2000—2007年珠峰自然保护区植被时空变化与驱动因子

采用遥感与GIS相结合的方法研究了珠峰自然保护区2000—2007年之间的植被时空变化过程和驱动机制问题。通过一元线性回归斜率计算获取了基于EVI数据的珠峰自然保护区植被变化趋势,以及表现2000—2007年植被变化的矢量图层。利用GIS时间动画技术,建立了7个时间点内不同间隔的植被时空演化过程快照,并结合ArcEngine构建了植被变化监测的时序分析流程,提取和分析了植被变化过程的时空特征。依据年平均温和年降水量观测记录进行了植被变化的气候因子分析,依据道路、河流缓冲区的居民点密度与植被退化面积比例的相关性,分析了人类活动影响,并讨论了不同植被退化区域在多重因素作用下的变化驱动因子。拟合了主要社会经济发展指标与植被变化的相关性,从统计数据方面讨论了珠峰自然保护区社会经济发展对植被变化的影响作用。结果表明：珠峰自然保护区植被变化的总体趋势以稳定为主,但植被退化趋势超过了变好趋势。同时,核心区植被变好趋势明显,实验区植被退化趋势严重。保护区南坡植被受气候变化干扰小,保持了大部分变好趋势;北坡由于降水减少造成湿地植被退化,对草地的长势带来消极作用。人类活动与植被状态变化有密切关系,在沟谷地带的破坏作用明显。并且,植被退化趋势与农业耕地面积扩大以及放牧影响关联紧密,而牲畜饲养与林业发展都未对保护区植被变化造成明显影响。     

对全球气候变化原因及发展趋势之浅见

分析了引起全球气候变化的各种可能原因，对温室气体、植被破坏、水汽变化等对全球气候变化的影响作了概括总结，阐述了全球气候变化发展趋势及气候变化预测中应注意的问题。     

1980—2015年青藏高原植被变化研究

青藏高原地形复杂,气候类型独特,是北半球气候变化的调节器。全球气候变化直接影响植被变化,探讨植被变化对了解青藏高原的环境状况及环境保护与恢复具有重要意义。选取青藏高原作为研究区域,基于1980年和2015年的1 km土地利用数据利用转移矩阵研究植被的转换变化,利用1981—2015年的GIMMS-NDVI数据借助趋势分析法分析土地利用未变化区域的植被覆被变化,并通过相关分析法研究植被变化与气候因子的关系。研究表明:1980—2015年,青藏高原植被的转换变化表现为转入面积大于转出面积,植被面积整体增加。植被类型变化的主要表现形式为农作物和草地面积增加,乔木林地和灌木林面积减少;草地的面积变化最大,农作物、乔木林地和灌木林面积变化很小。从不同植被类型和生态分区来看,植被覆被变化表现为农作物面积较小,分布于半干旱地区,NDVI呈上升趋势;乔木林地位于东南部湿润半湿润地区,生长状况呈现退化趋势;灌木林位于东部边缘和东南部的湿润半湿润和半干旱地区,呈退化趋势;草地分布范围最大,生长情况趋于改善。近35年来,青藏高原的植被覆盖整体趋于好转,低覆盖度、干旱半干旱地区趋于改善,高覆盖度、湿润半湿润地区出现退化。研究时段内,青藏高原趋于暖湿化,NDVI变化与年平均气温、年降水量变化呈正相关,对降水变化更为敏感。不同植被类型对气候变化响应不同,农作物相关系数最高。乔木林地与气温和降水变化呈负相关,农作物和草地则呈正相关,灌木林与降水变化呈正相关,与气温变化呈负相关。     

内蒙古地区近25年植被对气温和降水变化的影响

利用1982—2006年内蒙古地区GIMMS-NDVI和降水量、气温数据,分析了不同植被类型对气温和降水变化趋势的影响。结果表明：近25年来内蒙古地区气温整体上呈上升趋势,降水量呈微弱降低趋势,西部荒漠区呈暖湿化趋势,中东部草原、森林等植被类型区呈暖干化趋势;从不同植被类型NDVI与平均气温和降水量的变化趋势率相关分析表明,NDVI值越低,升温趋势越明显,其中春季和秋季各植被类型间NDVI与季均气温升高趋势率呈显著和较显著的相关,夏、冬季关系不明显;植被NDVI越高,降水量减少趋势越明显。基于栅格的NDVI与气温升高幅度、降水变化趋势相关分析表明,年均气温升高幅度基本随NDVI的增加而降低,其中春、夏和秋季的季均气温升高幅度均随NDVI的增加而显著降低,冬季趋势不明显;而年降水量减小趋势率随植被NDVI的增加而显著增加,其中春季和冬季NDVI变化对降水的变化几乎没有影响;夏季和秋季均表现为随NDVI的增加,降水减小趋势率呈增加趋势。     

基于多源遥感指数监测山区植被动态及其驱动因子的不确定性分析——以尼泊尔地区为例

准确获取山区植被动态数据对山区生态系统研究及其保护有着重要意义。卫星遥感数据作为获取大尺度山区植被动态的重要数据源,已被制作成各种植被监测产品并被应用于植被绿度、覆盖度以及生产力等研究。然而,不同遥感指数监测山区植被动态及其驱动因子的一致性尚不确定。以尼泊尔地区为例,基于5种遥感指数(MODIS NDVI、MODIS EVI、MODIS LAI、MODIS NPP和OCO-2 GOSIF)和5种气候因子(温度、降水、气压、太阳净辐射和CO₂浓度)数据,采用趋势分析和两种残差分析法(多元回归法和一阶偏导法),系统分析了不同遥感指数监测尼泊尔地区植被动态及其驱动因子的不确定性。结果表明：1)2000—2020年尼泊尔地区5种遥感指数均呈现增加趋势,但不同遥感指数空间分布存在差异,MODIS NPP在中山带增加趋势更明显,其他遥感指数在低海拔地区增加态势更明显。2)不同残差分析方法所估算的气候变化对植被变化贡献率差异极大,多元回归法可能严重低估了气候变化的贡献,而一阶偏导法可能高估气候变化的影响。3)基于不同遥感指数的归因结果差异大,气候变化对OCO-2 GOSIF的贡...     

黄河源区植被生长季NDVI时空特征及其对气候变化的响应

利用黄河源区MODIS/NDVI数据、1∶100万植被类型图和气象资料,分析了该区不同植被类型生长季NDVI时空特征以及与气候因子的关系。结果表明,1）2000—2011年,黄河源区植被生长呈改善趋势,生长季NDVI年际变化率每10 a为＋2.75%,高寒草原、高寒草甸、高寒灌丛生长季NDVI年际变化率分别为每10 a＋2.84%、＋2.65%、＋2.77%。2）黄河源区植被改善面积占全区总面积的29.39%,主要分布在卡日曲和玛曲上游、扎曲流域、布青山南麓、扎陵湖北部和鄂陵湖周边地区。植被退化面积仅占全区总面积的0.98%,主要分布在约古宗列曲东南部山地和卡日曲北部山地。受水热条件控制,植被改善表现为：①植被改善面积南坡大于北坡;②植被改善面积随海拔升高先增加后减小;③植被改善面积随坡度增加迅速减小。3）黄河源区植被生长季NDVI与同期气温和降水分别存在显著正相关性,其中高寒草原和高寒草甸生长受降水影响更为明显,而高寒灌丛生长受气温影响更为明显。气候的暖湿化趋势可能是促使黄河源区植被生长改善的主要原因。     

1982-2006年华北植被覆盖变化及其与气候变化的关系

利用1982-2006年GIMMSNDVI数据反映华北地区植被覆盖变化状况,结合1982--2006年该地区85个气象站点的气温和降水数据,分别从年际变化、季节变化和月变化三个时间尺度分析华北地区植被覆盖变化及其与气候变化的关系。结果表明,从年际变化来看,华北植被变化与气温变化关系较与降水关系密切;从季节变化来看,华北地区植被生长在不同季节对水热条件变化的响应不同,春季和秋季植被生长与气温的关系较与降水的关系密切,而夏季植被生长主要受降水的影响;从月变化来看,4月和5月植被变化受气温变化影响较明显,一定程度上说明4月和5月植被生长的NDVI值增加可能是由于气候变暖引起的植被生长季提前产生的;6-9月植被生长与前2个月降水变化关系密切,说明植被生长对降水变化具有一定的滞后性。     

增温、刈割对高寒草甸地上植被生长的影响

近些年由于气候变化和土地利用方式变化的双重影响,高寒草甸植被逐渐表现出退化现象。探讨高寒草甸植被生长特征在气候变化和人类活动中的动态变化规律,对高海拔地区植被的保护和合理利用,防止草地退化和沙漠化发生具有重要意义。以青藏高原高寒草甸为研究区,利用增温实验模拟气候变暖、刈割实验模拟人类放牧,采用随机区组设计,设置对照、增温、刈割、增温+刈割交互作用四种实验处理,于2012─2013年植被生长季调查高度、盖度和地上生物量,研究高寒草甸地上植被生长特征对增温、刈割的响应,以此探讨青藏高原高寒草甸地上植被在气候变化和人类活动中的变化趋势。结果表明:(1)夏季是高寒草甸植被生长的最佳季节,其中7月是其生长的最佳月份;高寒草甸地上植被生长特征年内生长季和年际间的变化趋势差异较大,表现为植被高度在生长季中期高于初期和末期(P0.05),植被盖度和地上生物量在生长季中期和末期高于初期(P0.05);2012年的植被高度和地上生物量略高于2013年(P0.05),但植被盖度略低于2013年(P0.05)。(2)植被高度、盖度和地上生物量在增温第2年(2012年)的各实验处理间均未出现显著差异(P0.05),而在第3年(2013年)开始出现显著差异(P0.05),其中2年刈割显著降低植被高度和地上生物量(P0.05),3年增温和2年刈割的交互作用显著降低植被盖度和地上生物量(P0.05)。以上结果表明,增温、刈割对高寒草甸地上植被生长的影响在短期和长期尺度上存有差异,初期并不显著,但随着时间推移,影响开始加强。     

2000-2021年汾河流域植被时空演变特征及地形效应

运用NDVI数据在长时序上考虑不同地形绝对面积差异来评价汾河流域植被变化趋势的研究目前比较匮乏。为科学认识汾河流域植被变化及其地形效应,基于2000-2021年的MODIS NDVI数据并结合地形数据,采用线性趋势分析与地形差异修正的方法,分析了汾河流域植被的时空分布及演变特征,并探讨了其在海拔、坡向和坡度上的生长变化差异。结果表明,（1）近22年汾河流域植被NDVI呈流域中部低、外围高、低海拔盆地平川区小于高海拔山脉区的分布格局,随地形和土地覆盖类型变化规律性显著。2000-2021年汾河流域植被总体呈改善趋势,年际变化速率为0.07/(10 a),其中,63.24%的区域植被NDVI显著增加,33.78%的区域植被基本不变。（2）汾河流域植被NDVI分布和变化存在明显的地形效应,随着海拔递增,植被NDVI先减小后增大再减小,2 200-2 400 m海拔范围内NDVI最大;不同坡向的植被NDVI差异较小,但总体北坡大于南坡、东坡大于西坡,东北坡最大;随着坡度增加,植被NDVI阶梯式增大,20°-35°坡度范围内NDVI最大。（3）2000-2021年汾河流域不同地形的植被NDVI年...     

2001-2020年内蒙古植被碳源/碳汇时空动态及对气候因子的响应

掌握植被动态及其对气候变化的响应,对于提升全球变化背景下陆地生态系统的固碳能力至关重要。内蒙古作为中国北方的重要生态屏障,是气候和生态系统最为多样化的省份之一。虽然已有研究表明植被碳源/碳汇与气候变化密切相关,但这种响应在生态脆弱且包含多种生态过渡带与植被类型的内蒙古,是否存在及如何响应尚不清楚。以净生态系统生产力(NEP)为固碳评估指标,基于遥感植被指数数据、土地覆被数据和气象观测数据,采用净初级生产力和土壤呼吸模型估算了2001-2020年内蒙古植被碳源/碳汇,并通过实测数据验证,重点研究了不同植被类型NEP的时空变化及其对降水、温度和太阳辐射等3种典型气候因子的响应。结果表明,(1)内蒙古植被碳源/碳汇有明显的时空异质性,植被NEP由东北向西南逐渐降低,平均NEP为C 61.2 g·m^-2;不同植被类型的NEP有显著差异,森林、草地和耕地的年均NEP分别为C 270g·m^-2、54.7 g·m^-2、140 g·m^-2。(2)2001-2020年,内蒙古陆地生态系统碳汇呈上升趋势,但存在一定波动...     

Greening the structural change process: ranking sustainability of countries in climate change

This paper proposes an analytical toolkit to measure the sustainability of industrialization across countries. Drawing from a methodology developed to analyze economic development as a process of modernization, it ranks countries on the basis of the emissions they produce and their stage of development. The proposed index penalizes environmental pressures taking into account the modernization level of a country. The paper also proposes an assessment of the environmental performance of countries at the same level of modernization. It introduces the notion of policy space as the difference between the best and worst environmental performer at a given level of modernization. An important finding of the paper is that the magnitude of the policy space is not homogenous across different levels of income and environmental targets.     

Revisiting Kappa to account for change in the accuracy assessment of land-use change models

Land-use change models are typically calibrated to reproduce known historic changes. Calibration results can then be assessed by comparing two datasets: the simulated land-use map and the actual land-use map at the same time. A common method for this is the Kappa statistic, which expresses the agreement between two categorical datasets corrected for the expected agreement. This expected agreement is based on a stochastic model of random allocation given the distribution of class sizes. However, when a model starts from an initial land-use map and makes changes to it, that stochastic model does not pose a meaningful reference level. This paper introduces K_Simulation, a statistic that is identical in form to the Kappa statistic but instead applies a more appropriate stochastic model of random allocation of class transitions relative to the initial map. The new method is illustrated on a simple example and then the results of the Kappa statistic and K_Simulation are compared using the results of a land-use model. It is found that only K_Simulation truly tests models in their capacity to explain land-use changes over time, and unlike Kappa it does not inflate results for simulations where little change takes place over time.     

Climate change and poverty in Africa

Africa is most vulnerable to climate change, although it makes the least contribution to factors that result in global and regional climatic changes. High levels of vulnerability and low adaptive capacity across the continent have been linked to, among other things, poverty. This paper discusses and analyses the relationship between climate change and poverty in Africa. It investigates the relationship between climate change and poverty patterns in Africa, analyses the resultant impact, and discusses potential adaptation policies for moderating the consequences of climatic changes on poverty in the region. The record shows that climate change is happening. What is not discussed or is little researched is the potential devastating impact of climate change on socio-economic development in Africa and the policy measures available to the continent for adaptation.     

Environmental change and normalization of cash crop systems in Africa: preventing agrarian change in West Africa cocoa

ABSTRACT

In recent years, environmental and demographic crises have often been associated with increasing hunger and poverty in agrarian societies. The potential of such crisis to play a positive role in the evolution of agriculture and agricultural societies has been overlooked. Environmental crises such as deforestation for example (in a production where forestland is a production factor) are points of resource alteration that require corresponding alterations in farming systems. Normalization occurs when farmers are induced to defy such signals indicating the need to diversify and instead choose to continue along their existing path regardless of the changing resource endowment. In the absence is replacement of the vital production factor such continuity has to be paid for.     

Climate change and human security in Africa

Climate change poses a major threat to human security and poverty in Africa. In Africa, where livelihoods are mainly based on climate-dependent resources and environment, the effect of climate change will be disproportionate and severe. Moreover, Africa's capacity to adapt to and cope with the adverse effects of climate variability is generally weak. This article discusses how climate change affects human security in Africa. It also assesses the policy options available to policymakers in terms of mitigation and adaptation to climate change to reduce vulnerability and human insecurity in Africa.     

Rewilding in the face of climate change

Expansion of the global protected-area network has been proposed as a strategy to address threats from accelerating climate change and species extinction. A key step in increasing the effectiveness of such expansion is understanding how novel threats to biodiversity from climate change alter concepts such as rewilding, which have underpinned many proposals for large interconnected reserves. We reviewed potential challenges that climate change poses to rewilding and found that the conservation value of large protected areas persists under climate change. Nevertheless, more attention should be given to protection of microrefugia, macrorefugia, complete environmental gradients, and areas that connect current and future suitable climates and to maintaining ecosystem processes and stabilizing feedbacks via conservation strategies that are resilient to uncertainty regarding climate trends. Because a major element of the threat from climate change stems from its novel geographic patterns, we examined, as an example, the implications for climate-adaptation planning of latitudinal, longitudinal (continental to maritime), and elevational gradients in climate-change exposure across the Yellowstone-to-Yukon region, the locus of an iconic conservation proposal initially designed to conserve wide-ranging carnivore species. In addition to a continued emphasis on conserving intact landscapes, restoration of degraded low-elevation areas within the region is needed to capture sites important for landscape-level climate resilience. Extreme climate exposure projected for boreal North America suggests the need for ambitious goals for expansion of the protected-area network there to include refugia created by topography and ecological features, such as peatlands, whose conservation can also reduce emissions from carbon stored in soil. Qualitative understanding of underlying reserve design rules and the geography of climate-change exposure can strengthen the outcomes of inclusive regional planning processes that identify specific sites for protection.     

Bi-directional sex change in a coral-dwelling goby

Bi-directional sex change has recently been reported among obligate coral-dwelling gobies of the genus Gobiodon. However, neither the functional role of this pattern of sex change nor the frequency of sex change in either direction in natural populations is known. We investigated the social structure and pattern of sex change of Gobiodon histrio at Lizard Island on the Great Barrier Reef. The social structure of G. histrio within coral colonies usually consisted of a single juvenile or a heterosexual adult pair. The size of adult social groups was not constrained by coral colony size. In contrast to expectations for pair-forming species, G.␣histrio was primarily a protogynous hermaphrodite. All immature G. histrio were females and sex change from female to male occurred readily when two mature females were placed in a coral colony. In addition, male G. histrio were able to change back to females when two mature males were placed in a coral. Sex change from female to male, however, occurred with over twice the frequency of sex change from male to female. Where two males were placed in a coral colony, heterosexual pairs were most frequently re-established by immigration of females from outside the treatment population. This pattern might be predicted if sex change from male to female is more expensive than sex change from female to male for G. histrio. Where sex change is expensive, movement may be favoured over sex change, particularly where coral densities are high and movement among corals incurs little mortality risk. Received: 10 November 1997 / Accepted after revision: 16 May 1998     

Knowledge gain and behavioral change in citizen-science programs

Citizen-science programs are often touted as useful for advancing conservation literacy, scientific knowledge, and increasing scientific-reasoning skills among the public. Guidelines for collaboration among scientists and the public are lacking and the extent to which these citizen-science initiatives change behavior is relatively unstudied. Over two years, we studied 82 participants in a three-day program that included education about non-native invasive plants and collection of data on the occurrence of those plants. Volunteers were given background knowledge about invasive plant ecology and trained on a specific protocol for collecting invasive plant data. They then collected data and later gathered as a group to analyze data and discuss responsible environmental behavior with respect to invasive plants. We tested whether participants without experience in plant identification and with little knowledge of invasive plants increased their knowledge of invasive species ecology, participation increased knowledge of scientific methods, and participation affected behavior. Knowledge of invasive plants increased on average 24%, but participation was insufficient to increase understanding of how scientific research is conducted. Participants reported increased ability to recognize invasive plants and increased awareness of effects of invasive plants on the environment, but this translated into little change in behavior regarding invasive plants. Potential conflicts between scientific goals, educational goals, and the motivation of participants must be considered during program design.