Monitoring Cropland Abandonment in Southern China from 1992 to 2020 Based on the Combination of Phenological and Time-Series Algorithm Using Landsat Imagery and Google Earth Engine

Abstract

Cropland abandonment is one of the most widespread types of land-use change in Southern China. Quickly and accurately monitoring spatial-temporal patterns of cropland abandonment is crucial for food security and a good ecological balance. There are still enormous challenges in the long-term monitoring of abandoned cropland in cloud and rain-prone and cropland-fragmented regions. In this study, we developed an approach to automatically obtain Landsat imagery for two key phenological periods, rather than as a time series, and mapped annual land cover from 1989 to 2021 based on the random forest classifier. We also proposed an algorithm for pixel-based, long-term annual land cover correction based on prior knowledge and natural laws, and generated cropland abandonment maps for Guangdong Province over the past 30 years. This work was implemented in Google Earth Engine. Accuracy assessment of the annual cropland abandonment maps for every five years during study period revealed an overall accuracy of 92–95%, producer (user) accuracy of 90–96% (73–87%), and Kappa coefficients of 0.81–0.88. In recent decades, the cropland abandonment area was relatively stable, at around 50 × 104 ha, while the abandonment rate gradually increased with a decrease in the cultivated area after 2000. The Landsat-based cropland abandonment monitoring method can be implemented in regions such as southern China, and will support food security and strategies for maintaining ecological balance.

An Empirical Investigation of the “Mezzogiorno Trap” in China’s Agricultural Economy: Insights from Data Envelopment Analysis (2015–2021)

“…Su et al developed an algorithm based on phenology and time series and, after analyzing satellite imagery from Google Earth Engine, highlighted that abandoned lands in Guangdong Province have consistently measured around 500,000 hectares. Post-2000, due to the rapid urbanization of Guangdong, the rate of land abandonment has been increasing yearly [63]. In 2021, the Guangdong provincial government announced a cultivated land area of 28,480,000 mu, equivalent to 1,898,667 hectares, with a land abandonment rate reaching 26%.…”

Is Abandoned Cropland Continuously Growing in China? Quantitative Evidence and Enlightenment from Landsat-Derived Annual China Land Cover Dataset

“…The results showed that the abandoned cropland was mainly abandoned at once, among which 23.61 million hectares (89.20%) had been abandoned once, 2.75 million hectares (10.39%) had been abandoned twice, and 0.11 million hectares (0.41%) had been abandoned three times or more. Multiple abandonment requires multiple reclamation, each time requiring large investments for treatment and restoration, wasting agricultural input costs [39]. To reduce these negative impacts, the soil and ecological environment can be protected by adopting circular and sustainable agriculture methods, such as rational fertilization, crop rotation, and afforestation.…”

Extraction and Mapping of Cropland Parcels in Typical Regions of Southern China Using Unmanned Aerial Vehicle Multispectral Images and Deep Learning

“…The satellite remote sensing technology has been widely employed in the extraction of cropland parcels. Various satellites, such as the Moderate-Resolution Imaging Spectroradiometer (MODIS) [10][11][12], Landsat [13][14][15][16], Satellite Pour l'Observation de la Terre (SPOT) [17,18], Sentinel [19][20][21][22], WorldView [23], and QuickBird [24], have achieved good results. Some studies have performed research in cropland extraction in southern China.…”