Fragmentation of remnant vegetation

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Key finding

Southeastern bioregions are the most heavily fragmented and prone to further degradation being in close proximity to cleared land. In particular South East Queensland has the lowest proportion of remnant intact patches of at least 1,000ha at 13.7% of the bioregion.

Bioregion (information applies statewide, map locations are for reference only)

Fragmentation of the landscape is the ‘breaking up’ of large areas of intact native vegetation for the purposes of clearing for development. Fragmentation reduces ecological connectivity the connection between habitats that allows for wildlife to cross the landscape for food, breeding and, ultimately, survival. Heavily fragmented landscapes can become biodiversity-poor and the surrounding areas can further decrease species survival with increased likelihood of death (through car strikes and feral animals).

Statistics on fragmentation of remnant vegetation were derived from the Queensland Regional Ecosystems mapping version 9. The larger the patch sizes, the more intact and less fragmented the native vegetation is. ‘Core’ means remnant native vegetation that has a separation distance between cleared land—a buffer, allowing for less chance of interaction with weeds and feral animals. ‘Periphery’ is land that has no separation with cleared land, meaning there is greater risk of a poorer outcome for the condition of the remnant vegetation.

Core versus periphery percentages indicate that in the northern and western bioregions, less than 1% of the remnant borders cleared land. In contrast, the fragmentation of remnant in the three south-eastern bioregions means a lot more remnant lies in border zones: 7.2% (Brigalow Belt), 12.2% (South East Queensland) and 16.4% (New England Tablelands) respectively. These are some of the bioregions with the most pressure for development in which remnant has been replaced by cleared land.

Size frequencies of contiguous patches of remnant native vegetation show each bioregion has its own unique distribution of remnant patch sizes: there are no simple trends. The Wet Tropics and South East Queensland are the two bioregions with the greatest proportions of heavily fragmented remnant native vegetation in patches smaller than 10 hectares representing 5.3% and 2.8% of the bioregion respectively (8% and 6.9% of remnant). However the bioregion with the lowest overall proportion of remnant vegetation, New England Tablelands, has only 1.3% of the bioregion (or 3.6% of its remnant) in patches smaller than 10 hectares, meaning what’s left remains fairly intact.

At the other end of the size scale, the bioregions with the greatest proportion of remnant in patches of at least 1,000ha (intact patches) are Channel Country (84.1% of bioregion, 84.7% of remnant) and Mitchell Grass Downs (77.8% of the bioregion, 82.8% of remnant). The Wet Tropics and Central Queensland Coast also have relatively low proportions of remnant in patches of this size (26.3% and 21.6% of the bioregion, 39.8% and 46.6% of remnant respectively). South East Queensland has only 13.7% of the bioregion (33.8% of its remnant) of intact patches of at least 1,000ha.

Indicator: Fragmentation of remnant vegetation

Distribution of remnant vegetation in the 13 bioregions, expressed as numbers of patches in 7 size classes, and the percent area each class occupies, per bioregion. Also proportions of remnant core and periphery per bioregion. Data based on Regional Ecosystems mapping (version 9, 2013).

Download data from Queensland Government data