Measurement of microclimates in a warming world: problems and solutions

Area of Science:

• Environmental science
• Zoology
• Climate change biology

Background:

• Terrestrial animals' biological responses to warming are often linked to air temperature.
• However, radiant heat significantly influences animal heat exchange, sometimes causing heat gain even when body surface temperature exceeds air temperature.
• While refuges like burrows offer protection, other shelters provide only partial relief from radiant heat.

Purpose of the Study:

• To highlight the limitations of using air temperature to assess animal thermal environments.
• To propose improved metrics for quantifying the microclimate experienced by terrestrial animals.
• To ensure accurate assessment of an animal's thermal environment for predicting biological responses to climate change.

Main Methods:

• Discussing the role of radiant heat load versus air temperature in animal heat exchange.
• Analyzing the effectiveness of different shelters in mitigating radiant heat exposure.
• Evaluating evaporative cooling as a heat dissipation mechanism and its dependence on water vapor pressure.
• Examining the discrepancy between meteorological wind speed and animal-experienced wind.
• Proposing black-globe temperature as a superior metric for dry heat load and water vapor pressure for humidity.

Main Results:

• Air temperature is a less significant factor in animal heat exchange compared to radiant heat.
• Animals utilize refuges and evaporative cooling to manage heat load, with varying effectiveness.
• Evaporative cooling depends on water vapor pressure, not solely relative humidity.
• Microclimatic conditions, including wind, humidity, and radiation, directly impact animals.
• Black-globe temperature and water vapor pressure are proposed as accurate metrics.

Conclusions:

• Accurate assessment of an animal's thermal environment requires quantifying microclimate, not just ambient air temperature.
• Black-globe temperature is a more appropriate metric for dry heat load than air temperature.
• Water vapor pressure is a more suitable humidity metric than relative humidity for analyzing animal responses to heat.
• These refined metrics are crucial for understanding and predicting animal adaptations to a warming world.