Queensland
What is fragmentation?
Landscape fragmentation creates pressure on ecological communities by breaking up large areas of intact native vegetation, reducing connectivity. Ecological connectivity is critical in allowing wildlife to cross the landscape searching for food, shelter and suitable breeding sites. Fragmenting native vegetation can impact species survival through predation, exposure and decreased food availability.
Fragmentation occurs when large areas of intact vegetation are increasingly separated into smaller areas (Figure 1). Fragmentation happens for various reasons, including increasing urbanisation and infrastructure development.
Vegetation patterns
In Queensland, we assess landscape fragmentation by examining vegetation patterns and how they change over time. We describe these vegetation patterns as follows.
- Core areas – large vegetation tracts relatively far (further than 100 metres) from cleared areas. These areas are less susceptible to ecological edge effects and are more likely to sustain viable populations of native flora and fauna.
- Edges – the boundaries of core areas, which are more exposed to pressures like weed incursion, predation and biodiversity loss. The exposure of these areas is called an ‘edge effect’.
- Patches – isolated fragments of remnant vegetation most vulnerable to threatening processes and likely to have impaired ecosystem functioning.
Statewide regional ecosystem mapping
We measure the state of remnant vegetation fragmentation at a point in time, represented as the mean (or average) area of distinct cores across the landscape, using the statewide regional ecosystem mapping time series (biennial from 1997 to 2021). Changes in the average core area over time provide a measure of the rate of fragmentation.
A large decrease in the average core area over two years is synonymous with a high fragmentation rate. ‘Patch’ and ‘Edge’ areas, while important concepts for describing fragmentation, are not presented in this report.
Landscape Fragmentation and Connectivity Tool
The statistics are derived from a landscape fragmentation analysis of the Queensland regional ecosystem remnant cover time series (1997 to 2021) for each bioregion and subregion. The analysis is based on the Landscape Fragmentation and Connectivity (LFC) Tool developed to test for Significant Residual Impact on Connectivity Areas under the Environmental Offsets Framework.
© Queensland Government
Interpretation of results for biogeographical subregions requires extra care in some instances. Some subregions are themselves non-contiguous. For instance, coastal regions may include islands, which might get classified as many small cores, or inland subregions, which are non-contiguous for other reasons. This can lead to an unfairly inflated number of cores and deflated average core area, meaning that comparisons with other subregions in terms of average core areas of core count densities might be misleading. Nonetheless, temporal trends for these subregions, communicated through percentage change, would still be relevant.
Historic landscape fragmentation
From 1997 to 2021, the key overall landscape fragmentation trends across the state were:
- Landscape fragmentation has increased across Queensland since 1997.
- The rate of fragmentation peaked between 1999-2003, with a notable decline between 2003-2009
- From 2009 to 2021, there was still a gradual increase in fragmentation, though at a slower rate.
Recent landscape fragmentation
For the most recent reporting period (2019-2021), we examined landscape fragmentation across the Queensland bioregions and found:
- 12 of the 13 Queensland bioregions had a declining average core area, which suggests increasing pressure on the remnant vegetation due to fragmentation
- The New England Tableland bioregion had the smallest average core area (approximately 50ha)
- The Channel Country and Northwest Highlands bioregions had the largest average core area (approximately 100,000ha).
- These bioregions had the largest declines in average core areas:
- The Mitchell Grass Downs (6.6%)
- Einasleigh Uplands (3.4%)
- Northwest Highlands (2.7%)
- Gulf Plains (1.4%)
- Brigalow Belt (1.2%)
- Mulga Lands (1.1%)
- Central Queensland Coast (1.0%)
