Quantifying the contributions of human activities and climate change to vegetation net primary productivity dynamics in China from 2001 to 2016

The intensity of human activity, habitat loss and habitat degradation have significant impacts on biodiversity. Habitat quality plays an important role in spatial dynamics when evaluating fragmented landscapes and the effectiveness of biodiversity conservation. This study aimed to evaluate the status and characteristic variation in habitat quality to analyze the underlying factors affecting habitat quality in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). Here, we applied Kendall’s rank correlation method to calculate the sensitivity of habitat types to threat factors for the Integrated Valuation of Ecosystem Services and Tradeoffs habitat quality (InVEST-HQ) model. The spatiotemporal variation in habitat quality of the GBA in the period 1995–2015 was estimated based on the InVEST-HQ model. We analyzed the characteristic habitat quality using different ecosystem classifications and at different elevation gradients. Fractional vegetation cover, the proportion of impervious surface, population distribution and gross domestic product were included as the effect factors for habitat quality. The correlation between the effect factors and habitat quality was analyzed using Pearson’s correlation tests. The results showed that the spatial pattern of habitat quality decreased from fringe areas to central areas in the GBA, that the forest ecosystem had the highest value of habitat quality, and that habitat quality increased with elevation. In the period from 1995 to 2015, habitat quality declined markedly and this could be related to vegetation loss, land use change and intensity of human activity. Built-up land expansion and forest land fragmentation were clear markers of land use change. This study has great significance as an operational approach to mitigating the tradeoff between natural environment conservation and rapid economic development.

Estimating the Characteristic Spatiotemporal Variation in Habitat Quality Using the InVEST Model—A Case Study from Guangdong–Hong Kong–Macao Greater Bay Area

Evolution of NDVI secular trends and responses to climate change: A perspective from nonlinearity and nonstationarity characteristics

This study investigates the relations between climate change and both runoff and sediment yield in watersheds and provides a scientific basis for water resources planning and design as well as watershed-scale soil and water conservation. The impact of climate change on runoff and sediment yield in a watershed does not occur in isolation, but is a synergistic process in which climate and vegetation jointly influence runoff and sediment yield. Previous studies have seldom addressed this synergistic effect. For this study, a regression model between climate factors (temperature and precipitation) and the Normalized Difference Vegetation Index (NDVI) was established using data from the Zhenjiangguan Watershed in China. By combining data on climate-driven changes in vegetation cover, the Soil and Water Assessment Tool (SWAT) model was built to simulate runoff and sediment yield in the watershed under two scenarios: changes in climate, and synergistic changes in climate and vegetation cover. The simulation results show that precipitation is the most sensitive factor affecting runoff and sediment yield; 10% change in annual precipitation can cause 10%–14% change in annual runoff and 17%–24% change in annual sediment yield. Temperature is also an important factor affecting runoff and sediment yield in the watershed. Each temperature increase of 0.7 °C can result in a decrease of 1.4%–2% in annual runoff and 2%–3.7% in annual sediment yield. This research reveals that accounting for synergetic change in vegetation has an impact on runoff and sediment yield results, and that the magnitude and nature of this influence vary among different combinations of temperature and precipitation changes. When temperature was kept constant, the effect of vegetation cover change caused by precipitation change on runoff and sediment yield was relatively small (only 0.9%–1.5% of the total change), and vegetation cover change inhibited the effects of precipitation change on runoff and sediment yield. When precipitation was kept constant, the effects of vegetation cover change caused by temperature change on runoff and sediment yield were relatively large (20%–30% of the total change), and vegetation cover change enhanced the effects of temperature change on runoff and sediment yield. This investigation considers the synergistic effects of climate and vegetation cover change, and thus further clarifies the extent to which climate change impacts water and ecological resources.

Zhiguang Tang

Papers

Spatiotemporal changes of vegetation and their responses to temperature and precipitation in upper Shiyang river basin