Each night, a dark cloud of flying foxes, or fruit bats, moves through the skies of eastern Australia on their way to gorge on nectar and fruits. With a meter-wide (3.2-foot) wingspan, they transport large quantities of pollen and rain down seeds in their poop, helping establish new trees. A new study in Scientific Reports provides the first economic valuation of the ecosystem services provided by flying foxes in Australia, focusing on their significant contribution to the timber industry.
Recent fires and heat stress events have led to colony loss and a dramatic drop in bat numbers; more than 80% of some populations have been wiped out amid extreme heat events. Justin Welbergen, an animal ecology professor at Western Sydney University who was not part of the study, told The New York Times, “A single hot afternoon can result in mortality on a regional scale and in biblical proportions, with tens of thousands of dead flying foxes.”
Flying foxes can travel thousands of kilometers per year, spreading pollen and seeds over large distances, making their economic value immense. First author Alfredo Ortega González, a University of Sydney scientist, said in a video interview with Mongabay, “There is no bird that can move the distance, on average, that a flying fox can move in a night.”
The study authors calculated the spatial extent of the bats’ nightly foraging, based on the locations of 1,209 roosts of four mainland Australian flying fox species (Pteropus poliocephalus, P. Alecto, P. scapulatus and P. conspicillatus). They used data compiled by Australia’s national science agency.
They combined that foraging data and estimates of the distances they travel with maps of suitable habitat to find the overall “Bat Ripple,” the spatial extent of ecosystem services the mammals provide. They found an overall area of influence up to 41.4 million hectares (102 million acres), nearly the size of Sweden.
To work out the value of bats for the timber industry, the authors focused on 465 roosts of the more well-studied grey-headed flying fox (P. poliocephalus). They found the 700-gram (1.5-pound) mammals overlapped with the eucalypt timber industry across 36,038 square kilometers (13,914 square miles) and may help regenerate up to 91.6 million trees per year.
Author Alexander Braczkowski said in an email to Mongabay that Australia’s flying foxes “may be responsible for generating between AUD $271 million and $955 million [$190 million to $668 million] annually for the Australian timber industry through their pollination services alone.”
The authors emphasize that these estimates are conservative and don’t include the broader value of bats for ecosystem health or their specific contributions to carbon sequestration.
Flying foxes deserve to be a conservation priority, said Ortega González, and he hopes the research helps dispel their reputation as noisy, smelly pests. “They are really important, much more important than the general public can imagine.”
Banner image: A grey-headed flying fox. Image by Lawrence Hylton, via iNaturalist (CC-BY).
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