For over 2,000 years, Australia's Aboriginal Martu people hunt kangaroos and set small grass fires to catch lizards. A University of Utah researcher found such man-made disruption boosts kangaroo populations - showing how co-evolution helped marsupials and made Aborigines into unintentional conservationists.
"We have uncovered a framework that allows us to predict when human subsistence practices might be detrimental to the environment and when they might be beneficial," says Brian Codding, an assistant professor of anthropology.
"When subsistence practices have long histories, they are more likely to sustain ecosystem stability," he says. "But when there are sudden changes to the way people make a living on the land, expect the result to be detrimental to the environment."
The findings, published online today in the journal Human Ecology
, suggest that Australia might want to encourage small-scale burning to bolster wildlife populations in certain areas, Codding says.
"In some parts of Australia where Aboriginal people no longer are burning the bush, ecologists are recording rapid declines in threatened species, which also might be due to increased predation by invasive predators," he adds.
The study concludes: "To be successful, management schemes should facilitate traditional burning and hunting regimes in remote communities, and incorporate this traditional ecological practice into future management protocols."
The new study found that small grass fires set by Martu to reveal sand monitor lizard holes created a patchy mosaic of five stages of vegetation at different post-fire ages, increasing hill kangaroo populations because the animals can hide from predators like dingoes in older bush grass and spend most of their time eating shoots and fruits in patches of younger vegetation. Counts of kangaroo scats showed kangaroo populations were largest at moderate distances from Martu settlements. At those distances, there also were moderate levels of both kangaroo hunting and burning to expose lizard burrows.
"As people spend more time hunting in a region, kangaroos densities actually increase, but only up to a threshold, after which their populations decline," Codding says.