长江中游城市群土地利用生态风险分析——以长株潭城市群为例

为揭示城市群发展对区域生态风险的影响,以位于长江经济带的长株潭城市群为研究区,利用1993-2013年Landsat遥感数据,定量获取土地利用变化特征,并基于移动窗口的景观生态风险指数,获得区域空间连续的生态风险指数等级分布图,分析长株潭城市群土地利用动态变化及生态风险时空变化特征。结果表明,近20年来,研究区土地利用变化较为显著,建设用地呈持续增加的趋势,耕地、林地面积在波动中减少且变化明显;近20年,生态风险等级面积变化显著,低风险区波动减少,中等风险区先减少后增加,较高风险区、高风险区均波动性增加。本研究为长株潭城市群土地资源可持续利用、生态风险的有效防范,以及对城市建设用地开发边界和生态红线的确定提供了参考,也为区域生态风险定量评价提供了有效的技术方法。     

Long run agricultural land expansion,booms and busts

Agricultural land expansion is a prominent feature in today’s developing countries. It is associated with a structural pattern of land use in many remote land-abundant regions where large-scale commercial primary product activities coexist with increased concentration of smallholders in more marginal areas. The result may be boom-bust cycles of development. If these phenomena are widespread across developing countries, then long-run expansion of agricultural land could be associated with lower levels of real income per capita, which may also fluctuate with prolonged expansion. A panel analysis conducted over 1961–2015 for 98 developing economies fails to reject this hypothesis. Policies should aim to decouple socio-economic gains through agricultural development from continued land expansion, and greater investments are needed to support smallholder agriculture, land distribution and livelihoods in these areas.     

The role of land use conversion in shaping the land cover of the Central American Dry Corridor

The Central American Dry Corridor (CADC) is a trans-border region characterized by climatic and ecological continuities. It is expected to experience rising aridity and severe hydro-climatic events due to climate change. Subsistence agriculture and other rural livelihoods to which land cover is central are widely practiced in this impoverished territory of approximately eleven million people.The CADC’s land cover was profiled to determine: a) how it differs from Non-CADC areas, and b) the role of land use in shaping these differences. Spatial autocorrelation analysis using satellite data showed that forest cover is a third less prevalent in the CADC than in the Non-CADC while the share of mosaic vegetation and mosaic cropland is nearly double. A naturally prevalent cover type in the CADC, tropical dry forest (TDF), has been largely eliminated.The significantly lesser proportion of forest and greater percentage of coverage consistent with agriculture and ranching implicate land use conversion, specifically deforestation for agricultural expansion and cattle ranching, in shaping CADC land coverage. The process began in the mid-1800s when small-scale agriculturalists migrated to the region followed by large-scale export crop and beef production, primarily for international markets. Deforestation peaked after WWII, concluding by the 1990s with the conversion of most woodlands. Similar patterns now threaten forests along the Caribbean coast.Traditional land use practices cannot sustain local communities or preserve the resource base, thereby contributing to rural outmigration. Adopting sustainable practices and promoting livelihoods strategies leading to forest regeneration will be fundamental for CC adaptation in the CADC.     

Impact of local payments for ecosystem services on land use in a developed area of China: A qualitative analysis based on an integrated conceptual framework

Payments for ecosystem services (PES) have increasingly been applied as economic incentives for improving ecosystem services around the world. However, due to difficulties in measuring and attributing ecosystem services provisioning, a land-based approach has been popularly adopted as a proxy for the desired ecosystem services. In this study, we demonstrate the impact mechanism and outcomes of locally financed PES programs on conservation-based land use in a developed area of China. We present this work using a PES-land use proxy framework that is examined empirically through a variety of qualitative assessments. Our framework illustrates that, within the ecological, socioeconomic, and institutional conditions of developed areas, land use class, pattern and function would be impacted by (a) conservation effect, (b) stakeholder response, and (c) institutional adaptation mechanisms of local PES programs, with multiple land use trends as potential outcomes. We examine the framework using materials from Suzhou, China, which has implemented a top-down, partly involuntary (ecosystem services supply side), land based PES program. Our results show that, expected land use class, land use pattern and land use function are observed in areas where the PES programs were implemented. We also find that the conditions of developed areas and locally financed payments mechanism indeed played a crucial role in promoting conservation-based land use in Suzhou.     

A portfolio analysis of incentive programmes for conservation,restoration and timber plantations in Southern Ecuador

This paper uses portfolio analysis to study how the Ecuadorian incentive programme for forest conservation and restoration (Socio Bosque), and an incentive programme for timber plantations, may reduce income risk and/or maximise returns for a given level of risk for farmers in the municipality of Loja. The main existing land use in the research area is milk production on pasture, with some farmers having forest land. Our results suggest that most farmers would significantly increase the area under conservation and/or restoration as part of their risk reduction strategies, compared to a decision based solely on expected returns. However, in land use allocations that maximise the return per unit of risk, a small group of milk producers without forest would continue milk production on most of their land. In addition, milk producers with forest would significantly decrease deforestation under the land use allocations made when conservation incentives are available. Against this we also identify a likely shift of milk production from existing pasture to new pasture established on deforested land, which provides evidence of a potential ‘leakage effect’. In addition, the incentive programmes would only lead to small areas of tree plantations being established. None of the land use combinations (portfolios) analysed would increase the income of all households to above the poverty line, as the monetary incentives are too low and many farms are too small. For forest holders all the land use combinations we studied would have a positive impact on income, but we observed a negative impact on household income for milk producers without forest. For producers without any forest, there seems to be a trade-off between maximising household income and risk reduction through combining incentives for restoration and tree plantations.     

郑州市土地生态安全评价及障碍因素研究 ——基于DPSIR模型

本研究基于DPSIR模型构建郑州市土地生态安全评价指标体系,并利用熵值法对指标进行客观赋权,计算得出2010～2018年郑州市土地生态安全的综合评价值和五个子系统的安全评价值.最后引入障碍度模型,探究影响郑州市土地生态安全的障碍因素.研究结果表明,(1)2010～2018年郑州市土地生态安全水平呈现先下降后上升的趋势,...     

土地利用动态规划研究

研究目的:重新审视中国土地利用规划的思路和实践,引入动态规划理念,使动态规划理论成为土地利用规划理论的有机组成部分。研究方法:借助时空锥理论、人地权籍时空系统理论,探讨动态规划的机理问题。研究结果:(1)土地利用时空系统的综合性、过程性和多元性带来了纵向时间上和横向空间上的不确定性;(2)在保持土地利用规划原则性和框架性不动的前提下,应增加规划实施过程中的灵活性和弹性;(3)土地利用规划的本质是一种过程性和发展性规划,然而当前中国土地利用规划并没有反映土地利用规划的这种本质。研究结论:(1)时空锥理论论证了土地利用系统是一个动态的时空系统,人们对其演进和发展的认知和利用存在着渐进性、困难性和不确定性,因而土地利用规划也必然存在确定性和不确定性、刚性和弹性之间的矛盾。人地权籍时空系统理论指出地籍限定了土地利用的空间位置、权能边界和土地利用发展权,人们为了克服可利用土地数量的制约,不得不采用土地利用深度开发、提高土地节约集约利用程度的方式,从而实现人与地及其之上的人与人开展土地利用活动关系的平衡。(2)土地利用动态规划认为在规划期内特定地块的类型、用途及规模是可变的,即在固定数量空间资源的情况下,通过发掘规划区的各种内在空间潜力,增加可支配空间资源,为其他用地提供释放和回旋的余地。动态规划的"动"是有原则、有约束的动,这个原则就是通过土地利用效益的提升作为补偿和保证。(3)土地利用动态规划的实现路径从时间尺度来看,规划时序采用逐渐缩口的指标分配办法;规划期限采用区域层级的差别化管理;规划期内采用滚动调整的规划方法。从空间尺度来看,坚持底线思维的前提下,从数量指标分配和土地空间分配两方面着手,促进土地集约节约利用,发挥土地利用规划实施的激励机制作用。(4)在明确土地利用动态规划的原则后,下一步重点需要研究土地利用动态规划的具体技术方法和实践应用。     

Simulating the impacts of future land use change on soil erosion in the Kasilian watershed,Iran

Predicting soil erosion potential is important in watershed management. A rapidly growing Iranian population and climate change are expected to influence land use and soil sustainability. In recent years, northern Iran has experienced significant land use changes due to internal migration along the Caspian coast and conversion of forests and rangelands. Considering the effect of these changes in the future, the purpose of this study is to forecast land use patterns and investigate soil erosion scenarios using the Revised Universal Loss Equation and Markov Cellular Automata. Data from 1981 to 2011 were used as a baseline to estimate changes that might occur in 2030. The results reveal that the mean erosion potential will increase 45% from the estimated 104.52 t ha⁻¹ year⁻¹ in the baseline period. Moreover, the results indicate that land use change from forest area to settlements will be the most significant factor in erosion induced by land use change, showing the highest correlation among erosional factors. Projecting land use change and its effect on soil erosion indicate that conversion may be unsustainable if change occurs on land that is not suited to the use. The method predicts soil erosion under different scenarios and provides policymakers a basis for altering programs related to land use optimization and urban growth. Those results indicated the necessity of appropriate policies and regulations particularly for limiting land use changes and urban sprawl in areas of unfavorable soil erosion risk factors.     

A comprehensive framework on land-water resources development in Mu Us Sandy Land

Land and water resources are two basic factors for sustaining the development of agriculture. The two are scare resources with rapid social economic development gradually, especially in Mu Us Sandy Land (MUSL) with severe desertification. Arsenic sandstone is a special rock type of MUSL with strong water holding capacity, which appropriately makes up the shortage of sand on water and fertilizer losing. Based on it, a comprehensive framework on land-water resources development was proposed including engineering treatment measures, appropriate irrigation management and farming measures after a series of experiments designed for sandy land treated with arsenic sandstone. Results of the experiments showed that both water content and fertility increased after using a 1:2 arsenic sandstone/sand ratio by mixing both together. An area of 151.3 ha arable land was newly-increased by applying the framework in Dajihan village sandy land of the MUSL, which created direct economic efficiency of 14.1 million Yuan RMB by tomato planting, and obtained 61% of water saving effect compare to untreated sand. The application of the framework in Dajihan village also got huge social-ecological efficiency such as on soil and water conservation, sand-fixing and forming high quality farmland. The framework helped to completed the process from soil synthesize to agricultural production, then to real soil, which transformed the traditional sandy land treatment to sandy land development, and was proved to be practicable and sustainable in local sandy agriculture.     

The Farmland Rental Paradox: Extreme land ownership fragmentation as a new form of land degradation

Extreme farmland ownership fragmentation is becoming a limiting factor for sustainable land management in some countries. Scattered, excessively small parcels cease to be viable for individual farming, and owners feel forced to rent these parcels to larger enterprises farming on adjacent land. Our study demonstrates a phenomenon that we call the Farmland Rental Paradox, where very small parcels tend to create large production blocks by being rented to larger farmers, and therefore to significantly homogenize the land-use pattern. The parcel size established as the threshold for this phenomenon is 1.07 ha. Below this threshold, the smaller the parcels were, the larger the blocks that they tended to create.Using the example of the Czech Republic, a state with extremely high farmland ownership fragmentation, it is demonstrated that this phenomenon can currently determine the land use of up to 40% of the country's farmland. Our study also points to other countries where this phenomenon may apply, especially the transitional countries of Central and Eastern Europe.The study discusses the tempo of the fragmentation process, which accelerates exponentially in countries with the equal inheritance system. It goes on to discuss defragmentation, social impacts of the dominance of the land rental market, and environmental impacts of significant homogenization of the land-use pattern. The serious negative impacts of extreme land-ownership fragmentation show that this phenomenon can be considered as a significant form of land degradation.