Long-term changes in phytoplankton, zooplankton and salmon related to climate

Recently, large‐scale changes in the biogeography of calanoid copepod crustaceans have been detected in the northeastern North Atlantic Ocean and adjacent seas. Strong biogeographical shifts in all copepod assemblages were found with a northward extension of more than ° in latitude of warm‐water species associated with a decrease in the number of colder‐water species. These changes were attributed to regional increase in sea surface temperature. Here, we have extended these studies to examine long‐term changes in phytoplankton, zooplankton and salmon in relation to hydro‐meteorological forcing in the northeast Atlantic Ocean and adjacent seas. We found highly significant relationships between (1) long‐term changes in all three trophic levels, (2) sea surface temperature in the northeastern Atlantic, (3) Northern Hemisphere temperature and (4) the North Atlantic Oscillation. The similarities detected between plankton, salmon, temperature and hydro‐climatic parameters are also seen in their cyclical variability and in a stepwise shift that started after a pronounced increase in Northern Hemisphere Temperature anomalies at the end of the 1970s. All biological variables show a pronounced change which started after circa 1982 for euphausiids (decline), 1984 for the total abundance of small copepods (increase), 1986 for phytoplankton biomass (increase) and Calanus finmarchicus (decrease) and 1988 for salmon (decrease). This cascade of biological events led to an exceptional period, which is identified after 1986 to present and followed another shift in large‐scale hydro‐climatic variables and sea surface temperature. This regional temperature increase therefore appears to be an important parameter that is at present governing the dynamic equilibrium of northeast Atlantic pelagic ecosystems with possible consequences for biogeochemical processes and fisheries.     

Predicted short-term radial-growth changes of trees based on past climate on Vancouver Island, British Columbia

Tree-ring radial expansion estimator (TREE) is an integrated radial growth model that allows users to define short-term climate change scenarios to anticipate the impact upon mature trees found growing at high elevation on Vancouver Island, British Columbia. Five individualistic models were built to represent the radial growth behaviour of mountain hemlock (Tsuga mertensiana (Bong.) Carr), yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach), western red-cedar (Thuja plicata Donn), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and western hemlock (Tsuga heterophylla (Raf.) Sarg.) trees. The models were developed on climate-radial growth relationships incorporating Nanaimo climate station data, and were able to explain from 55 to 68 per cent of the variance in radial growth. The models can be run with modifications to yearly precipitation and temperature variables, giving the user the ability to investigate the radial-growth impacts of a wide range of possible climate change scenarios. Results from eight such scenarios show that species growing within their ecological limits illustrate a limited change in radial growth to forecasted climate, while species growing at an ecotonal boundary are usually very sensitive to a specific climate variables (e.g., July temperature). A forecasted alteration to this key variable will then radically alter the radial-growth rate of the species.     

Projected latitudinal and regional changes in vascular plant diversity through climate change: short-term gains and longer-term losses

A simple approach is suggested to project potential changes in the diversity of vascular plants. We use the current (recent past) relationship between plant diversity and geographic variation in the climate, as well as elevation range, to project changes in regional species richness (at 100 × 100 km resolution), concentrating on six climate scenarios for 2020, 2050 and 2080. The results show an overall trend towards increased vascular plant species richness. Increases in richness by 2050 and 2080 are expected over approximately three-quarters of the land surface, but decreases are expected in other regions. The magnitudes of richness gains and losses both increase over time, as the level of warming grows. The latitudinal pattern of change suggests that richness increases will be greatest at high latitudes, where plant productivity and diversity are largely limited by temperature. Richness decreases are not projected consistently in any latitudinal band, but are most likely to be observed at 5–40ºN, where declines in precipitation drive most projected decreases in richness.     

Seasonal changes in endocrine organs of the male common frog,Rana temporaria

Summary The annual cycle of the five morphological cell types in the pars distalis of the adenohypophysis of male common frogs,Rana temporaria, was studied in variously stained sections of the pituitary, collected at monthly intervals. All cell types showed a maximal development at the end of hibernation, a strong extrusion of secretory granules in the breeding season, and a more gradual release during later spring and early summer. A minimal development occurred in mid-summer, and a restoration followed in autumn and the hibernation period. During the phase of extrusion production was low, and vice-versa. These seasonal changes correspond with those of the testes and interrenal tissue of the same animals as well as with those of the thyroids and other endocrine tissues, and seems to be an important part of the biphasic annual life cycle of the species.The authors gratefully acknowledge the patient and skilful technical assistance of MissFemmy Brands. They thank Mr.H. van Kooten for making the photographs.     

Long-term effects of climate and phosphorus fertilisation on serpentine vegetation

The long-term effects of phosphorus fertilisation and climate on serpentine plant communities in Tuscany, central Italy have been investigated by using data from a 12 year before-after control-impact (BACI) experiment. Using the point quadrat method, data on plant communities were collected in June of each year from 1994 to 2005 in eight 2 × 2 m plots, four fertilised with phosphorus and four used as controls. Climatic data were obtained from a nearby meteorological station and summarised in 24 variables. Phosphorus addition significantly affected vegetation cover of both vascular and cryptogamic vegetation but did not influence species richness. The effects on species composition were clear but not marked, and consisted in promoting the abundance of some species already present in the community but not leading to the colonisation of other species. Interannual climate differences affected vegetation cover in the fertilised plots but not in the control ones, while climate affected the species richness values of different/various life-forms in both groups of plots, with more evident effects in the fertilised one. The effects of climate on plant community composition were weak once both the variability among individual plots and the successional dynamics were subtracted from the variance in species composition.     

Long-term common dormouse monitoring: effects of forest management on abundance

The common dormouse (Muscardinus avellanarius) is a species included in Annex IV of the Habitat Directive and red-listed in many European countries. Monitoring of M. avellanarius is implemented in several countries using different methods. In Lithuania, regular control of standard bird nestboxes and marking of all dormice caught were used during 1984–1990 and 1999–2007. Nestboxes were spaced in a grid system at 50 m intervals in an area of 60 ha. Monitoring of the M. avellanarius population was carried out in a managed forest with varying levels of human activity occurring in most parts of the forest (felling of all understorey, selective felling of trees, clear felling, etc.). During the entire study period, the average density of the population was comparatively low (about 1 ind./ha in spring and 3 ind./ha in autumn), but stable and without substantial fluctuations in spite of considerable human activity. The forestry management operations that were used in different parts of the forest over different years had only temporary and localised negative effects on the abundance of M. avellanarius, and did not influence the whole population substantially. The spacing of nestboxes in a grid system in a large forest area increased the level of accuracy with which the monitoring scheme reflected the population status. This enabled both the state of the entire population of M. avellanarius and temporary changes in abundance in selected smaller plots to be tracked. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Glacier foreland colonisation: distinguishing between short-term and long-term effects of climate change

By comparing short-term (6 years) observations with long-term (>100 years) community changes reconstructed from the chronosequence along a glacier foreland, I show that the colonisation of recently deglaciated terrain by invertebrates may constitute a process reacting sensitively to temperature fluctuations. Early colonising stages (<30 years old) currently develop faster, and intermediate successional stages (30-50 years old) slower, than would be indicated by the long-term chronosequence pattern. These differences between the chronosequence approach and direct observation can be explained by a simple model relating the rate of community evolution to the temperature record. It would mean that an increase of 0.6°C in summer temperatures approximately doubled the speed of initial colonisation, whereas later successional stages were less sensitive to climate change. The present situation appears to result from unusually warm summers around 1950 and a warm period accelerating glacier retreat since 1980. In contrast to the long-term trend, all except the youngest communities have suffered a loss in diversity in recent years.     

The impact of recombination on short-term selection gain in plant breeding experiments

Recombination is a requirement for response to selection, but researchers still debate whether increasing recombination beyond normal levels will result in significant gains in short-term selection. We tested this hypothesis, in the context of plant breeding, through a series of simulation experiments comparing short-term selection response (≤20 cycles) between populations with normal levels of recombination and similar populations with unconstrained recombination (i.e., free recombination). We considered additive and epistatic models and examined a wide range of values for key design variables: selection cycles, QTL number, heritability, linkage phase, selection intensity and population size. With few exceptions, going from normal to unconstrained levels of recombination produced only modest gains in response to selection (≈11 % on average). We then asked how breeders might capture some of this theoretical gain by increasing recombination through either (1) extra rounds of mating or (2) selection of highly recombinant individuals via use of molecular markers/maps. All methods tested captured less than half of the potential gain, but our analysis indicates that the most effective method is to select for increased recombination and the trait simultaneously. This recommendation is based on evidence of a favorable interaction between trait selection and the impact of recombination on selection gains. Finally, we examined the relative contributions of the two components of meiotic recombination, chromosome assortment and crossing over, to short-term selection gain. Depending primarily on the presence of trait selection pressure, chromosome assortment alone accounted for 40–75 % of gain in response to short-term selection.     

Effect of climate,topography and habitat on species-richness of breeding birds in Poland

We developed predictive maps of farmland and forest species richness which are based on the “focal species concept” and remote sensing data. We explored environmental preferences of 17 farmland and 33 forest species in Poland, using data from the Pan-European Monitoring Scheme. The largest number of farmland species was noted in the central and eastern parts, while the opposite trend was observed in the case of forest species, where the preferred areas were in the north and south-east. The most important environmental component affecting the bird faunas of farmland and forest was a gradient from arable fields to forest. This relationship is unimodal, which means that on a meso-geographical scale the highest species richness occurred in heterogeneous landscapes where fields are interspersed with forest. Our results also indicate that the geographical gradient in Poland's bird fauna can simply be attributed to the habitat-based distinction: western and central parts are dominated by large agricultural habitats and coniferous forest, while in other areas predominate mixed forests and extensively used farmland. Among the climatic factors, only rainfall influenced the farmland bird species. Its effect is non-linear, but positive, which means that in areas with higher rainfall more species are recorded.Our predictive maps are complementary to research on population trends, and can be an essential tool for effective management and conservation of species populations on a trans-national scale.     

The importance of topography and climate on short-term revegetation of coal wastes in Spain

The initial colonization phase is the crucial start point for succession and therefore for restoration. However, little is known about abiotic factors that influence the early stages of revegetation dynamics on restored coal mines, particularly in a Mediterranean climate. This information is crucial for improving our ability to reclaim land despoiled by mining. Here, we characterized the short-term plant community development in the first 3 years after hydroseeding on a topographically diverse reclaimed open-pit coal mines in Spain. Topography influenced both community composition and diversity producing different trajectories between the three different aspects (north-facing, south-facing, flat). Hydroseeded species provided most of the initial vegetation cover, which brought about most of the compositional differences between these aspects. We also found that the changing climate through the growing season also influenced floristic composition and diversity. Summer drought reduced the cover of hydroseeded perennial species and allowed native species to colonize. These results emphasize the need to take topography into account when developing reclamation management plans in Mediterranean ecosystems, and an acknowledgement that climate might drive the succession in the desired direction, hence increasing success in restoring mining impacts.     

Modelling population dynamics of seabirds: importance of the effects of climate fluctuations on breeding proportions

Environmental factors and their interactions are likely to have shaped specific breeding and survival strategies in top predators. Understanding how climatic factors affect populations requires detailed investigation of the demographic parameters and population modelling. Here, we focus on the modelling of a southern fulmar population over a 39 year period in Terre Adélie, Antarctica, using Leslie matrix models to understand from a prospective and retrospective point of view, how vital rates and their variations, affect the cyclic population dynamics. The elasticity of population growth rate to adult survival was very high (0.95), as predicted by a slow–fast continuum in avian life histories. However, adult survival varied little between years (mean±SD: 0.92±0.07), and could not explain the strong fluctuations observed in the number of breeders and chicks. The high temporal fluctuations of the proportion of breeders (0.57±0.22) and breeding success (0.70±0.14) had the strongest impact on population dynamics, despite their weak elasticities (0.05). Before the 1980s, population fluctuations were mainly explained by a direct impact of sea-ice extent (SIE) anomalies during summer (by a threshold effect) on the proportion of breeders. After 1980s, 3 years periodic population fluctuations were best predicted by 3 years cyclic variations in the proportion of breeders. SIE showed a marked change of periodicity during the 1980s, and SIE during winter fluctuated with a 3 years periodicity during 1980–1995. The marked change in population dynamics, through a change of the variations of the proportion of breeders, may be explained in the light of a regime shift that probably occurred around the 1980s, and which affected the sea ice environment, the availability of prey, and thus the demographic parameters and population dynamics of southern fulmars.     

Conflicts between touristic recreational activities and breeding shearwaters: short-term effect of artificial light and sound on chick weight

Human disturbances are increasingly becoming a conservation concern for many populations of colonial seabirds. Colonially reproducing species are particularly vulnerable to localised disturbances because detrimental elements can simultaneously affect the entire population. Studies of petrels and shearwaters have shown that light pollution, in particular, can be harmful for both fledglings and adults, but little is known of the way such anthropogenic elements affect the quality of parental care at the nest. Chick provisioning in petrels and shearwaters occurs exclusively at night and is also negatively correlated with the amount of moonlight. We tested the hypothesis that high-intensity light and sound disturbances will disrupt nest attendance and thus affect weight gain in chicks but that the magnitude of such effects would be modulated by moonlight conditions. We measured the effect of two outdoor disco events on overnight weight gain in 26 chicks of Scopoli’s shearwaters (Calonectris diomedea) from a breeding colony on Linosa Island. The two disco events occurred under contrasting moonlight conditions (moonless vs moonlight). Chicks situated closer to the disturbance gained significantly less weight compared to conspecifics from nests further away but the effect was only evident on the moonless night.Our results suggest that light and sound disturbances can have a negative effect on parental care in C. diomedea but moonlight might moderate the bird’s perception and thus the magnitude of the disturbance. However, while occasional disturbances may impact short-term weight gain in C. diomedea chicks, such effects are not perceivable at fledging when measured as differences in the weight or the date at which they left the nest.     

Effects of territory competition and climate change on timing of arrival to breeding grounds: a game-theory approach

Phenology is an important part of life history that is gaining increased attention because of recent climate change. We use game theory to model phenological adaptation in migratory birds that compete for territories at their breeding grounds. We investigate how the evolutionarily stable strategy (ESS) for the timing of arrival is affected by changes in the onset of spring, the timing of the resource peak, and the season length. We compare the ESS mean arrival date with the environmental optimum, that is, the mean arrival date that maximizes fitness in the absence of competition. When competition is strong, the ESS mean arrival date responds less than the environmental optimum to shifts in the resource peak but more to changes in the onset of spring. Increased season length may not necessarily affect the environmental optimum but can still advance the ESS mean arrival date. Conversely, shifting a narrow resource distribution may change the environmental optimum without affecting the ESS mean arrival date. The ESS mean arrival date and the environmental optimum may even shift in different directions. Hence, treating phenology as an evolutionary game rather than an optimization problem fundamentally changes what we predict to be an adaptive response to environmental changes.     

North American Brant: effects of changes in habitat and climate on population dynamics

We describe the importance of key habitats used by four nesting populations of nearctic brant (Branta bernicla) and discuss the potential relationship between changes in these habitats and population dynamics of brant. Nearctic brant, in contrast to most geese, rely on marine habitats and native intertidal plants during the non‐breeding season, particularly the seagrass, Zostera, and the macroalgae, Ulva. Atlantic and Eastern High Arctic brant have experienced the greatest degradation of their winter habitats (northeastern United States and Ireland, respectively) and have also shown the most plasticity in feeding behavior. Black and Western High Arctic brant of the Pacific Flyway are the most dependent on Zostera, and are undergoing a shift in winter distribution that is likely related to climate change and its associated effects on Zostera dynamics. Variation in breeding propensity of Black Brant associated with winter location and climate strongly suggests that food abundance on the wintering grounds directly affects reproductive performance in these geese. In summer, salt marshes, especially those containing Carex and Puccinellia, are key habitats for raising young, while lake shorelines with fine freshwater grasses and sedges are important for molting birds. Availability and abundance of salt marshes has a direct effect on growth and recruitment of goslings and ultimately, plays an important role in regulating size of local brant populations.     

Long-term dataset reveals declines in breeding success and high fluctuations in the number of breeding pairs in two skua species breeding on King George Island

Marine ecosystems face a variety of threats induced by environmental changes and anthropogenic activities. Seabirds are predators often used as indicator species to monitor the status and health of their communities and the environment. Here, we present the results from a 35-year monitoring time series of Brown Skuas (Catharacta antarctica lonnbergi) and South Polar Skuas (C. maccormicki) breeding sympatrically in the Maritime Antarctic on Fildes Peninsula and Potter Peninsula, King George Island. Our results reveal high annual variability in the number and proportions of breeding pairs across the entire study period. Apart from that, the breeding pair numbers of Brown Skuas were relatively stable. By contrast, the breeding pair number of mixed species and South Polar Skua pairs increased substantially until 2003/2004 and 2010/2011, respectively. Both pair types experienced a decline in the breeding pair numbers within recent years. Despite the strong fluctuations in the number of breeding pairs, the sum of occupied territories has been stable during the last 9 years. The breeding success of all pair types declined significantly, and within recent years, both South Polar Skuas and mixed species pairs completely failed to produce offspring. The ultimate causes driving the breeding success decline remain unclear. The overall increase in the number of skuas might have raised density-dependent factors and resulted in a higher predation rate between conspecifics. The more recent total breeding failures, however, indicate a drastic shortage in local food availability.     

Scale-dependent climate signals drive breeding phenology of three seabird species

Breeding at the right time is essential for animals in seasonal climates in order to ensure that the energy demands of reproduction, particularly the nutritional requirements of growing young, coincide with peak food availability. Global climate change is likely to cause shifts in the timing of peak food availability, and in order to adapt successfully to current and future climate change, animals need to be able to adjust the time at which they initiate breeding. Many animals use environmental cues available before the breeding season to predict the seasonal peak in food availability and adjust their phenology accordingly. We tested the hypothesis that regulation of breeding onset should reflect the scale at which organisms perceive their environment by comparing phenology of three seabird species at a North Sea colony. As predicted, the phenology of two dispersive species, black-legged kittiwake ( Rissa tridactyla ) and common guillemot ( Uria aalge ), correlated with a large-scale environmental cue (the North Atlantic Oscillation), whereas a resident species, European shag ( Phalacrocorax aristotelis ), was more affected by local conditions (sea surface temperature) around the colony. Annual mean breeding success was lower in late years for European shags, but not for the other two species. Since correlations among climate patterns at different scales are likely to change in the future, these findings have important implications for how migratory animals can respond to future climate change.     

Dynamics of climate and ecosystem coupling: abrupt changes and multiple equilibria

Interactions between subunits of the global climate-biosphere system (e.g. atmosphere, ocean, biosphere and cryosphere) often lead to behaviour that is not evident when each subunit is viewed in isolation. This newly evident behaviour is an emergent property of the coupled subsystems. Interactions between thermohaline circulation and climate illustrate one emergent property of coupling ocean and atmospheric circulation. The multiple thermohaline circulation equilibria that result caused abrupt climate changes in the past and may cause abrupt climate changes in the future. Similarly, coupling between the climate system and ecosystem structure and function produces complex behaviour in certain regions. For example, atmosphere-biosphere interactions in the Sahel region of West Africa lead to multiple stable equilibria. Either wet or dry climate equilibria can occur under otherwise identical forcing conditions. The equilibrium reached is dependent on past history (i.e. initial conditions), and relatively small perturbations to either climate or vegetation can cause switching between the two equilibria. Both thermohaline circulation and the climate-vegetation system in the Sahel are prone to abrupt changes that may be irreversible. This complicates the relatively linear view of global changes held in many scientific and policy communities. Emergent properties of coupled socio-natural systems add yet another layer of complexity to the policy debate. As a result, the social and economic consequences of possible global changes are likely to be underestimated in most conventional analyses because these nonlinear, abrupt and irreversible responses are insufficiently considered.