Abstract
Vegetation plays a dominant role in and serves as the structural foundation of island-land ecosystems. Island cities, as sea-land ecological complexes, are able to somewhat reflect the general realities of island ecological environments. By using the Landsat series remote-sensing images and an ecosystem service value (ESV) evaluation system, in this paper, the temporal and spatial evolution characteristics of the NDVIs and ESVs of China’s 12 island counties over the past three decades are analyzed. According to the research results, (1) The average NDVI of China’s island counties dropped from 0.380 to 0.347 in 1990-2018, reflecting a continuous downtrend. The NDVIs of Changhai County and Changdao County show significant changes, with decreases of 45.24% and 37.57%, respectively. (2) The total ESV of China’s island counties showed a “V”-shaped change trend from 1990-2018; the minimum value reached USD 362 million in 2010, then essentially recovered to the 2000 level in 2018. (3) The high and low values of NDVI and ESV in island counties over the years were distributed with the spatial characteristics of high values in the center of the islands and low values at the edges of the islands. The island counties north of the Yangtze River showed the largest changes in NDVI and ESV. (4) Forest cover is the main factor that drives ESV reduction in China’s island counties, followed by grassland cover. This study provides an effective method to study the changes in the NDVI and ESV of island cities and proposes the strengthening of island vegetation protection and the promotion of sustainable development in the ecological environments and economies of island cities.
Highlights
Vegetation is a critical ecological factor affecting ecosystems, and vegetation cover and changes in vegetation cover are important indicators that reflect ecosystem changes [1], [2]
This study provides an effective method to study the changes in the normalized difference vegetation index (NDVI) and ecosystem service value (ESV) of island cities and proposes the strengthening of island vegetation protection and the promotion of sustainable development in the ecological environments and economies of island cities
The lowest average NDVI value appeared in Chongming District, and the average NDVI values in Chongming District ranged between 0.154 and 0.188
Summary
Vegetation is a critical ecological factor affecting ecosystems, and vegetation cover and changes in vegetation cover are important indicators that reflect ecosystem changes [1], [2]. The normalized difference vegetation index (NDVI), the optimum indicator of vegetation growth and cover and an effective index for monitoring regional and global vegetation and ecological environments [3], [4], has been widely used in the study of vegetation dynamics [5], vegetation dynamic analysis [6], [7], land cover change detection [8], ecosystem assessment [9], etc. Vegetation is an important factor affecting ecosystem services, as it penetrates the whole process of the cycle of matter, the flow of energy and information.
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