The sustainable management of peri-urban agriculture requires cultivated land to not only be a source of food production, but also contribute ecological resources. This paper presents a method for assessing the landscape ecological security (LES) of peri-urban cultivated land that considers both cultivated landscape and interactions with the surrounding landscape. The situation in Changchun City was assessed at three time nodes. Furthermore, its spatiotemporal variations in several landscape characteristics were also measured. The results suggest that the peri-urban cultivated landscape was affected to varying extents by urbanization. The metrics of PD (patch density), ED (edge density), AWMSI (area-weighted mean shape index), FRAC (fractal dimension) and DIVISION (landscape division index) progressively increased during urbanization for cultivated land within 20 km of the urban gravity center. Elevated fragmentation and vulnerability of the cultivated landscape was also detected. The traditional method for quantifying LES of cultivated land neglects interactions with other landscape types. When the impacts of the ecological and construction landscapes were included, the results better reflected the dynamics of cultivated landscape in a peri-urban area. Decreased LES of cultivated land poses an impediment to the sustainable peri-urban agriculture, and better management practices should be applied for maintaining the LES of peri-urban cultivated land resources.

Analyzing spatiotemporal changes in land use and land cover could provide basic information for appropriate decision-making and thereby plays an essential role in promoting the sustainable use of land resources, especially in ecologically fragile regions. In this paper, a case study was taken in Zhenlai County, which is a part of the farming-pastoral ecotone of Northern China. This study integrated methods of bitemporal change detection and temporal trajectory analysis to trace the paths of land cover change for every location in the study area from 1954 to 2005, using published land cover data based on topographic and environmental background maps and also remotely sensed images including Landsat MSS (Multispectral Scanner) and TM (Thematic Mapper). Meanwhile, the Lorenz curve and Gini coefficient derived from economic models were also used to study the land use structure changes to gain a better understanding of human impact on this fragile ecosystem. Results of bitemporal change detection showed that the most common land cover transition in the study area was an expansion of arable land at the expense of grassland and wetland. Plenty of grassland was converted to other unused land, indicating serious environmental degradation in Zhenlai County during the past decades. Trajectory analysis of land use and land cover change demonstrated that settlement, arable land, and water bodies were relatively stable in terms of coverage and spatial distribution, while grassland, wetland, and forest land had weak stability. Natural forces were still dominating the environmental processes of the study area, while human-induced changes also played an important role in environmental change. In addition, different types of land use displayed different concentration trends and had large changes during the study period. Arable land was the most decentralized, whereas forest land was the most concentrated. The above results not only revealed notable spatiotemporal features of land use and land cover change in the time series, but also confirmed the applicability and effectiveness of the methodology in our research, which combined bitemporal change detection, temporal trajectory analysis, and a Lorenz curve/Gini coefficient in analyzing spatiotemporal changes in land use and land cover.

The competition for land resources created by the need for food security and ecological security is intensifying globally. To resolve the issue of land scarcity in agriculture following rapid urbanization, China implemented its requisition–compensation balance policy of cultivated lands in 1997, the introduction of which consumed numerous areas of land, such as river shoal and bare land, through reclamation. Moreover, these reclaimed and newly cultivated lands were mainly distributed in the northern part of China. Most previous studies of this subject have only examined the overall balance of cultivated lands in well-developed regions, and there is a lack of knowledge about the indigenous gains and losses before and after reclamation in important areas such as northeast China. Therefore, this study selected two representative county-level units in northeast China as the study area to analyze the conversion of cultivated land reserves during 1996–2015, evaluate the performance of reclaimed cultivated lands in terms of quality and productivity and calculate reclamation-induced changes in ecosystem service value. The results indicated that by 2015 only 16.02% of the original cultivated land reserves remained unconverted; nearly 60% were reclaimed as cultivated lands and over 20% were converted to other land resources. River shoal and ruderal land were the primary resources for cultivated lands compensation, and marsh, bare land and saline-alkaline land were found to be converted the most thoroughly. The gain of 23018.55 ha reclaimed cultivated lands were of relatively inferior quality and lower productivity, contributing approximately 4.32% of total grain output. However, this modest gain was at the expense of a 768.03 million yuan ecosystem services loss, with regulating services and supporting services being undermined the most. We argue that even if northeast China continues to shoulder the responsibility of compensating for a majority of cultivated land losses, it still needs to carefully process reclamation and introduce practical measures to protect indigenous ecosystems, in order to better serve the local residents and ensure prolonged food security with sustainability.

Rapid urbanization in China has increased the demand of land resources for urban areas and caused a series of environmental problems. Ecological security under the pressure of urban sprawl has become one typical indicator for illustrating regional environmental conditions and thus inform urban development. As an important farming area and one of the core economic development regions in northeast China, Changchun City is now confronted with severe contradictions between economic growth, habitat conservation and food security. Therefore, with the aim of developing an approach to optimize a regional ecological security pattern and land use structure, this study built a comprehensive ecological security pattern taking into account regional ecological processes including water regulation, soil and water conservation, species protection and recreation. Three patterns of ecological security were identified responding to different levels of ecological conservation: the basic security pattern, the buffer security pattern and the optimal security pattern. Based on the constraint of the ecological security pattern, the preservation area of prime farmland was added to an urban expansion suitability pattern as an additional constraint to simulate scenarios of urban expansion. The results indicate that the basic security pattern covers an area of 374.23 km², accounting for 19.27% of the total area of Changchun City. This pattern is considered as the ecological baseline that maintains the basic ecological functions, and it is the area where ecological land cannot be occupied for construction purposes. Furthermore, co-constrained by the preservation area of prime farmland, the ecological conservation area, the ecological restriction area and the suitable development area are 190.34 km², 384.75 km² and 152.83 km², respectively, accounting for 9.80%, 19.80% and 7.87% of the total area. It can be concluded that the suitable expansion area for the city is relatively limited when the conservation of farmland and regional ecological environment is considered. Therefore, positive actions such as industrial structure transformation and land use efficiency improvements should be perceived as a preferable pathway for urban development to balance economic growth, and regional ecological and food security.