it? Sure, many of the missing species are locally (re)established in Hong Kong already but if we want a particular species we should ensure that we start with a genetically diverse group of founders from the most appropriate source, rather than a couple of individuals which happened to escape from Mongkok. What forest reptiles are we missing? Which butterflies?
P.39
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