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.

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.

Ecological land is a land use category provided with considerable ecological value and a vital indicator reflecting regional eco-environmental quality. However, it has experienced severe fragmentation during the rapid urbanization in China which strongly threatened the regional ecological security, land use pattern and human living environment. Therefore, analysis of spatiotemporal change of ecological land use and ecological landscape pattern is particularly essential. In this paper, a case study was made in Nong’an County, which is a typical black soil farming area located in northeast China facing severe conflicts among cultivated land protection, urban expansion and ecological security. A landscape fragmentation evaluation model was proposed to measure the degree of regional ecological land fragmentation. We also determined the land use change features through the methods of dynamic change information exploration and by performing transfer trajectory analysis during the period from 1996 to 2014. The results showed that the ecological land in Nong’an County has experienced increasing fragmentation during the past 18 years. The statistical results showed that the land transition between ecological land and other land categories was quite frequent, and it especially appeared as a dramatic decline of grassland and severe increase of saline-alkali land. In addition, human interferences especially construction activities and cultivated land occupation were still the dominant factors to the fragmentation of ecological land and the frequent transition among the land use categories. The fragmentation degree showed a downward tendency at the end of the study, which indicated noticeable benefits of land use regulation and land protection policies directed towards land ecological value. This study aims to provide a scientific evaluation model for measuring ecological land fragmentation degree, and figure out the regional land use transition relationships to offer suggestions for decision-making and provide a practical case in a typical region.

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.

Under rapid urban sprawl in Northeast China, land conversions are not only encroaching on the quantity of cultivated lands, but also posing a great threat to black soil conservation and food security. This study’s aim is to explore the spatial relationship between comprehensive cultivated soil heavy metal pollution and peri-urban land use patterns in the black soil region. We applied spatial lag regression to analyze the relationship between PLI (pollution load index) and influencing factors of land use by taking suburban cultivated land of Changchun Kuancheng District as an empirical case. The results indicate the following: (1) Similar spatial distribution characteristics are detected between Pb, Cu, and Zn, between Cr and Ni, and between Hg and Cd. The Yitong River catchment in the central region, and the residential community of Lanjia County in the west, are the main hotspots for eight heavy metals and PLI. Beihu Wetland Park, with a larger-area distribution of ecological land in the southeast, has low level for both heavy metal concentrations and PLI values. Spatial distribution characteristics of cultivated heavy metals are related to types of surrounding land use and industry; (2) Spatial lag regression has a better fit for PLI than the ordinary least squares regression. The regression results indicate the inverse relationship between heavy metal pollution degree and distance from long-standing residential land and surface water. Following rapid urban land expansion and a longer accumulation period, residential land sprawl is going to threaten cultivated land with heavy metal pollution in the suburban black soil region, and cultivated land irrigated with urban river water in the suburbs will have a higher tendency for heavy metal pollution.