Entomologist Jonathan Majer had disturbing news from the jarrah forests of southwest
Australia, the ants are marching out. Source: The Australian
For 37 years, Professor Majer has tracked the presence of a hundred species of ants in the native forests, in one of the longest studies of its kind in the world.
He has found the forest is changing; the ant species that prefer shaded and cool forest habitat have gone.
“It’s not conclusive but there’s a striking result and we’re seeing something tangible,” he said, adding that in nearly four decades of visiting his study site, rainfall over much of the southwest had dropped by up to 25%.
One of the disappearing ants is Heteraponera majeri, named in Professor Majer’s honour. Regularly found in one part of moist jarrah forest, it hasn’t been recorded since the late 1990s.
With Curtin University colleague Brian Heterick, Professor Majer has pioneered the study of ants as indicators of environmental health.
“The presence or absence of certain species tells us a lot,” said Majer, who has tracked ant populations in other parts of Australia, South Africa and Brazil’s Amazon jungle.
“In the southwest, we’ve noticed a gradual disappearance of more specialised native species.”
“It’s changed quite drastically, in almost exactly the same period when the drop in rainfall began,” said Heterick.
“We think the forest has become a more hostile environment for cryptic ants that like moist leaf litter and shady shrub layers. The litter and shade are starting to disappear. There’s nowhere for the ants to go because land is drying out around them.”
Majer’s findings support other studies tracking the effect of climate change on forests.
Giles Hardy, from Murdoch University’s Centre of Excellence for Climate Change, has recorded the mass death of eucalypts, visible in forests around Perth and tourist spots like Margaret River.
Majer said that decreased rainfall in the forests of southwest Australia might be responsible for disappearing ant species. He said that trees stressed by heat and dryness are more prone to fungal disease, borer insects and leaf damage from cold frosts associated with high pressure systems.
“There are potentially very serious effects being caused by both drought and frosts,” Hardy said.
He said Australia’s southwest corner is “a canary-in-the-mine case” for climate change.
“The consensus is it’s happening here a bit earlier than other places. Foresters tell me it’s taking much longer for forests to recover from fires, and good timber is becoming scarcer. These are all indications we’re reaching a tipping point . . . we need to listen to it.”
The federal Department of Climate Change predicts that by 2070, the annual average number of days above 35 celcius in Perth could increase from 28 to 67.
Southwest Australia is recognised globally as an ecological hotspot for unique plant and animal species, but the insect scientists said that between 20 and 50% of jarrah forest ant species, which move seeds and soil around, have become scarce.
“All these ants have a role and if they are disappearing, who knows what effect that will have
on the ecosystem,” Heterick said.
“We’ve had cases where a multi-billion-dollar iron ore mine has been held up by a single spider-like organism. Here we have a disappearance of species . . . not due to one industry but to all of our activity as human beings. We have a moral obligation to look after our biodiversity.”
