It's fair to say that such trees, often the only landmarks in bare paddocks and on naked hillsides, don't seem like prime koala habitat.

But researchers from the University of Sydney who tracked 23 of the marsupials in an agricultural landscape in northwest NSW have shown they are.

"We found they continually go back to these trees because they are so good," says the study's lead author, Associate Professor Mathew Crowther.

It turns out such trees are rich in nitrogen, one of the building blocks of life. That has little to do with their isolation and everything to do with the quality of the land they're growing on.

"The reasons these places were cleared in the first place was for farming, and farmers pick fertile land, and land with water," Assoc Prof Crowther says.

"These trees are on property that's often flat, fertile and well watered and they benefit from that."

The study showed the 23 koalas tracked near Gunnedah repeatedly returned to isolated gum trees, risking exhaustion and dog attacks by leaving more protected bushland and dashing across exposed landscapes.

The koalas also stayed in isolated nutrient-rich trees longer than they did in other trees.

Assoc Prof Crowther says the study demonstrates the importance of farm trees as habitat for koalas, which were listed as endangered earlier this year.

"Don't cut down those paddock trees," he says.

"And make it easier for koalas to get there by removing threats where possible, and planting green corridors."

The study has been published in the journal Behavioural Ecology.

Australian Associated Press