Effects Of Extreme Climatic Events Research Articles

Knocking back invasions: variable resistance and resilience to multiple cold spells in native vs. nonnative fishes

AbstractExtreme climate events can interact synergistically with invasions to dramatically alter ecosystem structure, function, and services. Yet, the effects of extreme climate events on species invasions remain unresolved. Extreme climate events may increase resources and decrease biotic resistance by causing physiological stress and/or mortality of native taxa, resulting in invasion opportunities for nonnative species. Alternatively, extreme climate events may regulate nonnative populations, preventing them from achieving dominance. We examined whether a sequence of three cold spells had a negative or positive effect on fish invasions in the coastal Everglades. We compared resistance (initial effects) and resilience (rate of recovery) to the cold spells between native fishes and the dominant nonnative invader, the Mayan cichlid, across eight populations expanding two mangroves drainages in the southern Everglades. We tracked native fish and nonnative Mayan cichlid populations for 10 yr including 3 yr pre‐ and 4 yr post‐cold spells. In both drainages, native fishes were more resistant to the cold spells than the nonnative species. While native fishes experienced declines at only one site, nonnative Mayan numbers were reduced by 90–100% across six sites where they were abundant pre‐disturbances. Four years after the last cold spell, we saw limited resilience in the affected nonnative populations. Only one of the six affected sites fully recovered, whereas the other five sites showed no recovery in Mayan cichlid numbers. The recovered site was closest to a canal, known to act as thermal refuges for nonnative fishes. In summary, cold spells can reduce nonnative abundances, but whether cold spells can effectively knock back invasions (and range expansions) by tropical/subtropical nonnative species will depend on how the frequency and severity of cold spells are affected by climate change. We propose that these mortality‐causing extreme events could provide rare management opportunities late in an invasion.

The relative contribution of climate to changes in lesser prairie‐chicken abundance

AbstractManaging for species using current weather patterns fails to incorporate the uncertainty associated with future climatic conditions; without incorporating potential changes in climate into conservation strategies, management and conservation efforts may fall short or waste valuable resources. Understanding the effects of climate change on species in the Great Plains of North America is especially important, as this region is projected to experience an increased magnitude of climate change. Of particular ecological and conservation interest is the lesser prairie‐chicken (Tympanuchus pallidicinctus), which was listed as “threatened” under the U.S. Endangered Species Act in May 2014. We used Bayesian hierarchical models to quantify the effects of extreme climatic events (extreme values of the Palmer Drought Severity Index [PDSI]) relative to intermediate (changes in El Niño Southern Oscillation) and long‐term climate variability (changes in the Pacific Decadal Oscillation) on trends in lesser prairie‐chicken abundance from 1981 to 2014. Our results indicate that lesser prairie‐chicken abundance on leks responded to environmental conditions of the year previous by positively responding to wet springs (high PDSI) and negatively to years with hot, dry summers (low PDSI), but had little response to variation in the El Niño Southern Oscillation and the Pacific Decadal Oscillation. Additionally, greater variation in abundance on leks was explained by variation in site relative to broad‐scale climatic indices. Consequently, lesser prairie‐chicken abundance on leks in Kansas is more strongly influenced by extreme drought events during summer than other climatic conditions, which may have negative consequences for the population as drought conditions intensify throughout the Great Plains.

Facing complexity in tropical conservation: how reduced impact logging and climatic extremes affect beta diversity in tropical amphibian assemblages

AbstractBiodiversity in pristine forest biomes is increasingly disturbed by human activity. Drivers such as logging and climate extremes are thought to collectively erode diversity, but their interactions are not well understood. However, ignoring such complexities may result in poor conservation management decisions. Here, we present the first study dealing with the complexity arising from the effects of interactions of two increasingly important disturbance factors (selective logging and climatic extreme events) on beta diversity patterns at different scales. Specifically, we examined extensive amphibian assemblage datasets obtained within a quasi‐experimental pre‐/post‐harvesting scheme in the lowland rainforests of Central Guyana. Changes in small‐scale patterns of beta diversity were not detectable at the higher landscape level, indicating that local‐scale dynamics are more informative for evaluating disturbance impacts. The results also underscore the importance of including abundance data when investigating homogenization or heterogenization effects, which should be considered when designing post‐logging impact assessments and selecting impact indicators. Moreover, logging should be regarded as a multifaceted driver that contributes to changes in biodiversity patterns in different ways, depending on interactions with other drivers. The effects of extreme climate events were significantly more pronounced in unlogged forest, while logged forest assemblages appeared buffered due to the presence of novel habitats. Imprudent post‐logging renaturation measures may thus counteract conservation targets. These findings highlight the fact that indicator bias and unaccounted interactions between multiple drivers can lead to misguided management strategies.

The Effect of Extreme Climatic Events on Extreme Runoff in the Past 50 Years in the Manas River Basin, Xinjiang, China

To analyze extreme climatic change features and effects on runoff in the Manas River basin, Xinjiang, data were collected including daily mean temperature, daily highest and lowest temperatures, and daily precipitation from six meteorological stations in the Manas River basin as well as daily runoff data from the Kensiwate hydrologic stations during 1960-2010. By adopting the threshold value of extreme climatic events defined by ET ALDDMI and with the aid of nonparametric statistical tests, Pearson III methods, and others, the effect of extreme climatic events on extreme runoff in the past 50 years in the Manas River basin, Xinjiang, was analyzed. The results showed that in the past 50 years, 1) extreme warming events (annual extreme maximum temperature, warm-day and warm-night index) have risen significantly (P < 0.05). Among these the warm-day and warm-night indices decreased abruptly in 2001 and 1996, respectively. With respect to extreme cold events (annual extreme minimum temperature, cold-day and cold-night indices), the extreme minimum temperature was high after 1976, and the cold-day index weakened significantly, similar to the cold-night index. 2) Except for the continuous drought days (CDD), the other five indices of extreme precipitation events appeared to trend upward, with an abrupt change around 1993. 3) Flood events in 1990, mostly in summer, accounted for 42.9% of the total number of floods since 1960. Floods increased mainly because extremely high summer temperatures increased snowmelt, increasing inflow to the rivers, which combined with more precipitation to cause the increase in summer peak flood discharge.

Riparian tree cover enhances the resistance and stability of woodland bird communities during an extreme climatic event

Summary Ecosystems world‐wide increasingly are subject to multiple interacting disturbances. Biodiversity in anthropogenic landscapes can be enhanced by manipulating landscape patterns, but could such landscape management also assist biota to cope with the effects of extreme climatic events, such as drought? We surveyed woodland bird communities in 24 ‘whole’ landscapes (each 100 km2) in an agricultural region of south‐eastern Australia near the beginning (2002–2003), middle (2006–2007) and after (2011–2012) an extreme drought (the ‘Millennium Drought’). We quantified the resistance, resilience and stability of the avifauna to the decade of drought and related these measures to properties of the study landscapes: the extent of wooded habitat, configuration of habitat, land‐use composition, landscape productivity and geographic context. Landscape productivity, represented by the extent of riparian tree cover in the landscape, was the strongest driver of the resistance, resilience and stability of avifaunal richness to severe drought. Woodland bird communities in landscapes with larger areas of riparian tree cover retained a larger proportion of their species richness during the Millennium Drought and consequently had greater stability over the drought's duration. Synthesis and applications. Landscape properties can influence the resistance, resilience and stability of faunal communities to an extreme climatic event. By protecting, restoring and enhancing native vegetation in productive areas of landscapes along stream systems, drainage lines and floodplains, land managers can effectively build climatic refugia and thereby enhance the resistance of biota to climatic extremes. However, a net decline over the entire study period suggests this will not, by itself, arrest decline during periods of extreme drought.

Phytoremediation of salt-affected soils: a review of processes, applicability, and the impact of climate change.

Soil salinization affects 1-10 billion ha worldwide, threatening the agricultural production needed to feed the ever increasing world population. Phytoremediation may be a cost-effective option for the remediation of these soils. This review analyzes the viability of using phytoremediation for salt-affected soils and explores the remedial mechanisms involved. In addition, it specifically addresses the debate over plant indirect (via soil cation exchange enhancement) or direct (via uptake) role in salt remediation. Analysis of experimental data for electrical conductivity (ECe) + sodium adsorption ratio (SAR) reduction and plant salt uptake showed a similar removal efficiency between salt phytoremediation and other treatment options, with the added potential for phytoextraction under non-leaching conditions. A focus is also given on recent studies that indicate potential pathways for increased salt phytoextraction, co-treatment with other contaminants, and phytoremediation applicability for salt flow control. Finally, this work also details the predicted effects of climate change on soil salinization and on treatment options. The synergetic effects of extreme climate events and salinization are a challenging obstacle for future phytoremediation applications, which will require additional and multi-disciplinary research efforts.

Ecological effects of extreme climatic events on riverine ecosystems: insights from Australia

Summary Climate extremes and their physical impacts – including droughts, fires, floods, heat waves, storm surges and tropical cyclones – are important structuring forces in riverine ecosystems. Climate change is expected to increase the future occurrence of extremes, with potentially devastating effects on rivers and streams. We synthesise knowledge of extremes and their impacts on riverine ecosystems in Australia, a country for which projected changes in event characteristics reflect global trends. Hydrologic extremes play a major structuring role in river ecology across Australia. Droughts alter water quality and reduce habitat availability, driving organisms to refugia. Extreme floods increase hydrological connectivity and trigger booms in productivity, but can also alter channel morphology and cause disturbances such as hypoxic blackwater events. Tropical cyclones and post‐cyclonic floods damage riparian vegetation, erode stream banks and alter water quality. Cyclone‐induced delivery of large woody debris provides important instream habitat, although the wider ecological consequences of tropical cyclones are uncertain. Wildfires destroy catchment vegetation and expose soils, increasing inputs of fine sediment and nutrients to streams, particularly when followed by heavy rains. Research on the impacts of heat waves and storm surges is scarce, but data on temperature and salinity tolerances, respectively, may provide some insight into ecological responses. We identify research gaps and hypotheses to guide future research on the ecology of extreme climate events in Australia and beyond. A range of phenomenological, experimental and modelling approaches is needed to develop a mechanistic understanding of the ecological impact of extreme events and inform prediction of responses to future change.

Effects of extreme climate events on tea (Camellia sinensis) functional quality validate indigenous farmer knowledge and sensory preferences in tropical China.

Climate change is impacting agro-ecosystems, crops, and farmer livelihoods in communities worldwide. While it is well understood that more frequent and intense climate events in many areas are resulting in a decline in crop yields, the impact on crop quality is less acknowledged, yet it is critical for food systems that benefit both farmers and consumers through high-quality products. This study examines tea (Camellia sinensis; Theaceae), the world's most widely consumed beverage after water, as a study system to measure effects of seasonal precipitation variability on crop functional quality and associated farmer knowledge, preferences, and livelihoods. Sampling was conducted in a major tea producing area of China during an extreme drought through the onset of the East Asian Monsoon in order to capture effects of extreme climate events that are likely to become more frequent with climate change. Compared to the spring drought, tea growth during the monsoon period was up to 50% higher. Concurrently, concentrations of catechin and methylxanthine secondary metabolites, major compounds that determine tea functional quality, were up to 50% lower during the monsoon while total phenolic concentrations and antioxidant activity increased. The inverse relationship between tea growth and concentrations of individual secondary metabolites suggests a dilution effect of precipitation on tea quality. The decrease in concentrations of tea secondary metabolites was accompanied by reduced farmer preference on the basis of sensory characteristics as well as a decline of up to 50% in household income from tea sales. Farmer surveys indicate a high degree of agreement regarding climate patterns and the effects of precipitation on tea yields and quality. Extrapolating findings from this seasonal study to long-term climate scenario projections suggests that farmers and consumers face variable implications with forecasted precipitation scenarios and calls for research on management practices to facilitate climate adaptation for sustainable crop production.

Households’ Coping Strategies in Drought- and Flood-Prone Communities in Northern Ghana

This study seeks to explore stakeholders’ perceptions, causes, and effects of extreme climatic events, such as droughts and floods, in the Wa West District of Ghana’s Upper West Region. A multi-stage sampling procedure is used to select 184 respondents. Data collection methods include individual questionnaire administration, focus group discussions, and a stakeholders’ forum in the Wa West District Assembly. While frequencies are used to show respondents’ perceptions of the severity of climate change effects, a treatmenteffect model is used to determine the factors influencing farmers’ choices of on-farm coping strategies over off-farm activities in both periods of drought and flood. Findings are the following: farmers perceive that climate change is real and has severe consequences. Consequently, they resort to both on-farm and off-farm strategies to cope with the effects of climate change. While men mostly adopt the former, women adopt the latter. Both strategies are, however, not viable for taking them out of poverty, though offfarm activities are more effective. Education and extension services are other important factors influencing the choice of coping strategies as well as farmers’ welfare. Farmers must be supported with more viable income-earning activities, ones that can take them out of poverty. Women should be given priority. Access to education and extension services must also be stepped up to facilitate the adoption of the coping strategies and to increase welfare.

Combined Effects of Extreme Climatic Events and Elevation on Nutritional Quality and Herbivory of Alpine Plants

Climatic extreme events can cause the shift or disruption of plant-insect interactions due to altered plant quality, e.g. leaf carbon to nitrogen ratios, and phenology. However, the response of plant-herbivore interactions to extreme events and climatic gradients has been rarely studied, although climatic extremes will increase in frequency and intensity in the future and insect herbivores represent a highly diverse and functionally important group. We set up a replicated climate change experiment along elevational gradients in the German Alps to study the responses of three plant guilds and their herbivory by insects to extreme events (extreme drought, advanced and delayed snowmelt) versus control plots under different climatic conditions on 15 grassland sites. Our results indicate that elevational shifts in CN (carbon to nitrogen) ratios and herbivory depend on plant guild and season. CN ratios increased with altitude for grasses, but decreased for legumes and other forbs. In contrast to our hypotheses, extreme climatic events did not significantly affect CN ratios and herbivory. Thus, our study indicates that nutritional quality of plants and antagonistic interactions with insect herbivores are robust against seasonal climatic extremes. Across the three functional plant guilds, herbivory increased with nitrogen concentrations. Further, increased CN ratios indicate a reduction in nutritional plant quality with advancing season. Although our results revealed no direct effects of extreme climatic events, the opposing responses of plant guilds along elevation imply that competitive interactions within plant communities might change under future climates, with unknown consequences for plant-herbivore interactions and plant community composition.

Spatial variation in photosynthetic recovery of intertidal turf algae from acute UVB and temperature stress associated with low tides along the central coast of Chile

Ecological consequences of punctuated, extreme climate events depend largely upon species' physiological capacity to tolerate and recover from such stressful events. However, physiological responses of intertidal organisms to repetitive exposure to severe conditions using natural patterns are rarely explored, and we know little about how physiological sensitivity within a species varies over local scales or among natural populations, making it difficult to extrapolate results to the naturally variable environmental conditions encountered in the field. Here, we simulate realistic scenarios of the exposure of the turf-forming alga (Gelidium chilense) to atmospheric stressors (UVB and temperature) associated with natural mild or harsh weather conditions that occur when summertime midday low tides coincide with unusually calm seas and particularly warm, sunny days along the central Chilean coast. We show that sudden, short-term exposure to artificial UVB radiation during daytime low tides represents a strong stress factor for Gelidium turf algae as measured by the changes in maximal photosynthetic quantum yield (Fv/Fm), and repetitive exposure over a period of 5d, as it occurs naturally during spring–summer days, can critically compromise the ability of the fronds to recover once the stressor is removed. In contrast, while increased aerial temperature had important effects on the photosynthetic system, this source of stress had no lasting effects on the fronds' capacity to recover, nor did it modify the UVB effects on photosynthesis (i.e. no synergistic effects between these common stressors). The ability of Gelidium turf to recover from UVB-induced damage to the photosynthetic apparatus differed between tidal heights and among populations from different sites along the central coast. These results suggest that for many shore communities, abrupt, unpredictable short-term stress events will have greater consequences lower on the shore. We found no evidence that greater upwelling intensity and associated nutrient enrichment of coastal waters could consistently ameliorate recovery from the negative effects of UVB. The complex spatial variation in the turf's ability to recover rapidly from a stress event may alter predictions regarding the effects of extreme climate events and/or climate change on species interactions and species' geographic distribution.

Impacts on Coralligenous Outcrop Biodiversity of a Dramatic Coastal Storm

Extreme events are rare, stochastic perturbations that can cause abrupt and dramatic ecological change within a short period of time relative to the lifespan of organisms. Studies over time provide exceptional opportunities to detect the effects of extreme climatic events and to measure their impacts by quantifying rates of change at population and community levels. In this study, we show how an extreme storm event affected the dynamics of benthic coralligenous outcrops in the NW Mediterranean Sea using data acquired before (2006–2008) and after the impact (2009–2010) at four different sites. Storms of comparable severity have been documented to occur occasionally within periods of 50 years in the Mediterranean Sea. We assessed the effects derived from the storm comparing changes in benthic community composition at sites exposed to and sheltered from this extreme event. The sites analyzed showed different damage from severe to negligible. The most exposed and impacted site experienced a major shift immediately after the storm, represented by changes in the species richness and beta diversity of benthic species. This site also showed higher compositional variability immediately after the storm and over the following year. The loss of cover of benthic species resulted between 22% and 58%. The damage across these species (e.g. calcareous algae, sponges, anthozoans, bryozoans, tunicates) was uneven, and those with fragile forms were the most impacted, showing cover losses up to 50 to 100%. Interestingly, small patches survived after the storm and began to grow slightly during the following year. In contrast, sheltered sites showed no significant changes in all the studied parameters, indicating no variations due to the storm. This study provides new insights into the responses to large and rare extreme events of Mediterranean communities with low dynamics and long-lived species, which are among the most threatened by the effects of global change.

Effects of simulated heat waves on an experimental plant–herbivore–predator food chain

Greater climatic variability and extreme climatic events are currently emerging as two of the most important facets of climate change. Predicting the effects of extreme climatic events, such as heat waves, is a major challenge because they may affect both organisms and trophic interactions, leading to complex responses at the community level. In this study, we set up a simple three-level food chain composed of a sweet pepper plant, Capsicum annuum; an aphid, Myzus persicae; and a ladybeetle, Coleomegilla maculata, to explore the consequences of simulated heat waves on organism performance, trophic interactions, and population dynamics. We found that (1) heat waves do not affect plant biomass, significantly reduce the abundance and fecundity of aphids, and slightly affect ladybeetle developmental time and biomass, (2) heat waves decrease the impact of ladybeetles on aphid populations but do not modify the effect of aphids on plant biomass, and (3) food chains including predatory ladybeetles are more resistant to heat waves than a simple plant-aphid association, with aphid abundance being less influenced by heat waves in the presence of C.maculata. Our results suggest that more biodiverse ecosystems with predators exerting a strong biotic control are likely to be less influenced by abiotic factors and then more resistant to extreme climatic events than impoverished ecosystems lacking predators. Our study emphasizes the importance of assessing the effects of climatic change on each trophic level as well as on trophic interactions to further our understanding of the stability, resilience, and resistance of ecological communities under climatic forcing.

Climate justice: framing a new discourse in Brazil

In this article, we evaluate to what extent the Climate Justice discourse has been associated by the press to extreme climate events in Brazil. The text is based on the examination of articles published by important newspapers in Rio de Janeiro and São Paulo, after two major rain events which produced floods and landslides in these two cities. Based on these findings, we suggest that the adoption of the Climate Change discourse in Brazil could produce three main positive outcomes: improve the discourse's acceptance in the international arena, increase the chances that the claims of affected groups are heard by Brazilian government, and turn current policies designed to correct effects of extreme climate events into structural policies designed to reduce vulnerability and to adapt to Climate Change.

Effects of extreme climatic events on small-scale spatial patterns: a 20-year study of the distribution of a desert spider

Individuals of most animal species are non-randomly distributed in space. Extreme climatic events are often ignored as potential drivers of distribution patterns, and the role of such events is difficult to assess. Seothyra henscheli (Araneae, Eresidae) is a sedentary spider found in the Namib dunes in Namibia. The spider constructs a sticky-edged silk web on the sand surface, connected to a vertical, silk-lined burrow. Above-ground web structures can be damaged by strong winds or heavy rainfall, and during dispersal spiders are susceptible to environmental extremes. Locations of burrows were mapped in three field sites in 16 out of 20 years from 1987 to 2007, and these grid-based data were used to identify the relationship between spatial patterns, climatic extremes and sampling year. According to Morisita's index, individuals had an aggregated distribution in most years and field sites, and Geary's C suggests clustering up to scales of 2 m. Individuals were more aggregated in years with high maximum wind speed and low annual precipitation. Our results suggest that clustering is a temporally stable property of populations that holds even under fluctuating burrow densities. Climatic extremes, however, affect the intensity of clustering behaviour: individuals seem to be better protected in field sites with many conspecific neighbours. We suggest that burrow-site selection is driven at least partly by conspecific cuing, and this behaviour may protect populations from collapse during extreme climatic events.

The perception and adaptation of herdsmen to climate change and climate variability in the desert steppe region of northern China

The herdsmen in the desert steppe region in Northern China live primarily on the native rangelands. The semiarid climate has a profound impact on the economy and the livelihood of rural communities. Adaptation to the highly variable climate is the norm in pastoral management in the region but the increasing aridity and variability projected by climate change models provides new challenges for sustainable living in the harsh environment. The study surveyed the herdsmen’s perception of climate change and variability in the desert steppe region of Inner Mongolia, and compared it with the observed climatic patterns and the recorded disastrous climatic events. The existing rangeland and livestock management strategies used by local herdsmen to cope with variable climate were also investigated in order to assist in the development of better management adaptation strategies. The herdsman perceived temperature changes over the past 30 years, which matched well with the meteorological observations, while their perceived change in precipitation (decrease) did not agree with the meteorological records (no change). The discrepancy between the observed and perceived precipitation changes may have arisen from the combination of large seasonal and inter-annual fluctuation of precipitation, more recent drought years and a herdsmen’s desire to have a ‘wet year’, and more forage demand from increased livestock numbers. Herdsmen also had a reasonably good perception of strong wind/dust storms and snow storms, and their sensitivity to these extreme disastrous climatic events appeared to be related to the perception of drought. The herdsmen had better perceptions of recent short-term climate change and possibly to use it to assess the long-term changes. The major adaptive management strategies to cope with disastrous climatic events included selling livestock, buying feed, seeking other grazing resources, housing livestock and looking for other alternative jobs to compensate for the economic loss. Grazing other resources, either the reserved winter rangelands in the growing season in current household farm systems or the common winter rangelands in a traditional nomadic system, played a vital role in buffering the effects of extreme climatic events. Setting appropriate stocking rates and growing forage crops in suitable land areas may contribute to increasing the resilience of rangeland systems. Raising the herdsmen’s awareness of long-term climate change and its effects on rangelands is needed to improve their preparedness to adapt to the future climate.

Effects of extreme climate events on adult survival of three Pacific auks

ABSTRACT. Climate change is predicted to increase the frequency and severity of extreme climate events, and it is important that we understand how this might affect natural systems. We examined the effects of extreme climate events on adult survival rates in three species of auks breeding on Triangle Island, British Columbia: Cassin's Auklet (Ptychoramphus aleuticus), Rhinoceros Auklet (Cerorhinca monocerata), and Tufted Puffin (Fratercula cirrhata). Our 15-year study period (1994–2008) included two extreme climate events: a strong El Nino event in 1997–1998 and an atmospheric blocking event in 2005. Neither event had any detectable effect on the annual adult survival rate (± 95% confidence interval) of either Tufted Puffins (females: 0.96 ± 0.05; males: 0.91 ± 0.06) or Rhinoceros Auklets (0.86 ± 0.02 in both sexes). By contrast, the adult survival of female Cassin's Auklets was halved during both extreme climate events (from a background rate of 0.84 ± 0.05 to 0.44 ± 0.10), whereas survival of males was ...

Community responses to extreme climatic conditions

Abstract Species assemblages and natural communities are increasingly impacted by changes in the frequency and severity of extreme climatic events. Here we propose a brief overview of expected and demonstrated direct and indirect impacts of extreme events on animal communities. We show that differential impacts on basic biological parameters of individual species can lead to strong changes in community composition and structure with the potential to considerably modify the functional traits of the community. Sudden disequilibria have even been shown to induce irreversible shifts in marine ecosystems, while cascade effects on various taxonomic groups have been highlighted in Mediterranean forests. Indirect effects of extreme climatic events are expected when event-induced habitat changes (e.g. soil stability, vegetation composition, water flows altered by droughts, floods or hurricanes) have differential consequences on species assembled within the communities. Moreover, in increasing the amplitude of trophic mismatches, extreme events are likely to turn many systems into ecological traps under climate change. Finally, we propose a focus on the potential impacts of an extreme heat wave on local assemblages as an empirical case study, analysing monitoring data on breeding birds collected in France. In this example, we show that despite specific populations were differently affected by local temperature anomalies, communities seem to be unaffected by a sudden heat wave. These results suggest that communities are tracking climate change at the highest possible rate.

Why responses to dramatic climate change are important?

Climate change is proceeding at an unprecedented pace with global temperatures and sea-levels setting new records almost every year (IPCC, 2007). While these changes are worrisome due to effects on all biological systems and hence also on humans, even more problematic changes may be in the waiting, because not only is the climate changing, but it is also becoming more extreme. Extreme temperatures, rainfall, droughts, storms and fires are already becoming more common with severe consequences for humans, their crops and domestic animals and all wild organisms. For example, the severe heat wave in 2003 caused an excess mortality of 2,600 humans in France alone (INSERM, 2003), and primary production was suppressed across Europe (Ciais et al. 2004). There is a long history of biological studies of extreme events going back to Bumpus’ (1895) study of mortality and selection on house sparrows Passer domesticus during a severe snowstorm. Extreme climatic events are poorly studied simply because they are rare, and such events have been defined to happen less than 5% of the time relative to the expected distribution (http://www.emc.ncep.noaa.gov). This lack of studies of the biological consequences is highly problematic because we know very little about the ability of plants and animals to adapt to such extreme situations. Here a number of specialists reviewed the scattered literature on effects of extreme climate change. Moller starts by analyzing the behavioral effects of extreme climatic events, while Wingfield et al. review the physiological underpinnings of such behavioral responses. Next, Moreno & Moller review the demographic and life-history consequences of extreme climatic conditions, showing that fecundity and survival are dramatically reduced. Dolenec et al. analyze a case study of response of a bird species to extreme climatic conditions. Martinez & Merino provide an over-view of the parasitological consequences of extreme climate and review the consequences for domestic animals and humans. Finally, Jiguet et al. provide a review of the consequences of extreme climatic events on communities of animals. This special section on biological effects of extreme climate change raises many questions and provides guidelines for future studies in this area of major significance.

Experimental simulation of the effects of extreme climatic events on major ions, acidity and dissolved organic carbon leaching from a forested catchment, Gårdsjön, Sweden

Climate change is predicted to lead to an increase in extreme rainfall and, in coastal areas, sea-salt deposition events. The impacts of these two climatic extremes on stream hydrochemistry were separately evaluated via a novel watering manipulation at the Gardsjon experimental catchment, SW Sweden. In summer 2004, a 2000 m2 hillslope draining to a defined stream reach was brought to a high-flow hydrological steady state for a 9 day period by sustained addition of ‘clean’ water using a distributed sprinkler system. Marine ions were then added, to generate a realistic ‘sea salt’ episode. A remarkably well constrained hydrological response was observed, such that a simple two-compartment mixing model could reasonably well reproduce observed conservative tracer (chloride, Cl) measurements, and 78% of added water was recovered in runoff. Stream base cation concentrations and acidity responded predictably to clean water and sea-salt addition, with the former leading to an increase in pH and acid neutralising capacity, and the latter to episodic acidification through hydrogen ion and aluminium displacement from soil exchange sites by marine base cations. Anion responses were less predictable: water addition caused a flush of nitrate, but this was apparently independent of rainfall composition. Sulphate remained near-constant during clean water addition but declined sharply during sea-salt addition, indicative of a strong, pH-dependent solubility control on leaching, presumably adsorption/desorption in the mineral soil. Most strikingly, dissolved organic carbon (DOC) concentrations were stable during clean water addition but varied dramatically in response to sea-salt addition, exhibiting a strong negative correlation with Cl concentrations in water draining the organic soil. These observations provide a robust experimental verification of the hypothesis that deposition chemistry, through its influence on acidity and/or ionic strength, has a major influence on DOC leaching to surface waters.