Abstract
The Huangshui River Basin (HRB) is the main grain production and key implementation region of the “Grain for Green Program” (GGP) of Qinghai Province, and has experienced a quick urbanization during the last 20 years. Therefore, identifying the farmland change and its ecological effects is significant for farmland and ecological protection in the HRB. To this end, this study analyzed the farmland change between 2000 and 2018, based on 1 m spatial resolution farmland data visually interpreted from Google Earth high-resolution images, and then estimated its ecological impact based on the Normalized Difference Vegetation Index (NDVI) data of MODIS, using an ecological impact index of farmland change. The study found that: (1) The farmland area in the HRB decreased from 320.15 k ha in 2000 to 245.01 k ha in 2018, reduced by 23.47% or 1.48% per year, as mainly caused by ecological restoration and built-up land occupation; (2) from 2000 to 2018, the natural environment showed a greening trend in the HRB, with the mean NDVI increasing by 0.74% per year; (3) the farmland changes had a positive ecological effect, contributing 6.67% to the regional increase in the NDVI, but had a negative impact on grain production; (4) it is suggested to strengthen farmland protection by strictly controlling the urban land occupation and over-conversion of farmland in the HRB.
Highlights
Huangshui River Basin (HRB) decreased from 320.15 k ha in 2000 to 245.01 k ha in 2018, reduced by 23.47% or 1.48% per year, as mainly caused by ecological restoration and built-up land occupation; (2) from 2000 to 2018, the natural environment showed a greening trend in the HRB, with the mean Normalized Difference Vegetation Index (NDVI) increasing by
Where NDV Ij and NDV Ii are the mean values of the NDVI for each pixel in the j-th and i-th years, 2000 ≤ i < j ≤ 2018; f is the sign function; n is the years of the study period; β is the change rate of the NDVI per year, where β > 0 indicates that the NDVI is on the rise and β < 0 on decline; and Z represents the significance level of the NDVI change
Β h × Ah where Cer is the contribution percentage of Ecological restoration (ER) to the regional mean NDVI change; β er is the mean NDVI change rate of the grids with farmland fully converted to forestland or grassland; β h is the mean change rate of the NDVI for the whole HRB; Aer and Ah are the total areas of ER and HRB, respectively; β f is the mean change rate of the NDVI for mature forests, roughly representing the influence of climate changes during 2000 to 2018
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The Huangshui River Basin (HRB) is the dominant area of population, economy, and agricultural production in Qinghai Province [5,6]. Academy of Sciences [21], are the highest resolution long-term series data product available for the HRB. We obtained 1 m spatial resolution farmland data of the HRB in 2000 of the HRB in 2000 and 2018 by visual interpretation based on Google Earth high-resoluand 2018 by visual interpretation based on Google Earth high-resolution images.
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