Cropland Loss Research Articles

Assessing the Consistency of Five Remote Sensing-Based Land Cover Products for Monitoring Cropland Changes in China

The accuracy assessment of cropland products is a critical prerequisite for agricultural planning and food security evaluations. Current accuracy assessments of remote sensing-based cropland products focused on the consistency of spatial patterns for specific years, yet the reliability of these cropland products in time-series analysis remains unclear. Using cropland area data from the second and third national land surveys of China (referred to as NLSCD) as a benchmark, we evaluate the area-based and spatial-based consistency of cropland changes in five 30 m time-series land cover products covering 2010 and 2020, including the annual cropland dataset of China (CACD), the annual China Land Cover Dataset (CLCD), China’s Land-use/cover dataset (CLUD), the Global Land-Cover product with Fine Classification System (GLC_FCS30), and GlobeLand30. We also employed the GeoDetector model to explore the relationships between the consistency in cropland change and the environmental factors (e.g., cropland fragmentation, topographic features, frequency of cloud cover, and management practices). The area-based consistency analysis showed that all five cropland products indicate a declining trend in cropland areas in China over the past decade, while the amount of cropland loss ranges from 5.59% to 57.85% of that reported by the NLSCD. At the prefecture-level city scale, the correlation coefficients between the cropland area changes detected by five cropland products and the NLSCD are low, with GlobeLand30 having the highest coefficient at 0.67. The proportion of prefecture-level cities where the change direction of cropland area in each cropland product is inconsistent with the NLSCD ranges from 13.27% to 39.23%, with CLCD showing the highest proportion and CLUD the lowest. At the pixel scale, the spatial-based consistency analysis reveals that 79.51% of cropland expansion pixels and 77.79% of cropland loss pixels are completely inconsistent across five cropland products, with the southern part of China exhibiting greater inconsistency compared to Northwest China. Besides, the frequency of cloud cover and management practices (e.g., irrigation) are the primary environmental factors influencing consistency in cropland expansion and loss, respectively. These results suggest low consistency in cropland change across five cropland products, emphasizing the need to address these inconsistencies when generating time-series cropland datasets via remote sensing.

Assessing land use change from food croplands to rubber in Ghana's Ellembelle district: Implications for food self-sufficiency

There is evidence that cocoa and cashew farmers are targeting croplands for expansion, reducing cropland areas with negative implications for food self-sufficiency in Ghana. However, research on the dynamics of rubber expansion and its possible impact on food self-sufficiency is limited. This study analysed the intensity of land use transition from food crops to rubber and its implications for food self-sufficiency among rubber-growing households in the Ellembelle District. Land use maps were used to analyse the intensity of transition associated with rubber and food crops from 1991 to 2022. Additionally, questionnaires were used to gather information on rubber expansion, cropland loss, and food self-sufficiency from 160 rubber farmers. A Chi-square test was used to determine the relationship between households that converted croplands to rubber and food self-sufficiency. The study showed that rubber had expanded by 9647.5 ha, mainly targeting food croplands. Majority (75.3 %) of farmers reported a decline in food availability, 68.5 % reported reduced access to food, and 49.3 % indicated a decline in dietary diversity, indicating a general decrease in food self-sufficiency. However, there was no statistically significant relation between farmers who converted cropland to rubber and food self-sufficiency. This suggests that the decline in food self-sufficiency is not a result of rubber expansion but of the disproportional cropland expansion to population growth and known challenges to crop production. To achieve food self-sufficiency, there is a need to increase food crop farming among rubber-growing farmers. This can be achieved by allowing rubber farmers to spare lands solely for food crop farming, providing subsidised agricultural inputs, and enhanced extension support. Also, creating a reliable market for staple food crops such as cassava and addressing supply chain obstacles like poor road networks are essential for making food crop farming competitive.

Past and future land use change dynamics: assessing the impact of urban development on agricultural land in the Pantura Jabar region, Indonesia.

The conversion of large-scale agricultural land into urban areas poses a significant challenge to achieving national and global food security targets, as outlined in Sustainable Development Goal number 2, which aims to eradicate hunger. Indonesia has experienced a significant decline in rice field areas, with a reduction of approximately 650 thousand hectares within a year (2017-2018), the largest being in Java. Hence, this study aims to examine the impact of urban expansion on agricultural land in the north coast region of West Java Province from 2013 to 2020 and develop a predictive model for 2030 to support sustainable land use planning. The primary methods employed were random forest (RF) analysis using Google Earth Engine, intensity analysis, multilayer perceptron-neural network (MLP-NN), Markov chains-cellular automata (Markov-CA), and stakeholder interviews. The model also evaluated the influence of "distance to tollgates" as a previously unexplored driving factor in existing land use modeling studies. Landsat image classification results using the RF algorithm showed 87-88% accuracy. Cropland has historically been and is projected to remain the primary target for the expansion of built-up areas. Spatial planning irregularities were found in the growth of these areas that adversely affected farmers' socioeconomic and environmental conditions. Evaluation of land use models using MLP-NN and Markov-CA demonstrated an accuracy rate of 86.29-86.23%. The distance to tollgates factor significantly impacts the models, albeit less than population density. The 2030 intervention scenario, which implements a firm policy for sustainable agricultural land use, offers the potential to maintain the predicted cropland loss compared to business as usual.

Analysis of Land Use Gravity Center Change and Carbon Emission Impact in Chengdu Plain of China from 2006 to 2022

As the economic center and major grain-producing area in Southwest China, the calculation of the carbon budget and the protection of cultivated land in the Chengdu Plain are of vital significance for China to achieve a carbon peak strategy and ensure food security. For the purpose of clarifying the trend of land use focus and carbon emissions in the Chengdu Plain, the carbon peak level of land use in 33 counties in the Chengdu Plain was explored. Based on the gravity center model and IPCC carbon emission coefficient method, the changing trend of land use gravity center and carbon emission in Chengdu Plain from 2006 to 2022 was clarified. PLS regression model and LMDI model were used to explore the main influencing factors of the carbon emission of cropland and the carbon emission of building land. PLUS model was used to simulate future land use patterns and carbon emissions. (1) The center of gravity of cropland, building land, water, and other and unused land shifted to the northeast by 4.23 km, 5.46 km, 8.44 km, and 31.58 km, respectively, and that of forest and grass shifted to the southeast by 11.12 km and 3.41 km, respectively. For major food crops, the centers of gravity of rice and maize moved northeastward by 15.47 km and 7.52 km, respectively, while wheat moved southwestward by 17.77 km. (2) From 2006 to 2022, carbon emissions from land use in the 33 counties of the Chengdu Plain are all on the rise, with a total increase of 13.552 million tons, and carbon sinks in the 31 counties continue to decline, with a total decrease of 0.691 million tons. (3) Under the natural scenario, carbon sink scenario, and carbon reduction scenario, the carbon emissions from land use decrease by 0.5391 million tons, 3.4728 million tons, and 4.5265 million tons from 2022, respectively. Among the 33 counties in the Chengdu Plain, 11 counties did not achieve carbon peak under the natural scenario, 5 counties did not achieve carbon peak under the carbon sink scenario, and all the counties achieved carbon peak under the carbon sink scenario. During the study period, there was a serious loss of cropland in the Chengdu Plain, mainly to building land in the central part of the Chengdu Plain and to forests within the Longmen Mountain, Longquan Mountain, and Leshan City, and there is a need to strengthen cropland protection in this region in the future. Under the natural scenario, carbon sink scenario, and carbon reduction scenario, land use in the Chengdu Plain region can achieve carbon peak, and the carbon reduction model will be more helpful for the counties to achieve carbon peak.

Green or grain? Impact of green space expansion on grain production in Chinese cities and its implications for national urban greening schemes

ContextExpansion of urban green space (UGS) enhances greenery and its benefits in cities. However, the impacts of such expansions on regional landscape sustainability and their spatiotemporal traits across the national scale remain unclear.ObjectivesThis study uncovers a trade-off between agricultural ecosystem services and urban human well-being—the loss of grain production due to UGS expansion consuming cropland—in China from 2000 to 2020. It proposes a safety boundary for UGS expansion to minimize the costs of grain production while addressing the escalating demand for UGS exposure.MethodsUGS expansion and cropland loss are quantified using land cover products, with statistical data contributing to the established relationship between grain loss and UGS coverage. UGS expansion scenarios for 2040 are simulated through bottom-up modeling.ResultsQuadrupled UGS area growth contributed approximately one-third to urban expansion during 2000–2020 in China. Despite improvements in per capita UGS area implying enhanced UGS exposure during rapid urbanization, UGS expansion resulted in a national grain production loss of 4.2 ± 1.4 million t from 2000 to 2020, accelerating post-2010. This loss is equivalent to the annual food intake of 9.3 million Chinese people. We propose a 30.87% UGS coverage target in China by 2040 to preserve UGS access while minimizing grain loss under future urbanization.ConclusionsAcknowledging the critical role of UGS expansion in the issue of cropland loss to urbanization is imperative. Our results offer insights into ensuring human well-being and ecosystem services through landscape and urban planning.

Eyes in the sky on Tigray, Ethiopia - Monitoring the impact of armed conflict on cultivated highlands using satellite imagery

The war in Tigray, Ethiopia has triggered a massive humanitarian crisis, displacing millions. Yet, the impact on cultivated land and local food production remains poorly understood, impeding effective aid. Leveraging Sentinel-2 satellite imagery and a decision tree algorithm with Normalized Difference Vegetation Index (NDVI) time series, we developed a model to map well-cultivated cropland, defined as fields judged by field surveyors to have satisfactory to optimal crop condition in 2021–2022 field observations. Assessing satellite estimated well-cultivated land in highland croplands (> 1200 m a.s.l), we found a net loss of 543 sq. km (95% CI: 81 sq. km) well-cultivated land in highland croplands equivalent to ≈ 8% of the average total surveyed cropland estimate from Central Statistical Agency between 2015 and 2019 (ESS, 2023a) in potential highland cropland. The net loss was positively associated with the density of recorded conflict incidents and sub-regions with high numbers of internally displaced persons (IDPs), consistent with a causal effect of the conflict on cultivated land.Employing a two-way fixed effect model causal analysis with rainfall covariates, we quantified the impact of conflict incidents on cultivated land during the pre-war (2019/20) and in-war (2021) periods. Results indicated a ≈ 6.17 sq. km (SE: 2.06) additional loss per unit increase in conflict incidents during the growing season (June to October), eight times higher than total incidents occurring throughout the entire study period. We estimated the kilocalories lost due to loss of well-cultivated croplands in 2021 could have supported at least 90% of all recorded IDPs in Tigray as of June 2021, discounting for Western Tigray. Our study showcases the utility of satellite data, coupled with local agricultural knowledge, for timely and cost-effective information crucial for aid agencies and long-term rehabilitation initiatives in smallholder farming contexts.

A 30 m annual cropland dataset of China from 1986 to 2021

A 30 m annual cropland dataset of China from 1986 to 2021

Spatial patterns of urban expansion and cropland loss during 2017–2022 in Guangdong, China

Urban expansion often occurs at the expense of cropland loss, posing challenges to sustainable urban growth and food security. However, detailed investigations into urban expansion and cropland loss remain limited, particularly in regions with varying levels of urbanization. Here, we take Guangdong Province, China, as a case study to exemplify how urban expansion affects cropland using remotely sensed land use products. We adopted geospatial analysis, correlation indicators, and landscape metrics to uncover their spatial relationships at 10-m spatial resolutions. Results showed that urban areas increased by 6335 km2 while cropland decreased by 3780 km2 from 2017 to 2022. Notably, 41 % of newly expanded urban areas were from croplands, and 45 % of lost croplands were converted to urban areas. Western Guangdong experienced the largest extent of urban expansion and cropland loss, emerging as a hotspot region in recent years. Additionally, our analysis observed the increasing compactness of urban areas and the growing fragmentation of cropland landscapes over time. These findings shed light on the intricate dynamics between urban expansion and cropland loss in rapidly urbanizing regions, which provide valuable insights for sustainable urban development, agricultural practice, and land management in the future.

Two decades of cropland monitoring in Changsha-Zhuzhou-Xiangtan city group: trends and future predictions

Rapid urbanization currently poses a threat to cropland areas. Therefore, exploring the pattern of change in cropland areas and its driving mechanism is of great significance in safeguarding regional economic development and food security. In this study, data regarding cropland in the Changsha-Zhuzhou-Xiangtan city group (CZTCG) from 2000 to 2020 were collected, and dynamic changes in cropland in the past 20 years were analyzed. Based on this, the mechanisms that drive cropland change were explored in the context of multiple dimensions. Furthermore, an Inertial Development Scenario and a Cropland Priority Scenario were designed to simulate land use/land cover (LULC) changes in the CZTCG in 2025 and 2035, and, in particular, to analyze the characteristics of future spatiotemporal changes of cropland. The results demonstrated that the cropland area in the CZTCG in the past 20 years has shown a two-stage trend of increasing (2000–2015, increase of 8.25%) and decreasing (2015–2020, decrease of 2.91%), and the main reasons for cropland loss in the whole process of change were forest and building, with serious loss of cropland area in Changsha County and Wangcheng District. Between 2000 and 2020, socio-economic factors (GDP, total agricultural output), topography (elevation, slope), and climate change (average annual temperature, annual precipitation) were highly correlated with changes in cropland area, exhibiting significant temporal and regional variability. The simulation results indicate that until 2035, the Cropland Priority Scenario shows a significant increase in the area of cropland in the study area compared to the Inertial Development Scenario. Consequently, the implementation of a strategy that prioritizes cropland can effectively protect it, while helping to promote ecological development and regional socio-economic development.

Measuring environmental and cost benefits of riparian buffers for drinking water production in a Midwest watershed

AbstractThis study focuses on the economic value and carbon benefits of riparian buffers in urban drinking water production. The impact of riparian buffers on the waterworks operation in the Raccoon River watershed was quantified using the following metrics: nitrate concentration, days of nitrate removal operation, material and energy cost (based on 17 years of historical records with a watershed model), regression, and cost analysis. The findings indicate that the presence of riparian buffers in agricultural land can substantially decrease nitrate concentration in the water intake of the waterworks during the crop‐growing season: 19% in April, 9% in May, and 11% in June. These reductions mean less nitrate treatment of the plant intake flow: 23% in April, 12% in May, and 3% in June. These changes lead to significant resource savings: 425 metric tons of sodium chloride (NaCl), 147 810 kWh of electricity, 253 metric tons of powdered activated carbon, and 20.8 million liters of fresh water. The buffers would also reduce greenhouse gas emissions by 86.9 metric tons (CO2 equivalent) in 17 years. The total cost saving was estimated at $327 326, with the highest potential savings in May ($215 100), followed by April ($65 465), and June ($46 761). When factoring in buffer installation, cropland loss, nitrate removal, and cost associated with buffer harvest for biofuel in an established biomass market, the benefit to the entire watershed community would be $2.63 million annually. The results underscore the significant cost benefits and environmental benefits associated with cropland riparian buffers in a watershed community. The approach employed in this study holds promise for assessing riparian buffer benefits in other watersheds, contributes to an understanding of sustainable water management practices, and provides a basis for decision making in a wide range of agricultural regions.

Temporal and spatial distribution and development of permanent gully in cropland in the rolling hill region (phaeozems area) of northeast China

The cropland in the Songnen phaeozems area (SPA) experiences an extensive gully erosion in the black soil region of northeast China. This study investigates the historical trends, current status, and future trajectories of permanent gully (PG) development, aiming to reveal the mechanisms behind PG development and protect the black soil. We selected nine study areas, totalling 378 km2, across three latitudinal zones in the SPA with slopes of 0–1 %, 1–3 %, and 3–5 %. The results revealed a consistent rise in gully density over time in the SPA, with values increasing from 0.87 km/km2 in 1970 to 0.94 km/km2 in 2010, and 1.32 km/km2 in 2021. Conversely, the ground lacerative degree significantly decreased from 0.025 km2/ km2 in 1970 to 0.010 km2/ km2 in 2010, and rebounding slightly to 0.019 km2/ km2 in 2021. The development rate of PG in the northern area was higher than that in the middle and southern areas, with steeper slopes (3–5 %) having more PGs compared to gentler slopes. The average rate of gully area extension increased with increasing gully level. From 1970 to 2010, the area of PG experienced a decline attributed to extensive gully management. However, subsequent decade (2010–2021) experienced a more rapid PG development, resulting in an annual cropland loss of 0.097 %. The northern area has consistently exhibited the fastest PG development rate in 1970–2021. It is noteworthy that managing gullies through reclamation after filling PG has resulted in the re-generation of secondary gullies in the same locations, which developed more rapidly than natural gullies. The reclamation after filling PG, without improvement of field drainage systems, contributes to an accelerated development rate of PG in cropland. Despite significant reductions in the total area and length of PGs through large-scale gully management, the notable increase in the development rate of gullies warrantsattention in the SPA of northeast China. Furthermore, the global community should take caution with inappropriate gully management measures because they not only prove ineffective but aggravate gully erosion.

Scenario Simulation of Land Use and Cover under Safeguarding Ecological Security: A Case Study of Chang-Zhu-Tan Metropolitan Area, China

Scenario-based simulation in land use and cover change (LUCC) is a practical approach to maintaining ecological security. Many studies generally set constraints of LUCC utilizing ecological patches but without consideration of corridors connecting these patches. Here, we constructed a framework to balance urban growth and ecological security by integrating ecological security patterns (ESPs) into the PLUS model. This study selected Chang-Zhu-Tan Metropolitan Area (CZTMA) in central China as a typical case. Specifically, coupling quantitative demand with spatial constraints of multiple levels of ESPs, this study designed four scenarios, including historical tendency (HT), urban growth (UG), ecological conservation (EC), and coordinating city development and ecological protection (CCE). Then, the transformations and landscape patterns of LUCC were analyzed to evaluate the future land change from 2020 to 2050. The results show sixty-one key ecological sources in the CZTMA, mainly in higher-elevation forested areas. Forty-six ecological corridors were estimated using circuit theory. The building expansion was driven by accessibility to transportation and government locations and will contribute to the loss of forest and cropland in the future. The feature of different scenarios in alleviating the increasing fragmentation of patches and reducing the loss amount of ecological land showed EC > CCE > HT > UG. This study developed the ESP-PLUS framework and its modeling idea, which has the potential to be applied in other regions. This extension would assist decision-makers and urban planners in formulating sustainable land strategies that effectively reconcile eco-environmental conservation with robust economic growth, achieving a mutually beneficial outcome.

Implications of changes in land use for ecosystem service values of two highly eroded watersheds in Lake Abaya Chamo sub-basin, Ethiopia

Ecosystems provide a variety of ecosystem services and functions for mankind, and their sustainable use plays an important role in livelihoods. However, the resulting land degradation due to land use and land cover changes leads to loss of valuable ecosystems and associated ecosystem functions and services. This study takes two highly degraded watersheds, Aba-Bora and Guder, in Ethiopia and uses the value transfer valuation method to estimate changes in ecosystem service values. The study shows how loss of cropland and grazing lands can significantly affect ecosystem services even when plantations and shrubland increase. The results suggest that over a period of 41 years, the ecosystem service value of exclosures/shrublands and plantations increased, whereas that of crop and grazing lands decreased. The loss of ecosystem service values due to the decrease in cropland and grazing lands outweigh the gains due to the expansion of plantations and exclosures and resulted in a total loss of ecosystem service values of US$ 1.6 million in Aba-Bora watershed and US$ 24.4 million in Guder. In both watersheds, the greatest contributor to ecosystem service loss was a decline in supporting services, while the increase in plantation and shrublands (mainly through establishment of exclosures) meant that regulating ecosystem services suffered the smallest loss. Given their importance to livelihoods in these areas, the loss in crop and grazing lands significantly increase the vulnerability to shocks and narrow future livelihood options for many households. Given that severe gully erosion is the major contributor to the reduction in crop and grazing lands, catchment management that integrates the conservation of upstream areas using diverse sustainable land management practices, and gully rehabilitation measures in downstream areas could be an important option to reducing the expansion of big gullies, and conserving crop and grazing lands and ecosystem service values. However, the results suggest that the risks to livelihoods may be underestimated while the effectiveness of current actions to address land degradation over-estimated by communities.

Illustrating land cover change associated with erosion management of the Little Blue River, Kansas, USA

AbstractErosion is a concern due to environmental degradation, loss of valuable cropland, increased sediment loads in aquatic systems, and reduced reservoir capacity. To manage erosion, riparian forest buffers and bendway weirs were installed in the Little Blue River, Kansas, during years 2002–2010. To illustrate land cover changes associated with management for upland and streambank erosion, indicated through terrestrial land gains, particularly of permanent tree cover relative to short‐lived crop cover, we digitized 1 m orthoimagery. For the pretreatment interval of 1991–2002, we digitized streambank edges to approximate change in river area. Due to river dynamics, for the 2002 and 2014 interval before and after treatment, we used land ownership parcels as fixed locations to assess changes in land area and land classes for 24 treated and 24 untreated parcels, each parcel group totaling 1575 ha. We appraised two extents of the unified streambank for both years and all land in parcels rather than isolating the river from the surrounding watershed. During 1991 to 2002, treated land parcels lost terrestrial land, whereas untreated land parcels gained land. During 2002–2014, treated land had greater river and crop cover, and less tree cover than untreated land. For the entire extent, with similar trends for the unified streambank extent, by 2014, treated parcels gained 27.3 ha of terrestrial land compared to 4.6 ha gained by untreated parcels. Gains occurred in tree cover and losses in river water and sediments cover. In treated parcels crop cover decreased, whereas in untreated parcels crop cover increased. Streamflows decreased over time, likely contributing to streambank stability. Despite lack of documented cost‐share agreements, in untreated parcels, landowners managed land by increasing tree cover to protect soil from erosion. All measurements were consistent with erosion followed by management for erosion through terrestrial land gains of tree cover.

Do adaptive policy adjustments deliver ecosystem-agriculture-economy co-benefits in land degradation neutrality efforts? Evidence from southeast coast of China.

Ecosystem restoration projects (ERPs) facilitate land degradation neutrality (LDN). However, the response dynamics and interactions of sectors within ecosystem-agriculture-economy nexus (EAEN) have not been sufficiently explored, which constrains the coordinated efficacy of LDN efforts. To bridge the knowledge gaps, the present study selected a land restoration hotspot in southeastern China as a case to investigate the simultaneous responses of the EAEN sectors to ERPs from a novel social-ecological system (SES)-based LDN perspective. Various biophysical models and Manne-Kendall trend test as well as multi-source spatially explicit data and socioeconomic statistics were applied to quantify the co-evolution of natural and socioeconomic indicators. ERPs converting cropland to woodland and grassland promoted vegetation restoration, reduced soil erosion, and enhanced carbon sequestration. However, cropland loss initially resulted in a decline in grain productivity. Policy adjustments and improvements in ecosystem restoration efforts and agricultural production conditions improved food security and increased agricultural production capacity. Effective policymaking and favorable resident engagement accelerated the transformation from a grain-production-based agriculture to diversified industries and, by extension, economic output, income, and population. The success of socioeconomic development under the SES framework for LDN demonstrated that this strategy could achieve the desired environmental, agricultural, and economic targets. EAEN under the SES conceptual framework provides an inclusive, comprehensive LDN perspective and improves ERP efficacy. The findings of the present work might be applicable to other land restoration areas challenged by the complex interactions among multidimensional factors. Comparably successful implementation of these ERPs could be realized if individual environmental and socioeconomic conditions are thoroughly considered during the formulation of coordinated development policies.

Data-Driven Projections Demonstrate Non-Farming Use of Cropland in Non-Major Grain-Producing Areas: A Case Study of Shaanxi Province, China

The non-farming use of cropland has led to food insecurity in China due to drastic land use (LU) changes under the stresses of ecological restoration and urbanization, particularly in non-major grain-producing areas. Questions were raised about spatiotemporal cropland losses/gains and their drivers in these areas in the future for sustainable development of the agriculture sector. However, the answers to these questions have not been well acknowledged. This study, therefore, presents analyses of cropland area change from 1990 to 2018 and from 2018 to 2051 in Shaanxi province based on the Future Land Use Simulation (FLUS) model that follows the integration of the Shared Socioeconomic Pathway 2 and the Representative Concentration Pathway 4.5 (SSP245) within the International Coupled Model Intercomparison Project 6 (CMIP6). The results highlight that ecological restoration and fast-paced urbanization mainly drove the alarming non-farming use of cropland. The per capita cropland area is projected to increase, but the cropland loss will still occur, which potentially causes food insecurity. Thus, food security will be a challenging issue in the near future. The quantitative findings call for careful designs of LU policies, taking into account cropland protection, socio-economic development, and ecological restoration.

Greening rate in North Korea doubles South Korea

South and North Korea have experienced contrasting economic developments since the 1950s while sharing similar climates. Previous studies revealed an overall long-term greening trend across the Korean Peninsula based on greenness data from coarse-resolution satellite images. However, there has been no comprehensive comparison of the greenness patterns and the driving mechanisms between two countries due to the limitations of coarse-resolution satellite data. Here, we performed cross-calibration among Landsat sensors and adopted a phenology-based approach to generate Landsat annual maximum Normalized Difference Vegetation Index (NDVImax) time series for each pixel from 1986 to 2017. We found that over 1986–2017, the greening rate in North Korea was almost twice that of South Korea. Cropland in South Korea is the main source of the greening discrepancy. The expansion of agricultural facilities in the stable cropland area and urbanization in the cropland loss area of South Korea contributed 57% to the significant negative NDVImax trend, which was dominant over the forest NDVImax increase resulting from rising temperatures, CO2 fertilization effects and afforestation projects. However, in North Korea, CO2 fertilization effects in the stable cropland area and transition from grassland to cropland promoted an increase in NDVImax, despite decreasing NDVImax in forest areas due to deforestation. Our results highlight the need for delineating fine-scale land-use changes to advance our understanding of regional vegetation dynamics.

Assessing the response of vegetation photosynthesis to flash drought events based on a new identification framework

Flash drought events pose serious threats to terrestrial ecosystems due to their rapid intensification. However, the comprehensive assessment of recovery stage in flash drought is hindered by the insufficient consideration of reduplicative decline in soil moisture. Besides, how the vegetation photosynthesis respond to flash drought remains unknown. Here, a new method for explicitly characterizing flash drought events was proposed, incorporating both development rate and duration, with particular emphasis on the process of soil moisture change during the recovery stage. Then the temporal and spatial evolutions of the flash drought over the Pearl River Basin were analyzed. Solar-induced chlorophyll fluorescence (SIF) was used to explore the responses of different vegetation types to flash drought. The results indicated that the onset speed may be increasing, and the flash drought in 2007 was quite serious. Most flash drought events lasted 32 to 48 days. Besides, this study focused on the response of forests, grasslands and crops to flash drought, and the forestlands were less sensitive to flash droughts, while croplands experienced the most flash drought events, and the time of photosynthesis loss of croplands was the shortest. Moreover, precipitation deficit, high temperature, high evapotranspiration (ET) and high potential evapotranspiration (PET) were the main driving factors triggering flash drought. The soil moisture was above 40th percentile after the end of a flash drought, which demonstrate the accuracy of the framework in identifying the development of flash drought in the concern area. Our findings also demonstrated the great effectiveness of SIF in monitoring the resistance of ecosystems, deepening our understanding of the response of vegetation photosynthetic capacity to flash drought events.

Urban sprawl at the expense of cultivated land: decadal land use and land cover changes and future projections in the upper Awash basin of central Ethiopia

IntroductionUrban sprawl in developing countries affects future sustainability concerns related to environment, ecology and cropland losses. This study aimed at identifying, classifying and quantifying the changes in land-use and land-cover (LULC) during the last two decades (2000–2020) and predict the decadal pattern for the next three decades (2030–2050), with particular emphasis on urban sprawl at the expense of cultivated land in the upper Awash basin of central Ethiopia.MethodsLandsat images were used to analyze the LULC change dynamics using hybrid image classification and maximum likelihood classifier techniques. The Cellular Automata-Markov Chain (CAMC) Model was used to predict its future LULC change dynamics. A detailed analysis of the urban sprawl in the cities of Addis Ababa, Adama, and Mojo was also conducted.ResultsIt was observed that during the last two decades, settlements, particularly urban sprawls, substantially expanded at the expense of cultivated land, whereas the latter modestly expanded at the expense of forestland, bare land, and shrubland. From its size in 2000, the urban sprawl of Addis Ababa has grown in all directions towards cultivated land by more than six times in 2020 and is expected to become double of that by 2050 in the urban and peri-urban areas of the basin. Adama city has expanded by the same rate of 9.7% in the past two decades, while Mojo town has sprawled 9 folds between 2010 and 2020. The predicted percentage change in settlement for Addis Ababa and its neighboring districts within 22 km radius from the centroid shows a 40% expansion in 2030, 77% in 2040, and 87% in 2050 compared with the reference year 2020. Similarly, the Mojo town will expand significantly in 2030 (54%), 2040 (119%), and 2050 (by a staggering magnitude of 244%), while Adama will expand within the 12 km radius by 18%, 42%, and 117% in the next three respective decades.DiscussionThe rapid cultivated land conversions in the basin may contribute to major shifts in urban and peri-urban ecological environments. Our predictive LULC change maps and urban sprawling could be useful for developing effective and sustainable land-use policies for environmental and ecological management in the upper Awash basin.

Changing cropland in changing climates: quantifying two decades of global cropland changes

Climate change is impacting global crop productivity, and agricultural land suitability is predicted to significantly shift in the future. Responses to changing conditions and increasing yield variability can range from altered management strategies to outright land use conversions that may have significant environmental and socioeconomic ramifications. However, the extent to which agricultural land use changes in response to variations in climate is unclear at larger scales. Improved understanding of these dynamics is important since land use changes will have consequences not only for food security but also for ecosystem health, biodiversity, carbon storage, and regional and global climate. In this study, we combine land use products derived from the Moderate Resolution Imaging Spectroradiometer with climate reanalysis data from the European Centre for Medium-Range Weather Forecasts Reanalysis v5 to analyze correspondence between changes in cropland and changes in temperature and water availability from 2001 to 2018. While climate trends explained little of the variability in land cover changes, increasing temperature, extreme heat days, potential evaporation, and drought severity were associated with higher levels of cropland loss. These patterns were strongest in regions with more cropland change, and generally reflected underlying climate suitability—they were amplified in hotter and drier regions, and reversed direction in cooler and wetter regions. At national scales, climate response patterns varied significantly, reflecting the importance of socioeconomic, political, and geographic factors, as well as differences in adaptation strategies. This global-scale analysis does not attempt to explain local mechanisms of change but identifies climate-cropland patterns that exist in aggregate and may be hard to perceive at local scales. It is intended to supplement regional studies, providing further context for locally-observed phenomena and highlighting patterns that require further analysis.