Scattered trees on farm paddocks have always been prized by landscape artists and overheated cattle looking for shade.
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But new research by the Australian National University and Industry &Investment NSW is uncovering just how important scattered trees are to the agricultural landscape.
I&I NSW Wildlife Ecology Research Officer, Brad Law was a junior co-author on the recently published paper titled: The disproportionate value of scattered trees.
Dr Law began studying the ecological value of paddock trees 13 years ago and said the ANU paper was an extension of that work.
“Scattered trees are declining in agricultural landscapes worldwide and this research shows how important they are to the agricultural ecosystem,” Dr Law said.
“The work by the ANU staff is very interesting and it was a pleasure to be able to play a part in the paper.
“The research demonstrates the disproportionate value of scattered trees for birds and bats in an Australian livestock grazing landscape.
“Their effect on ecosystem functioning is believed to be disproportionate relative to the small area occupied by any individual tree,” he said.
The researchers surveyed birds at 108 sites and bats at 63 sites. The sites spanned the full range of tree densities from zero to over 100 trees per hectare.
Dr Law said the researchers found the marginal value of individual trees was highest when trees occurred at low densities.
“Compared to treeless sites, bird richness doubled with the presence of the first tree,” Dr Law said.
“Bat richness tripled with the presence of just 3-5 trees and bat activity increased by a factor of 100 with the presence of 3–5 trees,” he said.
Dr Law said future land management activities should take into account the value of scattered trees.
“The trees effectively maintained moderate levels of bird and bat activity throughout largely cleared parts of the landscape. It is also important to remember that large areas of dense tree cover are also required for more specialised species,” he said.
