Decrease In Cropland Research Articles

Spatial and Temporal Changes of Ecosystem Service Value in Airport Economic Zones in China

With the rapid development of the aviation industry, many negative effects on the local environment have been reported. This study examined the land use and land cover (LULC) and ecosystem service value (ESV) of airport economic zones (AEZs) in China and assessed the changes in LULC and ESV. The results indicate that LULC changed significantly from 1990 to 2015, characterized by the increase in construction land (increase rate, 68.53%) and water bodies (increase rate, 2.32%) and the decrease in cropland (decrease rate, 4.28%), forest (decrease rate, 0.73%), grassland (decrease rate, 4.64%) and unused land (decrease rate, 6.36%). The ESV of AEZs in 1990 and 2015 was RMB 3454 and 3483 million, respectively, with an overall ESV change of RMB 29 million. The ESV of AEZs is characterized by high value in the coastal area of China. From 1990 to 2015, AEZs with a high ESV were located in Inner Mongolia, while those with a high decrease in ESV were located in the southeastern coastal area. From 1990 to 2000, the AEZs with a high increase in ESV were located in Inner Mongolia and Qinghai and the AEZs with decreased ESV were mostly located in central and south China. However, from 2000 to 2010, AEZs with high and low increases in ESV were located in central China and the south coastal area of China, respectively. From 2010 to 2015, AEZs with a high decrease in ESV were located in southeast China.

The 30 m annual land cover dataset and its dynamics in China from 1990 to 2019

Abstract. Land cover (LC) determines the energy exchange, water and carbon cycle between Earth's spheres. Accurate LC information is a fundamental parameter for the environment and climate studies. Considering that the LC in China has been altered dramatically with the economic development in the past few decades, sequential and fine-scale LC monitoring is in urgent need. However, currently, fine-resolution annual LC dataset produced by the observational images is generally unavailable for China due to the lack of sufficient training samples and computational capabilities. To deal with this issue, we produced the first Landsat-derived annual China land cover dataset (CLCD) on the Google Earth Engine (GEE) platform, which contains 30 m annual LC and its dynamics in China from 1990 to 2019. We first collected the training samples by combining stable samples extracted from China's land-use/cover datasets (CLUDs) and visually interpreted samples from satellite time-series data, Google Earth and Google Maps. Using 335 709 Landsat images on the GEE, several temporal metrics were constructed and fed to the random forest classifier to obtain classification results. We then proposed a post-processing method incorporating spatial–temporal filtering and logical reasoning to further improve the spatial–temporal consistency of CLCD. Finally, the overall accuracy of CLCD reached 79.31 % based on 5463 visually interpreted samples. A further assessment based on 5131 third-party test samples showed that the overall accuracy of CLCD outperforms that of MCD12Q1, ESACCI_LC, FROM_GLC and GlobeLand30. Besides, we intercompared the CLCD with several Landsat-derived thematic products, which exhibited good consistencies with the Global Forest Change, the Global Surface Water, and three impervious surface products. Based on the CLCD, the trends and patterns of China's LC changes during 1985 and 2019 were revealed, such as expansion of impervious surface (+148.71 %) and water (+18.39 %), decrease in cropland (−4.85 %) and grassland (−3.29 %), and increase in forest (+4.34 %). In general, CLCD reflected the rapid urbanization and a series of ecological projects (e.g. Gain for Green) in China and revealed the anthropogenic implications on LC under the condition of climate change, signifying its potential application in the global change research. The CLCD dataset introduced in this article is freely available at https://doi.org/10.5281/zenodo.4417810 (Yang and Huang, 2021).

Impact of cropland development intensity and expansion on natural vegetation in different African countries

The world's rapid population growth is also fueling the high demand for food. Cropland intensification and expansion as the primary source of increasing food production thrives everywhere, yet hinders natural vegetation. This study aims to examine the extent to which the development of Cropland intensity affects natural vegetation and scrutinizes its relationship with Gross Domestic Product (GDP) on the African continent from 1992 to 2015. The ratio of total Crop area harvested and Cropland extent (CE) datasets used to compute the cropping intensity CI (yr−1) for each year over 24 years. The correlation coefficient and comparison method were applied for cropland intensity and natural vegetation to reveal the rate at which cropland intensity affects natural vegetation. The same method was applied between CI, CE and GDP percentage from Agriculture to know their relationship. The results revealed that Cropland extended at a rate of about 9130.17 km2 yr−1, leading to a rise of 219,123.99 km2 of increase. Shrubland was the most devastated natural vegetation at a rate of −9461.96 km2 and cleared about 227,087.1 km2. The CI and GDP percentage from agriculture showed a strong negative correlation in most of the countries, especially in developing countries. The CI is low and the CE is high, which means the degradation of existing natural vegetation and the eradication of potential environment health. Ethiopia and Tanzania have been the only two countries which experienced cropland decrease among the top 10 African countries with a large cropland area, while Nigeria and Sudan have increased the most. Further Malawi witnessed the highest percentage growth for cropland. South Sudan has identified strong trends in GDP percent from agriculture, while Libya has seen substantial decline. On the other hand, Liberia, Sierra Leone, Guinea-Bissau, Ethiopia, and Chad identified to have the biggest % of agriculture to GDP during the study period.

The 300 years cropland changes reflecting climate impacts and social resilience at the Yellow River–Huangshui River Valley, China

Changes of croplands often reflect the combined impacts of both natural environment changes and social agriculture activities. Such reflections manifested more significantly in agro-pastoral transition zones, e.g. in the North and West of China. In this study, cropland changes at the Yellow River–Huangshui River Valley, as a typical agro-pastoral transition zone in northwestern China, is analyzed in terms of the changes of the total amount and spatial pattern over the past 300 years (majorly in the Qing Dynasty). The reconstructed cropland data indicated a fluctuation of cropland areas in accordance with changes of regional climate conditions, natural hazards, agriculture activities and socio-economic development. A significant decrease of cropland in the middle of the 19th century was detected, which appeared a good consistency with the frequent natural disasters in the same period and the climate cooling trend across the whole 19th century. Though in the worsening conditions, three major copping strategies maintained and developed the local socio-agriculture system: (a) land reclamation policy encouraged immigrants and military farming; (b) construction of water conservancy facilities increased agricultural productivity; (c) increasing local Tibetans learned and transformed to implementing both agriculture and pastoral productions with flexibilities depending on climate conditions. The study demonstrates that the social-agriculture system held certain resilience, which can be maintained and enhanced with appropriate political, engineering, economic, and social-cultural measures.

Assessing potential ecosystem service dynamics driven by urbanization in the Yangtze River Economic Belt, China

Ecosystem services (ESs) link natural and social processes and play an important role in sustaining ecological security, human well-being, and sustainable development. However, uncertainties in future socioeconomic land use drivers may result in very different land use dynamics and consequences for land-based ESs. In this study, land use transitions in the Yangtze River Economic Belt (YREB) were simulated in the short term (2018–2030), medium term (2030–2040), and long term (2040–2050) using the future land use simulation (FLUS) model based on the local shared socioeconomic pathways (SSPs). According to the projected land use types, six ESs were quantified and assessed regarding how they would evolve under particular land use changes. The results of land use simulations showed that the main features were urban sprawl and a decrease in cropland. In particular, intensive urban sprawl occurred around existing urban areas, and a large amount of cultivated land was converted into urban land. In the YREB, urban land will increase from 88,441 km2 in 2018 to 156,173–192,900 km2 in 2050, while the cropland area will decrease from 607,131 km2 in 2018 to 500,183–596,313 km2 in 2050. As a consequence of urban expansion, all ESs exhibited decreasing trends, except for several services under SSP1. Food production (FP), carbon storage (CS), water conservation (WC), soil retention (SR), air purification (AP), and habitat quality (HQ) will decline by 8.98–21.4%, 1.95–6.781%, 2.97–6.5%, 0.9–1.7%, 1.20–5.15%, and 6.11–12.86%, respectively. The ES integrative assessment indicated distinct provincial differences. Developed eastern provinces have higher populations and urbanization; however, these traits result in greater ES losses. We suggest that future land management should control the blind expansion of urban land and enhance the protection of cropland and natural habitats to reduce ES losses.

Impact of Land Use Change on Vegetation Carbon Storage During Rapid Urbanization: A Case Study of Hangzhou, China

Land use changes have significant impacts on the carbon balance in an urban ecosystem. When there is rapid development in urbanizing regions, land use changes have a dramatic effect on vegetation carbon storage (VCS). This study investigates the impact of land use change on VCS in a period of rapid urbanization in Hangzhou, China. The results show that: 1) from 2000 to 2015, land use in Hangzhou underwent huge changes, mainly reflected in decrease in cropland and wetland and the increased settlement. More than 34.58% of the land was transformed, and the land use changes are primarily characterized by a significant decrease in cropland due to the occupation by settlement. 2) over the 15 years, changes in land use led to a decrease of 3.93 × 105 t of VCS in the urban ecosystem. The large-scale transformation of cropland and wetland, which have a comparatively high carbon density, into land for settlement exerted a negative impact on VCS. 3) The central city, which with the Circle-E/I/O mode, had the lowest comprehensive land use dynamic degree, leading to moderate land use change and an increase in VCS; Yuhang and Xiaoshan, which with Multicore-E/O/I mode and Fan-E/O/I modes, had a higher comprehensive land use dynamic degree, drastic changes in land use, and a decrease in VCS. This study proposes a reliable method of estimating changes in VCS, clarifies the relationship between land use change and VCS during rapid urbanization, and provides recommendations for sustainable urban development.

30 m annual land cover and its dynamics in China from 1990 to 2019

Abstract. Land cover (LC) determines the energy exchange, water and carbon cycle between Earth's spheres. Accurate LC information is a fundamental parameter for the environment and climate studies. Considering that the LC in China has been altered dramatically with the economic development in the past few decades, sequential and fine-scale LC monitoring is in urgent need. However, currently, fine-resolution annual LC dataset produced by the observational images is generally unavailable for China due to the lack of sufficient training samples and computational capabilities. To deal with this issue, we produced the first Landsat-derived annual China Land Cover Dataset (CLCD) on the Google Earth Engine (GEE) platform, which contains 30 m annual LC and its dynamics of China from 1990 to 2019. We first collected the training samples by combining stable samples extracted from China’s Land-Use/Cover Datasets (CLUD), and visually-interpreted samples from satellite time-series data, Google Earth and Google Map. Using 335,709 Landsat images on the GEE, several temporal metrics were constructed and fed to the random forest classifier to obtain classification results. We then proposed a post-processing method incorporating spatial-temporal filtering and logical reasoning to further improve the spatial-temporal consistency of CLCD. Finally, the overall accuracy of CLCD reached 79.31 % based on 5,463 visually-interpreted samples. A further assessment based on 5,131 third-party test samples showed that the overall accuracy of CLCD outperforms that of MCD12Q1, ESACCI_LC, FROM_GLC, and GlobaLand30. Besides, we intercompared the CLCD with several Landsat-derived thematic products, which exhibited good consistencies with the Global Forest Change, the Global Surface Water, and three impervious surface products. Based on the CLCD, the trends and patterns of China’s LC changes during 1985 and 2019 were revealed, such as expansion of impervious surface (+148.71 %) and water (+18.39 %), decrease of cropland (−4.85 %) and grassland (−3.29 %), increase of forest (+4.34 %). In general, CLCD reflected the rapid urbanization and a series of ecological projects (e.g., Gain for Green) in China and revealed the anthropogenic implications on LC under the condition of climate change, signifying its potential application in the global change research. The CLCD dataset introduced in this article is freely available at http://doi.org/10.5281/zenodo.4417810 (Yang and Huang, 2021).

Changes in soil physical and hydraulic properties following the conversion of forest to cropland in the black soil region of Northeast China

Black soils (Mollisols) are inherently productive and fertile but are deteriorating due to long-term intensive cultivation. Understanding the changes in soil physical and hydraulic properties in topsoils and deep soils after converting forest to cropland would reveal the mechanism related to the black soil degradation. Herein, we investigated the variations in the soil water-stable aggregates, soil water content, bulk density, field capacity, total porosity, saturated hydraulic conductivity, and parameters of soil water retention curve at the 0–100 cm depth in four sampling fields. These fields included a forest as control and three croplands that were converted from forest 41, 50 and 65 years ago in the black soil region of Northeast China. We showed that converting forest to cropland decreased >2 mm aggregates and aggregate stability especially at 0–15 and 70–100 cm depths, with a greater decrease in cropland after relatively longer time of cultivation. Conversion of forest to cropland significantly decreased the soil water content at the 0–15 cm depth but increased it at the 15–100 cm depth, and the increase in the 50–100 cm soil layer was strengthened with cultivation time. The decreases in field capacity, total porosity and saturated hydraulic conductivity and increase in bulk density at the 0–50 cm depth following the conversion of forest to cropland were higher after 41 and 50 years of cultivation than those after 65 years of cultivation. However, changes in these metrics at the 50–100 cm depth increased with cultivation time. The parameters (i.e., θr, θs, α and n) of the soil water retention curve were not affected by the cultivation time after converting forest to cropland. These results highlighted that long-term cultivation after the conversion of forest to cropland resulted in the changes in soil physical and hydraulic properties in the 0–100 cm soil profiles, and thus, the response of deep soils should not be ignored in this black soil region.

Assessing Impacts of Land Use/Land Cover Conversion on Changes in Ecosystem Services Value on the Loess Plateau, China

The Loess Plateau is not only a critical region that suffers from ecological threats but also a valuable region that provides various fundamental ecosystem services, including provisioning, regulating and cultural services to about 8% of the Chinese population. The specific natural environment and extensive human activities have led to substantial land use/land cover changes between 1990 and 2015, such as the decrease in cropland with the increase in forests and grasslands due to the implementation of the Grain for Green Program since 2000 and the expansion of built-up areas with economic development and population growth. However, the effects of these changes on ecosystem service values have not yet been considered. In this study, the approach based on a combination of land use/land cover proxies and benefit transfer is applied to assess ecosystem service value changes resulting from land use/land cover changes in the 1990–2000, 2000–2010 and 2010–2015 periods. The results reveal that the total value of ecosystem services has been reduced by $6.787 million from 1990 to 2000 and increased by $4.6 million from 2000 to 2015. The elasticity analysis shows that a 1% area conversion has induced average value changes of 1.03%, 0.38% and 0.05% in the three periods, respectively. Elasticity is developed as an indicator for locating unusual changes among different regions and identifying specific needs for ecosystem management.

Impact of sub-watershed characteristics and changes on sediment DOM quantity and quality over Jiaozhou Bay

Dissolved organic matter (DOM), which is influenced by watershed characteristics, plays an important role in carbon (C) budgets and reflects human impacts on the river ecosystem. This study aims to analyze the changes of land use and landscape patterns in three sub-watersheds and the effects of these sub-watershed characteristics on the content and quality characteristics of DOM. We collected sediment samples of different depth from exits of three sub-watersheds. Samples were analyzed for content and quality of DOM based on absorbance and fluorescence properties using ultraviolet–visible spectroscopy (UV–vis) absorbance and fluorescence spectroscopy. Results show that the land use types of the three sub-watersheds are mainly cropland and construction land. And the construction land area of three sub-watersheds increase from 2000 to 2018, while the area of cropland decrease. In addition, we find that forestland and cropland negatively influence sediment DOC contents and positively influence the proportion of humic fluorescence. And the water area has positive effect on protein-like DOM compounds. Moreover, the degree of fragmentation of the landscape has negative effects on sediment DOC contents. The connectivity of the landscape and the agglomeration of the patch have positive effects on humic-like components in sediment DOM at the exit of the sub-watershed. In general, sub-watershed characteristics have stronger effects on DOM quality than on its content. This study provides new insights on the importance of watershed characteristics on the content and quality of sediment DOM in river and supplies the support for river ecosystem management.

Global cropland intensification surpassed expansion between 2000 and 2010: A spatio-temporal analysis based on GlobeLand30

Cropland expansion and intensification are the two main strategies for increasing food production. Here, we investigated the spatio-temporal patterns of global cropland expansion and intensification between 2000 and 2010 using the GlobeLand30 dataset. In doing so, we first analyzed the expansion and loss of global cropland at different spatial scales. Second, we quantified cropland intensification from the perspective of output and mapped its global spatial distribution. Third, nine coupled patterns of cropland expansion and intensification were identified, and the contributions of these two strategies to global crop production were finally estimated and compared. The results show that global cropland increased slightly (2.19%) during 2000–2010, with the American continent having the largest net increase (0.21 million km2) and Africa having the highest magnitude of increase (7.42%) as well as the most substantial spatial variation. Among the world's top ten countries with the largest cropland areas, China was the only country which experienced cropland decrease, while cropland in Brazil and Argentina increased the most. Moreover, we found that Brazil ranked first in cropland intensification, followed by China, India and Ukraine. More than one-third of countries' cropland had stable area and moderate intensification, suggesting that agricultural land systems did not cause significant environmental harm globally during this period. Ten countries (e.g., Brazil and Algeria) experienced significant cropland expansion as well as a high level of intensification, suggesting that they could be major contributors to global crop production as well as environmental change. Cropland expansion largely boosted crop production improvement in Asia, while cropland intensification was the dominant factor for crop production in Europe and America. Overall, cropland intensification contributed much more than expansion to improving global agricultural production during 2000 and 2010. Our results gain a comprehensive overview of spatio-temporal patterns of global cropland expansion and intensification, which can provide helpful insights for the international community and individual countries to better guide land use planning, adjust agricultural structure and coordinate food trade so as to achieve a sustainable development of agriculture.

Temporal and spatial relationships between soil erosion and ecological restoration in semi-arid regions: a case study in northern Shaanxi, China

ABSTRACT To assess the effects of the Grain for Green Program (GGP) on soil erosion is essential to support better land management policies in the Chinese Loess Plateau. Studies on the evaluation of the effects of the GGP on soil erosion have garnered heightened attention. However, few studies examined the efficiency of GGP on soil erosion control through spatial relationship analysis. Thus, this study focuses on analyzing the spatial variation relationship between soil erosion and GGP in northern Shaanxi, Chinese Loess Plateau, from 1988 to 2015. The Universal Soil Loss Equation was used to quantify changes in soil erosion at the regional and watershed scales, and the Geographically Weighted Regression model was used to analyze the spatial relationships between land use and land cover (LULC) and soil erosion. Our results indicated that the major characteristic of LULC change during the GGP was a rapid increase of vegetation area and a rapid decrease of cropland. Bare lands contributed to the most serious soil loss, followed by croplands and sparse grasslands. The GGP had a globally positive influence on the decrease in soil erosion over the study area, but the amount of soil erosion in western and northern regions maintained a severe level. Spatial heterogeneity in the nature of the relationships among different vegetation, croplands, and soil erosion was also observed. The change rate of wood and the change rate of soil erosion in northern sub-watershed represented a negative relationship, while the change rate of sparse grassland was negatively correlated to the change rate of soil erosion in 21 sub-watersheds, account for 72% of the study area. The GGP implemented in northern sub-watersheds were more effective for soil erosion control than southern sub-watersheds. We propose that current areas of vegetation can support soil erosion control in the whole northern Shaanxi, but local-scale ecological restoration can be considered in northern sub-watersheds.

Trade-Offs between Economic Benefits and Ecosystem Services Value under Three Cropland Protection Scenarios for Wuhan City in China

Over the past few decades urbanization and population growth have been the main trend all over the world, which brings the increase of economic benefits (EB) and the decrease of cropland. Cropland protection policies play an important role in the urbanization progress. In this study, we assess the trade-offs between EB and ecosystem services value (ESV) under three cropland protection policy scenarios using the LAND System Cellular Automata for Potential Effects (LANDSCAPE) model. The empirical results reveal that trade-offs between EB and ESV in urbanizing areas are dynamic, and that they considerably vary under different cropland protection policy scenarios. Especially, the results identify certain “turning points” for each policy scenario at which a small to moderate growth in EB would result in greater ESV losses. Among the three scenarios, we found that the cropland protection policy has the most adverse effect on trade-offs between EB and ESV and the results in the business as usual scenario have the least effect on the trade-offs. Furthermore, the results show that a strict balance between requisition and compensation of cropland is an inappropriate policy option in areas where built-up areas are increasing rapidly from the perspective of mitigating conflict between EB and ESV and the numbers of cropland protection that restrained by land use planning policy of Wuhan is a better choice.

Land Use Landcover Change Monitoring and Projection in the Dano Catchment, Southwest Burkina Faso

Burkina Faso has long been experiencing intense land-use landcover changes (LULCC) which have resulted in widespread land degradation. Hence, the need to obtain LULC information for improved land-use planning and sustainable management of land-resources cannot be overemphasized. This study examined the historical LULCC in the Dano catchment and projected the situation in 2050 for business-as-usual (BAU) and afforestation scenarios. Multitemporal Landsat images of 1990, 2000, 2010 and 2016 were classified with an overall accuracy of more than 90%. The Cellular-Automata Markov approach was used to project the future LULC pattern after identifying major driving forces of LULCC. The results revealed a substantial expansion in settlement and cropland area of about 62% and 6% respectively, which triggered a 15% decrease in forest cover, thus paving the way for severe soil degradation. The increase in cropland, settlement area, water bodies, and the decrease of forest were at an annual rate of 3.8%, 10.5%, 6.97% and 2.53% respectively within the past 26 years. The projected LULC under the BAU scenario revealed further forest loss from 46.72% in 2016 to 38.54%, owing to an extension in agriculture from 38.51% to 46.69%. The afforestation scenario projected a potential increase in forest by 2.13% and a decrease in cropland by 2.09% in the future relative to 2016. This study illustrates the accelerated land degradation and the challenges on ecosystem sustainability of the Dano landscape, hence, appropriate interventions like reforestation, protection measures and policy option in strategic land-use planning are needed to resolve the further loss of forest cover. https://doi.org/10.23953/cloud.ijarsg.445

Scale effects of vegetation restoration on soil and water conservation in a semi-arid region in China: Resources conservation and sustainable management

The scale effect of vegetation restoration on soil and water conservation has received little attention, despite numerous studies on the assessments of vegetation restoration at different spatial scales. This study investigated the scale effect of vegetation restoration on soil erosion and water yield at Yanhe watershed, Chinese Loess Plateau. It provides the site-based temporal and spatial varying relationships among vegetation restoration, soil erosion, and water yield. Spatial modeling and mapping methods were used to analyze the scale effect at regional and sub-watershed scales. Our results indicated vegetation restoration has generated positive impacts on soil erosion reduction and negative impacts on water provision in the whole watershed. Croplands, sparse grasslands, and moderate grasslands were the land types which contributed the most to soil erosion. The decrease of cropland was the major contribution to soil erosion reduction. Moreover, the trade-off relationship between soil erosion and water yield existed in the whole watershed, but the degree of trade-off varied from one sub-watershed to another. High-risk soil erosion regions were concentrated in the central watershed. But in this region, the impacts of vegetation restoration on soil erosion control varied with different sub-watersheds. A simple increase of vegetation might not help reduce soil erosion in sub-watersheds where are characterized by low vegetation coverage and scattered vegetation restoration. Vegetation restoration should be based on past spatial LULC patterns. Soil erosion control should focus on the current level of cropland management and areas of vegetation maintenance than new afforestation in the high-risk soil erosion regions.

Integrating the SD-CLUE-S and InVEST models into assessment of oasis carbon storage in northwestern China.

Spatio-temporal integrated assessment of land-use change impacts on carbon storage services is a new and important research field in land science and landscape ecology. The objective of this paper is to use an integrated SD-CLUE-S and InVEST model to simulate and predict land-use changes impacts during 2000–2018 on carbon storage at pixel and regional scales in the Zhangye oasis, Northwest China. The SD-CLUE-S model was used to simulate land-use change, and three land-use scenarios (current trend, moderate protection, and strict protection) were defined in collaboration with oasis socioeconomic development and ecological environment conservation by local government. The InVEST model was then used to simulate land-use change impacts on carbon storage at different scales in the oasis. The results showed that: (1) the effects of built-up land expansion were especially notable, with a rapid decrease in cropland during 2009–2018; (2) the strict protection scenario saved the largest amount of carbon storage for the oasis compared with the current trend and moderate protection scenarios. The scientific value of this study has been to show that the proposed modeling method can be used to reflect different land-use patterns and their effects on ecosystem services at multiple scales in the oasis. Furthermore, this research can be used to help government managers encourage stakeholders to contribute funds and strategies to maintain oasis landscape patterns and ecological processes by implementing local plans for potential conservation projects.

Modelling the dynamics of landscape transformations and population growth in the highlands of Ethiopia using remote-sensing data

ABSTRACTThis study models landscape transformations and settlement dynamics in a highland area of Ethiopia over a 56 year period (1957–2013). The analyses were performed using aerial photographs, satellite images, and field data. The remotely sensed images were geometrically and radiometrically corrected. Visual interpretation of aerial photographs and supervised classification of multispectral satellite images using the maximum likelihood algorithm were chosen for land-cover mapping. The population size was estimated by counting the houses on the aerial photographs and on the high-resolution images, and by direct census. The overall trend showed an increase of cropland and a decrease of other types of land cover. Landscape transformation rates recently slowed down due to ownership and policy restrictions. The average cropland holding size per family has decreased from 2.6 to 1.1 ha due to the exponential growth of the population. The relationship between settlement and cropland expansion is statistically significant. Models of logistic growth were fitted to the cropland area, and models of exponential and logistic growth to the population development to estimate the carrying capacity. The concomitant increase of population and the decrease of cropland per head resulted in a shortage of food and energy, highlighting the importance of policy decisions on land management.

Can China Feed Itself under Climate Change? A High-Resolution Analysis

Climate change remains as a major threat to food security, particularly for China because of its enormous population living off limited cropland. Evaluating the cost of climate change on agriculture requires estimates on both crop yields and cropland, where analysis on the latter has been limited. This paper utilizes unique high-resolution satellite data from 1980 to 2010 to estimate the effect of temperatures on cropland in China. We find that extremely high temperatures have significantly negative effects on the area of cropland. Our preferred specification suggests that an additional day with daily average temperature above 30 degree C in the past 10 years decreases the area of cropland by 0.81%, relative to the effect of temperatures between 10-20 degree C. We find that the majority of the decrease in cropland is likely to be the conversion to built-up lands. Under a business-as-usual scenario, climate change is likely to reduce croplands by 28.24%, or 500,000 km2, by the end of century. This will severely threaten the food security in China in the absence of countervailing investments.

Identification of land cover changes in the coastal area of Dakshina Kannada district, South India during the year 2004–2008

This study investigates land cover (LC) changes in the coastal area of Dakshina Kannada district in the state of Karnataka, South India, during the years 2004–2008 as a case study. IRS P-6, Linear Imaging Self Scanning sensor (LISS-IV) satellite images were used in the present work. Classification was carried out using artificial bee colony algorithm and support vector machine (SVM) which gave a better result compared to other traditional classification techniques. The best overall classification accuracy for the study area was achieved with an ABC classifier with an OCA of 80.35% for 2004year data and OCA of 80.40% for 2008year data, whereas the OCA in SVM, for the same training set is 71.42% for 2004 data and 71.38% for 2008 data on study area 1 and the results were optimised with respect to multispectral data. In study area 2, ABC algorithm achieved an OCA of 78.17% and MLC of 62.63% which was used to check the universality of the classifier. The classification results with post-classification technique for study area 1 indicate that urbanisation in the study area has almost increased twice. During the same time there is an increase in the forest plantation, agricultural plantation and a decrease in crop land and land without scrubs, indicates rapid changes in the coastal environment.

Cropland Dynamics and their Influence on the Productivity in Northern Shaanxi, China, for the Past 20 Years: Based on Remotely Sensed Data

In this paper, we mainly focused our research on northern Shaanxi district, which is a pilot area of the Grain for Green Project. We compared the spatial distribution patterns of croplands and their productivity for the past 20 years (from the end of the 1980s to 2010). Cropland dynamics for the past 20 years were Interpreted from medium- and high-resolutlon remote sensing images (Landsat TM/ETM ). In addition, using the GLO-PEM and AGRO-VPM models with a medium resolution and long time series remote sensing dataset (AVHRR/MODIS), net primary productivity (NPP) and its relationship with cropland were estimated. Finally, the effect of cropland change on productivity was analyzed. The results show that during the first decade of the research period, cropland area and productivity in northern Shaanxi experienced a small boost, while in the latter decade, both cropland area and NPP were significantly reduced. The main cause of the increase in cropland was the reclamation of large area of grassland and unutilized land to meet the food demands of the local population as well as to compensate for the occupation of urban constructions. While the main cause of the decrease in cropland was the implementation of the Grain for Green Project. In addition, urbanization was also a key factor. Overall, during the past 20 years, the total area of cropland in northern Shaanxi decreased by 42.56%, and cropland NPP dropped by 41.90%. This study is of great importance for the assessment of regional cropland security, food security and scientific planning of regional land use.