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A new University of Queensland koala habitat study has raised serious questions about the adequacy of habitat protection guidelines currently employed by conservation planners.

Planning to ensure the ongoing survival and biodiversity of a species inevitably requires the identification of habitat thresholds – that is, the minimum amount of habitat needed to ensure the species' persistence.

According to Dr Jonathan Rhodes, however, conservation planners may be overlooking critical factors in their calculation and prescription of habitat targets.

“It is generally accepted that appropriate habitat targets or habitat thresholds differ among different species, but we know very little about how they vary among different regions for the same species,” Dr Rhodes said.

“The vast majority of conservation planning tends to set exactly the same targets across all regions.

“The implicit assumption is that thresholds everywhere are the same [but as our research shows], this may be erroneous.”

Dr Rhodes and colleagues conducted a study of koala habitats in three different regions across Australia (Noosa, QLD; Port Stephens, NSW; and Ballarat, VIC), aiming to measure and compare their minimum habitat needs and to test whether those requirements were consistent across the different regions.

They discovered not only that thresholds varied vastly across the three regions, but also that they were generally higher than widely used rules-of-thumb that call for the preservation of at least 15 to 30 percent of a landscape as habitat.

“Our work suggests appropriate targets for the proportion of native forest in the landscape for koala conservation of around 60 percent in Noosa, 50 percent in Port Stephens, and 30 percent in Ballarat,” Dr Rhodes said.

“The implications for conservation planning are that we need to think carefully about what our targets are and whether it is appropriate to set uniform conservation targets across broad regions… or whether we need to set more specific targets for each area.

“Simple rules-of-thumb may be a practical solution to setting conservation targets, especially where the amount of data is limited. However, as our study shows, the real world is often more complex than this, and basing decisions on such simple [tenets] may be misguided.”

In fact, as Dr Rhodes warns, adherence to this type of across-the-board approach to planning could have serious ecological consequences.

“Unless conservation and planning efforts are effectively coordinated across regions, and priorities recognise the importance of a hierarchy of habitat factors, including landscape context, the long term prospects for managing koala (and other wildlife populations) will be diminished,” he said.

While the process of accounting for such factors and accordingly developing area-specific targets may be time-consuming, Dr Rhodes said ongoing research might allow planners to develop habitat guidelines for different types of landscapes.

“Future research should focus on understanding why these variations occur and on developing generic models capable of predicting how different species will respond to different landscape management actions.

“Being able to predict what thresholds are likely to be in different landscapes will be an important challenge… [Which, once tackled], would have significant beneficial impacts on conservation planning in Australia and the rest of the world.”