Spatial distribution of urban ecosystem health in Guangzhou, China

Methods and indicators are needed to assess the urban ecosystem health status, amongst which energy and material metabolism should be integrated to enhance understanding of ecological patterns and processes of urban ecosystems. Therefore, emergy synthesis combining energetics with systems ecology is applied to assess systematically the health status of urban ecosystems. Combining ecosystem health levels with spatial geographical information of different land use subsystems, the spatial distribution of urban ecosystem health is obtained, which is helpful for urban ecological regulation and spatial optimization. Taking the situation of Guangzhou, China in 2005 as a case study, the relative health states based on emergy indicators and set pair analysis is evaluated. Results show that the health levels of the cultivated land, as well as areas with middle and low density buildings are relatively positive, while that of high density building and traffic areas are relatively weak. Through analysis of different land use subsystems, required factors of a healthy ecosystem are summarized, including moderate economic productivity but without much exploitation and disturbance, reasonable structure of energy and resources usage, medium resilience under pressure, moderate ecosystem service provisioning, and small environmental impact on surroundings. The spatial distribution of urban ecosystem health states is also obtained, such that the northern part of Guangzhou is defined as the conservation area, the middle and southern parts are defined as the maintenance area, while the south central and south western parts are defined as the key regulation area where a suitable scheme should be implemented to control the population density and resolve the concomitant problems. Moreover, the impact power of different indicators on the final health status is classified into five levels when combining the indicator weights with the main assessment factors of urban ecosystem health, which is useful for defining the regulation priority amongst a few indicators.