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An alternative perspective on land clearing

14, December 2006

Most bird-lovers and conservationists would accept the commonly held view that land clearing for agriculture is one of the greatest threats to Australia’s wildlife, and should be halted at all costs. However throughout vast tracts of western New South Wales and Queensland a different problem has been worsening for over 100 years - and has so far been largely ignored by most conservation groups.

Western NSW landholders claim that grasslands and open woodlands are being invaded by native shrub and tree species (invasive native species - INS - or “woody weeds”) leading to loss of biodiversity and landscape productivity.

The landholders have many supporters among experienced ecologists, botanists, and soil conservationists. In August this year Channel 9 The Sunday Program aired a program entitled “The Great Land Clearing Myth”, focusing on this issue in the vast Cobar Peneplain bioregion of central western NSW.

This bioregion covers about 73,500 square km surrounding the township of Cobar. The program quoted Geoff Cunningham, ecologist and co-author of The Plants of Western NSW: “there are probably many places in Australia where one would say land clearing is undesirable, but the problem is that in this area it’s different.”

Dick Condon, former Western Lands Commissioner, soil scientist, and author of Out of the West, concurred: “the original native grasses were very tall and very deep rooted and the trees were a long way apart.” He claimed there are 12 million hectares (or 120,000 square km) of grasslands and open woodlands throughout western NSW that are invaded and degraded by “woody weeds”, and that the problem is worsening with time.

The original explorers and early pastoralists of this region described a mosaic landscape of thick luxuriant grasslands, open woodlands, and patches of dense shrub lands. The vital tool for maintaining this landscape was fire, both natural from lightning strikes and deliberately lit by the Aboriginals.

It appears that periodically a series of favourably wet summers caused the massive germination of the invasive native shrub and tree species, and at the same time caused luxuriant growth of native grasses. When the inevitable dry conditions returned the vegetation was ripe for hot fires fuelled by the dry grasses. These fires destroyed the young shrubs and trees, allowing the grasses to dominate the landscape.

Early settlement caused massive changes to the ecology of the region. Grasslands were overgrazed, fires were put out, native shrubs and trees began to invade grasslands as early as 1870, rabbits invaded, drought struck, and wool prices collapsed.

By 1901 the Western Division of NSW was in an economic and ecological crisis, and a Royal Commission was called to try and formulate some solutions. Today landholders claim they are still battling the invading scrub, and that recently introduced native vegetation regulations are making their job almost impossible.

Six species are designated as Invasive Native Species or INS in the Native Vegetation Conservation Act 1997. In addition some further species can behave as INS in some areas, and are listed (PDF 99KB) as such by different Catchment Management Authorities. Over time these Invasive Native Species form woodlands and shrublands of increasing density. Living groundcover (grasses and forbs) are starved for moisture and light and gradually disappear, leaving bare ground, leaf litter, and fallen branches.

So how is all this affecting the bird life of the region? In 2000 intensive biodiversity surveys were carried out by “West 2000” at a number of sites in the Cobar, Wanaaring, and Ivanhoe localities.

The sites varied in woody shrub cover from 1 per cent to 40 per cent. The results showed that the number of bird species recorded did not change significantly with increasing woody shrub cover. However bird species that feed on seeds, plants, and insects on the ground consistently preferred landscapes with a lower level of woody shrub cover. Two examples of threatened species that were found to prefer less woody shrub cover were the Pink Cockatoo and Hooded Robin.

Landholders of the Cobar Peneplain claim that 80 per cent of the threatened species of the region are dependent on grasslands and open woodland habitat. They claim that while many fauna species use the dense shrublands and trees for roosting and nesting, they are almost always seen feeding in the grasslands and croplands nearby. Their claims are supported by the known habitat requirements of the threatened birds recorded from the Cobar region. The majority of species listed rely on open woodlands and different types of grasslands as feeding habitat.

Of interest in this debate are the nationwide findings on woodland bird populations reported in The State of Australia’s Birds 2005: Woodlands and Birds, a Birds Australia publication. This document compared the reporting rates of the two nationwide atlases carried out by Birds Australia in 1977-81 and 1998-2002.

Surprisingly, despite the “doom and gloom” text, the reporting rate of the majority of woodland-grassland birds had actually remained unchanged or increased over the 20- year period (for all woodland-grassland species: 48 per cent increased, 38 per cent did not change, and 13 per cent decreased). However the results were very different for grassland-dependent and ground-feeding woodland-grassland birds. These species showed much higher rates of decline over the 20-year period than the species that feed in the canopy layer.

Landholders in western NSW suggest that the invasion of grasslands and open woodlands by invasive native species needs to be considered as a possible contributing cause to these results. It would seem that the landscape of maximum biodiversity in western NSW is a landscape of variety - open grasslands, open woodlands, crops, and belts of thicker timber and shrubland. Maintaining tree cover in riparian areas appears most important, as are fallen logs and leaf litter.

Landholders need enough flexibility to remain financially viable and to cover the cost of actively managing invasive native species.

A real opportunity exists for conservation groups to work with the landholders of western NSW to achieve good environmental outcomes for the future. Considering the huge areas of NSW affected, it is surprising there has been so little interest in this issue from conservation groups.

One group, the Australian Environment Foundation, chaired by media personality and long time environmentalist Don Burke, has shown a real interest in working with landholders to achieve workable and environmentally successful solutions.

By Gillian Hogendyk. 

Gillian lives on a property in central western NSW. She is a member of Birds Australia, NSW Birds Atlassers, and the WIRES Raptor Rehabilitation Team. She is also the secretary of the Australian Environment Foundation which is an evidence-based, solutions-focused environmental group. She is a keen amateur naturalist and has an Honours degree in Veterinary Science.

Published in On Line Opinion

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