Pest distribution survey mapping

Spatial datasets and services

The Queensland Spatial Catalogue (QSpatial) contains spatial data.

• Pest distribution—includes invasive animals
• Weed distribution—distribution data only for invasive plants

The spatial data is also available via map services, which can be found within both distribution data sets by clicking on 'View metadata' and then looking for the ‘Distribution’ section.

Survey

The data for these maps comes from the pest distribution survey series, which describes the broad-scale distribution of invasive plants and animals across Queensland.

Regional mapping workshops are held across Queensland. A grid framework is laid over a map of Queensland, and pest presence or absence is mapped to the grid. If the pest is present, the distribution and density of each pest is rated by survey participants. Cell size is 10min x 10min latitude/longitude, roughly 17km x 17km.

Survey participants include:

• local government staff
• Biosecurity Queensland officers
• pest management officers from Natural Resource Management groups and from other state government departments
• individuals with knowledge of local pest locations.

The dataset is also informed by other mapping data such as Atlas of Living Australia, Feral Scan and Queensland Herbarium, and is reviewed prior to publication by pest management experts where available.

The 2022–23 survey included a density/distribution value of 'extirpated', to indicate where the pest was historically present but has been removed or locally eradicated.

• Extirpated cells include records where the pest has not naturalised.
• 'Absent' cells have been removed to reduce dataset size.

Species

Species include restricted and prohibited (but present) invasive plants and animals listed under the Biosecurity Act 2014, as well as several unlisted but emerging pests. See the APDS species list.

Criteria

During the survey workshops, species are assessed using 3 criteria — each has a different level of accuracy:

• Species occurrence: if the species is present within the cell (present, absent or unknown)
• Distribution: how much of the cell contains infestations of the species (localised or widespread)
• Density: how thick or sparse the infestations are (occasional, common, abundant or extirpated).

Species occurrence

It is essential to know if a pest is present or absent in each cell. If the survey participants cannot say with a very high degree of accuracy whether the pest is present or absent, the cell is flagged as unknown.

This criterion has the highest level of accuracy.

Distribution

Once it has been established that a pest is present within a cell, it is necessary to indicate how much of the cell contains infestations of the species.

Infestations that occur across more than half the cell in any density are considered widespread, while those that cover less than half the cell are considered localised.

While distribution gives us a useful indication of the size of pest infestations within grid cells, its accuracy should not be relied on too heavily. Reasons for this include:

• survey participants may have differing perceptions of distribution measures
• survey participants may lack knowledge of particular species
• it is difficult to accurately assess large areas of remote and impenetrable land.

This criterion has a lower level of accuracy than species occurrence, and should only be used as a guide when making state wide comparisons.

Density

Density refers to how thick or sparse pest infestations are.

The following 4 descriptors are used:

• occasional: single plants/animals spaced apart at wide intervals
• common: a middle measure between occasional and abundant
• abundant: infestations that have reached their full potential and provide little opportunity for additional plants/animals to survive in that area
• extirpated: species that were previously present but have been eradicated from an area — this should only be used where there is reasonable confidence that eradication has been achieved.

Density is a particularly difficult criterion to apply due to factors such as:

• different species have different density measures, e.g. grasses spaced 1m apart may be considered occasional, whereas trees spaced 1m apart may be considered abundant
• size of the species will directly influence the perception of density, e.g. many small seedlings may receive the same density rating as a few mature trees
• some areas may be able to support higher densities of a species than other areas, due to environmental conditions.

This criterion has a lower level of accuracy than distribution. Density can be considered more accurate at the shire level than at the state level and should only be used as a guide when making state-wide comparisons.