Effects of Climate Change on the Potential Species Richness of Mesoamerican Forests

The realized species richness of tropical forests cannot yet be reliably mapped at a regional scale due to lack of systematically collected data. An estimate of the potential species richness (PSR), however, can be produced through the use of species distribution modelling. PSR is interpretable as a climatically determined upper limit to observed species richness. We mapped current PSR and future PSR under climate change scenarios for Mesoamerica by combining the spatial distributions of 2000 tree species as predicted by generalized additive models built from herbaria records and climate layers. An explanatory regression tree was used to extract conditional rules describing the relationship between PSR and climate. The results were summarized by country, ecoregion and protected area status in order to investigate current and possible future variability in PSR in the context of regional biodiversity conservation. Length of the dry season was found to be the key determinant of PSR. Protected areas were found to have higher median PSR values than unprotected areas in most of the countries within the study area. Areas with exceptionally high PSR, however, remain unprotected throughout the region. Neither changes in realized species richness nor extinctions will necessarily follow changes in modelled PSR under climate change. However model output suggests that an increase in temperature of around 3°C, combined with a 20 percent decrease in rainfall could lead to a widespread reduction of around 15 percent of current PSR, with values of up to 40 percent in some moist lower montane tropical forests. The modelled PSR of dry forest ecoregions was found to be relatively stable. Some cooler upper montane forests in northern Mesoamerica, where few species of tropical origin are currently found, may gain PSR if species are free to migrate.     

Coevolution and the Effects of Climate Change on Interacting Species

Background

Recent studies suggest that environmental changes may tip the balance between interacting species, leading to the extinction of one or more species. While it is recognized that evolution will play a role in determining how environmental changes directly affect species, the interactions among species force us to consider the coevolutionary responses of species to environmental changes.

Methodology/Principle Findings

We use simple models of competition, predation, and mutualism to organize and synthesize the ways coevolution modifies species interactions when climatic changes favor one species over another. In cases where species have conflicting interests (i.e., selection for increased interspecific interaction strength on one species is detrimental to the other), we show that coevolution reduces the effects of climate change, leading to smaller changes in abundances and reduced chances of extinction. Conversely, when species have nonconflicting interests (i.e., selection for increased interspecific interaction strength on one species benefits the other), coevolution increases the effects of climate change.

Conclusions/Significance

Coevolution sets up feedback loops that either dampen or amplify the effect of environmental change on species abundances depending on whether coevolution has conflicting or nonconflicting effects on species interactions. Thus, gaining a better understanding of the coevolutionary processes between interacting species is critical for understanding how communities respond to a changing climate. We suggest experimental methods to determine which types of coevolution (conflicting or nonconflicting) drive species interactions, which should lead to better understanding of the effects of coevolution on species adaptation. Conducting these experiments across environmental gradients will test our predictions of the effects of environmental change and coevolution on ecological communities.     

Climate Change,Habitat Loss,Protected Areas and the Climate Adaptation Potential of Species in Mediterranean Ecosystems Worldwide

Mediterranean climate is found on five continents and supports five global biodiversity hotspots. Based on combined downscaled results from 23 atmosphere-ocean general circulation models (AOGCMs) for three emissions scenarios, we determined the projected spatial shifts in the mediterranean climate extent (MCE) over the next century. Although most AOGCMs project a moderate expansion in the global MCE, regional impacts are large and uneven. The median AOGCM simulation output for the three emissions scenarios project the MCE at the end of the 21^st century in Chile will range from 129–153% of its current size, while in Australia, it will contract to only 77–49% of its current size losing an area equivalent to over twice the size of Portugal. Only 4% of the land area within the current MCE worldwide is in protected status (compared to a global average of 12% for all biome types), and, depending on the emissions scenario, only 50–60% of these protected areas are likely to be in the future MCE. To exacerbate the climate impact, nearly one third (29–31%) of the land where the MCE is projected to remain stable has already been converted to human use, limiting the size of the potential climate refuges and diminishing the adaptation potential of native biota. High conversion and low protection in projected stable areas make Australia the highest priority region for investment in climate-adaptation strategies to reduce the threat of climate change to the rich biodiversity of the mediterranean biome.     

Effects of Climate Change on Plant Population Growth Rate and Community Composition Change

The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades) based on long-term monitoring data from two plots—Dinghushan Biosphere Reserve, China (DBR) and Barro Colorado Island, Panama (BCI)—that are located in tropical and subtropical regions. We proposed a relatively more concise index, Slnλ, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change.     

Effects of Previous Land-Use on Plant Species Composition and Diversity in Mediterranean Forests

At some point in their history, most forests in the Mediterranean Basin have been subjected to intensive management or converted to agriculture land. Knowing how forest plant communities recovered after the abandonment of forest-management or agricultural practices (including livestock grazing) provides a basis for investigating how previous land management have affected plant species diversity and composition in forest ecosystems. Our study investigated the consequences of historical “land management” practices on present-day Mediterranean forests by comparing species assemblages and the diversity of (i) all plant species and (ii) each ecological group defined by species’ habitat preferences and successional status (i.e., early-, mid-, and late-successional species). We compared forest stands that differed both in land-use history and in successional stage. In addition, we evaluated the value of those stands for biodiversity conservation. The study revealed significant compositional differentiation among stands that was due to among-stand variations in the diversity (namely, species richness and evenness) of early-, intermediate-, and late-successional species. Historical land management has led to an increase in compositional divergences among forest stands and the loss of late-successional forest species.     

Predicting the Long-Term Effects of Hunting on Plant Species Composition and Diversity in Tropical Forests

Hunting can change abundances of vertebrate seed predators and seed dispersers, causing species‐specific changes in seed dispersal and seed predation and altering seedling communities. What are the consequences of these changes for the adult plant community in the next generation and beyond? Here, I derive equations showing how reduced seed dispersal reduces plant reproduction by intensifying kin competition, increasing vulnerability to natural enemies, and reducing the proportion of seeds passing through disperser guts. I parameterize these equations with available empirical data to estimate the likely effects on next‐generation abundances. I then consider the indirect effects and longer‐term feedbacks of changed seed or adult abundances on reproductive rates due to density‐dependent interactions with natural enemies and mutualists, as well as niche differentiation with competitors, and discuss their likely qualitative effects. The factors limiting seed disperser and seed predator populations in natural and hunted forests emerge as critical for determining the long‐term effects of hunting on rates of seed dispersal and seed predation. For example, where seed dispersers are held to a constant abundance by hunters, decreases in the availability of their preferred food plants are expected to lead to increased per‐seed dispersal probabilities, potentially to the point of compensating for the initial disperser decline. I close by discussing the likely reversibility of hunting‐induced changes in tropical forests and key questions and directions for future research.     

Influence of Forest Management on the Species Richness and Composition of Wood-inhabiting Basidiomycetes in Swiss Forests

In order to investigate the diversity of wood-inhabiting aphyllophoroid basidiomycetes in Swiss forests, 86 plots of 50 m ² were established. They harboured a total of 3339 samples of woody debris, classified according to three categories (coarse, fine, and very fine woody debris), yielding 238 species of wood-inhabiting fungi. The selected sites cover the main forest types of Switzerland and various degrees of management intensity. A multiple linear regression analysis showed that substrate variation, i.e. differences in the quality of dead wood, including volume, age, degree of decomposition and host tree species, are the most important factors influencing diversity of wood-inhabiting fungi. In addition, a Principle Coordinate Analysis highlighted differences in the fungal communities in the different forest types. The greatest fungal species richness is found on thermophilic deciduous tree and woody shrub species. Fine and very fine woody debris, even present in intensively managed forests, often serve as important refuges for many species. Forests with a recent management intervention were found to be either species poor or species rich. Possible reasons for these differences may lay in forest size and landscape fragmentation, the distance to the nearest species pool or microclimatic factors. In Switzerland intensively managed forests harbour significantly less wood-inhabiting, aphyllophoroid fungi than non-managed or extensively managed forests. This is the case in both deciduous forests and in conifer forests. However, occasionally intensively managed forest will also harbour rare and endangered species.     

气候变化对农业害虫的潜在影响

气候变化对农业害虫的潜在影响张润杰何新凤（中山大学昆虫学研究所生物防治国家重点实验室,广州５１０２７５）ＰｏｔｅｎｔｉａｌＥｆｅｃｔｓｏｆＣｌｉｍａｔｅＣｈａｎｇｅｏｎＡｇｒｉｃｕｌｔｕｒａｌＩｎｓｅｃｔＰｅｓｔｓ．ＺｈａｎｇＲｕｎｊｉｅ,ＨｅＸｉ...     

河北拟步甲多样性组成与区系分析

本文在对河北(含京、津地区)拟步甲科昆虫进行种类鉴定和地理分布资料整理的基础上,得出该地区已知拟步甲科昆虫5亚科19族38属64种(亚种),并以此为依据分析了该地区拟步甲的物种多样性组成及地理分布特点。结果显示,河北拟步甲在种类组成上由多到少依次为:拟步甲亚科Tenebrioninae 20属40种(62.5%)>漠甲亚科Pimeliinae 9属12种(18.8%)>朽木甲亚科Alleculinae 3属5种(7.8%)>伪叶甲亚科Lagriinae 3属4种(6.2%)>菌甲亚科Diaperinae 3属3种(4.7%);在区系组成上,河北拟步甲与华北区关系最为密切,共计38属63种(98.4%),其次为蒙新区28属47种(73.4%),其他动物区的成分较少;河北拟步甲在河北昆虫地理区划的分布呈现:山麓平原区30属42种(65.6%)>冀西北间山盆地区24属40种(62.5%)>冀北山区12属14种(21.9%)>坝上高原区11属14种(21.9%)>冀西山区9属10种(15.6%)>低平原区8属9种(14.1%);河北特有种7种,其中6种分布在山麓平原区。     

Climatic influences on fire regimes in the northern Sierra Nevada mountains, Lake Tahoe Basin, Nevada, USA

Aim The goal of this study was to understand better the role of interannual and interdecadal climatic variation on local pre‐EuroAmerican settlement fire regimes in fire‐prone Jeffrey pine (Pinus jeffreyi Grev. & Balf.) dominated forests in the northern Sierra Nevada Mountains. Location Our study was conducted in a 6000‐ha area of contiguous mixed Jeffrey pine‐white fir (Abies concolor Gordon & Glend.) forest on the western slope of the Carson Range on the eastern shore of Lake Tahoe, Nevada. Methods Pre‐EuroAmerican settlement fire regimes (i.e. frequency, return interval, extent, season) were reconstructed in eight contiguous watersheds for a 200‐year period (1650–1850) from fire scars preserved in the annual growth rings of nineteenth century cut stumps and recently dead pre‐settlement Jeffrey pine trees. Superposed epoch analysis (SEA) and correlation analysis were used to examine relationships between tree ring‐based reconstructions of the Palmer Drought Severity Index (PDSI), Southern Oscillation Index (SOI), Pacific Decadal Oscillation (PDO) and pre‐EuroAmerican fire regimes in order to assess the influence of drought and equatorial and north Pacific teleconnections on fire occurrence and fire extent. Results For the entire period of record (1650–1850), wet conditions were characteristic of years without fires. In contrast, fire years were associated with drought. Drought intensity also influenced fire extent and the most widespread fires occurred in the driest years. Years with widespread fires were also preceded by wet conditions 3 years before the fire. Widespread fires were also associated with phase changes of the PDO, with the most widespread burns occurring when the phase changed from warm (positive) to cold (negative) conditions. Annual SOI and fire frequency or extent were not associated in our study. At decadal time scales, burning was more widespread during decades that were dryer and characterized by La Niña and negative PDO conditions. Interannual and interdecadal fire–climate relationships were not stable over time. From 1700 to 1775 there was no interannual relationship between drought, PDO, and fire frequency or extent. However, from 1775 to 1850, widespread fires were associated with dry years preceded by wet years. This period also had the strongest association between fire extent and the PDO. In contrast, fire–climate associations at interdecadal time scales were stronger in the earlier period than in the later period. The change from strong interdecadal to strong interannual climate influence was associated with a breakdown in decadal scale constructive relationships between PDO and SOI. Main conclusions Climate strongly influenced pre‐settlement pine forest fire regimes in northern Sierra Nevada. Both interannual and interdecadal climatic variation regulated conditions conducive to fire activity, and longer term changes in fire frequency and extent correspond with climate‐mediated changes observed in both the northern and southern hemispheres. The sensitivity of fire regimes to shifts in modes of climatic variability suggests that climate was a key regulator of pine forest ecosystem structure and dynamics before EuroAmerican settlement. An understanding of pre‐EuroAmerican fire–climate relationships may provide useful insights into how fire activity in contemporary forests may respond to future climatic variation.     

气候变化对5种植物分布的潜在影响

利用CART(分类和回归树Classification and regression tree)模型,采用A2和B2气候情景,模拟分析了气候变化对观光木(Tsoongiodendron odorum)、鹅掌楸(Liriodendron chinense)、独叶草(Kingdonia uniflora)、草苁蓉(Boschniakia rossica)和刺五加(Acanthopanax senticosus)分布范围及空间格局的影响。结果表明:与目前适宜分布范围相比,气候发生变化后,观光木的分布范围变化不大,其它植物则缩小;观光木的新适宜与总适宜分布范围扩大,而其它植物缩小;草丛蓉和刺五加的目前适宜、新适宜及总适宜分布范围缩小幅度较大,鹅掌楸和独叶草次之;观光木和鹅掌楸向目前适宜分布区北部区域扩展,独叶草向西南区域扩展,草丛蓉和刺五加的适宜范围在2081～2100年会散失。气候变化下,这些植物的适宜分布范围随年降水量和年均气温的变化不一致,观光木的目前适宜、独叶草的新适宜及总适宜分布范围与年降水量和年均气温,以及草苁蓉的分布范围与降水量的相关性不显著(P0.05)。这些植物的空间分布格局将随气候变化而发生变化。     

Present and past old‐growth forests of the Lake Tahoe Basin,Sierra Nevada,US

Abstract. We described 38 relictual old‐growth stands – with data on the mortality, regeneration, floristic richness, fuel load and disease incidence in our study area in the Tahoe Basin of California and Nevada. The stands are within the lower and upper montane zones (1900–2400 m a.s.l.) and they are rare, occupying < 2% of the land in the Basin's watershed. Correlation matrices and ANOVAs of forest types and conifer species with environmental gradients revealed significant relationships with elevation, distance east of the Sierran crest, slope aspect, annual precipitation, date of complete snow melt, litter depth and degree of soil profile development. Pathogens, parasites and wood‐boring insects were present on 23% of living trees; 16% of all trees were dead. We compared these stands to a reconstruction of pre‐contact Basin forests and to ecologically analogous old‐growth forests of Baja California that have never experienced fire suppression management. Currently, overstorey trees (> 180 yr old) in the Basin stands have ca. 33% cover, 54 m².ha^‐1 basal area and 107 individuals.ha^‐1, values very similar to reconstructions of pre‐contact Basin forests and to modern Baja California forests. Understorey trees (60–180 yr old), however, are several times more dense than historic levels and species composition is strongly dominated by A. concolor, regardless of the overstorey composition. The ratio of Pinus: Abies has increased – and the age structure of extant stands predicts that it will continue to increase – from approximately 1:1 in pre‐contact time to 1:7 within the next century. Disease incidence and mortality in Baja forests were lower. Although we quantitatively defined current Basin old‐growth forests – in terms of stand structure – we realize that our definition will differ from that of both past and future old‐growth forests unless management protocols are changed.     

Elevation,Topography, and Edge Effects Drive Functional Composition of Woody Plant Species in Tropical Montane Forests

Tropical montane forests comprise heterogeneous environments along natural gradients of topography and elevation. Human‐induced edge effects further increase the environmental heterogeneity in these forests. The simultaneous effects of natural and human‐induced gradients on the functional diversity of plant leaf traits are poorly understood. In a tropical montane forest in Bolivia, we studied environmental gradients associated with elevation (from 1900 m to 2500 m asl), topography (ridge and gorge), and edge effects (forest edge vs. forest interior), and their relationship with leaf traits and resource‐use strategies. First, we investigated associations of environmental conditions (soil properties and microclimate) with six leaf traits, measured on 119 woody plant species. Second, we evaluated changes in functional composition with community‐weighted means and functional structure with multidimensional functional diversity indices (FRic, FEve and FDiv). We found significant associations between leaf traits and soil properties in accordance with the trade‐off between acquisition and conservation of resources. Functional composition of leaf traits shifted from the dominance of acquisitive species in habitats at low altitudes, gorges, and forest interior to the dominance of conservative species in habitats at high altitudes, ridges, and forest edges. Functional structure was only weakly associated with the environmental gradients. Natural and human‐induced environmental gradients, especially soil properties, are important for driving leaf traits and resource‐use strategies of woody plants. Nevertheless, weak associations between functional structure and environmental gradients suggest a high redundancy of functional leaf traits in this tropical montane forest.     

Potential Effects of Climate Change on the Water Level,Flora and Macro-fauna of a Large Neotropical Wetland

Possible consequences of climate change in one of the world’s largest wetlands (Ibera, Argentina) were analysed using a multi-scale approach. Climate projections coupled to hydrological models were used to analyse variability in wetland water level throughout the current century. Two potential scenarios of greenhouse gas emissions were explored, both resulting in an increase in the inter-annual fluctuations of the water level. In the scenario with higher emissions, projections also showed a long-term negative trend in water-level. To explore the possible response of biota to such water-level changes, species-area relationships of flora and aerial censuses of macro-fauna were analysed during an extraordinary dry period. Plant species richness at the basin scale was found to be highly resistant to hydrological changes, as the large dimension of the wetland acts to buffer against the water-level variations. However, local diversity decreased significantly with low water levels, leading to the loss of ecosystem resilience to additional stressors. The analysis of macro-fauna populations suggested that wetland provides refuge, in low water periods, for the animals with high dispersal ability (aquatic and migratory birds). On the contrary, the abundance of animals with low dispersal ability (mainly herbivorous species) was negatively impacted in low water periods, probably because they are required to search for alternative resources beyond the wetland borders. This period of resource scarcity was also related to increased mortality of large mammals (e.g. marsh deer) around water bodies with high anthropogenic enrichment and cyanobacteria dominance. The synergy between recurrent climatic fluctuations and additional stressors (i.e. biological invasions, eutrophication) presents an important challenge to the conservation of neotropical wetlands in the coming decades.     

气候变化对7种保护植物分布的潜在影响

利用CART（classification and regression tree,分类和回归树）模型,采用A2和B2气候变化情景,模拟分析了气候变化对桫椤（Alsophila spinulosa（wall.ex hook.）Tryon）、水青树（Tetracentron sinenseOliv）、十齿花（Dipentondon sinicus Dunn）、青檀（Pteroceltis tatarinowii Maxim）、桃儿七（Sinopodophyllum emodi（Wall.）Ying）、太白红杉（Larix chinensis Beissn）和山白树（Sinowilsonia henryi Hemsl）的分布范围及空间格局的可能影响。结果显示：在气候变化下,这些植物目前适宜分布范围将缩小,其中太白红杉、山白树和水青树减少幅度较大,十齿花和青檀次之,桫椤和桃儿七较小。就植物新适宜及总适宜分布范围,太白红杉和山白树从1991～2020年到2081～2100年时段呈现减少趋势,其它植物却呈现增加趋势。气候变化下,这些植物空间分布格局将发生较大改变,太白红杉将失去适宜分布范围,其它植物目前适宜分布区的西部、南部、西南、东部和东南部一些区域将不再适宜,新适宜分布区将主要向北部、东北部、西部、西南或西北部一些区域扩展。气候变化下,这些植物适宜分布范围与年均气温和降水量变化的相关性并不一致,一些植物适宜分布范围与年均气温和降水量变化相关系数并不显著（p〉0.05）;除了桫椤新适宜及总适宜、十齿花和桃儿七目前适宜分布范围与年均气温和年降水量变化回归关系较密切外,其它植物适宜分布范围与年均气温和年降水量变化的多元线性回归关系都较弱。这说明,在气候变化情况下,这些植物空间分布格局将发生改变,目前适宜分布范围缩小,除太白红杉和山白树外,其他几种植物新适宜范围扩大。     

气候变化对6种荒漠植物分布的潜在影响

分析气候变化对植物分布的影响,对保护生物多样性具有重要意义。利用CART(分类和回归树)模型及A2和B2情景,分析了气候变化对短叶假木贼(Anabasis brevifolia)、裸果木(Gymnocarpos przewalskii)、梭梭(Haloxylon ammoden-dron)、膜果麻黄(Ephedra przewalskii)、驼绒藜(Ceratoides latens)和喀什膜果麻黄(Ephedra przewalskii var.kaschgarica)分布范围及空间格局的影响。结果表明:气候变化下,这些植物目前适宜分布范围减小;从新适宜及总适宜分布范围而言,短叶假木贼和梭梭从1991-2020年到2051-2080年时段增加,之后减小,其它植物从1991-2020年到2081-2100年时段减小;喀什膜果麻黄和驼绒藜适宜分布范围减小并破碎化,其它植物向目前适宜分布的西部、西北部(或青海西南部)、昆仑山、阿尔金山和祁连山区扩展;除驼绒藜和喀什膜果麻黄与年均气温变化具显著相关性外,其它植物分布范围与年均气温和降水量变化的相关性较弱(P0.05),除驼绒藜、喀什膜果麻黄和裸果木目前分布范围与年均气温和降水量变化的回归关系较强外,其它植物分布范围与年均气温和年降水量变化多元线性回归关系较弱。上述研究结果表明,气候变化下,这些植物空间分布格局改变,目前分布范围减少,新适宜及总适宜分布范围近期增加,随着气候变化程度的增强,又逐渐减小。     

气候变化对6种荒漠植物分布的潜在影响

分析气候变化对植物分布的影响,对保护生物多样性具有重要意义。利用CART（分类和回归树）模型及A2和B2情景,分析了气候变化对短叶假木贼（Anabasis brevifolia）、裸果木（Gymnocarpos przewalskii）、梭梭（Haloxylon ammoden-dron）、膜果麻黄（Ephedra przewalskii）、驼绒藜（Ceratoides latens）和喀什膜果麻黄（Ephedra przewalskii var.kaschgarica）分布范围及空间格局的影响。结果表明：气候变化下,这些植物目前适宜分布范围减小;从新适宜及总适宜分布范围而言,短叶假木贼和梭梭从1991-2020年到2051-2080年时段增加,之后减小,其它植物从1991-2020年到2081-2100年时段减小;喀什膜果麻黄和驼绒藜适宜分布范围减小并破碎化,其它植物向目前适宜分布的西部、西北部（或青海西南部）、昆仑山、阿尔金山和祁连山区扩展;除驼绒藜和喀什膜果麻黄与年均气温变化具显著相关性外,其它植物分布范围与年均气温和降水量变化的相关性较弱（P〉0.05）,除驼绒藜、喀什膜果麻黄和裸果木目前分布范围与年均气温和降水量变化的回归关系较强外,其它植物分布范围与年均气温和年降水量变化多元线性回归关系较弱。上述研究结果表明,气候变化下,这些植物空间分布格局改变,目前分布范围减少,新适宜及总适宜分布范围近期增加,随着气候变化程度的增强,又逐渐减小。     

Effects of Climate Change and Shifts in Forest Composition on Forest Net Primary Production

Forests are dynamic in both structure and species composition, and these dynamics are strongly Influenced by climate.However, the net effects of future tree species composition on net primary production (NPP) are not well understood. The objective of this work was to model the potential range shifts of tree species (DISTRIB Model) and predict their impacts on NPP (PnET-Ⅱ Model) that will be associated with alterations in species composition. We selected four 200 × 200 km areas In Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-Ⅱ model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m2 per year. The effects of potential species redistributions on NPP were moderate (-12% to 8%) compared with the influence of future climatic changes (-60% to 25%). The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.     

Hydrological Response to Climate Change for Gilgel Abay River,in the Lake Tana Basin - Upper Blue Nile Basin of Ethiopia

Climate change is likely to have severe effects on water availability in Ethiopia. The aim of the present study was to assess the impact of climate change on the Gilgel Abay River, Upper Blue Nile Basin. The Statistical Downscaling Tool (SDSM) was used to downscale the HadCM3 (Hadley centre Climate Model 3) Global Circulation Model (GCM) scenario data into finer scale resolution. The Soil and Water Assessment Tool (SWAT) was set up, calibrated, and validated. SDSM downscaled climate outputs were used as an input to the SWAT model. The climate projection analysis was done by dividing the period 2010-2100 into three time windows with each 30 years of data. The period 1990-2001 was taken as the baseline period against which comparison was made. Results showed that annual mean precipitation may decrease in the first 30-year period but increase in the following two 30-year periods. The decrease in mean monthly precipitation may be as much as about -30% during 2010-2040 but the increase may be more than +30% in 2070-2100. The impact of climate change may cause a decrease in mean monthly flow volume between -40% to -50% during 2010-2040 but may increase by more than the double during 2070-2100. Climate change appears to have negligible effect on low flow conditions of the river. Seasonal mean flow volume, however, may increase by more than the double and +30% to +40% for the Belg (small rainy season) and Kiremit (main rainy season) periods, respectively. Overall, it appears that climate change will result in an annual increase in flow volume for the Gilgel Abay River. The increase in flow is likely to have considerable importance for local small scale irrigation activities. Moreover, it will help harnessing a significant amount of water for ongoing dam projects in the Gilgel Abay River Basin.