Habitat loss and fragmentation under urbanization: the spatio-temporal dynamics of causes, processes andconsequences at landscape level

Abstract

Landscape modification, especially those human-dominated changes, has been widely considered as one of the key drivers inducing the degradation of environment and ecosystem. The consequent habitat loss and fragmentation, which are closely related to ecological process, have attracted much scholarly attention. However, very few studies have systematically examined their causes and consequences at the landscape level. Integrating human activities into consideration in a holistic way remains poorly understood in particular. This thesis reports a systematic study of habitat loss and fragmentation under urbanization. This research distinguishes itself from previous works in its investigation of the spatio-temporal dynamics of causes and consequences of habitat loss and fragmentation, and its endeavor to disentangle habitat fragmentation from simple habitat loss in terms of their processes and effects.

The Shenzhen River cross-border watershed, shared by Hong Kong Special Administrative Region and Shenzhen, is used as a case to illustrate how these ideas can work in practice. The study period spans from 1988 to 2008.The main contents of the study include analysis of the processes and causes of habitat loss and fragmentation, and dynamic consequences on water quality and ecosystem services for biodiversity conservation at spatial and temporal scales. Various methods are employed, mainly including conventional and newly developed landscape metrics (such as the Urbanization Isolation Effect (UIE) and Habitat Isolation Degree (HID)), a spatial statistical approach based on the Geographically Weighted Regression (GWR) model, spatio-temporal analyses and cross-border comparison. Major findings of the research are highlighted as follows. First, habitat loss and fragmentation show great spatial heterogeneity as well as temporal variation due to extensive and rapid urban sprawl in the study area. Second, by adopting the GWR model, it is found that human-related factors have played a significant role in determining not only the “amount” but also the “location” of habitat loss. Third, by using two new landscape metrics, namely the UIE and HID, both the extent (urban sprawl) and intensity (population density) of urbanization are suggested to have significant influences in habitat isolation. Fourth, water quality in the watershed is recognized to be closely correlated with habitat loss and fragmentation, and the correlations show major discrepancies between the Hong Kong and the Shenzhen sides. Moreover, by proposing a compound indicator (NP/MPS) for measuring habitat fragmentation (independent of simple habitat loss), it is found that habitat loss has exerted a bigger influence on water quality degradation than habitat fragmentation. Fifth, by integrating habitat connectivity into the evaluation of ecosystem services for biodiversity conservation, both the habitat size and connectivity are recognized to be important in explaining the degradation of ecosystem services value. Habitat size has played a dominant role in the overall change of ecosystem services value, whereas the role of connectivity (fragmentation) is more critical when the “stepping stones” sites are lost. The study provides a new framework to examine the habitat loss and fragmentation under urbanization at the landscape level. The efforts show great effectiveness in providing sound and useful information for future landscape planning, biodiversity conservation and watershed management.