Cropland displacement contributed 60% of the increase in carbon emissions of grain transport in China over 1990-2015.

Rapid urbanization and population growth have increased the need for grain transportation in China, as more grain is being consumed and croplands have been moved away from cities. Increased grain transportation has, in turn, led to higher energy consumption and carbon emissions. Here we undertook a model-based approach to estimate the carbon emissions associated with grain transportation in the country between 1990 and 2015. We found that emissions more than tripled, from 5.68 million tons of CO2 emission equivalent in 1990 to 17.69 million tons in 2015. Grain production displacement contributed more than 60% of the increase in carbon emissions associated with grain transport over the study period, whereas changes in grain consumption and population growth contributed 31.7% and 16.6%, respectively. Infrastructure development, such as newly built highways and railways in western China, helped offset 0.54 million tons of CO2 emission equivalent from grain transport. These findings shed light on the life cycle environmental impact within food supply chains.

The impacts of cropland balance policy on habitat quality in China: A multiscale administrative perspective.

Cropland protection policies are implemented to guarantee food security, especially the cropland balance policy in China. Although these policies alleviate the quantitative loss of cropland, they cause a serious decline in habitat quality and reduce biodiversity. With the reform trial of China's cropland balance policy from the within-province scale to the cross-provincial scale, the evaluation of habitat quality for obtaining cropland balance at different administrative scales is necessary to help seek sustainable strategies of cropland protection. Thus, taking Chinese mainland as the study area, this research assessed the different impacts of the cropland balance policy on habitat quality during 2000-2015 and 2015-2030 at national, provincial, municipal and county scales on the basis of the LAND System Cellular Automata model for Potential Effects (LANDSCAPE) and the Integrated Valuation of Ecosystem Services and Tradeoffs model (InVEST). The results revealed that (1) the loss of habitat quality by compensated cropland was 4.02 times that of the loss by occupied cropland in 2000-2015. Compared with occupied cropland, compensated cropland dominated the impacts of cropland change on habitat quality. (2) For both cropland quantity balance and cropland quality balance, habitat quality was slightly lost the most on the national scale in 2030. In detail, the greatest loss of habitat quality mostly occurred in areas where the ecological environment is already vulnerable at the national scale, whereas habitat quality was relatively less in these areas at the provincial, municipal and county scales. (3) Under the same administrative scales, habitat quality was lost more in cropland quality balance scenarios than in cropland quantity balance scenarios. The loss of habitat quality caused by cropland quality balance at national, provincial, municipal and county scales was 1.25, 1.05, 0.90 and 1.37 times higher than that by cropland quantity balance, respectively. The research highlights that considering the differentiated loss of habitat quality caused by cropland protection is quite important when implementing the cropland balance policy and land use planning.

Spatial optimization of urban land and cropland based on land production capacity to balance cropland protection and ecological conservation.

Cropland protection strategies have provided a strong contribution to limit cropland transformation worldwide. However, it negatively affects ecological land (e.g., forest, grassland, and wetland). Identifying a win-win approach for cropland protection and ecological conservation is important. Land use optimization plays a vital role in solving conflicts among land uses. Thus, in this research, taking China (mainland) as the study area, we optimized the spatial distribution of urban land and cropland to balance the requirement of cropland protection strategies and their negative effects on ecological land according to the spatial heterogeneity of land agricultural production capacity by using the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). Specifically, we developed three optimization scenarios from compensational, occupancy, and occupancy and compensational sectors. We also developed one non-optimization scenario to remain comparable. Results show that compared with the non-optimization scenario, the reduced loss of ecological land in compensational, occupancy, and occupancy and compensational optimization scenario is 7180, 247, and 7277 km2, respectively. Our research indicates that we should prioritize the quality of compensated cropland when developing cropland protection strategies and planning, considering the low efficiency of the occupancy optimization and the cost of policymaking and implementing.

Which Should be Conserved According to Priority During Urban Expansion? Ecological Lands or Farmland?

Understanding the trade-off between the loss of ecological lands and farmland to urbanisation could alleviate negative consequences to the environment and food security. This study aims to analyse the impact of urbanisation on ecological lands and farmland by comparing respective losses of habitat quality and agricultural productivity potential. Different scenarios are established indicating the priority of conserving ecological lands or farmland based on their vulnerability as measured by weight. With a land-use simulation model LANDSCAPE, the demand for urban land is met by occupying inferior ecological lands or farmland. Land-use patterns in each scenario are projected to 2035 in Wuhan (a rapidly urbanising city in China). As the weight of habitat quality decreases, the loss of habitat quality increases from 2.56 to 5.80%, while the loss of agricultural productivity potential decreases from 4.16 to 2.94%. The higher vulnerability of habitat quality loss indicates that ecological lands need a priori conservation than farmland in exchange for urbanisation.

Disparity in Perceptions of Social Values for Ecosystem Services of Urban Green Space: A Case Study in the East Lake Scenic Area, Wuhan.

Urban green space can bring various ecosystem benefits to diverse social groups. Among those ecosystem benefits, intangible social values are often neglected but highly relevant to human welfare. Existing research on the social values of urban green space often focusses on the perspective of urban inhabitants rather than tourists, even though tourists are also major beneficiaries. By combining different data sources into a comprehensive source about green-space social values, we investigated the disparity between inhabitants' and tourists' perceptions about space-associated social values, and further explored the underlying environmental conditions in the East Lake scenic area, Wuhan. For this, we collected 347 questionnaires through an on-site survey and 11,908 photos uploaded by 2165 social media users (Sina Blog), and we used SolVES (Social Value for Ecosystem Services) to uncover the spatial patterns of social values and the relationships between social value indicators and natural surroundings. Social-value hotspots occurred near water and trails. Perceptions differed, however, between inhabitants and tourists. Inhabitants perceived a larger scale of social values and could benefit more from recreation and economic values. Tourists, on the other hand, showed greater appreciation for aesthetic and cultural values. Environmental features were associated with social values to differing extent; distance to water and land use/cover exerted significantly influence. These findings should be taken into consideration to improve urban spatial planning and to optimize green infrastructures for human welfare.

Impacts of cropland expansion on carbon storage: A case study in Hubei, China.

When cropland expansion encroaches on ecological land (e.g., forest, grassland, wetland), it seriously affects carbon storage which plays an important role in global climate change. Taking Hubei as the study area, this study explored the effects of cropland expansion on carbon storage in both 2000-2010 and 2010-2030 in different scenarios by using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model and the LAND System Cellular Automata model for Potential Effects (LANDSCAPE). The results showed that cropland expansion led to a massive loss of carbon storage (1.76 Tg C) during 2000-2010, which is expected to continue during 2010-2030 in different scenarios. The loss is predicted to be 3.70 Tg C in the Business-As-Usual scenario and be 0.88 Tg C in the Requisition-Compensation Balance of Cropland Policy scenario. Noticeably, the loss of carbon storage due to cropland expansion was 1.12 times more than that due to urban expansion during 2000-2010. For the period of 2010-2030, the loss of carbon storage caused by cropland expansion is predicted to be 3.89 times more than that caused by urban expansion in the Business-As-Usual scenario, while the losses caused by cropland expansion and urban expansion are predicted to be almost equal in the Requisition-Compensation Balance of Cropland Policy scenario. The main cause of carbon storage loss due to cropland expansion is that it leads to the considerable loss of forest and wetland. This study highlights the importance of considering the loss of carbon storage caused by cropland expansion when conducting cropland protection policies and land use planning.

Determinants of Farmland Abandonment on the Urban-Rural Fringe.

China's urban explosion has resulted in a substantial loss of agricultural production on the fringes of many cities. Farmland is not only converted into urban uses but also taken out of production because it has lost its value for those who can farm it. This farmland abandonment process has received little research attention. This paper studies the abandonment of farmland around the rapidly urbanizing city of Wuhan and aims to identify its important determinants based on an extensive field survey among local farmers. Around 800 semi-structured field interviews were conducted to capture the parcel and location characteristics, farming practices, and household characteristics. Important parcel-related drivers of land abandonment are lack of family members to work the land and fragmentation of parcels. Spatial characteristics are less important, except for the presence of certain soil types that favour cultivation and designation under the farmland protection policy. The planted crop species and the option to transfer land to other farmers are important farming practices to continue cultivation. Moreover, farmers with a higher farming income and lower education levels are less likely to abandon their farmland. We suggest that land use policies can help in preventing further farmland abandonment by steering urban development away from the most suitable soils for farming and concentrating development to limit the fragmentation of parcels. Strengthening the land market and removing the remaining barriers for farmers to transfer land to colleagues can further help to keep farmland in production.

Optimising land use allocation to balance ecosystem services and economic benefits - A case study in Wuhan, China.

The optimisation of land use allocation plays an important role in sustainable land use planning. It is crucial to realise the synergy between economic development and ecosystem conservation by optimising land use allocation. In this study, we developed a method to optimise land use allocation to balance ecosystem services and economic benefits based on the spatial difference of both ecosystem services value (ESV) and land use efficiency, based on the LAND System Cellular Automata model for Potential Effect (LANDSCAPE). In the optimisation model, spatial difference of ESV was represented by the parameter of resistance, while spatial difference of land use efficiency was expressed as the parameter of asynchronous rate of transition. Subsequently, land use allocation was optimised based on spatial difference of resistances and asynchronous rates. Taking Wuhan as the study area, the proposed optimisation model was used to conduct the optimisation of land use allocation during 2010-2020. Results showed that: economic benefits would increase by 444.77 million US$, while losses of ESV would decrease by 142.55 million US$ by optimisation of land use allocation. This indicated that the optimal allocation of land use based on spatial difference of ESV and land use efficiency can increase economic benefits at lower cost of ESV. In conclusion, it is feasible to allocate land resources to balance ecosystem services and economic benefits based on the differences of ESV and land use efficiency. This study highlights that taking the spatial difference of both ESV and land use efficiency into consideration is helpful for a sustainable land use planning.

Patterns of Cereal Yield Growth across China from 1980 to 2010 and Their Implications for Food Production and Food Security.

After a remarkable 86% increase in cereal production from 1980 to 2005, recent crop yield growth in China has been slow. County level crop production data between 1980 and 2010 from eastern and middle China were used to analyze spatial and temporal patterns of rice, wheat and maize yield in five major farming systems that include around 90% of China's cereal production. Site-specific yield trends were assessed in areas where those crops have experienced increasing yield or where yields have stagnated or declined. We find that rice yields have continued to increase on over 12.3 million hectares (m. ha) or 41.8% of the rice area in China between 1980 and 2010. However, yields stagnated on 50% of the rice area (around 14.7 m. ha) over this time period. Wheat yields increased on 13.8 m. ha (58.2% of the total harvest area), but stagnated on around 3.8 m. ha (15.8% of the harvest area). Yields increased on a smaller proportion of the maize area (17.7% of harvest area, 5.3 m. ha), while yields have stagnated on over 54% (16.3 m. ha). Many parts of the lowland rice and upland intensive sub-tropical farming systems were more prone to stagnation with rice, the upland intensive sub-tropical system with wheat, and maize in the temperate mixed system. Large areas where wheat yield continues to rise were found in the lowland rice and temperate mixed systems. Land and water constraints, climate variability, and other environmental limitations undermine increased crop yield and agricultural productivity in these systems and threaten future food security. Technology and policy innovations must be implemented to promote crop yields and the sustainable use of agricultural resources to maintain food security in China. In many production regions it is possible to better match the crop with input resources to raise crop yields and benefits. Investments may be especially useful to intensify production in areas where yields continue to improve. For example, increased support to maize production in southern China, where yields are still rising, seems justified.

[Prediction and simulation of urban area expansion in Pearl River Delta Region under the RCPs climate scenarios].

The sizes and number of cities in China are increasing rapidly and complicated changes of urban land use system have occurred as the social economy develops rapidly. This study took the urban agglomeration of Pearl River Delta Region as the study area to explore the driving mechanism of dynamic changes of urban area in the urbanization process under the joint influence of natural environment and social economic conditions. Then the CA (cellular automata) model was used to predict and simulate the urban area changes until 2030 under the designed scenarios of planning and RCPs (representative concentration pathways). The results indicated that urbanization was mainly driven by the non-agricultural population growth and social-economic development, and the transportation had played a fundamental role in the whole process, while the areas with high elevation or steep slope restricted the urbanization. Besides, the urban area would keep an expanding trend regardless of the scenarios, however, the expanding speed would slow down with different inflection points under different scenarios. The urban expansion speed increased in the sequence of the planning scenario, MESSAGE scenario and AIM scenario, and that under the MESSAGE climate scenario was more consistent with the current urban development trend. In addition, the urban expansion would mainly concentrate in regions with the relatively high urbanization level, e.g., Guangzhou, Dongguan, Foshan, Shenzhen, Zhanjiang and Chaoshan.