Assessing the effect of water deprivation on the efficacy of on-farm euthanasia methods for broiler chickens.

1. Moribund or diseased poultry requiring euthanasia are often dehydrated. To understand how dehydration influences the efficacy of various killing methods, this experiment investigated the effect of water deprivation (WD) on times to unconsciousness and death.2. Broiler chickens (n = 179) were water-deprived for 0, 24, 48 or 72 hours to mimic dehydration, then killed via manual cervical dislocation, mechanical cervical dislocation (Koechner Euthanising Device (KED)), or non-penetrating captive bolt (Zephyr-EXL), at 8, 22, 36 or 50 d of age. Degree of WD was confirmed by skin turgor, packed cell volume and body weight loss. Method efficacy was evaluated by the time to unconsciousness and death using pupillary light (PUP), palpebral blink (PAL) and nictitating membrane (NIC) reflexes, feather erection (FE), cloacal winking (CW) and convulsions (CN). The extent of damage caused by each method was examined via radiography, gross pathology and histopathology. The main effects of WD time and euthanasia method were analysed by two-way analyses of variance (CRD, PROC MIXED, SAS 9.4) with a-priori contrasts to compare water-deprived versus non-water-deprived (NON) birds.3. Skin turgor, packed cell volume and body weight loss had a quadratic relationship with WD, with highest values for those birds which were water-deprived for 72 h. WD level did not affect time to unconsciousness. Time to death was longer for WD birds than NON, with longer latencies to FE, CW and CN for water-deprived birds. WD only affected radiography or gross pathology scores on d 8, with the extent of subcutaneous haemorrhage within the neck decreasing as WD increased.4. The shortest latency to PUP loss, at all ages, and to PAL and NIC loss, at 22 d, was with the Zephyr-EXL. KED had the longest time to unconsciousness (PUP, PAL and NIC), at all ages, and to death, at 36 and 50 d.5. Overall, WD increased time to death, but did not affect the onset of unconsciousness, with no interaction between methods and WD level.

How do climate change experiments alter plot-scale climate?

To understand and forecast biological responses to climate change, scientists frequently use field experiments that alter temperature and precipitation. Climate manipulations can manifest in complex ways, however, challenging interpretations of biological responses. We reviewed publications to compile a database of daily plot-scale climate data from 15 active-warming experiments. We find that the common practices of analysing treatments as mean or categorical changes (e.g. warmed vs. unwarmed) masks important variation in treatment effects over space and time. Our synthesis showed that measured mean warming, in plots with the same target warming within a study, differed by up to 1.6  ∘ C (63% of target), on average, across six studies with blocked designs. Variation was high across sites and designs: for example, plots differed by 1.1  ∘ C (47% of target) on average, for infrared studies with feedback control (n = 3) vs. by 2.2  ∘ C (80% of target) on average for infrared with constant wattage designs (n = 2). Warming treatments produce non-temperature effects as well, such as soil drying. The combination of these direct and indirect effects is complex and can have important biological consequences. With a case study of plant phenology across five experiments in our database, we show how accounting for drier soils with warming tripled the estimated sensitivity of budburst to temperature. We provide recommendations for future analyses, experimental design, and data sharing to improve our mechanistic understanding from climate change experiments, and thus their utility to accurately forecast species' responses.

Warming experiments underpredict plant phenological responses to climate change.

Warming experiments are increasingly relied on to estimate plant responses to global climate change. For experiments to provide meaningful predictions of future responses, they should reflect the empirical record of responses to temperature variability and recent warming, including advances in the timing of flowering and leafing. We compared phenology (the timing of recurring life history events) in observational studies and warming experiments spanning four continents and 1,634 plant species using a common measure of temperature sensitivity (change in days per degree Celsius). We show that warming experiments underpredict advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold, respectively, compared with long-term observations. For species that were common to both study types, the experimental results did not match the observational data in sign or magnitude. The observational data also showed that species that flower earliest in the spring have the highest temperature sensitivities, but this trend was not reflected in the experimental data. These significant mismatches seem to be unrelated to the study length or to the degree of manipulated warming in experiments. The discrepancy between experiments and observations, however, could arise from complex interactions among multiple drivers in the observational data, or it could arise from remediable artefacts in the experiments that result in lower irradiance and drier soils, thus dampening the phenological responses to manipulated warming. Our results introduce uncertainty into ecosystem models that are informed solely by experiments and suggest that responses to climate change that are predicted using such models should be re-evaluated.

European and Mediterranean hydroclimate responses to tropical volcanic forcing over the last millennium.

Volcanic eruptions have global climate impacts, but their effect on the hydrologic cycle is poorly understood. We use a modified version of superposed epoch analysis, an eruption year list collated from multiple datasets, and seasonal paleoclimate reconstructions (soil moisture, precipitation, geopotential heights, and temperature) to investigate volcanic forcing of spring and summer hydroclimate over Europe and the Mediterranean over the last millennium. In the western Mediterranean, wet conditions occur in the eruption year and the following 3 years. Conversely, northwestern Europe and the British Isles experience dry conditions in response to volcanic eruptions, with the largest moisture deficits in post-eruption years 2 and 3. The precipitation response occurs primarily in late spring and early summer (April-July), a pattern that strongly resembles the negative phase of the East Atlantic Pattern. Modulated by this mode of climate variability, eruptions force significant, widespread, and heterogeneous hydroclimate responses across Europe and the Mediterranean.

Internal ocean-atmosphere variability drives megadroughts in Western North America.

Multidecadal droughts that occurred during the Medieval Climate Anomaly represent an important target for validating the ability of climate models to adequately characterize drought risk over the near-term future. A prominent hypothesis is that these megadroughts were driven by a centuries-long radiatively forced shift in the mean state of the tropical Pacific Ocean. Here we use a novel combination of spatiotemporal tree-ring reconstructions of Northern Hemisphere hydroclimate to infer the atmosphere-ocean dynamics that coincide with megadroughts over the American West, and find that these features are consistently associated with ten-to-thirty year periods of frequent cold El Niño Southern Oscillation conditions and not a centuries-long shift in the mean of the tropical Pacific Ocean. These results suggest an important role for internal variability in driving past megadroughts. State-of-the art climate models from the Coupled Model Intercomparison Project phase 5, however, do not simulate a consistent association between megadroughts and internal variability of the tropical Pacific Ocean, with implications for our confidence in megadrought risk projections.

Temporal ecology in the Anthropocene.

Two fundamental axes - space and time - shape ecological systems. Over the last 30 years spatial ecology has developed as an integrative, multidisciplinary science that has improved our understanding of the ecological consequences of habitat fragmentation and loss. We argue that accelerating climate change - the effective manipulation of time by humans - has generated a current need to build an equivalent framework for temporal ecology. Climate change has at once pressed ecologists to understand and predict ecological dynamics in non-stationary environments, while also challenged fundamental assumptions of many concepts, models and approaches. However, similarities between space and time, especially related issues of scaling, provide an outline for improving ecological models and forecasting of temporal dynamics, while the unique attributes of time, particularly its emphasis on events and its singular direction, highlight where new approaches are needed. We emphasise how a renewed, interdisciplinary focus on time would coalesce related concepts, help develop new theories and methods and guide further data collection. The next challenge will be to unite predictive frameworks from spatial and temporal ecology to build robust forecasts of when and where environmental change will pose the largest threats to species and ecosystems, as well as identifying the best opportunities for conservation.