Desert Ants Thriving, Despite Looming Insectageddon

Simpson Desert ants increase activity due to rainfall changes

Desert ants

The longest study of its kind has found the ‘workers of the desert’ are helping to stabilise fragile ecosystems.


Desert ants are thriving

A 22-year study has found growth in ant numbers, a positive story for the fragile Simpson Desert ecosystem.

A long-term study led by the University of Sydney’s Desert Ecology Research Group and in collaboration with La Trobe University has found that changes in climate in the Simpson Desert, such as increased rainfall, may have led to an increased number of ants and increased activity in ant communities.

This is unexpected given previous reports of world-wide insect decline and the so-called Insectageddon.

“Our findings are important as ants are truly the workers of the desert,” Professor of Ecology and Evolution Glenda Wardle said. “Always present, always active, come rain or shine. Ants contribute in so many ways by tending plants and helping them to reproduce by moving pollen or seeds. Ants are in turn food for many desert fauna species.”

photo of the Simpson Desert
View of dunefields on Ethabuka Reserve, Simpson Desert, with an open pitfall trap in the foreground. Usually red, late summer rain in 2019 stimulated a flush of new plant growth to turn the desert into a vibrant green just two months later. The ant fauna responds dramatically to these rainfall events. Photo: Chris Dickman.

The study published in the Journal of Animal Ecology, covers a 22-year-period, when annual rainfall fluctuated between 79 mm and 570 mm.

The Desert Ecology Research Group sampled ants using pitfall traps in paired dune and swale habitats (a shallow trough) in the Simpson Desert, Australia. They used climate records over this period to model changes in ant communities.

Black tyrant ants on a hakea
Black tyrant ants on a hakea branch. Photo: Glenda Wardle

“Ants are ecologically very important in Australia’s desert regions, acting as predators, scavengers, pollinators, seed dispersers, soil engineers and prey for specialist vertebrates, such as the iconic thorny devil lizard,” said Professor Chris Dickman, from the Desert Ecology Research Group in the School of Life and Environmental Sciences.

“This research – one of the world’s longest-running studies of desert invertebrates – describes for the first time the dynamics and astonishing diversity of the 106 ant species in the study area.”

photo of a thorny devil lizard
Thorny devil lizards feed on ants. Photo: Glenda Wardle

“A key finding of the study was that activity of the dominant ants increased dramatically following long-term increases in rainfall, and increases occurred also in the richness of other ant groups,” Professor Dickman said. “While species’ composition fluctuated over the period of study, the results show that the desert ant fauna, at least, is not suffering the devastating declines in numbers that are occurring with insects in many other parts of the world.”

Professor Wardle said: “The main finding from this study based on long-term field collected data is that ants respond to productivity during wet years but are not declining overall. This finding contrasts with the reported global decline in insects.”

“Ants may be small but the way they respond to resource pulses in arid Australia tells a big story,” Professor Wardle said. “Our study found that over the 22-year period ant communities showed changes in composition but did not decline.

Members of a field team on a recent (June 2019) field trip to Ethabuka Reserve, Simpson Desert, standing under the shade of an old coolibah tree. Left to right: James Vandersteen, Stephen Sarre, Ryan Sarre, Jacqui Meyers and Dara Albrecht. Photo: Chris Dickman
Members of a field team on a recent (June 2019) field trip to Ethabuka Reserve, Simpson Desert, standing under the shade of an old coolibah tree. Left to right: James Vandersteen, Stephen Sarre, Ryan Sarre, Jacqui Meyers and Dara Albrecht. Photo: Chris Dickman

Long-term ecological studies are crucial to tracking the health of ecosystems. The Desert Ecology Research Group has been doing this for 30 years. DERG is working on how animals and plants can survive dry conditions

Led by Professors Chris Dickman and Glenda Wardle, with critical support from Dr Chin-Liang Beh, Mr Bobby Tamayo (Operations Manager) and early-career researcher Dr Aaron Greenville, DERG aims to track shifts in biodiversity in arid Australia and identify and mitigate the processes that drive biodiversity declines.