Reduced oxygen levels and air pressure at higher elevations may limit the ability of insects to move upslope to escape a warming climate, with potential consequences for the essential services they provide, like pollination. This is according to a new review of research in The British Ecological Society journal, Functional Ecology.
Under a warming climate, many species are shifting their range to higher elevations to remain in suitable temperature zones. However, conditions at higher elevations such as thinner air and less oxygen pose unique challenges to insects because of their size, lifecycle and way of breathing.
To understand how moving to higher elevations could affect different insect species, researchers from the University of Montana reviewed research on the physiological effects of hypoxia (low oxygen levels) and hypobaria (low pressure) on insects.
They found that flying insects particularly struggle at higher elevations because the thinner air means they need to generate more lift and expend more energy flying, while reduced oxygen concentrations limit the ability of their breathing system to supply oxygen rapidly enough to the flight muscles.
Insects with active larval stages, like actively feeding caterpillars, also struggle because of their energy and oxygen demands. Insects with aquatic larval stages, like dragonflies, are already limited by the amount of oxygen in water, and this is exacerbated at higher elevations.
Higher rates of water loss at high altitudes were also identified as a barrier to insects' ability to survive in these conditions.
Professor Art Woods, the lead researcher of the study, said: "Our study suggests that low oxygen levels and low atmospheric pressure at higher elevations may negatively affect insect performance, meaning moving uphill may be more difficult than expected. We think of moving uphill as an 'escape valve' for animals but it may not be the solution we hope for."
Insects are key players in many ecosystems and perform essential services such as pollination and decomposition. If they are unable to move upslope under climate change, this could disrupt pollination services, affecting crop production and ecosystem functioning.
The researchers were particularly surprised by the limitations lower oxygen levels place on insects. Professor Woods added: "Because insects get their oxygen through a network of external openings and internal tubes throughout their body, it's easy to imagine that they have little problem getting all the oxygen they need. If humans can go to moderately high elevations with only minor discomfort, surely insects won't have a problem?
"But the data from several experiments suggest that demand for oxygen by active stages of insects, especially growing juveniles and flying adults, is high enough that their respiratory systems struggle to deliver oxygen fast enough at even modestly higher elevations."
The researchers call for more targeted research into high-elevation species to better understand the physiological constraints of shifting ranges upslope. Knowledge gained from this research will be vital for informing conservation strategies.
