Selecting small reserves in a human-dominated landscape: A case study of Hong Kong, China

Abstract

In this case study of a degraded tropical landscape, we examine how the protected area system in Hong Kong, China, should be modified to improve its efficiency in protecting the surprisingly rich biota. The challenge lies in the fine scale of site selection, and the absence of a core area with high species richness and rarity. Site selection was first conducted in 1 km grid units by selecting hotspots and irreplaceable sites using field records for eight groups of species (amphibians, reptiles, mammals, breeding birds, ants, butterflies, dragonflies and rare vascular plants). The habitats of conservation value within the selected grid units were then delineated on the basis of expert knowledge. Recommendations for increasing the total existing protected area by 6% (i.e. an additional 2% of Hong Kong's total land area) were submitted to the Government in August 2000. To test the robustness of the results, site selection was repeated in 2001 using updated data and different selection methods. The numbers of squares selected by complementarity-based algorithms were similar to those by the hotspots and irreplaceable site method. Sites selected for rare species were very sensitive to data completeness, implying that the application of complementarity-based algorithms at fine scales might be limited.

Introduction

Nature reserves in the tropics have traditionally consisted of large areas of government-controlled land that were either uninhabited or inhabited only by indigenous people with no political influence. Increasingly, however, reserve selection in the tropics must compete with alternative land uses and any new reserves must be justified to politically influential land owners. These problems are very familiar to conservationists working in the temperate zone, but they are exacerbated in the tropics by the generally much higher levels of biodiversity, coupled with generally much poorer information on its distribution. Hong Kong (22°09′–22°37′N) illustrates many of these problems: despite its tiny area (1098 km²), it supports 7 million people and more wild species than Great Britain (Dudgeon and Corlett, 2004). The current study gives an example of selecting additional sites for protection under these constraints.

Hong Kong has an extensive coastline and rugged topography, with three peaks over 800 m. The mean daily temperature ranges from 15.8 °C in January to 28.8 °C in July, and the mean annual rainfall is 2214 mm, with almost 80% falling between May and September. Hong Kong must have been covered in largely evergreen forests in the past, but no definite primary forest remnants survive, and the surviving vertebrate fauna has few, if any, forest specialists (Dudgeon and Corlett, 2004, Corlett and Turner, 1997). Some topographically protected patches contain old trees and poorly dispersed species not found in secondary forests, and some lowland feng shui woods are probably several hundred years old. Despite several centuries of human impacts and the present high population density (7 million), the biodiversity remaining in Hong Kong is still impressive, with, for example, 1920 species of flowering plants, 55 species of mammals, 23 species of amphibians, 73 species of reptiles, 233 species of butterflies and over 2000 species of moths recorded (Dudgeon and Corlett, 2001). Today, 38% of the total land area of Hong Kong is in Country Parks, Special Areas or Restricted Areas (Fig. 1), which correspond to IUCN Categories IV and V Protected Areas (IUCN, 1998). The existing system, however, offers varying degrees of protection to different taxa (Yip et al., 2004) since the boundaries were mostly drawn around hillsides and scenic areas at higher altitudes (>100 m), with many lowland habitats excluded due to the objection from residents (Dudgeon and Corlett, 2004). Gap analysis at the scale of 1 km grid square indicated that over half of the 623 species of conservation concern (globally, regionally, or locally restricted species) were under-represented in existing protected areas (Yip et al., 2004).

Additions to the protected area system require strong scientific support, since land values are extremely high in Hong Kong. Setting aside land for conservation purposes can be very expensive if the land has been leased to indigenous villagers. To provide explicit justification for the selection of each site in a process that is transparent to decision-makers, the current study has selected additional sites for protection on the basis of species richness and restrictedness, targeting only under-represented species of conservation concern (hereafter target species). The aim was to find out the minimum area of land needed to be conserved, so that all the known species (of which we have data) would be under protection.

In addition, it was an objective of this study to investigate the applicability of complementarity-based reserve selection algorithms (Kirkpatrick, 1983, Margules et al., 1988, Nicholls and Margules, 1993) in Hong Kong. These algorithms have been widely studied and utilised since the late 1980s, as they were found to select less land area to represent all species than the traditional ranking method (Pressey and Nicholls, 1989). The small size of Hong Kong and the heterogeneity of the habitats imply there is need to carry out analyses at fine scales. However, relatively few empirical studies of reserve selection have dealt with tropical habitats, and most of them were conducted at a much coarser resolution than the scale required for Hong Kong (e.g. Vane-Wright et al., 1994, Kitching, 1996, Muriuki et al., 1997, Ceballos et al., 1998, Howard et al., 1998, Villasenor et al., 1998, Anderson and Ashe, 2000, Moritz et al., 2001). Reserve selection algorithms at fine scales demand high quality data, which are seldom available, hence, preventing the wider application of such algorithms in making real-world conservation decisions (Prendergast et al., 1999).

The study is presented in two parts. Part 1 documents a pilot study to delineate additional sites for protection by a pragmatic two-tiered (coarse-scale followed by fine-scale) approach. Part 2 is an improvement of Part 1 using an updated database, to further investigate different criteria and algorithms for selecting sites. Although the result of Part 1 is partly superseded by those of Part 2, it is presented here as a case of a real-world reserve selection exercise.