Effects of El Niño Southern Oscillation on avian breeding phenology

Aim

Climate oscillations are known to influence the reproductive phenology of birds. Here, we quantify the effects of cyclic climatic variation, specifically El Niño Southern Oscillation (ENSO), on birds that breed opportunistically. We aim to show how inter‐decadal climate fluctuations influence opportunistic breeding. This knowledge is essential for tracking the phenological responses of birds to climate change.

Location

Temperate and arid Australia.

Methods

We assessed variation in egg‐laying (start, peak, conclusion, length) during the three phases of ENSO (El Niño, La Niña and Neutral) for 64 temperate and 15 arid region species using ~80,000 observations. Linear mixed‐effect models and analysis of variance were used to (1) determine if, on average within each region, egg‐laying dates differed significantly among species between Neutral‐El Niño and Neutral‐La Niña phases, and (2) assess how La Niña and El Niño episodes influence egg‐laying in birds which breed early in the year.

Results

During La Niña phases, which are characterized by mild/wet conditions, most bird species in the temperate and arid regions exhibited longer egg‐laying periods relative to Neutral phases. However, there was substantial variation across species. This effect was strongly seasonal; species breeding in spring experienced the greatest increases in egg‐laying periods during La Niña. Further, we found only small differences in peak egg‐laying dates during Neutral and La Niña in the arid region; suggesting that hot temperatures may constrain breeding regardless of rainfall. The effects of El Niño on breeding phenology were not consistent in the temperate and arid regions and may be confounded by highly mobile species opportunistically moving and breeding with localized rainfall during dry periods.

Main conclusions

In both arid and temperate regions, increased rainfall associated with La Niña phases positively influences avian breeding, and likely recruitment. However, dry El Niño phases may not have the dramatic impacts on breeding phenology that are commonly assumed.

     

The interacting effects of food,spring temperature,and global climate cycles on population dynamics of a migratory songbird

Although long‐distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black‐throated blue warbler (Setophaga caerulescens), a double‐brooded long‐distance migrant, we used Pradel models to analyze 25 years of mark–recapture data collected in New Hampshire, USA. We assessed the effects of spring temperature (local weather) and the El Niño Southern Oscillation index (a global climate cycle), as well as predator abundance, insect biomass, and local conspecific density on population growth in the subsequent year. Local and global climatic conditions affected warbler populations in different ways. We found that warbler population growth was lower following El Niño years (which have been linked to poor survival in the wintering grounds and low fledging weights in the breeding grounds) than La Niña years. At a local scale, populations increased following years with warm springs and abundant late‐season food, but were unaffected by spring temperature following years when food was scarce. These results indicate that the warming temperature trends might have a positive effect on recruitment and population growth of black‐throated blue warblers if food abundance is sustained in breeding areas. In contrast, potential intensification of future El Niño events could negatively impact vital rates and populations of this species.     

Proceedings of the New Zealand Society for Parasitology Inc.

Abstract

A study of the nesting habits and breeding biology of blue penguin Eudyptula minor was undertaken over the 1995–96 and 1996–97 breeding seasons on Matiu‐Somes Island, Wellington, New Zealand. Male and female blue penguins tended to be faithful to both mates and nest sites, although there was insufficient evidence to detect any association between a bird's breeding success in 1995 and a subsequent change of mate or nest in 1996. Over the 1995 and 1996 seasons the recorded hatching success (0.51 ±0.11 and 0.63 ± 0.10 respectively), fledging success (0.81 ±0.12 and 0.85 ±0.10 respectively) and reproductive success (0.41 + 0.11 and 0.54 ± 0.11 respectively) were similar each season. There was no significant difference between the proportion of eggs laid, or eggs hatched and chicks fledged, between the two seasons. The mean number of chicks raised over the two seasons was 0.94 ± 0.05 per nest. Replacement clutches were laid by 11 per cent of failed breeders in each season, but only in 1996 were they successful in fledging chicks.

No significant difference was found between the breeding success of the Matiu‐Somes Island blue penguin colony recorded during this study and a previous study undertaken on the island 40 years ago.     

The effects of El Niño–La Niña on reproductive parameters of elephant seals feeding in the Bellingshausen Sea

Aim To assess the impacts of El Niño–La Niña events on the pup weaning mass and diet of female southern elephant seals (Mirounga leonina) feeding in the Bellingshausen Sea, Antarctica, and to understand the ecological processes that drive these impacts. Location Atlantic southern elephant seal weaning mass and diet were measured at King George Island (62º14′ S, 58º30′ W). Feeding areas for pregnant female seals from King George Island are located west of Alexander Island in the Bellingshausen Sea. Methods Data on weaning mass were collected between 1985 and 1994 during the breeding season (September–November). Moulting females were anaesthetized and cephalopod beaks were isolated and identified from stomach contents obtained from stomach lavages. Sea‐surface temperature anomaly (SSTA) data for the ‘El Niño 3.4’ geographical region (5º N–5º S, 120º W–170º W) were used to define El Niño–Southern Oscillation (ENSO) event years (grouped as El Niño, La Niña and Neutral) as well as the strength of each ENSO event year. Using data from the US National Center for Environmental Prediction, temperature, sea ice concentration and atmospheric pressure anomalies in the Bellingshausen Sea were calculated from March to August, corresponding to the feeding period of pregnant female seals. Results Positive temperature anomalies and negative pressure anomalies in the Bellingshausen Sea were observed during La Niña years and negative temperature anomalies and positive pressure anomalies during El Niño years. These data correlate with sea ice concentration anomalies, which are highly negative during La Niña years and highly positive during El Niño years. Warm temperature conditions in the Bellingshausen Sea during La Niña years are strongly related to both higher weaning mass in elephant seals and to an increase in squid beaks in the stomach contents of females. Main conclusions It is possible that higher elephant seal weaning masses in La Niña years correlate with warmer waters in the Bellingshausen Sea leading to the rapid growth of squid and their more frequent descents to depths frequented by elephant seals. This results in increased predation by pregnant females, leading to a greater mass among weaned pups. This hypothesis may guide future research about interactions between climate and the marine biosphere.     

El Niño,Host Plant Growth,and Migratory Butterfly Abundance in a Changing Climate

In the wet forests of Panama, El Niño typically brings a more prolonged and severe dry season. Interestingly, many trees and lianas that comprise the wet forests increase their productivity as a response to El Niño. Here, we quantify the abundance of migrating Marpesia chiron butterflies over 17 yr and the production of new leaves of their hostplants over 9 yr to test the generality of the El Niño migration syndrome, i.e., whether increased abundance of migrating insects and productivity of their food plants are associated with El Niño and La Niña events. We find that the quantity of M. chiron migrating across the Panama Canal was directly proportional to the sea surface temperature (SST) anomaly of the Pacific Ocean, which characterizes El Niño and La Niña events. We also find that production of new leaves by its larval host trees, namely Brosimum alicastrum, Artocarpus altilis, and Ficus citrifolia, was directly proportional to the SST anomaly, with greater leaf flushing occurring during the period of the annual butterfly migration that followed an El Niño event. Combining these and our previously published results for the migratory butterfly Aphrissa statira and its host lianas, we conclude that dry season rainfall and photosynthetically active radiation can serve as primary drivers of larval food production and insect population outbreaks in Neotropical wet forests, with drier years resulting in enhanced plant productivity and herbivore abundance. Insect populations should closely track changes in both frequency and amplitude of the El Niño Southern Oscillation with climate change.     

THE BIRDS OF LANGEBAAN LAGOON

Data are presented on breeding success of Red Bishops (Euplectes orix) collected over four breeding seasons at a colony in the Addo Elephant National Park, Eastern Cape, South Africa. Overall hatching and fledging success were 53.8% and 26.0% of all eggs laid, respectively, and the overall mean number of fledglings per breeding attempt was 0.77. Hatching and fledging success varied significantly among seasons, with both clutch and brood losses due to predation being the main reason for the observed differences. Hatching success also differed significantly among clutch sizes, being highest for four-egg clutches (63.2%), intermediate for three-egg clutches (55.5%) and lowest for two-egg clutches and five-egg clutches (33.2% and 34.3%, respectively). However, fledging success was not significantly different among clutch sizes. The mean number of fledglings per breeding attempt was 0.44 for two-egg clutches, 0.80 for three-egg clutches, 1.10 for four-egg clutches, and 0.57 for five-egg clutches. The height of accepted nests (i.e.nests in which at least one egg was laid) was significantly lower than the height of nests not accepted. In addition, accepted nests in which eggs hatched and young fledged were significantly lower than accepted nests in which no eggs hatched and no young fledged. These overall effects of nest height on nest acceptance and hatching and fledging success were, however, due only to nests built above water, since no such effects were found when nests built above ground (i.e.on dry land) were analysed separately. I detected no effect of nest coverage on the probability of a nest being accepted, nor was there any effect of nest coverage on hatching or fledging success. Nests above water were significantly more likely to be accepted than nests above ground; however, hatching and fledging success of nests that were accepted did not differ significantly between nests built above water and those built above ground.     

Prokaryotic community dynamics and nitrogen-cycling genes in an oxygen-deficient upwelling system during La Niña and El Niño conditions

Dissolved oxygen regulates microbial distribution and nitrogen cycling and, therefore, ocean productivity and Earth's climate. To date, the assembly of microbial communities in relation to oceanographic changes due to El Niño Southern Oscillation (ENSO) remains poorly understood in oxygen minimum zones (OMZ). The Mexican Pacific upwelling system supports high productivity and a permanent OMZ. Here, the spatiotemporal distribution of the prokaryotic community and nitrogen-cycling genes was investigated along a repeated transect subjected to varying oceanographic conditions associated with La Niña in 2018 and El Niño in 2019. The community was more diverse during La Niña and in the aphotic OMZ, dominated by the Subtropical Subsurface water mass, where the highest abundances of nitrogen-cycling genes were found. The largest proportion of the Gulf of California water mass during El Niño provided warmer, more oxygenated, and nutrient-poor waters towards the coast, leading to a significant increase of Synechococcus in the euphotic layer compared with the opposite conditions during La Niña. These findings suggest that prokaryotic assemblages and nitrogen genes are linked to local physicochemical conditions (e.g. light, oxygen, nutrients), but also to oceanographic fluctuations associated with ENSO phases, indicating the crucial role of climate variability in microbial community dynamics in this OMZ.     

El Niño,Climate, and Cholera Associations in Piura,Peru, 1991–2001: A Wavelet Analysis

In Peru, it was hypothesized that epidemic cholera in 1991 was linked to El Niño, the warm phase of El Niño–Southern Oscillation. While previous studies demonstrated an association in 1997–1998, using cross-sectional data, they did not assess the consistency of this relationship across the decade. Thus, how strong or variable an El Niño–cholera relationship was in Peru or whether El Niño triggered epidemic cholera early in the decade remains unknown. In this study, wavelet and mediation analyses were used to characterize temporal patterns among El Niño, local climate variables (rainfall, river discharge, and air temperature), and cholera incidence in Piura, Peru from 1991 to 2001 and to estimate the mediating effects of local climate on El Niño–cholera relationships. The study hypothesis is that El Niño-related connections with cholera in Piura were transient and interconnected via local climate pathways. Overall, our findings provide evidence that a strong El Niño–cholera link, mediated by local hydrology, existed in the latter part of the 1990s but found no evidence of an El Niño association in the earlier part of the decade, suggesting that El Niño may not have precipitated cholera emergence in Piura. Further examinations of cholera epicenters in Peru are recommended to support these results in Piura. For public health planning, the results may improve existing efforts that utilize El Niño monitoring for preparedness during future climate-related extremes in the region.     

A boundary current drives synchronous growth of marine fishes across tropical and temperate latitudes

Entrainment of growth patterns of multiple species to single climatic drivers can lower ecosystem resilience and increase the risk of species extinction during stressful climatic events. However, predictions of the effects of climate change on the productivity and dynamics of marine fishes are hampered by a lack of historical data on growth patterns. We use otolith biochronologies to show that the strength of a boundary current, modulated by the El Niño‐Southern Oscillation, accounted for almost half of the shared variance in annual growth patterns of five of six species of tropical and temperate marine fishes across 23° of latitude (3000 km) in Western Australia. Stronger flow during La Niña years drove increased growth of five species, whereas weaker flow during El Niño years reduced growth. Our work is the first to link the growth patterns of multiple fishes with a single oceanographic/climate phenomenon at large spatial scales and across multiple climate zones, habitat types, trophic levels and depth ranges. Extreme La Niña and El Niño events are predicted to occur more frequently in the future and these are likely to have implications for these vulnerable ecosystems, such as a limited capacity of the marine taxa to recover from stressful climatic events.     

Potential impacts of a future persistent El Niño or La Niña on three subspecies of Australian butterflies

One of the major uncertainties of 21st century climate change is the potential for shifts to the intensity and frequency of the El Niño Southern Oscillation (ENSO) cycle. Although this phenomenon is known to have dramatic impacts on ecosystems regionally and globally, the biological consequences of climate change‐driven shifts in future ENSO events have been unexplored. Here, we investigate the potential impacts that a persistent El Niño, La Niña, or ‘Neutral' phase may have on species distributions. Using MaxEnt, we model the distribution of climatically suitable habitat for three northeast Australian butterfly subspecies (Doleschallia bisaltide australis, Hypolimnas alimena lamina, and Mycalesis terminus terminus) across the three ENSO phases. We find that the spatial extent and quality of habitat are lowest under conditions that would characterize a persistent El Niño (hot/dry). In contrast, suitable habitat is broadest under the warm/wet conditions associated with La Niña. Statistical analyses of the difference between pair‐wise combinations of suitability maps using Hellinger distance showed that projections for each subspecies and ENSO phase combination were significantly different from other combinations. The resilience of these, and other, butterfly (sub)species to changes in ENSO will be influenced by fluctuations in the strength of these events, availability of refugia, and life‐history characteristics. However, the population dynamics of wet‐ and dry‐season phenotypes of M. t. terminus and physiological limitations to high temperatures suggest that this subspecies, in particular, may have limited resilience should the strength and frequency of El Niño events increase.     

Preliminary Evidence of the Importance of ENSO in Modifying Food Availability for White‐tailed Deer in a Mexican Tropical Dry Forest1

The influence of El Niño/Southern Oscillation (ENSO) on rainfall and its possible effect on availability of food for white‐tailed deer (Odocoileus virginianus) in a tropical dry forest in the Pacific coast of Mexico was studied. From 1977 to 2003 there were three significant El Niño and La Niña events. During El Niño years rainfall decreased during the wet season ( June to October) and increased during the dry season (November to May), with the opposite effect during La Niña years. Plant diversity was monitored in permanent plots during the wet and dry seasons of 1989–1993. The results provide evidence that ENSO events affect deer food availability, particularly in the dry season.     

SCALE‐DEPENDENT PATTERNS OF DISTURBANCE AND RECOVERY IN GIANT KELP FORESTS

We studied spatial variability in giant kelp (Macrocystis pyrifera) forests at 84 sites along the west coast of North America in order to assess the impacts of the 1997–98 El Niño. Our sites spanned the geographic range of giant kelp in the Northern Hemisphere and were surveyed just before, immediately following, several months after, more than one year after, and nearly two years after the El Niño. Interspersion of sample units allowed us to compare the effects of this disturbance among spatial scales ranging from a few meters to more than a thousand kilometers. Variance components analyses revealed that El Niño shifted the relative importance of factors that regulate giant kelp communities from factors acting at the scale of a few meters (local control) to factors operating at hundreds of kilometers (regional control). Moreover, El Niño resulted in a near‐to‐complete loss of giant kelp populations throughout nearly two‐thirds of the species' range. Evaluation of these effects along with oceanographic data (at the “appropriate” spatial scales), along with closer examination of giant kelp populations in the most severely impacted region (Baja) suggested that the among‐region differences in giant kelp survival was due, at least in part, to El Niño‐induced differences in ocean climate. Giant kelp recovery following El Niño was also scale‐dependent, but driven by factors different from those of the disturbance. Here, we present results for several species of macroalgae in an attempt to relate the importance of El Niño to that of other processes in creating scale‐dependent patterns of variability.     

Moisture status during a strong El Niño explains a tropical montane cloud forest’s upper limit

Growing evidence suggests short-duration climate events may drive community structure and composition more directly than long-term climate means, particularly at ecotones where taxa are close to their physiological limits. Here we use an empirical habitat model to evaluate the role of microclimate during a strong El Niño in structuring a tropical montane cloud forest’s upper limit and composition in Hawai‘i. We interpolate climate surfaces, derived from a high-density network of climate stations, to permanent vegetation plots. Climatic predictor variables include (1) total rainfall, (2) mean relative humidity, and (3) mean temperature representing non-El Niño periods and a strong El Niño drought. Habitat models explained species composition within the cloud forest with non-El Niño rainfall; however, the ecotone at the cloud forest’s upper limit was modeled with relative humidity during a strong El Niño drought and secondarily with non-El Niño rainfall. This forest ecotone may be particularly responsive to strong, short-duration climate variability because taxa here, particularly the isohydric dominant Metrosideros polymorpha, are near their physiological limits. Overall, this study demonstrates moisture’s overarching influence on a tropical montane ecosystem, and suggests that short-term climate events affecting moisture status are particularly relevant at tropical ecotones. This study further suggests that predicting the consequences of climate change here, and perhaps in other tropical montane settings, will rely on the skill and certainty around future climate models of regional rainfall, relative humidity, and El Niño.     

Breeding biology of the Barn Owl Tyto alba in central Mali

Data were obtained on 178 clutches of African Barn Owls in central Mali from four breeding seasons during 1979–1983. Significantly more clutches were laid in 1979–1980 and significantly fewer in 1980– 1981 than the average for the 4 years and there were significantly more clutches laid in the middle period of the annual breeding season. The egg volume was significantly smaller at the beginning of the breeding season and significantly larger in the middle than the overall mean with eggs of second clutches being larger than those of first clutches. The clutch size was 605 eggs of which 479 hatched. The number of young fledged per successful nest was 319 and was 1 83 for all nesting attempts. The month was the only variable shown to affect significantly the clutch size, eggs hatched and fledging rate, the highest success rates being associated with the middle of the breeding period. The average interval between the hatching of eggs was 2–31 days. Survival rates (47'1%) to fledging were significantly affected by year (1981–1982 being the least) and month (mid-season birds the best). The order of hatching significantly affected age at death or disappearance, the first-hatched birds surviving the longest. The year significantly affected age at fledging, the young from the year in which most clutches were laid leaving the nest at the youngest age and those associated with the year having the least number of clutches remaining in the nest the longest. The month of hatching also affected fledging age, birds at the extremes of the breeding season fledging at older ages. The discussion compares these data with those from elsewhere.     

Phytoplankton chlorophyte structure as related to ENSO events in a saline lowland river (Salado River,Buenos Aires,Argentina)

We analyzed the phytoplankton present in the lower sector of the Salado River (Buenos Aires, Argentina) for 10 years (1995–2005) and detected significant changes occurring in chlorophyte abundance and species richness during La Niña event (1998–1999), which period was analyzed throughout the entire basin (main stream and tributaries). We compared the physicochemical and biologic variables between two El Niño–La Niña–Southern Oscillation (ENSO) periods – El Niño (March 1997–January 1998) and La Niña (May 1998–May 1999) – to identify possible indicators of a relationship between climatic anomalies and chlorophyte performance. Chlorophyte density increased during the La Niña. Under normal or extreme hydrologic conditions, mobile (Chlamydomonas spp.) and nonmobile (Monoraphidium spp.) chlorophytes codominated. These species belonged to Reynolds's functional groups X1 and X2, those typical of nutrient‐enriched environments. Comparative analyses between El Niño and La Niña periods indicated significant differences in physicochemical (K⁺, dissolved polyphenols, particulate reactive phosphorus, alkalinity, pH) and biologic (species diversity and richness, phytoplankton and chlorophyte total densities) variables between the two periods at all basin sites. During the La Niña condition, species richness was greater owing to interconnected shallow lakes and drainage‐channel inputs, while the Shannon diversity index was lower because of the high abundance values of Monoraphidium minutum. A detailed analysis of the chlorophytes in the entire basin, indicated that changes in density and species dominance occurred on a regional scale although diverse chlorophyte assemblages were identified in the different sectors of the Salado River basin. After La Niña event, the entire basin had the potential to revert to the previous density values, showing the resilience to global environmental changes and the ability to reestablish the general conditions of stability.     

Impacts of El Niño-Southern Oscillation Events on the Distribution of Wintering Raptors

Abstract We report the effects of El Niño-Southern Oscillation (ENSO) events on the distribution and abundance of 3 raptor species at continental, regional, and landscape scales. We correlated values from the southern oscillation index (SOI), an index of ENSO phase and strength, with Christmas Bird Count data over a 30-year period. We investigated the relationship between the SOI and winter raptor distributions at 3 spatial scales: continental (central United States), regional (TX, USA), and landscape (3 roadside transects within TX). At the continental scale, ENSO events resulted in regional shifts for American kestrel (Falco sparverius), northern harrier (Circus cyaneus), and red-tailed hawk (Buteo jamaicensis) winter abundances. As expected, these shifts were northward during El Niño (warm) winters, and southward for red-tailed hawks and northern harriers during La Niña (cold) winters. Within Texas, northern harrier distributions shifted towards arid west Texas during wet El Niño winters but were restricted to mesic coastal Texas during dry La Niña winters. Red-tailed hawk abundance increased in eastern Texas during La Niña winters responding to cooler than normal temperatures throughout the northern Midwest. Data from local roadside transects over a 3-year period encompassing 2 El Niño winters and one La Niña winter supported the abundance patterns revealed by continental and regional data, and added evidence that fluctuations in winter abundances result from demographic pulses as well as spatial shifts for wintering populations. This study underscores the need for long-term monitoring at both local and regional spatial scales in order to detect changes in continental populations. Short-term or local studies would have erroneously assumed local population declines or increases associated with ENSO events, rather than facultative movements or demographic pulses supported by this study.     

Factors affecting breeding success of the Flea Bay white-flippered penguin (

The little blue penguin (Eudyptula minor) is in decline throughout much of its range in New?Zealand and Australia, largely due to introduced predators, human disturbance and roadkill mortalities. The white-flippered penguin is a unique morphological variant of the blue penguin, which is traditionally given subspecific status (Eudyptula minor albosignata), and is found only on Banks Peninsula and Motunau Island in Canterbury, New?Zealand. We monitored a varying number of nest boxes from 1996 to 2009. Overall breeding success was 64% over 13 years of monitoring, with a hatching success rate of 75% and a fledging success rate of 85%. We used a set of generalised linear mixed models and model selection to examine the relative influence of various explanatory variables on hatching, fledging and overall breeding success. Breeding success in nest boxes significantly increased with shorter average pair bond length, longer guard period and later relative lay date. Guard period length was the best predictor of breeding success, followed by relative lay date and average pair bond length. Hatching success also increased with later relative lay date but fledging success was not influenced by any of the explanatory variables measured.     

Effects of El Niño drought on seedling dynamics in a seasonally dry tropical forest in Northern Thailand

As El Niño is predicted to become stronger and more frequent in the future, it is crucial to understand how El Niño-induced droughts will affect tropical forests. Although many studies have focused on tropical rainforests, there is a paucity of studies on seasonally dry tropical forests (SDTFs), particularly in Asia, and few studies have focused on seedling dynamics, which are expected to be strongly affected by drought. Seedlings in SDTFs are generally more drought-tolerant than those in the rainforests, and the effects of El Niño-induced droughts may differ between SDTF and tropical rainforests. In this study, we explored the impact of El Niño-induced drought at an SDTF in northern Thailand by monitoring the seedling dynamics at monthly intervals for 7 years, including a period of strong El Niño. The effects were compared between two forest types in an SDTF: a deciduous dipterocarp forest (DDF), dominated by deciduous species, and an adjacent lower montane forest (LMF) with more evergreen species. El Niño-induced drought increased seedling mortality in both the forest types. The effect of drought was stronger in evergreen than in the deciduous species, resulting in higher mortality in the LMF during El Niño. However, El Niño increased seedling recruitment only in the DDF, mainly because of the massive recruitment of the deciduous oak, Quercus brandisiana (Fagaceae), which compensated for the mortality of seedlings in the DDF. As a result, El Niño increased seedling density in the DDF and decreased it in the LMF. This is the first long-term study to identify the differences in the impacts of El Niño on seedlings between the two forest types, and two leaf habits, evergreen and deciduous, in Southeast Asia. Our findings suggest that future climate change may alter the species composition and spatial distribution of seedlings in Asian SDTFs.     

Fluctuations of Vanessa cardui butterfly abundance with El Niño and Pacific Decadal Oscillation climatic variables

Annual 4th of July Butterfly Count data spanning more than 20 years are examined to explore Vanessa cardui (Painted Lady) population fluctuations with ENSO (El Niño) and Pacific Decadal Oscillation (PDO) indices. California, Colorado and Nebraska censuses exhibit a strong positive correlation with the strong El Niño events of 1982–1983 and 1997–1998 and the weaker event of 1991–1992. Regression analysis shows the population fluctuations are strongly coupled to climate variations on both short (El Niño) and longer (Pacific Decadal Oscillation) time scales. Recognizing the sensitivity to these time scales is important for predicting longer‐term global climate change effects.     

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation

Methane (CH₄) emissions from tropical wetlands contribute 60%–80% of global natural wetland CH₄ emissions. Decreased wetland CH₄ emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño–Southern Oscillation (ENSO) on CH₄ emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models’ projections. We use a process‐based model of global wetland CH₄ emissions to investigate the impacts of the ENSO on CH₄ emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH₄ emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8‐month time lag was detected between tropical wetland CH₄ emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH₄ emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH₄ emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH₄ concentrations throughout the 1980s and 1990s and to stable atmospheric CH₄ concentrations from 1999 to 2006, resulting in negative feedback to global warming.