Drivers of ecosystem change and their impacts on human well-being in Lake Victoria basin

To offer an increased understanding of the spatial patterns, temporal, social and physical predictors of the conversion and transformations of land use in Lake Victoria basin, an assessment of proximate and underlying forces is presented. This study discusses key theoretical underpinnings for the manifold linkages existing between selected drivers of land-use changes around the basin and their consequences on human well-being. Using a meta-analytical research design, the paper analyses ecosystems level cases of the causes of land use and cover changes in the basin, to determine any spatio-temporal or institutional patterns and dynamics. A suite of recurrent core variables has been identified to influence land use and cover changes in the basin. The most prominent of these at the underlying category are climatic factors, economic factors, institutions, national and regional policies, population growth and other remote influences. At the proximate level, these factors drive cropland expansion, overgrazing, infrastructure extension and rates of land degradation. These are supported by empirical evidence from the basin. This assessment is crucial for appropriate local and transboundary policy interventions, which have to be fine-tuned to the locale-specific dynamic patterns associated with the inherent ecosystems changes.     

整治"三滥"是从源头遏制生态脆弱地区土地荒漠化的必由之路——以科尔沁沙地为例

针对中国土地荒漠化的现状和关键问题,以科尔沁沙地为例,阐述了荒漠化的发展历程、主要动因与未来趋势。科尔沁沙地正处在现代土地荒漠化过程之中,导致快速发展的荒漠化动因主要是源于人们不合理的土地利用方式,即滥垦、滥牧和滥伐(简称“三滥”);而在各种利农政策下,滥垦可能会重新滋生和蔓延,是非常值得借鉴的历史教训。本文应用复合生态系统的观点剖析了“三滥”与荒漠化的关系,并据此提出从源头减轻土地压力的6项对策。     

Modelling climate response to historical land cover change

In order to estimate the effect of historical land cover change (deforestation) on climate, we perform a set of experiments with a climate system model of intermediate complexity – CLIMBER-2. We focus on the biophysical effect of the land cover change on climate and do not explicitly account for the biogeochemical effect. A dynamic scenario of deforestation during the last millennium is formulated based on the rates of land conversion to agriculture. The deforestation scenario causes a global cooling of 0.35 °C with a more notable cooling of the northern hemisphere (0.5 °C). The cooling is most pronounced in the northern middle and high latitudes, especially during the spring season. To compare the effect of deforestation on climate with other forcings, climate responses to the changing atmospheric CO₂ concentration and solar irradiance are also analysed. When all three factors are taken into account, dynamics of northern hemisphere temperature during the last 300 years within the model are generally in agreement with the observed (reconstructed) temperature trend. We conclude that the impact of historical land cover changes on climate is comparable with the impact of the other climate forcings and that land cover forcing is important for reproducing historical climate change.     

Simulating Deforestation in Minas Gerais,Brazil, under Changing Government Policies and Socioeconomic Conditions

Agricultural expansion is causing deforestation in Minas Gerais, Brazil, converting savanna and tropical dry forest to farmland, and in 2012, Brazil’s Forest Code was revised with the government reducing deforestation restrictions. Understanding the effects of policy change on rates and locations of natural ecosystem loss is imperative. In this paper, deforestation in Minas Gerais was simulated annually until 2020 using Dinamica Environment for Geoprocessing Objects (Dinamica EGO). This system is a state-of-the-art land use and cover change (LUCC) model which incorporates government policy, landscape maps, and other biophysical and anthropogenic datasets. Three studied scenarios: (i) business as usual, (ii) increased deforestation, and (iii) decreased deforestation showed more transition to agriculture from shrubland compared to forests, and consistent locations for most deforestation. The probability of conversion to agriculture is strongly tied to areas with the smallest patches of original biome remaining. Increases in agricultural revenue are projected to continue with a loss of 25% of the remaining Cerrado land in the next decade if profit is maximized. The addition of biodiversity value as a tax on land sale prices, estimated at over $750,000,000 USD using the cost of extracting and maintaining current species ex-situ, can save more than 1 million hectares of shrubland with minimal effects on the economy of the State of Minas Gerais. With environmental policy determining rates of deforestation and economics driving the location of land clearing, site-specific protection or market accounting of externalities is needed to balance economic development and conservation.     

How does climate change cause extinction?

Anthropogenic climate change is predicted to be a major cause of species extinctions in the next 100 years. But what will actually cause these extinctions? For example, will it be limited physiological tolerance to high temperatures, changing biotic interactions or other factors? Here, we systematically review the proximate causes of climate-change related extinctions and their empirical support. We find 136 case studies of climatic impacts that are potentially relevant to this topic. However, only seven identified proximate causes of demonstrated local extinctions due to anthropogenic climate change. Among these seven studies, the proximate causes vary widely. Surprisingly, none show a straightforward relationship between local extinction and limited tolerances to high temperature. Instead, many studies implicate species interactions as an important proximate cause, especially decreases in food availability. We find very similar patterns in studies showing decreases in abundance associated with climate change, and in those studies showing impacts of climatic oscillations. Collectively, these results highlight our disturbingly limited knowledge of this crucial issue but also support the idea that changing species interactions are an important cause of documented population declines and extinctions related to climate change. Finally, we briefly outline general research strategies for identifying these proximate causes in future studies.     

Bibliometrical study method on tidal freshwater marshes loss and research orientation

Many studies concerning wetland loss have been conducted in the last two decades. However, tidal freshwater marsh’s research topics, mirroring hot points, vary in scientific community and change over time. A bibliometrical analysis method is demonstrated in this paper to describe tidal freshwater marsh research and changes in the research over time. For example, habitat restoration, soil composition, plantation pattern and coastal wetland have drawn increasing attention since 2005. The bibliographic methods described in this paper involved the use of 54 case studies to find critical paths regarding how tidal freshwater wetland loss has been induced by different causes. From case studies, it has been concluded that urbanization is the most important cause of tidal freshwater marsh loss. Critical paths of tidal freshwater marsh loss driving forces have been also demonstrated in this paper.     

Discerning Fragmentation Dynamics of Tropical Forest and Wetland during Reforestation,Urban Sprawl,and Policy Shifts

Despite the overall trend of worldwide deforestation over recent decades, reforestation has also been found and is expected in developing countries undergoing fast urbanization and agriculture abandonment. The consequences of reforestation on landscape patterns are seldom addressed in the literature, despite their importance in evaluating biodiversity and ecosystem functions. By analyzing long-term land cover changes in Puerto Rico, a rapidly reforested (6 to 42% during 1940–2000) and urbanized tropical island, we detected significantly different patterns of fragmentation and underlying mechanisms among forests, urban areas, and wetlands. Forest fragmentation is often associated with deforestation. However, we also found significant fragmentation during reforestation. Urban sprawl and suburb development have a dominant impact on forest fragmentation. Reforestation mostly occurs along forest edges, while significant deforestation occurs in forest interiors. The deforestation process has a much stronger impact on forest fragmentation than the reforestation process due to their different spatial configurations. In contrast, despite the strong interference of coastal urbanization, wetland aggregation has occurred due to the effective implementation of laws/regulations for wetland protection. The peak forest fragmentation shifted toward rural areas, indicating progressively more fragmentation in forest interiors. This shift is synchronous with the accelerated urban sprawl as indicated by the accelerated shift of the peak fragmentation index of urban cover toward rural areas, i.e., 1.37% yr⁻¹ in 1977–1991 versus 2.17% yr⁻¹ in 1991–2000. Based on the expected global urbanization and the regional forest transition from deforested to reforested, the fragmented forests and aggregated wetlands in this study highlight possible forest fragmentation processes during reforestation in an assessment of biodiversity and functions and suggest effective laws/regulations in land planning to reduce future fragmentation.     

博斯腾湖小湖区湿地景观变化特征研究

以博斯腾湖小湖区为研究区,采用5个不同时期的Landsat影像为主要数据源,运用景观转换系数和重心迁移模型对1996~2015年研究区湿地景观变化进行分析,以揭示博斯腾湖小湖区的景观变化类型与景观的重心变化特征。结果显示:(1)近20年有地表水的湿地与旱地的重心变化强烈,1996~2001年有地表水的湿地重心变化达到最大值,向西南迁移10.57km,旱地重心变化也达到最大值,向东南迁移8.78km。(2)近20年明水与旱地的重心迁移呈顺时针向心偏移。(3)稳定型景观是研究区的主要构成类型,占总类型的89.72%,非稳定型景观保持在总类型的11.28%,研究区湿地景观变化逐渐呈稳定趋势。研究表明,气候因素、湖泊水位和区域湿地保护措施是影响研究区湿地景观变化的主要驱动因素。     

Deforestation and land farming as regulators of population size and climate

This work reveals that deforestation and farming of the cleared land may be considered as regulators of the size of world population and climate. When the green matter is cleared, it decomposes, oxidizes, and releases to the climate the heat of carbon conversion to carbon dioxide. The farmed land provides carrying capacity that sustains population growth. As world population grows, energy consumption increases. Most of this energy has been fossil fuel based, and the heat released is gained by the climate. Warming of the surface and population growth are thus processes that depend on land clearing and conversion into farmland. If deforestation increases, the size of the farmland increases, population size increases, and the surface accumulates heat and vice versa. Therefore, analyses of the correlation between deforestation, population growth, and climate change may have merit for research and society. Through 1990, deforestation has contributed at least 36% of the total heat added to the surface. Therefore, deforestation contribution to climate change is substantial. At the current rate of deforestation, the world population may approach 14.5 billion by the year 2100. Should deforestation decrease and approach zero by then, the world population may steady at nearly 10.3 billion instead.     

土地利用变化对陆地生态系统碳贮量的影响

陆地生态系统是重要的碳库之一,在碳素生物地球化学循环中起着重要作用．本文就森林、农田生态系统,综述了土地利用变化对陆地生态系统碳贮量的影响及其可能的作用机制．土地利用变化显著地影响陆地生态系统的结构和功能,造成系统碳贮量的变化,这很大程度取决于生态系统类型和土地利用方式的改变．森林砍伐后变为农田和草地,使生态系统中植被和土壤碳贮量大大降低．土壤碳含量的降低主要是由于凋落物输入的减少,有机质分解速度的提高,以及耕种措施对有机质物理保护的破坏造成的．土壤碳损失主要发生在森林砍伐后较短的时期内,而其降低速率取决于诸多因素以及土壤理化和生物过程．农田和草地弃耕恢复为森林,以及农田保护性管理措施的利用．能够使大气中的碳在植被和土壤中得到汇集．森林恢复过程中植被可以大量汇集大气中的碳,而由于农田耕种历史不同以及土壤空间异质性。导致土壤碳汇集速率差异极大．保护性农田管理措施(诸如免耕、合理的种植制度、化肥的施用等)可以影响土壤理化特性、作物根系生长以及残茬数量和质量、土壤微生物数量和活性,维持和提高土壤碳含量水平．     

长沙城市斑块湿地资源的时空演变

利用GIS技术,对长沙市1955、1972和1990年地形图湿地数据及2007年长沙市湿地资源普查数据进行提取和分析,选取最具代表性的斑块湿地作为研究对象,从时间与空间、动态与静态、规模与填埋等视角,研究50年来城市斑块湿地生态系统各层次要素的时空演变过程和变化规律.结果表明:(1)时间层次上,长沙城市斑块湿地总面积呈现先增后减、总体增加的态势;斑块湿地面积变化幅度不断加大,速率逐步加快;(2)规模层次上,面积在32 hm2规模以下的斑块湿地呈增加态势,32 hm2规模以上斑块湿地呈减少态势;(3)动态空间层次上,被填埋斑块湿地的比例在建成区和郊区呈相反的演变结果;(4)静态空间层次上,斑块湿地密度在建成区范围和郊区范围演变结果相背.研究显示,伴随着城市化进程,不同时间尺度、不同规模尺度、不同空间属性、不同空间状态的城市斑块湿地常常呈现差异很大、甚至是截然相反的演变结果;无论是动态空间还是静态空间,建成区与郊区的空间分界线往往是城市斑块湿地演变态势的分水岭.     

Land use change and its drivers in Kurt Bahir wetland,north-western Ethiopia

The effects of land-use change on ecosystem services in Kurt Bahir wetland were investigated during 2013 to 2014 using LANDSAT satellite images from 1973, 1986, 2002 and 2013 to identify and map changes in land-use classes over time. To understand perceptions of changes in ecosystem services that resulted from observed land-use changes discussions were held with local key informants and focus group participants. Accuracy assessment was done on the 2013 classified image. In 1973, the land-use classes of the wetland comprised wetland and grazing land, with area coverages of 764.5 and 268.4 ha, respectively. The land-use classes in 1986 were wetland, grazing land and cultivated land, with area coverages of 585.7, 198.3 and 248.9 ha, respectively. The land use of the study area in 2002 was similar to that of 1986. In 2013–2014, however, there was a substantial increase in cultivation and grazing lands at the expense of the wetland, as compared to 2002. Respondents confirmed that free grazing, the harvesting of vegetation, deforestation and expansion of cultivated land were the major threats. This study indicated that land-use change is the main driver of wetland degradation and loss. It is recommended that government organisations should give due emphasis to overcome the anthropogenic effects and to develop a management plan for the sustainable utilisation of the wetland’s ecosystem services.     

资源型城市土地利用变化的景观过程响应——以黑龙江省大庆市为例

土地利用与土地覆盖变化直接或间接地改变着景观生态系统的结构和功能,进而影响地表各种景观过程。地表景观过程的改变,必然对人类赖以生存的生态环境产生程度不同的影响。黑龙江省大庆市作为典型的资源型城市(以石油、草场和耕地资源发展起来),是人地关系作用最强烈的区域之一,也是土地利用发生急剧变化且具有特色的区域。揭示该区域土地利用的时空变化特征和变化规律,探讨土地利用变化的景观生态趋势及对生态环境的可能影响等,对于资源型城市生态环境改善,产业结构调整及实现资源型城市可持续发展尤为重要。为此,基于大庆市1978,1988,1992,1996,2001年5个时段的MSS和TM影像,获取20余年不同时期的土地利用信息,以GIS技术为数据集成分析平台,计算土地利用转移概率矩阵,景观格局指数和主要景观组分的转移过程贡献率,以期从景观格局的角度定量刻画区域景观过程对土地利用变化的响应。结果表明,区域内耕地不断增加,草地持续减少,建设用地和林地逐渐扩大,而湿地则一直大幅度减少;耕地和草地是区域的主要景观类型,但二者的景观动态及过程却不相同,耕地的景观过程表现为空间集中性加强,而草地的破碎化程度加强,景观组分间的转移过程频繁,景观不稳定;对维持当地生态系统稳定起重要作用的湿地景观,其破碎化过程最为明显且面积和平均斑块面积都在迅速减少,这种景观过程将对当地生态环境变化造成负面影响。草地退化,湿地萎缩和功能减退,沙化和盐碱化日趋严重等生态过程,是土地利用变化的景观生态过程响应,恢复与建设生态脆弱的资源型城市的景观生态系统,须对景观尺度上的土地利用方式进行合理的调控,而这一调控的有效途径在于政策、体制的调整和观念的变化。     

城市化对鸟类的影响：从群落到个体

世界范围急剧的城市化进程所带来的生态问题,尤其是城市化对鸟类的影响引起了生态学家越来越多的关注。关注点从最初的群落水平,逐渐向种群水平和个体水平深入。在群落水平上,现有的研究展示了城市化对鸟类群落组成、物种的丰富度、多度、生物量和多样性等多方面存在的不同程度的影响;而物种水平的研究探讨了城市化影响鸟类群落格局的内在原因:不同的鸟类物种对城市化具有不同的反应;而个体水平的研究,更是进一步从鸟类行为、生活史特征等方面揭示城市化压力和鸟类的适应对策。大量的证据说明,城市化所带来的土地使用的改变、人为干扰、热岛效应、食物资源改变、巢捕食、夜间灯光等,不同程度地对城市鸟类产生了影响。     

岩溶山区景观多样性变化的生态学意义对比——以贵州四个典型地区为例

岩溶石漠化是中国西南典型的土地退化,但关于岩溶山区景观多样性的研究还不多见。岩溶山区景观异质性强,景观格局空间差异大,岩溶山区土地利用/土地覆被变化引起的景观多样性变化,其生态学意义有何差异,值得开展研究。本文采用高分辨率的航片和遥感影像,以100m?100m 网格为单元,分析了贵州省王家寨、后寨河、花江和茂兰4个典型岩溶地点的景观多样性指数在1963年和2004年的空间分布。 为了说明多样性指数变化的生态学意义,进一步,把4个研究地点景观多样性指数空间分布图与其土地退化图结合起来,对比其多样性指数变化与土地退化和生态恢复的关系。结果表明：（1）茂兰、后寨河和花江多样性指数都表现出随距聚落距离增加而减少的趋势,王家寨1963年和2004年则表现出随距聚落距离增加,多样性指数先减小后增加。（2）茂兰地区以森林为基质,后寨河地区坡耕地退耕为林、灌、草地,土地利用方式单一,景观破碎化程度降低;因此,茂兰、后寨河地区多样性指数的降低表明该地区生态实质上有所恢复;花江地区土地利用/土地覆被逐渐向多样化方向发展,石漠化景观逐渐被林灌斑块代替,多样性指数升高表明该地区植被有所恢复;王家寨地区峰丛坡地多样性指数增加表示生态有所恢复。（3）研究地点多样性的升、降不能简单地与生态变好、变差直接联系。只有正确区分岩溶地区的景观基质,才能准确运用景观指数分析石漠化土地的变化趋势。     

深圳市1988—2007年间湿地景观动态变化及成因分析

城市湿地是城市生态安全体系构成的重要组成部分。以深圳地区为工作区,利用多时段遥感资料和土地利用变更调查数据,进行1988—2007年期间工作区内湿地景观动态变化特征分析,探讨快速城市化背景下湿地景观动态变化的成因。结果表明,研究时段内深圳市湿地总面积损失了35.7%,不同湿地类型及不同行政单元内湿地的动态变化表现出明显差异。建设用地扩张是工作区内湿地损失的主要原因并且其影响表现为一种非均匀过程;功能差异是导致不同湿地类型之间动态变化差异的主要成因;区域社会经济和自然环境条件差异是导致不同行政单元之间湿地动态变化差异的主要影响因素。     

The national determinants of deforestation in sub-Saharan Africa

For decades, the dynamics of tropical deforestation in sub-Saharan Africa (SSA) have defied easy explanation. The rates of deforestation have been lower than elsewhere in the tropics, and the driving forces evident in other places, government new land settlement schemes and industrialized agriculture, have largely been absent in SSA. The context and causes for African deforestation become clearer through an analysis of new, national-level data on forest cover change for SSA countries for the 2000–2005 period. The recent dynamic in SSA varies from dry to wet biomes. Deforestation occurred at faster rates in nations with predominantly dry forests. The wetter Congo basin countries had lower rates of deforestation, in part because tax receipts from oil and mineral industries in this region spurred rural to urban migration, declines in agriculture and increased imports of cereals from abroad. In this respect, the Congo basin countries may be experiencing an oil and mineral fuelled forest transition. Small farmers play a more important role in African deforestation than they do in southeast Asia and Latin America, in part because small-scale agriculture remains one of the few livelihoods open to rural peoples.     

基于Meta分析的中国湖沼湿地生态系统服务价值转移研究

Meta分析价值转移方法作为资源价值评估的一种有效方法,在国外已经有大量的实证研究出现,但是在国内相应的实证研究非常稀少,有关该方法在湖沼湿地生态系统服务价值评估的应用研究还尚未见报道。通过收集有关中国湖沼湿地生态系统服务价值评估的实证研究文献的价值评估结果,建立价值转移数据库,应用Meta分析和多元回归分析方法构建中国湖沼湿地生态系统服务的Meta分析价值转移模型,并对该模型用于样本外价值转移的有效性做出评估,探讨Meta分析价值转移方法在中国湖沼湿地生态系统服务价值评估领域的可应用性及发展前景。研究结果表明:(1)在样本文献中,通常洪水调蓄和水源涵养服务是湖沼湿地提供的经济价值最高的生态系统服务,而水质净化服务的经济价值最低;(2)湖沼湿地面积、生态系统服务受益人口数量、不同生态系统服务之间的价值差异以及不同价值评估方法的使用会影响湖沼湿地生态系统服务价值的变化;(3)Meta分析价值转移模型用于样本外价值转移的有效性检验结果显示,样本外价值转移的转移误差范围在0.09%—234.61%之间,平均转移误差为19.99%,在自然资源价值转移的可接受误差范围内,因此Meta分析价值转移方法是评估湿地生态系统服务价值的一种可行且快速的方法。     

黄河源区沙漠化及其景观格局的变化

本研究以1975年的MSS数据、1990年和2005年的TM数据、以及2000年的ETM数据为数据源,通过遥感（RS）与地理信息系统（GIS）技术,获得了黄河源区在1975－2005年间沙漠化的发展特征,并采用景观指数运算软件（FRAGSTATS3.3）对黄河源区沙漠化土地的景观格局变化进行了分析。研究发现：在1975－1990年间,黄河源区的沙漠化土地面积大幅增加;在1990－2000年间,沙漠化土地面积保持稳定;在2000－2005年间,沙漠化土地面积出现了小幅度的减小趋势。黄河源区沙漠化土地的景观格局变化显著,在1975－1990年间,沙漠化土地发生了严重的破碎化;在1990－2000年间,沙漠化土地出现了连片的现象,从而使得沙漠化土地的破碎度有所下降,景观多样性降低;在2000－2005年间,沙漠化土地破碎度的增加,斑块形状趋于复杂。     

Evidence of incipient forest transition in southern Mexico

Case studies of land use change have suggested that deforestation across Southern Mexico is accelerating. However, forest transition theory predicts that trajectories of change can be modified by economic factors, leading to spatial and temporal heterogeneity in rates of change that may take the form of the Environmental Kuznets Curve (EKC). This study aimed to assess the evidence regarding potential forest transition in Southern Mexico by classifying regional forest cover change using Landsat imagery from 1990 through to 2006. Patterns of forest cover change were found to be complex and non-linear. When rates of forest loss were averaged over 342 municipalities using mixed-effects modelling the results showed a significant (p<0.001) overall reduction of the mean rate of forest loss from 0.85% per year in the 1990-2000 period to 0.67% in the 2000-2006 period. The overall regional annual rate of deforestation has fallen from 0.33% to 0.28% from the 1990s to 2000s. A high proportion of the spatial variability in forest cover change cannot be explained statistically. However analysis using spline based general additive models detected underlying relationships between forest cover and income or population density of a form consistent with the EKC. The incipient forest transition has not, as yet, resulted in widespread reforestation. Forest recovery remains below 0.20% per year. Reforestation is mostly the result of passive processes associated with reductions in the intensity of land use. Deforestation continues to occur at high rates in some focal areas. A transition could be accelerated if there were a broader recognition among policy makers that the regional rate of forest loss has now begun to fall. The changing trajectory provides an opportunity to actively restore forest cover through stimulating afforestation and stimulating more sustainable land use practices. The results have clear implications for policy aimed at carbon sequestration through reducing deforestation and enhancing forest growth.