Alexandra S. Gardner

Ectotherms are essential components of all ecosystems. They rely on external heat sources like air temperature and solar radiation to regulate their body temperature and optimise life history traits. Climate change, by altering air temperature and cloud cover, will likely impact these processes. To examine how air temperature and shade influence terrestrial insects, we reared nymphs of the field cricket (Gryllus campestris) at high (mean air temperature 13.4°C) and low (mean air temperature 9.6°C) sites in northern Spain, with partially shaded and unshaded treatments at each site. We tested for local adaptation to these climate variables by rearing nymphs from high and low altitude genetic lineages in all treatment combinations. Development time was significantly longer (on average 10 days) at low air temperature but was unaffected by a 40% increase in shade, suggesting crickets compensate for reduced sun exposure in shaded environments and may forgo some opportunities to gain energy from the sun in unshaded environments. Adult mass was affected by an interaction between shade and air temperature. At low air temperature, shaded crickets had higher mass (on average + 0.06 g) than unshaded crickets, whereas at high air temperature, shaded crickets had lower mass than unshaded crickets (on average − 0.08 g). This indicates that changes in cloud cover will impact insects differently in warmer and cooler parts of their range. We found no evidence for local adaptation in either development time or mass, suggesting these traits are not strongly differentiated between populations from high and low altitude environments. Our findings highlight the importance of considering both air temperature and solar radiation when predicting climate change impacts on insects. Shifts in temperature and cloud cover may have complex and region‐specific effects on these vital ecosystem components.

Ectotherms are essential components of all ecosystems and rely on external heat to regulate their body temperature. For most terrestrial ectotherms the primary sources of heat are ambient temperature and solar radiation. Many insects can use movement to respond to changes in temperature and solar radiation in order to manage their body temperature and optimise life history traits. However, we lack the understanding of the relative importance of temperature and shade that we need to predict how the combined effects of changes in air temperature and cloud cover will impact terrestrial insect populations. We reared developing nymphs of the field cricket ( Gryllus campestris ) at high and low air temperature sites with partially shaded and unshaded treatments at each site. Given the broad altitudinal range of this species, we tested the possibility of local adaptation to these climate variables by rearing nymphs from high and low altitude genetic lineages in all treatment combinations. We found that development time was strongly affected by air temperature, but not by a substantial increase in shade. This suggests that developing crickets can compensate for an increase in shade, presumably because in unshaded conditions they forgo some opportunities to gain energy from the sun. We found that mass at adulthood was affected by an interaction between availability of sun (shading treatment) and air temperature. This indicates that changes in cloud cover will impact insects differently in warmer and cooler areas. We found no evidence for local adaptation in these traits. Our findings underscore the need to consider both ambient temperature and solar radiation in predicting the impacts of climate change on insect populations, as shifts in temperature and cloud cover may have complex and region-specific effects on these vital ecosystem components.

Ectotherms make up the majority of terrestrial biodiversity, so it is important to understand their potential responses to climate change. Often, models aiming to achieve this understanding correlate species distributions with ambient air temperature. However, this assumes a constant relationship between the air temperature and body temperature, which determines an ectotherm's thermal performance. To test this assumption, we develop and validate a method for retrospective estimation of ectotherm body temperature using heat exchange equations. We apply the model to predict the body temperature of wild field crickets (Gryllus campestris) in Northern Spain for 1985–2019 and compare these values to air temperature. We show that while air temperature impacts ectotherm body temperature, it captures only a fraction of its thermal experience. Solar radiation can increase the body temperature by more than 20°C above air temperature with implications for physiology and behaviour. The effect of solar radiation on body temperature is particularly important given that climate change will alter cloud cover. Our study shows that the impacts of climate change on species cannot be assumed to be proportional only to changing air temperature. More reliable models of future species distributions require mechanistic links between environmental conditions and thermal ecophysiologies of species.

Protected areas (PAs) are a core component in global efforts to prevent further declines in biodiversity. We examine whether the United Kingdom's PA portfolio has reduced local extinctions of breeding birds and consider how the characteristics of different PA designations may have affected conservation outcomes. We use breeding bird atlas data to calculate the proportion of species in each 10 × 10‐km grid cell confirmed as breeding in 1988–1991 but not in 2008–2011. We find that the protection offered by PAs is little to no different from that of the wider landscape and, depending on the type of PA, attribute this to PAs being either too small or not managed for biodiversity outcomes. To meet the ambitious new global targets for expanding PA coverage set at the 15th UN Biodiversity Conference, all countries need to monitor and ensure PA effectiveness; high PA coverage does not guarantee that biodiversity is protected.

Biodiversity is declining worldwide. When species are physically active (i.e., their diel niche) may influence their risk of becoming functionally extinct. It may also affect how species losses affect ecosystems. For 5033 terrestrial mammals, we predict future changes to diel global and local functional diversity through a gradient of progressive functional extinction scenarios of threatened species. Across scenarios, diurnal species were at greater risk of becoming functionally extinct than nocturnal, crepuscular, and cathemeral species, resulting in deep functional losses in global diurnal trait space. Redundancy (species with similar roles) will buffer global nocturnal functional diversity; however, across the land surface, losses will mostly occur among functionally dispersed species (species with distinct roles). Functional extinctions will constrict boundaries of cathemeral trait space as megaherbivores, and arboreal foragers are lost. Variation in the erosion of functional diversity across the daily cycle will likely profoundly affect the partitioning of ecosystem functioning between night and day.

Aim: Species respond to environmental conditions and so reliable assessments of climate suitability are important for predicting how climate change could alter their distributions. Long‐term average climate data are often used to evaluate the climate suitability of an area, but in these aggregated climate datasets, inter‐annual variability is lost. Due to non‐linearity in species’ biological responses to climate, estimates of long‐term climate suitability from average climate data may be biased and so differ from estimates derived from the average annual suitability over the same period (average response). We investigate the extent to which such differences manifest in a regional assessment of climate suitability for 255 plant species across two 17‐year time periods.Location: Cornwall in South‐West England provides a case study.Taxon: Plantae.Methods: We run a simple mechanistic climate suitability model and derive quantitative estimates of climate suitability for 1984–2000 and 2001–2017. For each period, we run the model using climate data representing average monthly values for that period. We then run the model for each year using monthly climate data for that year and average the annual suitability scores across each period (average response). We compare estimates of climate suitability from these two approaches.Results: Average climate data gave higher estimates of suitability than the average response, suggesting bias against years of poor suitability in temporally aggregated climate datasets. Differences between suitability estimates were larger in areas of high climate variability and correlated with species’ environmental requirements, being larger for species with small thermal niches and narrow ranges of precipitation tolerance.Main Conclusions: Incorporating inter‐annual variability into climate suitability assessments or understanding the extent to which average climate data might obscure this variance will be important to predict reliably the impacts of climate change on species distributions and should be considered when using mechanistic species distribution models.

The impacts of the changing climate on the biological world vary across latitudes, habitats and spatial scales. By contrast, the time of day at which these changes are occurring has received relatively little attention. As biologically significant organismal activities often occur at particular times of day, any asymmetry in the rate of change between the daytime and night‐time will skew the climatic pressures placed on them, and this could have profound impacts on the natural world. Here we determine global spatial variation in the difference in the mean annual rate at which near‐surface daytime maximum and night‐time minimum temperatures and mean daytime and mean night‐time cloud cover, specific humidity and precipitation have changed over land. For the years 1983–2017, we derived hourly climate data and assigned each hour as occurring during daylight or darkness. In regions that showed warming asymmetry of >0.5°C (equivalent to mean surface temperature warming during the 20th century) we investigated corresponding changes in cloud cover, specific humidity and precipitation. We then examined the proportional change in leaf area index (LAI) as one potential biological response to diel warming asymmetry. We demonstrate that where night‐time temperatures increased by >0.5°C more than daytime temperatures, cloud cover, specific humidity and precipitation increased. Conversely, where daytime temperatures increased by >0.5°C more than night‐time temperatures, cloud cover, specific humidity and precipitation decreased. Driven primarily by increased cloud cover resulting in a dampening of daytime temperatures, over twice the area of land has experienced night‐time warming by >0.25°C more than daytime warming, and has become wetter, with important consequences for plant phenology and species interactions. Conversely, greater daytime relative to night‐time warming is associated with hotter, drier conditions, increasing species vulnerability to heat stress and water budgets. This was demonstrated by a divergent response of LAI to warming asymmetry.