Humpback whale diets respond to variance in ocean climate and ecosystem conditions in the California Current

Large, migratory predators are often cited as sentinel species for ecosystem processes and climate‐related changes, but their utility as indicators is dependent upon an understanding of their response to environmental variability. Documentation of the links between climate variability, ecosystem change and predator dynamics is absent for most top predators. Identifying species that may be useful indicators and elucidating these mechanistic links provides insight into current ecological dynamics and may inform predictions of future ecosystem responses to climatic change. We examine humpback whale response to environmental variability through stable isotope analysis of diet over a dynamic 20‐year period (1993–2012) in the California Current System (CCS). Humpback whale diets captured two major shifts in oceanographic and ecological conditions in the CCS. Isotopic signatures reflect a diet dominated by krill during periods characterized by positive phases of the North Pacific Gyre Oscillation (NPGO), cool sea surface temperature (SST), strong upwelling and high krill biomass. In contrast, humpback whale diets are dominated by schooling fish when the NPGO is negative, SST is warmer, seasonal upwelling is delayed and anchovy and sardine populations display increased biomass and range expansion. These findings demonstrate that humpback whales trophically respond to ecosystem shifts, and as a result, their foraging behavior is a synoptic indicator of oceanographic and ecological conditions across the CCS. Multi‐decadal examination of these sentinel species thus provides insight into biological consequences of interannual climate fluctuations, fundamental to advancing ecosystem predictions related to global climate change.     

Increasing variance in North Pacific climate relates to unprecedented ecosystem variability off California

Changes in variance are infrequently examined in climate change ecology. We tested the hypothesis that recent high variability in demographic attributes of salmon and seabirds off California is related to increasing variability in remote, large‐scale forcing in the North Pacific operating through changes in local food webs. Linear, indirect numerical responses between krill (primarily Thysanoessa spinifera) and juvenile rockfish abundance (catch per unit effort (CPUE)) explained >80% of the recent variability in the demography of these pelagic predators. We found no relationships between krill and regional upwelling, though a strong connection to the North Pacific Gyre Oscillation (NPGO) index was established. Variance in NPGO and related central Pacific warming index increased after 1985, whereas variance in the canonical ENSO and Pacific Decadal Oscillation did not change. Anthropogenic global warming or natural climate variability may explain recent intensification of the NPGO and its increasing ecological significance. Assessing non‐stationarity in atmospheric‐environmental interactions and placing greater emphasis on documenting changes in variance of bio‐physical systems will enable insight into complex climate‐marine ecosystem dynamics.     

Evaluation of multi-scale climate effects on annual recruitment levels of the Japanese eel, Anguilla japonica, to Taiwan

Long-term (1967–2008) glass eel catches were used to investigate climatic effects on the annual recruitment of Japanese eel to Taiwan. Specifically, three prevailing hypotheses that potentially explain the annual recruitment were evaluated. Hypothesis 1: high precipitation shifts the salinity front northward, resulting in favorable spawning locations. Hypothesis 2: a southward shift of the position of the North Equatorial Current (NEC) bifurcation provides a favorable larval transport route. Hypothesis 3: ocean conditions (eddy activities and productivity) along the larval migration route influence larval survival. Results of time series regression and wavelet analyses suggest that Hypothesis 1 is not supported, as the glass eel catches exhibited a negative relationship with precipitation. Hypothesis 2 is plausible. However, the catches are correlated with the NEC bifurcation with a one-year lag. Considering the time needed for larval transport (only four to six months), the one-year lag correlation does not support the direct transport hypothesis. Hypothesis 3 is supported indirectly by the results. Significant correlations were found between catches and climate indices that affect ocean productivity and eddy activities, such as the Quasi Biennial Oscillation (QBO), North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation (PDO), and Western Pacific Oscillation (WPO). Wavelet analysis reveals three periodicities of eel catches: 2.7, 5.4, and 10.3 years. The interannual coherence with QBO and the Niño 3.4 region suggests that the shorter-term climate variability is modulated zonally by equatorial dynamics. The low-frequency coherence with WPO, PDO, and NPGO demonstrates the decadal modulation of meridional teleconnection via ocean–atmosphere interactions. Furthermore, WPO and QBO are linked to solar activities. These results imply that the Japanese eel recruitment may be influenced by multi-timescale climate variability. Our findings call for investigation of extra-tropical ocean dynamics that affect survival of eels during transport, in addition to the existing efforts to study the equatorial system.     

Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal‐scale biological variability

In areas of the North Pacific that are largely free of overfishing, climate regime shifts – abrupt changes in modes of low‐frequency climate variability – are seen as the dominant drivers of decadal‐scale ecological variability. We assessed the ability of leading modes of climate variability [Pacific Decadal Oscillation (PDO), North Pacific Gyre Oscillation (NPGO), Arctic Oscillation (AO), Pacific‐North American Pattern (PNA), North Pacific Index (NPI), El Niño‐Southern Oscillation (ENSO)] to explain decadal‐scale (1965–2008) patterns of climatic and biological variability across two North Pacific ecosystems (Gulf of Alaska and Bering Sea). Our response variables were the first principle component (PC1) of four regional climate parameters [sea surface temperature (SST), sea level pressure (SLP), freshwater input, ice cover], and PCs 1–2 of 36 biological time series [production or abundance for populations of salmon (Oncorhynchus spp.), groundfish, herring (Clupea pallasii), shrimp, and jellyfish]. We found that the climate modes alone could not explain ecological variability in the study region. Both linear models (for climate PC1) and generalized additive models (for biology PC1–2) invoking only the climate modes produced residuals with significant temporal trends, indicating that the models failed to capture coherent patterns of ecological variability. However, when the residual climate trend and a time series of commercial fishery catches were used as additional candidate variables, resulting models of biology PC1–2 satisfied assumptions of independent residuals and out‐performed models constructed from the climate modes alone in terms of predictive power. As measured by effect size and Akaike weights, the residual climate trend was the most important variable for explaining biology PC1 variability, and commercial catch the most important variable for biology PC2. Patterns of climate sensitivity and exploitation history for taxa strongly associated with biology PC1–2 suggest plausible mechanistic explanations for these modeling results. Our findings suggest that, even in the absence of overfishing and in areas strongly influenced by internal climate variability, climate regime shift effects can only be understood in the context of other ecosystem perturbations.     

Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current

Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity.     

Changes in spring arrival of Nearctic-Neotropical migrants attributed to multiscalar climate

Climate-related changes associated with the California marine ecosystem have been documented; however, there are no studies assessing changes in terrestrial vertebrate phenology on the Pacific coast of western North America. We analyze the spring phenology of 21 Nearctic-Neotropical migratory songbird species in central and northern CA. Using observational and banding data at multiple sites, we evaluate evidence for a change in arrival timing being linked to either nonclimatic or multiscalar climatic explanations. Using correlation analysis, of the 13 species with a significant ( P <0.10) change in arrival, the arrival timing of 10 species (77%) is associated with both temperature and a large-scale climate oscillation index (El Niño Southern Oscillation, ENSO; North Atlantic Oscillation, NAO; and/or Pacific Decadal Oscillation, PDO) at least at one location. Eight of the 13 species (62%) are advancing their migratory timing. All species for which spring arrival is associated with climate at multiple locations are exhibiting changes ( n =5) and all species lacking evidence for association between migration phenology and climate ( n =3) exhibit no change. Migrants tend to arrive earlier in association with warmer temperatures, positive NAO indices, and stronger ENSO indices. Twelve species negatively correlate ( P ≤0.05) with local or regional temperature at least at one location; five species negatively correlate with ENSO. Eleven species' arrival is correlated ( P ≤0.05) with NAO; 10 are negatively associated. After an exhaustive literature search, this is apparently the first documentation of an association between NAO and migratory phenology in western North America.     

Relationships of subalpine forest fires in the Colorado Front Range with interannual and multidecadal‐scale climatic variation

Aim An understanding of past relationships between fire occurrence and climate variability will help to elucidate the implications of climate‐change scenarios for future patterns of wildfire. In the present study we investigate the relationships between subalpine‐zone fire occurrence and climate variability and broad‐scale climate patterns in the Pacific and Atlantic Oceans at both interannual and multidecadal time‐scales. Location The study area is the subalpine zone of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa), and lodgepole pine (Pinus contorta) in the southern sector of the Rocky Mountain National Park, which straddles the continental divide of the northern Colorado Front Range. Methods We compared years of widespread fire from AD 1650 to 1978 for the subalpine zone of southern Rocky Mountain National Park, with climate variables such as measures of drought, and indices such as the El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO). Results Years of extensive subalpine‐zone fires are significantly related to climate variability, phases of ENSO, the PDO, and the AMO, as well as to phase combinations of ENSO, the PDO, and the AMO at both interannual and centennial time‐scales. Main conclusions Years of extensive fires are related to extreme drought conditions and are significantly related to the La Niña phase of ENSO, the negative (cool) phase of the PDO, and the positive (warm) phase of the AMO. The co‐occurrence of the phase combination of La Niña‐negative PDO‐positive AMO is more important to fire occurrence than the individual influences of the climate patterns. Low‐frequency trends in the occurrence of this combination of climate‐pattern phases, resulting from trends in the AMO, are the primary climate pattern associated with periods of high fire occurrence (1700–89 and 1851–1919) and a fire‐free period (1790–1850). The apparent controlling influence of the AMO on drought and years of large fires in the subalpine forests of the Colorado Front Range probably applies to an extensive area of western North America.     

An unstable tree-growth response to climate in two 500 year chronologies,North Eastern Qinghai-Tibetan Plateau

Two new Juniper tree-ring-width (TRW) chronologies spanning more than 500 years were developed in the Yellow River source area, North Eastern Qinghai-Tibetan Plateau (NE-QTP). For the two studied sites, located approximately 50 km apart, split correlation and coherence analysis reveal unstable tree-growth responses to local moisture availability. While significant correlations are obtained with April–June local precipitation, Palmer Drought Severity Index (PDSI) and river flow from 1948/1954 to 1998 and from 1948/1954 to 1970s, these correlations vanish for the time period 1970s-1998. The local instrumental climate data (precipitation, PDSI and river flow) exhibit opposite correlations with large scale modes of variability (El Niño Southern Oscillation, ENSO, and Pacific Decadal Oscillation, PDO) before and after the 1977 PDO shift. One tree-ring chronology is coherent and anti-phased with instrumental ENSO/PDO indices at 5.2-year frequency. On the longer time span, this TRW chronology is compared with PDO reconstructed from historical Chinese data. This comparison also exhibits unstable multi-decadal relationships, notably in the mid 19th century. Altogether, the comparison between our two chronologies, local instrumental climate records, and ENSO/PDO indices suggest a cautious use of local TRW records for paleoclimate reconstructions. Further studies are needed to explore both the spatial coherency of tree-ring records and the temporal stability of their response to local and large scale climate variability.     

Atmospheric forcing on chlorophyll concentration in the Mediterranean

Recent research suggests the coupling of climatic fluctuations and changes in biological indices that describe species richness, abundance and spatiotemporal distribution. In this study, large-scale modes of atmospheric variability over the northern hemisphere are associated with chlorophyll-a concentration in the Mediterranean. Sea level atmospheric pressure, air temperature, wind speed and precipitation are used to account for climatic and local weather effects, whereas sea surface temperature, sea surface height and salinity are employed to describe oceanic variation. Canonical Correlation Analysis was applied to relate chlorophyll concentration to the above-mentioned environmental variables, while correlation maps were also built to distinguish between localized and distant effects. Spectral analysis was used to identify common temporal cycles between chlorophyll concentration and each environmental variable. These cycles could be interpreted as mechanistic links between chlorophyll and large-scale atmospheric variability. Known teleconnection patterns such as the East Atlantic/Western Russian pattern, the North Atlantic Oscillation, the Polar/Eurasian pattern, the East Pacific/North Pacific, the East Atlantic jet and the Mediterranean Oscillation are found to be the most important modes of atmospheric variability related to chlorophyll-a concentration and distribution. The areas that are mostly affected are near the coasts and areas of upwelling and gyre formation. The results also suggest that this influence may arise either through local effects of teleconnection patterns on oceanic features or large-scale changes superimposed onto the general circulation in the Mediterranean. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Influence of long-distance climate teleconnection on seasonality of water temperature in the world's largest lake--Lake Baikal, Siberia

Large-scale climate change is superimposed on interacting patterns of climate variability that fluctuate on numerous temporal and spatial scales--elements of which, such as seasonal timing, may have important impacts on local and regional ecosystem forcing. Lake Baikal in Siberia is not only the world's largest and most biologically diverse lake, but it has exceptionally strong seasonal structure in ecosystem dynamics that may be dramatically affected by fluctuations in seasonal timing. We applied time-frequency analysis to a near-continuous, 58-year record of water temperature from Lake Baikal to examine how seasonality in the lake has fluctuated over the past half century and to infer underlying mechanisms. On decadal scales, the timing of seasonal onset strongly corresponds with deviation in the zonal wind intensity as described by length of day (LOD); on shorter scales, these temperature patterns shift in concert with the El Nino-Southern Oscillation (ENSO). Importantly, the connection between ENSO and Lake Baikal is gated by the cool and warm periods of the Pacific Decadal Oscillation (PDO). Large-scale climatic phenomena affecting Siberia are apparent in Lake Baikal surface water temperature data, dynamics resulting from jet stream and storm track variability in central Asia and across the Northern Hemisphere.     

Environmental factors influencing eastern North Pacific gray whale calf production 1994–2016

This paper describes the relationship between eastern North Pacific gray whale calf production and environmental conditions in the Pacific Arctic where they feed. The results show how interannual variation in sea ice cover in the Bering and Chukchi Seas along with broader indices of North Pacific climate, such as Pacific Decadal Oscillation (PDO) and North Pacific Index (NPI), are linked to variation in gray whale reproductive output. Estimates of gray whale calf production were derived from 23 consecutive years (1994–2016) of shore-based visual surveys conducted off California during the northward migration. PDO and NPI in combination with ice cover in the Bering and Chukchi Seas during the early phase of gestation appear to be important in explaining the observed variability in calf production. Of the 2,285 time series linear models evaluated, the model of best-fit included PDO(July), Ice(June), NPI(February), and explained 60% of the observed variability in calf production. After elimination of two data outliers in calf production estimates (2013 and 2014) a model including Ice(May), PDO(May), and NPI(July) explained 90% of the variability. We conclude that access to prey early in the gestation period is critical to reproductive success in this population and may be important for other capital breeding mammals.     

Coral Luminescence Identifies the Pacific Decadal Oscillation as a Primary Driver of River Runoff Variability Impacting the Southern Great Barrier Reef

The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence variability (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and decadal variability of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the variability in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate variability.     

Response of a rocky intertidal ecosystem engineer and community dominant to climate change

To evaluate how climate change might impact a competitively dominant ecological engineer, we analysed the growth response of the mussel Mytilus californianus to climate patterns [El Niño-Southern Oscillation, Pacific Decadal Oscillation (PDO)]. Mussels grew faster during warmer climatic events. Growth was initially faster on a more productive cape compared to a less productive cape. Growth rates at the two capes merged in 2002, coincidentally with a several year-long shift from warm to cool PDO conditions. To determine the mechanism underlying this response, we examined growth responses to intertidal sea and air temperatures, phytoplankton, sea level and tide height. Together, water temperature (32%) and food (12.5%) explained 44.5% of the variance in mussel growth; contributions of other factors were not significant. In turn, water temperature and food respond to climate-driven variation in upwelling and other, unknown factors. Understanding responses of ecosystem engineers to climate change will require knowing direct thermal effects and indirect effects of factors altered by temperature change.     

Climate and wildfires in the North American boreal forest

The area burned in the North American boreal forest is controlled by the frequency of mid-tropospheric blocking highs that cause rapid fuel drying. Climate controls the area burned through changing the dynamics of large-scale teleconnection patterns (Pacific Decadal Oscillation/El Niño Southern Oscillation and Arctic Oscillation, PDO/ENSO and AO) that control the frequency of blocking highs over the continent at different time scales. Changes in these teleconnections may be caused by the current global warming. Thus, an increase in temperature alone need not be associated with an increase in area burned in the North American boreal forest. Since the end of the Little Ice Age, the climate has been unusually moist and variable: large fire years have occurred in unusual years, fire frequency has decreased and fire–climate relationships have occurred at interannual to decadal time scales. Prolonged and severe droughts were common in the past and were partly associated with changes in the PDO/ENSO system. Under these conditions, large fire years become common, fire frequency increases and fire–climate relationships occur at decadal to centennial time scales. A suggested return to the drier climate regimes of the past would imply major changes in the temporal dynamics of fire–climate relationships and in area burned, a reduction in the mean age of the forest, and changes in species composition of the North American boreal forest.     

Relationship between fire,climate oscillations,and drought in British Columbia,Canada, 1920–2000

Climate oscillations such as El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are known to affect temperature and precipitation regimes and fire in different regions of the world. Understanding the relationships between climate oscillations, drought, and area burned in the past is required for anticipating potential impacts of regional climate change and for effective wildfire‐hazard management. These relationships have been investigated for British Columbia (BC), Canada, either as part of national studies with coarse spatial resolution or for single ecosystems. Because of BC's complex terrain and strong climatic gradients, an investigation with higher spatial resolution may allow for a spatially complete but differentiated picture. In this study, we analyzed the annual proportion burned–climate oscillation–drought relationships for the province's 16 Biogeoclimatic Ecosystem Classification (BEC) zones. Analyses are based on a digital, spatially explicit fire database, climate oscillation indices, and monthly precipitation and temperature data with a spatial resolution of 400 m for the period 1920–2000. Results show that (1) fire variability is better related to summer drought than to climate oscillations, and that (2) fire variability is most strongly related to both, climate oscillations and summer drought in southeastern BC. The relationship of area burned and summer drought is strong for lower elevations in western BC as well. The influence of climate oscillations on drought is strongest and most extensive in winter and spring, with higher indices being related to drier conditions. Winter and spring PDO and additive winter and spring PDO+ENSO indices show BC's most extensive significant relationship to fire variability. Western BC is too wet to show a moisture deficit in summer that would increase annual area burned due to teleconnections.     

Influences of the El Niño/Southern Oscillation and the North Atlantic Oscillation on avian productivity in forests of the Pacific Northwest of North America

To model the effects of global climate phenomena on avian population dynamics, we must identify and quantify the spatial and temporal relationships between climate, weather and bird populations. Previous studies show that in Europe, the North Atlantic Oscillation (NAO) influences winter and spring weather that in turn affects resident and migratory landbird species. Similarly, in North America, the El Niño/Southern Oscillation (ENSO) of the Pacific Ocean reportedly drives weather patterns that affect prey availability and population dynamics of landbird species which winter in the Caribbean. Here we show that ENSO‐ and NAO‐induced seasonal weather conditions differentially affect neotropical‐ and temperate‐wintering landbird species that breed in Pacific North‐west forests of North America. For neotropical species wintering in western Mexico, El Niño conditions correlate with cooler, wetter conditions prior to spring migration, and with high reproductive success the following summer. For temperate wintering species, springtime NAO indices correlate strongly with levels of forest defoliation by the larvae of two moth species and also with annual reproductive success, especially among species known to prey upon those larvae. Generalized linear models incorporating NAO indices and ENSO precipitation indices explain 50–90% of the annual variation in productivity reported for 10 landbird species. These results represent an important step towards spatially explicit modelling of avian population dynamics at regional scales.     

Long Term Variability in the Structure of Kelp Communities in Northern Chile and the 1997–98 ENSO

This is the first study on the south eastern Pacific coast of South America which details long term, interannual variability in the structure of subtidal rocky-bottom kelp-dominated communities before, during, and after the El Niño Southern Oscillation (ENSO) event of 1997–1998 in northern Chile (23^°S). The temporal patterns of the main components of these ecosystems, which included Macrocystis integrifolia, Lessonia trabeculata, echinoids and asteroids, were evaluated seasonally between 1996 and 2004. M. integrifolia demonstrated high interannual variability in temporal patterns of abundance. The 1997–1998 ENSO did not significantly modify the temporal patterns of Macrocystis, although local extinction of M. integrifolia beds occurred during negative thermal anomalies in 1999–2000 (La Niña event), facilitating the establishment of urchin dominated “barren grounds”. The abundance of Lessonia trabeculata showed little temporal variability, and this species dominated the deeper regions of the kelp assemblage (8–13 m depth). The structure of the kelp communities in the study area is regulated by a trophic cascade which modulates alternation between kelp dominated areas and sea urchin barrens. In this context, frequent and intense upwelling of cold water high in nutrients favors the establishment and persistence of kelp assemblages. During ENSO, coastal upwellings can mitigate superficial warming of coastal water and increase the nutrient concentration in the water column. Superficial warming during the 1997–1998 ENSO induced spawning by different species of echinoderms, which resulted in major recruitment of these species during 1999. Top-down events, such as the decrease in densities of the asteroids after the 1997–1998 ENSO event, favored increases in densities of benthic grazers, which caused significant decreases in abundance of M. integrifolia. The re-establishment of the adult fraction of the carnivore (starfish) guild coincided with a decrease in the density of sea urchins and thus re-establishment of the kelp. In the temperate south eastern Pacific, oceanographic events, which act on different spatial-temporal scales, trigger trophic cascades that act at local levels, producing interannual variability in the structure of kelp communities. On the other hand, considering the high macroinvertebrate diversity associated with kelp assemblages, the transitions between kelp-dominated areas and sea urchin barrens do not appear to significantly affect the biodiversity of these assemblages of benthic invertebrates.     

Complex structural effects of two hemispheric climatic oscillators on the regional spatio-temporal expansion of a threatened bird

Links between climatic conditions in the eastern equatorial Pacific and extratropical ecological processes remain unexplored. The analysis of a 20‐year time series of spatial and numeric dynamics of a threatened Mediterranean bird suggests, however, that such couplings can be remarkably complex. By providing a new ecological time‐series modelling approach, we were able to dissect the joint effects of the El Niño/Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), regional weather, population density and stochastic variability on the expansion dynamics of the White‐headed duck (Oxyura leococephala) in Spain. Our results suggest that the spatial and numeric dynamics of ducks between peak brood emergence and wintering were simultaneously affected by different climatic phenomena during different phases of their global cycles, involving time lags in the numeric dynamics. Strikingly, our results point to both the NAO and the ENSO as potentially major factors simultaneously forcing ecological processes in the Northern Hemisphere, and suggest a new pathway for non‐additive effects of climate in ecology.     

Global climate cycles and cyclones: consequences for rainfall patterns and lemur reproduction in southeastern Madagascar

Most studies that examine the influence of climatic change on flora and fauna have focused on northern latitudes; however, there is increasing recognition that tropical regions are also being affected. Despite this, regions such as Madagascar, which are rich in endemic biodiversity but may have low adaptive capacity to climatic change, are poorly represented in studies examining the effects of climate variability on biota. We investigated how El Niño Southern Oscillations (ENSO) influence precipitation patterns in the rainforest region of southeastern Madagascar (1962–2006) and then constructed models to assess the potential contribution of climatic variables on the reproductive parameters of the Milne Edward's sifaka, a threatened lemur species (Propithecus edwardsi), over a 20‐year period. The Southern Oscillation Index of sea surface temperature (SST) anomalies in the tropical Pacific was associated with precipitation patterns including wetter wet seasons during warmer phases and drier dry seasons following cooler phases. The best‐supported models of lemur fecundity (female offspring per female that survive to 1 year of age per year) included cyclone presence during gestation and ENSO phase before conception and during the first 6 months of life. Models also suggested that heavy rains during gestation may limit birth rates and that prolonged drought during female lactation may limit first year offspring survival; although these variables were given little importance for predicting overall fecundity relative to ENSO phases and cyclone presence. Our results linking lemur reproduction with climatic variability suggest that climatic changes may be an additional threat to Madagascar's unique and already endangered flora and fauna. The association between precipitation in southeastern Madagascar and SST anomalies in the tropical Pacific suggests that dynamics of wildlife populations even in tropical areas such as Madagascar can be affected by global climate cycles making them potentially vulnerable to global climate change.     

El Niño Southern Oscillation influences the abundance and movements of a marine top predator in coastal waters

Large‐scale climate modes such as El Niño Southern Oscillation (ENSO) influence population dynamics in many species, including marine top predators. However, few quantitative studies have investigated the influence of large‐scale variability on resident marine top predator populations. We examined the effect of climate variability on the abundance and temporary emigration of a resident bottlenose dolphin (Tursiops aduncus) population off Bunbury, Western Australia (WA). This population has been studied intensively over six consecutive years (2007–2013), yielding a robust dataset that captures seasonal variations in both abundance and movement patterns. In WA, ENSO affects the strength of the Leeuwin Current (LC), the dominant oceanographic feature in the region. The strength and variability of the LC affects marine ecosystems and distribution of top predator prey. We investigated the relationship between dolphin abundance and ENSO, Southern Annular Mode, austral season, rainfall, sea surface salinity and sea surface temperature (SST). Linear models indicated that dolphin abundance was significantly affected by ENSO, and that the magnitude of the effect was dependent upon season. Dolphin abundance was lowest during winter 2009, when dolphins had high temporary emigration rates out of the study area. This coincided with the single El Niño event that occurred throughout the study period. Coupled with this event, there was a negative anomaly in SST and an above average rainfall. These conditions may have affected the distribution of dolphin prey, resulting in the temporary emigration of dolphins out of the study area in search of adequate prey. This study demonstrated the local effects of large‐scale climatic variations on the short‐term response of a resident, coastal delphinid species. With a projected global increase in frequency and intensity of extreme climatic events, resident marine top predators may not only have to contend with increasing coastal anthropogenic activities, but also have to adapt to large‐scale climatic changes.