Long-Term Ecological Effects of Demographic and Socioeconomic Factors in Wolong Nature Reserve (China)

Human population has exerted enormous impacts on biodiversity, even in areas with “biodiversity hotspots” identified by Myers et al. (2000). For instance, the population density in 1995 and the population growth rate between 1995 and 2000 in biodiversity hotspots were substantially higher than world averages, suggesting a high risk of habitat degradation and species extinction (Cincotta et al. 2000). Many regression models have been built to establish correlated relationships between biodiversity and population (e.g., Forester and Machlis 1996; Brashares et al. 2001; Veech 2003; McKee et al. 2004). These models are important and necessary, but they use aggregate variables such as population size, density, and growth rate, which may mask the underlying mechanisms of biodiversity loss and could result in potentially misleading conclusions. For example, does a declining population growth reduce the impact on biodiversity? Although global population growth has been slowing down, household growth has been much faster than population growth (Liu et al. 2003). The continued reduction in household size (i.e., number of people in a household) has contributed substantially to the rapid increase in household numbers across the world, particularly in countries with biodiversity hotspots. Even in areas with a declining population size, there has nevertheless been a substantial increase in the number of households (Liu et al. 2003). More households require more land and construction materials and generate more waste. Furthermore, smaller households use energy and other resources less efficiently on a per capita basis (Liu et al. 2003). Thus, impacts on biodiversity may be increased despite a decline in population growth. To uncover the mechanisms associated with human population that underlie biodiversity loss and provide valuable information for biodiversity conservation, it is crucial to go beyond regression analyses and examine how demographic (e.g., population processes and distribution) and socioeconomic factors affect biodiversity at the landscape level. As many effects may not surface over a short period of time, it is essential to conduct long-term studies. However, landscape level longterm studies are costly, and it is very difficult to conduct experiments on some types of subjects, such as people. Fortunately, systems modeling has become a useful tool