Habitat change in the transboundary Deep Bay catchment : its implications for spatial integration and nature conservation

Abstract

The Deep Bay Catchment is a transboundary region of two Chinese metropolitan cities -Hong Kong and Shenzhen. The Shenzhen River serves as a natural border between these two cities with distinctive political, economic and social backgrounds. The wetland located at the river mouth has been recognized as an internationally important wetland under the Ramsar Convention since 1995. Nevertheless, the landscape in this border region has been transformed drastically due to rapid urbanization since the establishment of the Shenzhen Special Economic Zone in 1979. This study attempted to investigate habitat change in this transboundary region in the past two decades and its implications for spatial integration and nature conservation. Firstly, habitat and land cover change in the Deep Bay Catchment was quantified with the aid of remote sensing technology and GIS. Results demonstrated a pronounced contrast of landscape on the south and north side of the catchment. The north side of the catchment (Shenzhen) was highly urbanized with 248km2of urban area, compared with the relatively rural Hong Kong side with 89km2of urban area in 2013. Besides, the ecological value of habitats in Hong Kong was considerably higher than its Shenzhen counterpart. Overall, a degradation of the ecological value of the landscape was found between 1993 and 2013, as a consequence of the loss in agricultural area and fishponds. It is asserted that political and economic factors were primary drivers of the dissimilarity in land use. The establishment of China’s first Special Economic Zone in Shenzhen and the designation of a Frontier Closed Area by the British colonial government contributed substantially in shaping the land use. Secondly, data on rivers, marine water and sediment quality within the Deep Bay Catchment were explored. Results of statistical tests indicated that water quality of rivers on the Hong Kong side had been improving in the past two decades, albeit under conditions of considerable urban sprawl. Marine water quality in the Deep Bay has remained unacceptable and frequently failed the Marine Water Quality Objectives. Besides, some records of heavy metals including Cu, Cr, Ni, Pb and Zn exceeded the Hong Kong Lower Chemical Exceedance Level, suggesting that Deep Bay has been contaminated with heavy metals. 16 PAHs in marine sediment have been explored and the Mann-Kendall Trend test identified an increasing trend of pyrene at a monitoring station in Deep Bay. Analysis of the nesting population of egretries in the Deep Bay Catchment showed that the overall population has been stable, yet a decrease in species diversity from five to three species was found. Habitat change within two kilometers of egretries was analyzed with results suggesting that the loss of foraging habitat played a crucial role in reducing the nesting population.

This study is the first comprehensive research on changes inland use, water quality and egretries in this border region from catchment and transboundary perspectives. Several policy recommendations including the adoption of Integrated Coastal Zone Management and Strategic Environmental Assessment are proposed for improving the sustainability of this ecologically sensitive catchment.