Habitat requirements for the conservation of wood cricket (Nemobius sylvestris) (Orthoptera: Gryllidae) on the Isle of Wight, UK

In the UK, wood cricket (Nemobius sylvestris) is a ‘Species of Conservation Concern’, being restricted to only three areas in southern England. Little information is available on the specific habitat requirements of this species. In 2006, a field investigation within three woodlands on the Isle of Wight was undertaken to identify its habitat preferences. Factors positively influencing wood cricket presence within woodlands included the presence of a well-developed leaf litter layer, relatively low ground vegetation cover and height, low canopy cover and relatively short distances between individual populations. Regression models identified the degree of isolation and variables describing vegetation structure as the main predictors for wood cricket presence within woodland fragments. The results of this study indicate the preference of wood cricket for open wooded edges. Conservation efforts for this species should focus on continuation of regular management activities aimed at providing permanent open edge habitat within woodlands, to maintain viable populations.     

Temporal instability in tree-growth/climate response in the Lower Bavarian Forest region: implications for dendroclimatic reconstruction

This paper explores the temporal stability of growth/climate relationships in ring-width chronologies of Norway spruce [ Picea abies (L.) Karst] and silver fir ( Abies alba Mill) in the Lower Bavarian Forest region in southern Germany. These chronologies were compiled, using both historic and living tree-ring data, with the main aim of developing a dendroclimatic reconstruction for the region covering the last 500 years. Moving window correlation analysis shows that prior to the twentieth century, both species co-vary in a similar way (1480–1899 mean r =0.66). There is no significant correlation between the species chronologies since ca. 1930, which partly reflects anomalous growth trends in the fir chronology since ca. 1960. Multiple regression analysis was utilised to assess the ability of both species chronologies to model March–August precipitation. The precipitation signal of the spruce data was found to be both stronger than the fir data (1872–1930 calibration: r ²=0.45 vs 0.25) and more time stable. After ca. 1930, the fir chronology loses it ability to model March–August precipitation until there is no climate signal at all in the fir data in recent decades. The spruce data also express a later weakening in their climate signal in the mid 1970s. We present compelling evidence indicating that the anomalous trends observed in the fir data, since the mid 1960s, appear to be predominantly related to local SO₂ emissions from power plants and refineries. It is also likely that this local anthropogenic forcing is the cause of the weakening of the climate signal in the spruce data since the mid 1970s. The conclusions from this study are: (1) The fir tree-ring data cannot be used for traditional dendroclimatic calibration, although prior to the twentieth century the decadal variability in the fir data is very similar to spruce and so these data could be used to extend potential reconstructions in the future; (2) The recent decline and recovery event in the fir data appears to be unique to the twentieth century and is not part of a natural episodic phenomenon; (3) Traditional dendroclimatic calibration of March–August precipitation will be made using solely the spruce ring-width data. However, due to SO₂ forcing in recent decades, the calibration period will be shortened to the 1871–1978 period.     

Using Citizen Science Data to Model the Distributions of Common Songbirds of Turkey Under Different Global Climatic Change Scenarios

In this study, we evaluated the potential impact of climate change on the distributions of Turkey’s songbirds in the 21st century by modelling future distributions of 20 resident and nine migratory species under two global climate change scenarios. We combined verified data from an ornithological citizen science initiative (www.kusbank.org) with maximum entropy modeling and eight bioclimatic variables to estimate species distributions and projections for future time periods. Model predictions for resident and migratory species showed high variability, with some species projected to lose and others projected to gain suitable habitat. Our study helps improve the understanding of the current and potential future distributions of Turkey’s songbirds and their responses to climate change, highlights effective strategies to maximize avian conservation efforts in the study region, and provides a model for using citizen science data for biodiversity research in a large developing country with few professional field biologists. Our results demonstrate that climate change will not affect every species equally in Turkey. Expected range reductions in some breeding species will increase the risk of local extinction, whereas others are likely to expand their ranges.     

The Pinus pinea L. woodlands along the coast of South-western Spain: data for a new geobotanical interpretation

The origin and natural range of the Stone pine (Pinus pinea L.) has been questioned for more than a century. In this work, we focus the investigation on one of the most important and controversial regions, viz., the Iberian Peninsula and, specifically, the Huelva and Cadiz populations in Andalusia, one of the most representative population cores. Although some authors maintain that it is an autochthonous Iberian species, most of them consider it to be exotic. From this idea, many works have been done and a sintaxonomic scheme has been created, which is accepted by the majority of the scientific community, not including Pinus pinea, nor its formations, since they are considered as man-induced forest crops. However, Stone has been present for several thousand years in the Iberian Peninsula and in the territory studied, as several paleobotanic and historical data show, proving that Pinus pinea is an autochthonous species of this region. This is a clear consequence to the field of geobotany, since – at least – the Stone pine woodlands from the Iberian Southeast must be considered as communities predominated by an autochthonous species that must be included in the sintaxonomichal schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Where can managers effectively resist climate-driven ecological transformation in pinyon–juniper woodlands of the US Southwest?

Pinyon–juniper (PJ) woodlands are an important component of dryland ecosystems across the US West and are potentially susceptible to ecological transformation. However, predicting woodland futures is complicated by species-specific strategies for persisting and reproducing under drought conditions, uncertainty in future climate, and limitations to inferring demographic rates from forest inventory data. Here, we leverage new demographic models to quantify how climate change is expected to alter population demographics in five PJ tree species in the US West and place our results in the context of a climate adaptation framework to resist, accept, or direct ecological transformation. Two of five study species, Pinus edulis and Juniperus monosperma, are projected to experience population declines, driven by both rising mortality and decreasing recruitment rates. These declines are reasonably consistent across various climate futures, and the magnitude of uncertainty in population growth due to future climate is less than uncertainty due to how demographic rates will respond to changing climate. We assess the effectiveness of management to reduce tree density and mitigate competition, and use the results to classify southwest woodlands into areas where transformation is (a) unlikely and can be passively resisted, (b) likely but may be resisted by active management, and (c) likely unavoidable, requiring managers to accept or direct the trajectory. Population declines are projected to promote ecological transformation in the warmer and drier PJ communities of the southwest, encompassing 37.1%–81.1% of our sites, depending on future climate scenarios. Less than 20% of sites expected to transform away from PJ have potential to retain existing tree composition by density reduction. Our results inform where this adaptation strategy could successfully resist ecological transformation in coming decades and allow for a portfolio design approach across the geographic range of PJ woodlands.     

黑龙江省未来气候生态与森林的作用研究

本文在扼要概述全球气候变化背景的基础上,根据近百年气候历史资料以及海温、太阳黑子活动、火山爆发、ＣＯ２浓度变化、Ｏ３浓度变化、大气环流指数特征等因子与我省气修变化的定量与定性关系,分析了各因子的综合影响,预测了我省未来十年气候变化趋势。结果表明：我省未来十年气候以温暖、干旱为主,年际间仍存有波动。虽然总的气候变化趋势与全球变化是一致的,但具有明显的区域特征。同时提出了气候变化可能对森林的影响,初步探讨了应采取的森林对策。     

Climate change and fire effects on a prairie–woodland ecotone: projecting species range shifts with a dynamic global vegetation model

Large shifts in species ranges have been predicted under future climate scenarios based primarily on niche‐based species distribution models. However, the mechanisms that would cause such shifts are uncertain. Natural and anthropogenic fires have shaped the distributions of many plant species, but their effects have seldom been included in future projections of species ranges. Here, we examine how the combination of climate and fire influence historical and future distributions of the ponderosa pine–prairie ecotone at the edge of the Black Hills in South Dakota, USA, as simulated by MC1, a dynamic global vegetation model that includes the effects of fire, climate, and atmospheric CO₂ concentration on vegetation dynamics. For this purpose, we parameterized MC1 for ponderosa pine in the Black Hills, designating the revised model as MC1‐WCNP. Results show that fire frequency, as affected by humidity and temperature, is central to the simulation of historical prairies in the warmer lowlands versus woodlands in the cooler, moister highlands. Based on three downscaled general circulation model climate projections for the 21st century, we simulate greater frequencies of natural fire throughout the area due to substantial warming and, for two of the climate projections, lower relative humidity. However, established ponderosa pine forests are relatively fire resistant, and areas that were initially wooded remained so over the 21st century for most of our future climate x fire management scenarios. This result contrasts with projections for ponderosa pine based on climatic niches, which suggest that its suitable habitat in the Black Hills will be greatly diminished by the middle of the 21st century. We hypothesize that the differences between the future predictions from these two approaches are due in part to the inclusion of fire effects in MC1, and we highlight the importance of accounting for fire as managed by humans in assessing both historical species distributions and future climate change effects.     

Conservation Status of North American Birds in the Face of Future Climate Change

Human-induced climate change is increasingly recognized as a fundamental driver of biological processes and patterns. Historic climate change is known to have caused shifts in the geographic ranges of many taxa and future climate change is expected to result in even greater redistributions of species. As a result, predicting the impact of climate change on future patterns of biodiversity will greatly aid conservation planning. Using the North American Breeding Bird Survey and Audubon Christmas Bird Count, two of the most comprehensive continental datasets of vertebrates in the world, and correlative distribution modeling, we assessed geographic range shifts for 588 North American bird species during both the breeding and non-breeding seasons under a range of future emission scenarios (SRES A2, A1B, B2) through the end of the century. Here we show that 314 species (53%) are projected to lose more than half of their current geographic range across three scenarios of climate change through the end of the century. For 126 species, loss occurs without concomitant range expansion; whereas for 188 species, loss is coupled with potential to colonize new replacement range. We found no strong associations between projected climate sensitivities and existing conservation prioritizations. Moreover, species responses were not clearly associated with habitat affinities, migration strategies, or climate change scenarios. Our results demonstrate the need to include climate sensitivity into current conservation planning and to develop adaptive management strategies that accommodate shrinking and shifting geographic ranges. The persistence of many North American birds will depend on their ability to colonize climatically suitable areas outside of current ranges and management actions that target climate adaptation.     

Risk of genetic maladaptation due to climate change in three major European tree species

Tree populations usually show adaptations to their local environments as a result of natural selection. As climates change, populations can become locally maladapted and decline in fitness. Evaluating the expected degree of genetic maladaptation due to climate change will allow forest managers to assess forest vulnerability, and develop strategies to preserve forest health and productivity. We studied potential genetic maladaptation to future climates in three major European tree species, Norway spruce (Picea abies), silver fir (Abies alba), and European beech (Fagus sylvatica). A common garden experiment was conducted to evaluate the quantitative genetic variation in growth and phenology of seedlings from 77 to 92 native populations of each species from across Switzerland. We used multivariate genecological models to associate population variation with past seed source climates, and to estimate relative risk of maladaptation to current and future climates based on key phenotypic traits and three regional climate projections within the A1B scenario. Current risks from climate change were similar to average risks from current seed transfer practices. For all three climate models, future risks increased in spruce and beech until the end of the century, but remained low in fir. Largest average risks associated with climate projections for the period 2061–2090 were found for spruce seedling height (0.64), and for beech bud break and leaf senescence (0.52 and 0.46). Future risks for spruce were high across Switzerland. However, areas of high risk were also found in drought‐prone regions for beech and in the southern Alps for fir. Genetic maladaptation to future climates is likely to become a problem for spruce and beech by the end of this century, but probably not for fir. Consequently, forest management strategies should be adjusted in the study area for spruce and beech to maintain productive and healthy forests in the future.     

Potential risks for European beech (Fagus sylvatica L.) in a changing climate

Over large areas of Europe, coniferous monocultures are being transformed into mixed forests by the re-introduction of broadleaf tree species belonging to the potential natural vegetation. One important species of interest in this changing forest policy is European beech (Fagus sylvatica). However, at present, this forest management directive has ignored potential adverse effects of global climate change on wide-spread re-introduction of beech to these areas. Average global surface temperatures have risen by approx. 0.8°C in the period between 1861 and 2005 and are expected to continue to increase until the end of this century by 1.5–5.8°C above the 1990 value. To estimate the climate change in the southern part of central Europe in future, we reviewed calculations from regional climate models. Temperature increase for the southern part of central Europe is projected to be up to 2°C within the next 40 years. In contrast, the annual precipitation will most likely remain constant over the same time period, but will experience significant changes in seasonal patterns. Rising intensities of individual precipitation events may result in increasing number and intensities of flooding events and reduced precipitation during the growing season in a higher frequency of summer droughts. Growth and competitive ability of European beech will not, necessarily, respond to increasing CO₂ concentrations but may be strongly impacted by intensive drought that occurs during the growing season. Seedlings as well as adult trees may suffer from xylem embolism, restricted nutrient uptake capacity and reduced growth under limited water availability. However, it remains uncertain to what extent other environmental factors (e.g. soil properties, competitive interactions) may modify the drought response of beech, thus either enhancing susceptibility or increasing drought tolerance and resilience potential. Water-logged soils, predicted during the spring for several regions due to higher than average precipitation, could negatively impact nutrient uptake and growth of beech. Whereas other dominant species as, e.g. oak are well adapted to that environmental stress, beech is known to be sensitive to water-logging and flooding. Thus, the competitive capacity of beech might—depending on the other environmental conditions—be reduced under the expected future climate conditions. Silvicultural practices must be aware today of the potential risks which a changing climate may impose on sustainable forest development.     

A Plague on Your House? Some Impacts of Chromolaena odorata on Timorese Livelihoods

Following its introduction on the island of Timor, the shrub Chromolaena odorata has expanded dramatically across the landscape. A highly flammable but fire tolerant plant species, Chromolaena is an extremely successful plant coloniser of disturbed ground and open savanna woodlands. For Timorese semisubsistence agriculturalists, Chromolaena odorata represents the most recent in a long history of invasive weed species that have periodically covered their lands and challenged their ability to farm and prosper. Already its impact is being felt in a number of domains of socioeconomic life. This paper explores some of these issues and the prospects for future management and control strategies.     

The forests and woodlands of Labrador, Canada: ecology, distribution and future management

Labrador, Canada is the last relatively undeveloped landmass of Boreal and subarctic Canada. Its land area is over 288,000 km², with less than 1% developed, and a human population of below 30,000. Labrador is greater than 60% forest- and woodland-covered and over 30% tundra, soil and rock barrens. We review the ecology and distribution of forests, woodlands, and related vegetation of Labrador within the context of climate, forest site index, landform, soils, and disturbance. Recent ecosystem management through a public planning process with emphasis on past and future comanagement and development with traditional and western scientific principles is currently underway. Plant–animal interactions, traditional uses by aboriginal groups, and early history are also reviewed.     

Seasonality matters—The effects of past and projected seasonal climate change on the growth of native and exotic conifer species in Central Europe

Norway spruce is one of the economically most important tree species in Central European forestry. However, its high susceptibility to droughts poses a strong challenge to its cultivation under future conditions with likely more frequent and prolonged droughts and shifts in the seasonal climate. To compensate for expected losses of forest areas suitable for the cultivation of spruce, more drought-tolerant species are required. Silver fir and Douglas fir are two potential candidates, which promise lower drought susceptibility and equal or even higher yield when compared to Norway spruce.Using the Black Forest as a regional case study, we assessed the effects of seasonal climate change, including drought stress, on tree-ring width formation of these three economically relevant conifer species over the last 60 years. In addition, we projected potential species-specific growth changes under different climate change scenarios until 2100.Our results suggest that both silver fir and Douglas fir will possibly experience growth increases in a warmer future climate, as predicted under the 4.5 and 8.5 Representative Concentration Pathway (RCP) climate change scenarios, whereas growth of spruce is expected to decline. Moreover, drought susceptibility in silver fir and Douglas fir is lower than in spruce, as shown for past drought events, and their ability to benefit from milder winters and springs could play a major role in their capacity to compensate for drier summers in the near to mid-term future. This study highlights the need to advance our understanding of the processes that drive drought resistance and resilience in tree species to guide management strategies in the face of climate change.     

A Second Look at Mitochondrial DNA Variability in European Anchovy (Engraulis encrasicolus): Assessing Models of Population Structure and the Black Sea Isolation Hypothesis

Genetic architectures of marine fishes are generally shallow because of the large potential for gene flow in the sea. European anchovy, however, are unusual among small pelagic fishes in showing large differences among sub-basins and in harbouring two mtDNA phylogroups (‘A’ & ‘B’), representing 1.1–1.85 million years of separation. Here the mtDNA RFLP dataset of Magoulas et al. [1996, Mol. Biol. Evol. 13: 178–190] is re-examined to assess population models accounting for this subdivided population structure and to evaluate the zoogeographical origins of the two major phylogroups. Haplotype and nucleotide diversities are highest in the Ionian Sea and lowest in the Aegean and Black seas. However, this gradient is absent when ‘A’ and ‘B’ haplotypes are examined separately. Neither the self-sustaining nor the basin population models adequately describe anchovy population behaviour. Tests for neutrality, mismatch and nested clade analyses are concordant in depicting recent expansions of both phylogroups. Unimodel mismatch distributions and haplotype coalescences dating to the last (Eemian) interglacial (‘B’) and the Weichselian pleniglacial period (‘A’) indicate separate colonizations of the Mediterranean Basin. Phylogroup ‘A’ is unlikely to have arisen through continuous long-term isolation in the Black Sea because of climate extremes from displaced subpolar weather systems during the ice ages. Ancestors of both groups appear to have colonized the Mediterranean from the Atlantic in the late Pleistocene. Hence, zoogeographic models of anchovy in the Mediterranean must also include the eastern (and possibly southern) Atlantic.     

Bird community variation across <Emphasis Type="Italic">Polylepis</Emphasis> woodland fragments and matrix habitats: implications for biodiversity conservation within a high Andean landscape

The scattered and dwindling Polylepis woodlands of the high Andean global hotspot have been identified as being of particular importance to biodiversity conservation, and yet little is known of the make-up of their faunal communities, how these vary across landscapes, and how well species might tolerate matrix/edge habitats. We examined the bird communities and vegetation characteristics of Polylepis woodlands and the surrounding matrix habitats at three sites in the Cordillera Vilcanota, southern Perú (3,400–4,500 m). The vegetation structure of woodlands varied significantly across the three sites but all were dominated by two Polylepis tree species, with mossy ground cover. Matrix habitats were treeless and dominated by ground-level puna grass-steppe or boulder scree vegetation. Bird species richness and diversity, encounter rates and the number of globally-threatened and restricted-range bird species were consistently higher in the Polylepis forests, than in matrix habitat. We used canonical correspondence analysis (CCA) to identify habitat gradients across the landscape, and to classify bird species according to their association with Polylepis, the matrix or Polylepis-matrix interface. There were few matrix-restricted bird species, but around half the bird community, including fourteen threatened or restricted-range species, were Polylepis-dependant. Many of these species had very narrow niches. The Polylepis-matrix interface was dominated by species traditionally considered invasive ecological generalists. Our study illustrates the overriding importance of Polylepis interior habitats, indicating that conservation strategies for high Andean birds must focus on patch size maintenance/enlargement, enhancement of within-patch habitat quality, and efforts to safeguard connectivity of suitable habitat across what is essentially an inhospitable puna/scree matrix.     

Vulnerability of mires under climate change: implications for nature conservation and climate change adaptation

Wetlands in general and mires in particular belong to the most important terrestrial carbon stocks globally. Mires (i.e. bogs, transition bogs and fens) are assumed to be especially vulnerable to climate change because they depend on specific, namely cool and humid, climatic conditions. In this paper, we use distribution data of the nine mire types to be found in Austria and habitat distribution models for four IPCC scenarios to evaluate climate change induced risks for mire ecosystems within the 21st century. We found that climatic factors substantially contribute to explain the current distribution of all nine Austrian mire ecosystem types. Summer temperature proved to be the most important predictor for the majority of mire ecosystems. Precipitation—mostly spring and summer precipitation sums—was influential for some mire ecosystem types which depend partly or entirely on ground water supply (e.g. fens). We found severe climate change induced risks for all mire ecosystems, with rain-fed bog ecosystems being most threatened. Differences between scenarios are moderate for the mid-21st century, but become more pronounced towards the end of the 21st century, with near total loss of climate space projected for some ecosystem types (bogs, quagmires) under severe climate change. Our results imply that even under minimum expected, i.e. inevitable climate change, climatic risks for mires in Austria will be considerable. Nevertheless, the pronounced differences in projected habitat loss between moderate and severe climate change scenarios indicate that limiting future warming will likely contribute to enhance long-term survival of mire ecosystems, and to reduce future greenhouse gas emissions from decomposing peat. Effectively stopping and reversing the deterioration of mire ecosystems caused by conventional threats can be regarded as a contribution to climate change mitigation. Because hydrologically intact mires are more resilient to climatic changes, this would also maintain the nature conservation value of mires, and help to reduce the severe climatic risks to which most Austrian mire ecosystems may be exposed in the 2nd half of the 21st century according to IPCC scenarios.     

水菜花种群潜在生境选择与空间格局预测

国家二级保护野生植物水菜花(Ottelia cordata)，喜生于清洁的水环境中，对环境变化极为敏感，是检验湿地环境及气候变化的关键指示物种之一，在我国仅零星分布于海南北部的火山熔岩湿地区，生存状况不容乐观。研究水菜花种群潜在生境选择及其空间格局演变，有利于加强濒危物种保护保育及湿地生态系统修复、管理。该研究基于GIS平台和MaxEnt模型，结合气候、地形和土壤因子，探究水菜花种群环境限制因子及其在气候变化背景下潜在适宜生境的演变格局。结果表明，水菜花种群对温差与降水量变化敏感，等温性、最冷季度降水量、土壤类型和年均降水量对水菜花种群分布影响显著；全新世中期-当前-2070年气候变化背景下，水菜花适宜生境面积先减小后增大，分布重心呈西南-东北-西南转移格局；未来气候情景下，水菜花种群高度和中度适宜生境缩减，低适宜生境增加，南部地区将出现新增适宜生境，东北、西北及西南部适宜生境将发生消减。该研究从气候环境角度论证了水菜花种群的潜在生境选择及空间变化特征，可为濒危物种保护保育、湿地管理及其生物多样性维护工作提供参考和指导。     

Plans for a large regional forest in eastern Flanders (Belgium): assessment of spider diversity and community structure in the current forest remnants

The absence of large forests and the importance of natural elements for the welfare and health of people, made the Flemish government and the province of eastern Flanders, Belgium, investigate the establishment of one large regional forest out of existing forest remnants. After several studies, the location Makegem forests–Aelmoeseneiebos was withheld for future forest expansion. In this study, the spider fauna of five forest remnants from that region was sampled and differences and congruencies in spider diversity and community structure of these fragments were assessed. Our results show that (1) considering the limited forest areas and high degree of fragmentation, the overall observed spider diversity was high, but half of the spiders were non-forest species, (2) half of the encountered Red list species were restricted to only one of the studied woodlands and creating one large forest may be vital for their conservation, (3) diversity–rarefaction curves were higher for the more humid than for the dryer forest sites, and (4) dissimilarities between spider communities are mostly caused by historical factors and humidity and are therefore also linked with the properties of the litter layer and main tree species. We conclude that an expansion of the existing forest remnants will likely maintain or even improve the richness of the spider faunas. Because sufficiently large suitable habitats will develop, several (critical) species may be saved. This is, however, only possible if the characteristic properties of the forests are preserved.     

Patterns and ecological consequences of abiotic heterogeneity in managed cork oak forests of Southern Spain

Spatial heterogeneity of abiotic factors influences the structure and function of forests and must be taken into account for their conservation and sustainable management. In this study, we evaluate the heterogeneity of abiotic environmental variables in managed cork oak (Quercus suber L.) forests in southern Spain at patch, site and regional scales. The extent of spatial heterogeneity depended on the environmental variable examined and the scale considered. For example, soil Mn and P and light availability in the understorey were very heterogeneous at the regional scale, while soil N had low regional heterogeneity, but high spatial variability, at patch scale, attributed to open overstorey and grazing disturbance. There was a general trend of increasing heterogeneity with spatial scale. We also study the effects of a silvicultural practice—shrub clearing on the forest environment and its consequence for spatial heterogeneity. Shrub clearing increased understorey light and decreased its spatial heterogeneity with idiosyncratic effects on soil properties and their spatial heterogeneity at each site. Finally, we compare the heterogeneity (estimated by the coefficient of variation) obtained in these cork oak forests with a database compiled from published studies on other forest environments. The comparison revealed a remarkable extent of abiotic heterogeneity in the cork oak forests studied, suggesting that a sustainable management of these forests should combine intrinsic and human induced abiotic heterogeneity to preserve crucial ecological processes and to maintain high levels of biodiversity.     

Methionine oxidation: Implications for the mechanism of toxicity of the β-amyloid peptide from Alzheimer's disease

Summary The amyloid β-peptide, Aβ is toxic to neurons and this toxicity plays a central role in the progression of Alzheimer's disease. The mechanism(s) by which Aβ exerts its toxicity has been hotly debated with several theories postulated. Here we discuss the role of oxidation of the sulfur atom of Met35 in Aβ42 (Met(O)Aβ), a modification that has significant implications for the mechanism of Aβ toxicity. Both Met(O)Aβ and its native form display toxicity to primary neuronal cells in culture which can be rescued by catalase, a H₂O₂ inhibitor and clioquinol a mild copper chelator. However both native Aβ and Met(O)Aβ differ substantially in primary and secondary structures, solubility, ability to penetrate lipid membranes, and oligomerization profiles. It is clearly evident that metals play an important role in the oxidation of Aβ to Met(O)Aβ via Fenton chemistry and that regulation of this pathway has a potential therapeutic application for the regulation of Alzheimer's disease.