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CRC for Forestry News 11 - Plantations can be net positive for biodiversity

Eucalypt plantations on larger tracts of former agricultural land can be a net positive for biodiversity

bluegum plantation2

Blue gum plantation

by providing habitat and resources for some animals, according to a new study by the CRC for Forestry.

The study, Biodiversity outcomes from eucalypt plantation expansion into agricultural landscapes of Southern Australia; A Review, notes that replacing pastureland with plantations can reduce the negative impact of livestock grazing, limit biological degradation at edges of remnant vegetation, and can assist in the dispersal of organisms between patches of remnant vegetation.

The study reviewed the results of hundreds of published studies on biodiversity in eucalypt plantations in southern Australia. Most of the studies compared biodiversity in plantations against remnant eucalypt vegetation and cleared agricultural land. Studies of birds dominated the literature, although a wide range of organisms was covered.

The report’s author, Peter Grimbacher of the University of Melbourne’s School of Resource Management and Geography, who was previously a CRC for Forestry postdoctoral fellow, notes that plantations on agricultural land may negatively affect species that prefer open habitats like grasslands, or the edges of woodlands. However, forest or woodland species often benefit from plantation establishment on agricultural land.

Given the importance of remnant vegetation to maximising biodiversity, forest management may be better focused towards conserving and rehabilitating vegetation within plantation estates rather than maximizing structural complexity within plantations, the report says.

Eucalypt plantations in Australia have grown rapidly in recent years to approximately one million hectares as at 2010. Most new plantations are established on former agricultural land, and remnant vegetation from that land is often embedded within the plantations.

The biodiversity value of eucalypt plantations is generally greater than agricultural land but less than native eucalypt vegetation. It can provide habitat for a variety of animals, and biodiversity can be further enhanced by biological legacies such as old trees and other remnant vegetation.

The study finds plantations do not appear to be a source of pests that colonise adjacent land, though they can reduce stream-flows and affect aquatic biodiversity if they occupy too much of a water catchment area.

It also strikes a cautious note in acknowledging that considerable gaps remain in our understanding of biodiversity in eucalypt plantations, as the establishment of large-scale plantations is a relatively recent development. Longer term studies are needed, as no studies have tracked biodiversity changes in eucalypt plantations through a full rotation from planting to harvesting.