Recreating biodiversity in eucalypt plantings

An Australia-first study of older-aged eucalypt plantings on agricultural land has found they can significantly improve biodiversity.

The study by the NSW Department of Primary Industries, in conjunction with the Rural Industries Research and Development Corporation, found that habitat for a wide range of fauna can be greatly increased by plantings of native trees and shrubs - particularly in areas near remnant bush.

The research was carried out in the Albury-Wodonga region, where substantial areas were planted with local eucalypts and shrubs in the 1970s. These plantings now provide a unique opportunity for investigating biological diversity in older aged plantings.

NSW DPI Forests Biodiversity research leader, Dr Rod Kavanagh, said the study aimed to identify major factors influencing biodiversity in the lower rainfall (600-800mm), fragmented rural landscapes that are susceptible to salinity on the State’s western slopes.

A total of 120 sites were surveyed for the presence birds, bats, arboreal marsupials, terrestrial mammals, reptiles and amphibians, in an effort to provide a guide for future planting schemes.

Dr Kavanagh, together with DPI forest scientists Dr Brad Law and Mr Frank Lemckert, found the impact on biodiversity was uneven, in that birds and bats were more likely to benefit from plantings than ground mammals and herpetofauna.

“Mixed eucalypt and shrub plantings contain similar numbers of birds and bats as remnant native forest and woodland. In particular, birds and bats favoured stands of trees over ten years old.

“However even younger plantings attracted many birds – as long as the patch of vegetation was larger than five hectares.”

The size of the planting is a key factor, with both larger eucalypt plantings and larger remnants having more species of birds and more individuals than smaller patches of either vegetation type.

Bats were widespread in all vegetation types and were recorded flying over cleared paddocks, although they were more common in remnant vegetation.

Remnant vegetation was also the most important for arboreal mammals, nocturnal birds and reptiles, but the oldest plantings (greater than 20 years of age) also contributed habitat for these species.

“However, younger plantings and cleared, or sparsely-treed areas provided little habitat for these species. No reptiles were recorded in paddocks, and ground mammals were virtually absent.”

The scientists argue that remnant vegetation is particularly important because this was essential habitat for some species and also usually contained essential roosting and nesting sites in the form of old, hollow trees.

Other recommendations include:

• Not removing old paddock trees and logs on the ground when preparing sites for eucalypt plantings;
• Excluding grazing from areas where plantings are established primarily for nature conservation; and
• Excluding stock from some dams, or parts of dams because of their importance for frogs and many other species.

Dr Kavanagh said further research was needed to determine rankings for the various planting alternatives, as a way of weighing up the best management options for promoting biodiversity.

Further information: Dr Rod Kavanagh 9872 0111 or 0428 637960, rodk@sf.nsw.gov.au

Media contact: Joanne Finlay 6391 3171 or 0428 491813