Abstract
Urban expansion poses severe threats to ecosystems. It is therefore important we better understand the impact of different urban expansion level on ecosystems for developing regionally differentiated ecological protection policies. Here, we proposed a conceptual framework to describe the impacts of urbanization on bundles of ecosystem services. Referred to as the concept of land use degree by nighttime light data, we put forward and verified an urban expansion level model. According to this model, study area was divided into a slow increase zone, increase zone, and rapid increase zone. Then, taking Taihu Lake Basin in China as a case, we used Zonal-statistics and Pearson correlation coefficients to reveal the impact in different zones of urban expansion level on multiple ecosystem services: crop production, freshwater supply, aquatic production, net primary productivity, soil conservation, water retention, flood regulation, and forest recreation index. Our results revealed that urban expansion levels significantly impacted all ecosystem services. In either increase zone or rapid increase zone, we found lowered values of crop production, net primary productivity, soil conservation, water retention, and flood regulation, while both aquatic production and forest recreation index increased in all zones from 1990 to 2010. Across the levels of urbanization, urban expansion level was always negatively correlated with provisioning services. This result suggests local governors should improve crop production per unit area and increase the cultivated land area to guarantee food security. In addition, urban expansion level had positive correlations with the trade-offs between flood regulation and forest recreation index, and those among crop production, freshwater supply, and net primary productivity. Therefore, policy-makers should effectively maintain the land use balance among ecological protection, agriculture development, and urban expansion to better coordinate relationships between development and protection. In acquiring quantitative knowledge of how urban expansion level drives ecosystem changes, our findings may help guide future sustainable urban planning with respect to ecosystem services, urban development, and human welfare benefits.
Highlights
The Millennium Ecosystem Assessment [1] concluded that 15 of the 24 global ecosystem service functions—more than 60% of the total—are degrading, consistent with The Economics of Ecosystems and Biodiversity research that revealed the global ecological environment is under grave threat [2].Some researchers have suggested that the changes in land use patterns in recent years have already caused a decline in the global ecological environment [3], one that will directly threaten regional and global ecological security [1,4]
urban expansion level (UEL) based on nighttime light data can comprehensively reflect the urban expansion characteristics
We found that freshwater supply, net primary productivity, and flood regulation were negatively related to UEL (p < 0.01), while human activities index was uncorrelated with net primary productivity and carbon sequestration and oxygen production in Yanhe and Guanzhong economic regions
Summary
Some researchers have suggested that the changes in land use patterns in recent years have already caused a decline in the global ecological environment [3], one that will directly threaten regional and global ecological security [1,4]. Urban expansion level (UEL) is a comprehensive indicator of urban expansion, which can reflect the changes in urban construction land area, and in urban economic, population density, landscape pattern, etc., since UEL can be used to strengthen the monitoring of urban expansion, which is of great significance to regional sustainable management. The key and composite index methods are commonly used to measure urban expansion [7]. One-sidedness of a single indicator [8], regionality of composite indicators [9,10], and lags in statistical data [11,12], have rendered these two indexes insufficient in applicability, comparability, and timeliness [12]
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