The Bumblebees Scarcity Syndrome: Are heat waves leading to local extinctions of bumblebees (Hymenoptera: Apidae:Bombus)?

Severe heat waves have occasionally led to catastrophic avian mortality in hot desert environments. Climate change models predict increases in the intensity, frequency and duration of heat waves. A model of avian evaporative water requirements and survival times during the hottest part of day reveals that the predicted increases in maximum air temperatures will result in large fractional increases in water requirements (in small birds, equivalent to 150-200 % of current values), which will severely reduce survival times during extremely hot weather. By the 2080s, desert birds will experience reduced survival times much more frequently during mid-summer, increasing the frequency of catastrophic mortality events.

Little is known about the effects of temperature extremes on natural systems. This is of increasing concern now that climate models predict dramatic increases in the intensity, duration and frequency of such extremes. Here we examine the effects of temperature extremes on behaviour and demography of vulnerable wild flying-foxes (Pteropus spp.). On 12 January 2002 in New South Wales, Australia, temperatures exceeding 42 degrees C killed over 3500 individuals in nine mixed-species colonies. In one colony, we recorded a predictable sequence of thermoregulatory behaviours (wing-fanning, shade-seeking, panting and saliva-spreading, respectively) and witnessed how 5-6% of bats died from hyperthermia. Mortality was greater among the tropical black flying-fox, Pteropus alecto (10-13%) than the temperate grey-headed flying-fox, Pteropus poliocephalus (less than 1%), and young and adult females were more affected than adult males (young, 23-49%; females, 10-15%; males, less than 3%). Since 1994, over 30000 flying-foxes (including at least 24500 P. poliocephalus) were killed during 19 similar events. Although P. alecto was relatively less affected, it is currently expanding its range into the more variable temperature envelope of P. poliocephalus, which increases the likelihood of die-offs occurring in this species. Temperature extremes are important additional threats to Australian flying-foxes and the ecosystem services they provide, and we recommend close monitoring of colonies where temperatures exceeding 42.0 degrees C are predicted. The effects of temperature extremes on flying-foxes highlight the complex implications of climate change for behaviour, demography and species survival.

During August 2003, Europe sustained a severe heat wave that resulted in 14 800 heat-related deaths in France. Most of these excess deaths occurred in urban areas, where maximal temperatures broke all records. Heatstroke is the most severe form of heat-related illness. The clinical course of heatstroke in urban areas of temperate countries is poorly documented. During the French heat wave (August 1-20, 2003), we conducted a prospective study in a university hospital located in Lyon, one of the largest metropolitan areas in France. We evaluated survival and functional outcome for 2 years and looked for factors influencing the prognosis. A total of 83 patients presented with heatstroke. The 28-day and 2-year mortality rates were 58% and 71%, respectively. Mortality was influenced as early as admission by the level of fever and the number of organ dysfunctions. Multivariate analysis revealed an independent contribution to mortality if patients came from an institution (hazard ratio [HR], 1.98; 95% confidence interval [CI], 1.05-3.71), used long-term antihypertensive medication (HR, 2.17; 95% CI, 1.17-4.05), or presented at admission with anuria (HR, 5.24; 95% CI, 2.29-12.03), coma (HR, 2.95; 95% CI, 1.26-6.91), or cardiovascular failure (HR, 2.43; 95% CI, 1.14-5.17). Most surviving patients exhibited a dramatic alteration of their functional status at 1 and 2 years. Heatstroke is associated with poor outcomes in temperate urban areas. This could be explained at least in part by our lack of experience. Western temperate countries need to be more prepared for future heat waves.