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