Doubling protected land area may be inefficient at preserving the extent of undeveloped land and could cause substantial regional shifts in land use

Projection of land use and land-cover change is highly uncertain yet drives critical estimates of carbon emissions, climate change, and food and bioenergy production. We use new, spatially explicit land availability data in conjunction with a model sensitivity analysis to estimate the effects of additional land protection on land use and land cover. The land availability data include protected land and agricultural suitability and is incorporated into the Moirai land data system for initializing the Global Change Analysis Model. Overall, decreasing land availability is relatively inefficient at preserving undeveloped land while having considerable regional land-use impacts. Current amounts of protected area have little effect on land and crop production estimates, but including the spatial distribution of unsuitable (i.e., unavailable) land dramatically shifts bioenergy production from high northern latitudes to the rest of the world, compared with uniform availability. This highlights the importance of spatial heterogeneity in understanding and managing land change. Approximately doubling the current protected area to emulate a 30% protected area target may avoid land conversion by 2050 of less than half the newly protected extent while reducing bioenergy feedstock land by 10.4% and cropland and grazed pasture by over 3%. Regional bioenergy land may be reduced (increased) by up to 46% (36%), cropland reduced by up to 61%, pasture reduced by up to 100%, and harvested forest reduced by up to 35%. Only a few regions show notable gains in some undeveloped land types of up to 36%. Half of the regions can reach the target using only unsuitable land, which would minimize impacts on agriculture but may not meet conservation goals. Rather than focusing on an area target, a more robust approach may be to carefully select newly protected land to meet well-defined conservation goals while minimizing impacts to agriculture.     

A review of global potentially available cropland estimates and their consequences for model‐based assessments

The world's population is growing and demand for food, feed, fiber, and fuel is increasing, placing greater demand on land and its resources for crop production. We review previously published estimates of global scale cropland availability, discuss the underlying assumptions that lead to differences between estimates, and illustrate the consequences of applying different estimates in model‐based assessments of land‐use change. The review estimates a range from 1552 to 5131 Mha, which includes 1550 Mha that is already cropland. Hence, the lowest estimates indicate that there is almost no room for cropland expansion, while the highest estimates indicate that cropland could potentially expand to over three times its current area. Differences can largely be attributed to institutional assumptions, i.e. which land covers/uses (e.g. forests or grasslands) are societally or governmentally allowed to convert to cropland, while there was little variation in biophysical assumptions. Estimates based on comparable assumptions showed a variation of up to 84%, which originated mainly from different underlying data sources. On the basis of this synthesis of the assumptions underlying these estimates, we constructed a high, a medium, and a low estimate of cropland availability that are representative of the range of estimates in the reviewed studies. We apply these estimates in a land‐change model to illustrate the consequences on cropland expansion and intensification as well as deforestation. While uncertainty in cropland availability is hardly addressed in global land‐use change assessments, the results indicate a large range of estimates with important consequences for model‐based assessments.     

山地社区土地资源可持续管理评估

从联合国粮农组织提出的土地资源可持续管理目标出发 ,采用层次分析法 (AHP) ,以西双版纳地区爱尼族大卡老寨为研究点 ,选择 4 1个因素作为参评变量 ,建立区域土地可持续管理评价指标体系。评估结果表明 ,目前大卡老寨的土地经营管理仍处于初步可持续管理的前期阶段。主要因为土地生产力过低 ,其他保护性、安全性、生产性均处于较低水平。作者针对提出了改变土地经营模式等参考建议 :1发展生态农业模式 ,提高土地生产率 ;2应用科技成果 ,提高良种普及率 ;3保护耕地 ,推进规模经营 ;4充分发挥森林的经济、生态和社会效益 ;5提高人口素质 ,改变就业结构     

城市生态用地分类及其规划的一般原则

城市生态用地的规划布局是城市规划的难点之一,也是急待解决的问题.本文根据城市生态系统的特点,给出了城市生态用地定义,指出城市生态用地同时具有自然属性和社会属性,依据这个特点,将城市生态用地划分为服务型生态用地和功能型生态用地两大类型,并结合具体的城市生态规划对各种类型的生态用地规划进行了定性分析.     

基于RS与GIS的海南西部土地沙化/土地退化动态趋势研究

遥感和地理信息系统技术的发展为研究沙化／土地退化动态趋势变化提供了有效手段,以１９８７年和１９９８年的ＴＭ遥感资料为信息源,综合ＧＩＳ参与监督分类及目视读的方法,以ＧＩＳ为工具提取土地沙化／土地退化动态信息。结果表明海南省西部研究区土地沙化面积在减少,严重沙化区已基本得到整治,但由于对部分地区生态环境的保护不力,使得这些地区继续沙化同;同时,该研究区土地 化区明显的向着逆转的方向发展,但季雨林面积     

Land Transitions in the Tropics: Going Beyond the Case Studies

Estimates of the percent of Earth's land surface that has either been transformed or degraded by human activity range between 39 and 50 percent, with agriculture accounting for the vast majority of these changes. Although much of the focus of research on land use and cover change in the tropics has been on deforestation, ongoing socioeconomic changes both locally and globally have made land transitions in the tropics extremely fluid. In addition, feedbacks between land cover change and human behavior constrain the extent and trajectories of land transitions. The sustainability of land use systems in the tropics depends on an understanding of coupled human–natural systems that can lead to general frameworks for management and prediction. The unprecedented availability of land use/cover data together with ecological data collected at large spatial scales offer exciting opportunities for advancing our understanding of socioecological systems. We rely on six studies of land transitions in the tropics to illustrate some promising approaches and pose critical questions to guide this body of research.     

城市土地利用变化对生态系统服务的影响——以淮北市为例

城市是一类以人类活动为中心的社会-经济-自然复合生态系统.城市的快速蔓延及强烈的人类活动显著地改变了城市的土地利用结构,进而严重影响了城市生态系统服务及人居环境.通过遥感、GIS技术及生态系统服务价值评估等方法,对淮北市1987年、2000年和2007年3个时期20a间的土地利用结构及生态系统服务价值的演变进行定量评价.研究结果表明:1987-2007年间淮北市生态用地空间结构和面积发生剧烈变化,生态用地占城市面积的比例由91.45％降低至71.86％.1987-2000年,农田面积大幅度下降,而林地和水体都呈不同程度的增加趋势,建设用地面积增长迅速.2000-2007年,农田面积有所增加,林地和水体面积却明显下降,建设用地总面积虽然没有明显变化,但其聚集度显著增加.20年间,城市生态服务功能的价值呈现先增加后减少的趋势,在2000年达31.32亿元.2000-2007年,以废物处理和水源涵养功能退化最为严重.可见,城市土地利用结构的变化与生态服务功能密切相关,此结果可为淮北市景观格局优化及土地合理调控和管理提供一定的科学依据.     

基于长时间序列landsat数据的科尔沁沙地土地利用演变分析

以科尔沁沙地沙丘-草甸过渡带区域主要土地覆被类型为研究对象，以1987-2017年多时相Landsat TM/OLI遥感影像解译分类为基础，参考生态学植被演替研究方法，系统分析研究区30年来的土地利用/覆被动态演变规律，研究结果表明：（1）决策树法在复杂下垫面不同覆被类型的同步识别效果较好，所有影像分类精度均达到88%以上，分类效果较好，其中2017年分类精度最高为95.24%，达到了分类研究的要求；（2）研究区存在着"半灌丛-草甸地-灌丛"的植被结构特征，且整体表现为"南进北退"的变化趋势。结合土地利用动态度分析结果表明人类活动干涉下，研究区整体上遵循了半干旱区植被条件改善的一般规律，侧面反映该研究区域生态环境的持续不稳定性和脆弱性；（3）研究区覆被类型发生变化的总面积达到2623.59 hm²，总变化强度为63.76%。其中正向演替的比例为52.61%，以半灌丛面积的持续减小与沙地草甸面积的持续扩张为主要变化特征。但同时，半灌丛转为沙地的面积为184.95 hm²，表明以放牧为主的研究区同时发生着局部的逆行演变；（4）质心迁移结果反映了1987-2017年间，除人为影响较大的林地、草地以及耕地向北迁移外，其他植被类型的质心都有很明显的南迁，主要植被类型重心迁移距离依次由大到小为耕地 > 半灌丛 > 灌丛 > 沙地草甸 > 湿地草甸 > 林地。研究通过记录科尔沁沙地连续扩展的时空模式，展示了遥感-生态和时间序列影像在30 m分辨率下跟踪土地利用/覆被变化的潜力，为提高干旱半干旱区土地利用情况的动态监测效率，开展土地利用/覆被动态演变研究提供参考。     

A phylogenetic classification of the land plants to accompany APG III

A formal classification of the land plants that is compatible with the APG III classification is proposed. Previous classifications inflated taxonomic ranks, particularly of the angiosperms. If the major clades of green algae are recognized as classes, then all land plants, the embryophytes, should be included in a single class, here recognized as Equisitopsida. Accordingly, the 16 major clades of land plants, including the angiosperms, should all be recognized as subclasses, the angiosperms as Magnoliidae. Major clades within the angiosperms are then recognized as superorders. This classification still uses a few informal categories (e.g. eudicots, lamiids, etc.) within the angiosperms because this is convenient. Two new names are established: Amborellanae and Austrobaileyanae. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 122–127.     

Extensive land use and the logic of the latifundio: A case study in Guanacaste Province,Costa Rica

Traditional explanations of extensive land use on large unproductive estates in Latin American have failed to understand important aspects of the economic and political logic behind such enterprises. This article examines the reasons for the low productivity of cattle ranches over a period which spans the consolidation of haciendas in a frontier zone and their subsequent integration into the international beef market. The persistence of extensive land use in a modern export economy is explained as resulting from characteristics of the world beef market, local ecology, the Costa Rican credit and tax systems, and the social composition and political power of the landowning class.     

北京市生态用地规划与管理对策

不合理土地开发加速了对自然生态系统的干扰和侵占,导致生态系统服务功能下降,危机区域生态安全,开展生态用地规划是构建区域生态安全格局的基础。合理规划和管理不同土地利用类型的数量和空间分布对区域可持续发展具有重要意义。目前我国广泛应用的土地利用分类体系主要以土地的社会经济属性为基础,忽视其生态属性,导致以提供生态系统服务为主、保障生态安全的土地缺乏保护机制,具有重要生态功能的土地得不到有效保护。以北京市为例,建立了北京市生态用地分类与规划的思路与程序,在明确北京市生态安全与生态系统服务功能的关系基础上分析了北京市生态系统服务功能重要性及其空间格局,并进行了北京市生态用地规划。研究规划了保障北京市生态安全的7类生态用地:地表水涵养与保护用地、地下水保护用地、生物多样性保护用地、水土保持用地、河流防护用地、公路防护用地和城市绿地,总面积5137.37km2,占北京市域面积的31.31%。最后从生态用地识别和划分、将生态用地融入土地利用分类体系、生态用地管理措施和对策3个方面探讨了生态用地规划和管理的方法与措施。研究结果为北京市土地利用规划和有效管理提供依据,也为其它地区的生态用地规划提供参考。     

Winners and losers of national and global efforts to reconcile agricultural intensification and biodiversity conservation

Closing yield gaps within existing croplands, and thereby avoiding further habitat conversions, is a prominently and controversially discussed strategy to meet the rising demand for agricultural products, while minimizing biodiversity impacts. The agricultural intensification associated with such a strategy poses additional threats to biodiversity within agricultural landscapes. The uneven spatial distribution of both yield gaps and biodiversity provides opportunities for reconciling agricultural intensification and biodiversity conservation through spatially optimized intensification. Here, we integrate distribution and habitat information for almost 20,000 vertebrate species with land‐cover and land‐use datasets. We estimate that projected agricultural intensification between 2000 and 2040 would reduce the global biodiversity value of agricultural lands by 11%, relative to 2000. Contrasting these projections with spatial land‐use optimization scenarios reveals that 88% of projected biodiversity loss could be avoided through globally coordinated land‐use planning, implying huge efficiency gains through international cooperation. However, global‐scale optimization also implies a highly uneven distribution of costs and benefits, resulting in distinct “winners and losers” in terms of national economic development, food security, food sovereignty or conservation. Given conflicting national interests and lacking effective governance mechanisms to guarantee equitable compensation of losers, multinational land‐use optimization seems politically unlikely. In turn, 61% of projected biodiversity loss could be avoided through nationally focused optimization, and 33% through optimization within just 10 countries. Targeted efforts to improve the capacity for integrated land‐use planning for sustainable intensification especially in these countries, including the strengthening of institutions that can arbitrate subnational land‐use conflicts, may offer an effective, yet politically feasible, avenue to better reconcile future trade‐offs between agriculture and conservation. The efficiency gains of optimization remained robust when assuming that yields could only be increased to 80% of their potential. Our results highlight the need to better integrate real‐world governance, political and economic challenges into sustainable development and global change mitigation research.     

Rapid redistribution of agricultural land alters avian richness,abundance, and functional diversity

The conversion of natural, or seminatural, habitats to agricultural land and changes in agricultural land use are significant drivers of biodiversity loss. Within the context of land‐sharing versus land‐sparing debates, large‐scale commercial agriculture is known to be detrimental to biodiversity, but the effects of small‐scale subsistence farming on biodiversity are disputed. This poses a problem for sustainable land‐use management in the Global South, where approximately 30% of farmland is small‐scale. Following a rapid land redistribution program in Zimbabwe, we evaluated changes in avian biodiversity by examining richness, abundance, and functional diversity. Rapid land redistribution has, in the near term, resulted in increased avian abundance in newly farmed areas containing miombo woodland and open habitat. Conversion of seminatural ranched land to small‐scale farms had a negative impact on larger‐bodied birds, but species richness increased, and birds in some feeding guilds maintained or increased abundance. We found evidence that land‐use change caused a shift in the functional traits of the communities present. However, functional analyses may not have adequately reflected the trait filtering effect of land redistribution on large species. Whether newly farmed landscapes in Zimbabwe can deliver multiple benefits in terms of food production and habitat for biodiversity in the longer term is an open question. When managing agricultural land transitions, relying on taxonomic measures of diversity, or abundance‐weighted measures of function diversity, may obscure important information. If the value of smallholder‐farmed land for birds is to be maintained or improved, it will be essential to ensure that a wide array of habitat types is retained alongside efforts to reduce hunting and persecution of large bird species.     

Trade‐offs between land and water requirements for large‐scale bioenergy production

Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large‐scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade‐offs between land and water requirements of large‐scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land‐ and water‐use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr^?1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr^?1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large‐scale bioenergy production will require policies that balance associated water and land requirements.     

Multidimensional analysis of landscape dynamics in a Central African forest-savannah mosaic

Most landscape cover assessments for conservation programmes rely largely on remote sensing analyses. These analyses, however, neglect how people inhabiting protected zones perceive and structure land cover. Using socio-ecological systems (SES) analysis in a forest-savannah mosaic on the Congo Basin forest edge (Democratic Republic of Congo), we investigated how human practices, landscape perceptions and land use patterns affected forest cover. We conducted remote sensing analysis using a Sentinel-2 satellite image and 187 GPS landmarks, producing a land cover map with 11 classes. Our results yielded an 81.85% correspondence with additional 164 GPS landmarks, a robust score in tropical areas. We conducted 40 individual interviews, eighteen focus group discussion workshops and nine months of participant observation of human practices to identify 19 land units and elaborate a granular SES system structuring the landscape. Integrating local knowledge and practices with general ecological and agronomic processes, we developed a landscape dynamics model revealing progressive forest colonisation of savannahs. Our methods demonstrate that a forest-edge landscape cover evaluation through remote sensing and local knowledge can contribute to finer-grained assessment of land cover and ecosystem services. This assessment can assist conservation efforts by considering local populations' practices on and perceptions of landscape change.     

科尔沁沙地关键生态系统服务的约束关系分析

理解生态系统服务间的相互关系,对于区域生态系统服务的管理和优化具有重要意义。以科尔沁沙地为研究区,评估了2000-2018年植被净初级生产力、产水服务、土壤保持服务和风力侵蚀负服务的时空变化,基于分位数分割法提取生态系统服务对之间相互关系的约束线,分析景观水平和类水平上生态系统服务对之间的约束关系,并用约束关系的阈值、约束线回归方程的斜率和常数项来表征约束线的关键特征值。结果表明：（1）2000—2018年科尔沁沙地植被净初级生产力、产水量、土壤保持量和风力侵蚀量的多年均值分别为256.5 gC/m²,211.9 mm,26.3 t/km²和3.8 t/m²;整体上,这四项关键生态系统服务有所改善。在空间上,植被净初级生产力改善的区域主要位于东南部和中部地区;产水量在中部偏南的区域增加;土壤保持量主要在西北部和西南边缘有显著增加;中部和北部地区的风力侵蚀量有所减少,南部的翁牛特旗、奈曼旗和科尔沁左翼后旗等旗县作为风蚀重度区,风力侵蚀仍在加剧,应当重点治理。（2）植被净初级生产力与产水量、土壤保持量、风力侵蚀量的约束线,产水量与土壤保持量、风力侵蚀量的约束线均呈抛物线型;而土壤保持量与风力侵蚀量的约束关系呈线性类型。这些约束线的类型在2000-2018年间几乎保持不变。（3）植被净初级生产力的变化对其他生态系统服务的动态起到放大器的作用。它微小的变化会引起其他生态系统服务较大幅度的变化,是塑造约束关系强度的关键性服务。约束线阈值范围能够为合理利用区域植被净初级生产力提供初步依据,可以使植被净初级生产力对其他服务的负面约束作用最小化。（4）林地和草地提供土壤保持服务的能力较耕地水平高。在景观管理实践中,应重点发展草地、林地生态系统;在耕作条件适宜的地区选择需水量较少、耐旱的农作物并实施节水灌溉,以提高科尔沁沙地景观总体生态系统服务的供给能力。探究生态系统服务对的约束关系及识别其关键特征可以为土地利用优化,调整管理措施及实现区域可持续性提供科学依据。