How extreme is extreme? Demographic approaches inform the occurrence and ecological relevance of extreme events

Abstract

Projected increases in the variability of both temperature and precipitation will result in the greater likelihood and magnitude of extreme weather (e.g., cold snaps, droughts, heat waves) with potential implications for animal populations. Despite the ecological consequences of extreme weather, there are several challenges in identifying extreme events and measuring their influence on key demographic processes in free‐living animals. First, there is often a mismatch between the spatial and/or temporal resolution of biological and climate data that could hinder our ability to draw accurate inferences about how species and populations respond to extreme events. Second, there are multiple approaches for identifying an extreme event ranging from statistical definitions (e.g., standardized deviates) to species‐specific biological thresholds. Lastly, the impacts of extreme weather on species can vary as a function of differences in exposure and intrinsic sensitivity to climate variability. In the Northern Hemisphere, rapid warming has contributed to a “wobblier” jet stream that promotes the higher likelihood of cold Arctic air moving southward and leading to more extreme winter conditions. Due to these conditions, the Upper Midwest experienced two of the coldest winters in the past 35 yr during 2014 and 2015. We combined radiofrequency identification technologies with fine‐scale weather data and standard capture–mark–recapture analyses to estimate weekly and overwinter survival rates of a common winter passerine, the Black‐capped Chickadee (Poecile atricapillus), in a near continuous fashion. Using both statistical and biological definitions of weather extremes, we found that declining ambient temperatures reduced survival (despite the presence of favorable microclimates), and that biologically defined thresholds of extreme weather were better at explaining variation in survival than statistical ones. Moreover, habitat fragmentation interacted with temperature to modify the exposure of birds to extreme weather with survival consequences, but sensitivity, as measured by body condition, did not appear to play a significant role. These results provide a novel contribution to the understanding of how extreme weather may interact with local‐ and landscape features to influence the demography of species and populations, and suggest potential opportunities for climate‐change adaptation in human‐dominated landscapes.

Extreme winter weather disrupts bird occurrence and abundance patterns at geographic scales

“…Although extreme weather events are increasing in frequency throughout the year (Rahmstorf and Coumou 2011), extreme weather during winter may leave wildlife exceptionally vulnerable as many species are already living at the razor's edge – operating with scarce food resources and temperatures often at the lower end of their thermal limits (Salewski et al 2013, Penczykowski et al 2017, Casson et al 2019). Several types of winter weather events have the potential to impact northerly ecosystems and their dependent species – disrupting behavior, distributions and survival – despite lasting only days (Martin 2017, Birgander et al 2018, Kreyling et al 2019, Latimer and Zuckerberg 2019). For instance, the intrusion of the polar vortex into central and eastern North America during winter has become more common and intense as arctic warming has destabilized the jet stream separating arctic and temperate air masses, resulting in extremely cold air outbreaks in temperate areas sustained over several days to a week (Cohen et al 2014).…”

The effect of summer drought on the predictability of local extinctions in a butterfly metapopulation

“…Assessments of ECEs and their impacts are generally conducted by performing perturbation experiments (e.g., Bokhorst et al 2008;Pansch et al 2018) or by opportunistically taking advantage of a rare event (e.g., Smith 2011;Grant et al 2017;Latimer & Zuckerberg 2019). The latter type often concentrate on a single population and relatively small spatial scales or lack longterm ecological monitoring of the system prior to the ECE (but see Thibault & Brown 2008;Campbell-Staton et al 2017).…”

Shooting blanks: extreme climate event promotes phenological mismatch between sexes in hibernating ground squirrels

“…This de nition is useful for categorizing extreme events in a climatespeci c setting. In attempting to explore the biological effects of extreme climate events, however, it is becoming increasingly important to de ne extreme events in a more setting-and organism-speci c context [14,15] . For example, Gutschick and BassiriRad [16] de ne an extreme event as one that exceeds the acclimatory capacity of an organism, while Bailey and van de Pol [17] consider an episode to be extreme when the climate or the conditions trigger a negative threshold-dependent biological response.…”

“…In other words, once a climate event is deemed extreme, we must further consider the conditions of the event in terms of an organism's biological capacity to tolerate it [15] . Extreme climate events have elicited various biological responses, including reduced body condition, shifts in species distributions, changes in functional community structure and community dynamics, and mass mortality events [14,18−20] .…”