Avian mortality risk during heat waves will increase greatly in arid Australia during the 21st century

Shannon R Conradie; Stephan M Woodborne; Blair O Wolf; Anaïs Pessato; Mylene M Mariette; Andrew E McKechnie

doi:10.1093/conphys/coaa048

Avian mortality risk during heat waves will increase greatly in arid Australia during the 21st century

Conserv Physiol. 2020 Jun 4;8(1):coaa048. doi: 10.1093/conphys/coaa048. eCollection 2020.

Authors

Shannon R Conradie^{1

2}, Stephan M Woodborne^{3

4}, Blair O Wolf⁵, Anaïs Pessato⁶, Mylene M Mariette⁶, Andrew E McKechnie^{1

2}

Affiliations

¹ South African Research Chair in Conservation Physiology, South African National Biodiversity Institute, 2 Cussonia Ave, Brummeria, Pretoria 0184, South Africa.
² DST-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa.
³ iThemba LABS, Johannesburg, 514 Empire Rd, Johannesburg 2193, South Africa.
⁴ Mammal Research Institute, University of Pretoria, Lynnwood Rd., Pretoria 0002, South Africa.
⁵ UNM Biology Department, University of New Mexico, Albuquerque, NM 87131, U.S.A.
⁶ Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, 75 Pigdons Road, Waurn Ponds VIC 3216, Australia.

Abstract

Intense heat waves are occurring more frequently, with concomitant increases in the risk of catastrophic avian mortality events via lethal dehydration or hyperthermia. We quantified the risks of lethal hyperthermia and dehydration for 10 Australian arid-zone avifauna species during the 21st century, by synthesizing thermal physiology data on evaporative water losses and heat tolerance limits. We evaluated risks of lethal hyperthermia or exceedance of dehydration tolerance limits in the absence of drinking during the hottest part of the day under recent climatic conditions, compared to those predicted for the end of this century across Australia. Increases in mortality risk via lethal dehydration and hyperthermia vary among the species modelled here but will generally increase greatly, particularly in smaller species (~10-42 g) and those inhabiting the far western parts of the continent. By 2100 CE, zebra finches' potential exposure to acute lethal dehydration risk will reach ~ 100 d y^-1 in the far northwest of Australia and will exceed 20 d y^-1 over > 50% of this species' current range. Risks of dehydration and hyperthermia will remain much lower for large non-passerines such as crested pigeons. Risks of lethal hyperthermia will also increase substantially for smaller species, particularly if they are forced to visit exposed water sources at very high air temperatures to avoid dehydration. An analysis of atlas data for zebra finches suggests that population declines associated with very hot conditions are already occurring in the hottest areas. Our findings suggest that the likelihood of persistence within current species ranges, and the potential for range shifts, will become increasingly constrained by temperature and access to drinking water. Our model adds to an increasing body of literature suggesting that arid environments globally will experience considerable losses of avifauna and biodiversity under unmitigated climate change scenarios.

Keywords: Avian mortality; dehydration; desert; heat waves; hyperthermia; population declines.