Mapping Impacts of Human Activities from Nighttime Light on Vegetation Cover Changes in Southeast Asia

Nan Xia,Manchun Li,Liang Cheng

doi:10.3390/land10020185

Abstract

It is commonly believed that the impacts of human activities have decreased the natural vegetation cover, while some promotion of the vegetation growth has also been found. In this study, negative or positive correlations between human impacts and vegetation cover were tested in the Southeast Asia (SEA) region during 2012–2018. The Visible Infrared Imaging Radiometer Suite—Day/Night Band (VIIRS/DNB) nocturnal data were used as a measure of human activities and the moderate resolution imaging spectroradiometer (MODIS)/normalized difference vegetation index (NDVI) diurnal data were used as a measure of vegetation cover. The temporal segmentation method was introduced to calculate features of two sets of time series with spatial resolution of about 500 m, including the overall trend, maximum trend, start date, and change duration. The regions with large variation in human activities (V-change region) were first extracted by the Gaussian fitted method, and 8.64% of the entire SEA (VIIRS overall trend <−0.2 or >0.4) was set as the target analysis area. According to statistics, the average overall VIIRS trend for the V-change region in SEA was about 2.12, with a slight NDVI increment. The time lag effect was also found between vegetation cover and human impacts change, with an average of 10.26 months. Our results indicated a slight green overall trend in the SEA region over the most recent 7 years. The spatial pattern of our trend analysis results can be useful for vegetation management and regional planning.

Highlights

During the last decades of modern industrial societies, the world population has grown rapidly by 1.24% per year, and the rate dropped to 1.10% per year nowadays, still yielding an additional 83 million people annually [1,2]
We only focus on the human impacts change that could be detected from nighttime light (NTL) data, and areas with little human activity changes are excluded to minimize other influences
The VIIRS/DNB NTL time series represented the change of human activities, and the moderate resolution imaging spectroradiometer (MODIS)/normalized difference vegetation index (NDVI) time series represented the vegetation cover change

Summary

Introduction

During the last decades of modern industrial societies, the world population has grown rapidly by 1.24% per year, and the rate dropped to 1.10% per year nowadays, still yielding an additional 83 million people annually [1,2]. For developing countries, the urbanization becomes the irreversible process during the last decades, and it will occupy a certain amount of vegetation cover, such as croplands, forest, and grassland [3,6,7]. This kind of land-use conversion has resulted in serious ecological problems, such as loss of the ecosystem services [8] and biodiversity reduction [9]. Some researchers have found a remarkable growing trend of vegetation cover [10], even in some urban areas [5,11]. The positive or negative correlation between vegetation cover and human impacts is still under debate, and the magnitude of these correlations is ambiguous

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Methods

Results

Discussion

Conclusion