Framework for Biodiversity Assessment – Linear
module
Explanation sheet for calculations and input into the linear module of
the credit calculator
The following information is in addition to the instructions provided in Appendix 5 of the Framework for
Biodiversity Assessment and should be read in conjunction with the appendix. Input required by the credit
calculator is indicated in blue bold text.
Assessing landscape value for linear shaped developments or multiple
fragmentation impacts
The landscape value tab in the credit calculator presents two options: ‘site based development’ or ‘linear
based development’. Select linear based development and click ‘Add’. Provide a linear assessment name
and choose the appropriate IBRA subregion. The following sections assist in assessing the landscape
value.
Once you have chosen a method, the other option is no longer available and will be greyed out. If you wish
to change to the alternative method, you will need to delete the existing method. Please note this will
delete all other data related to the assessment proposal including information on plant community types
(PCTs) and threatened species. If you do this, it is recommended that you first make a new version of the
assessment using the copy function.
1. Assessing percent current extent of native vegetation cover (before development)
Step 1. Identify the buffer area surrounding the development footprint
Identify the centreline of the linear development using Geographic Information System (GIS) and create a
550 m buffer either side of the centreline. For developments that have multiple fragmentation impacts
create a 550 m buffer extending from the boundary of the development footprint.
Step 2. Calculate the area of the buffer
Use GIS to determine the total area of the buffer zone.
Step 3. Calculate the percent current extent of native vegetation cover
Use GIS to calculate the area of native vegetation cover within the buffer zone. Convert to a percent
current extent of native vegetation cover using the following equation:
𝑎𝑟𝑒𝑎 𝑜𝑓 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑛𝑎𝑡𝑖𝑣𝑒 𝑣𝑒𝑔𝑒𝑡𝑎𝑡𝑖𝑜𝑛 𝑐𝑜𝑣𝑒𝑟 𝑤𝑖𝑡ℎ𝑖𝑛 𝑏𝑢𝑓𝑓𝑒𝑟 𝑧𝑜𝑛𝑒
× 100%
𝑡𝑜𝑡𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑏𝑢𝑓𝑓𝑒𝑟 𝑧𝑜𝑛𝑒
Enter this value into the credit calculator for percent native vegetation cover before
development.
Step 4. Determine the score for the percent current extent of native vegetation cover
Use Table 16 in Appendix 5 of the FBA to determine the corresponding score for the percent current extent
of native vegetation cover. This will be automatically generated by the credit calculator. Please note that
only the final score will be shown in the credit calculator (i.e. before development – after development).
2. Assessing percent future extent of native vegetation cover (after development)
Step 1. Calculate the percent future extent of native vegetation cover
Use GIS to calculate the area of native vegetation cover within the buffer zone that is expected to remain
after taking into account the impacts from development. Convert to a percent future extent of native
vegetation cover using the following equation:
𝑎𝑟𝑒𝑎 𝑜𝑓 𝑓𝑢𝑡𝑢𝑟𝑒 𝑛𝑎𝑡𝑖𝑣𝑒 𝑣𝑒𝑔𝑒𝑡𝑎𝑡𝑖𝑜𝑛 𝑐𝑜𝑣𝑒𝑟 𝑤𝑖𝑡ℎ𝑖𝑛 𝑏𝑢𝑓𝑓𝑒𝑟 𝑧𝑜𝑛𝑒
× 100%
𝑡𝑜𝑡𝑎𝑙 𝑎𝑟𝑒𝑎 𝑜𝑓 𝑏𝑢𝑓𝑓𝑒𝑟 𝑧𝑜𝑛𝑒
Enter this value into the credit calculator for percent native vegetation cover after
development.
Step 2. Determine the score for the percent future extent of native vegetation cover
Use Table 16 in Appendix 5 of the FBA to determine the corresponding score for the percent future extent
of native vegetation cover. This will be automatically generated by the credit calculator. Please note that
only the final score will be shown in the credit calculator (i.e. before development – after development).
3. Assessing the connectivity value
Step 1. Identify the connecting links
Identify the connecting links as per the definition of a connecting link provided in Appendix 5 of the FBA.
Use Table 17 in Appendix 5 of the FBA to determine if an identified connecting link corresponds to one of
the listed categories of connecting links.
Step 2. Determine the connectivity value score
If the development will impact on an identified connecting link, use Table 17 in Appendix 5 of the FBA to
determine the score of that connecting link. If there is no connecting link or an identified connecting link will
not be impacted by the development, the connectivity value score is zero. Select the appropriate
connecting link category from the drop-down box in the credit calculator. The score for connectivity
value will be automatically generated in the credit calculator.
4. Assessing patch size
Step 1. Determine each Mitchell landscape in which the development occurs
Use the Mitchell landscape GIS layer (available from
mapdata.environment.nsw.gov.au/geonetwork/srv/en/main.home) to determine the Mitchell landscapes the
development occurs in. The most up-to-date data for overcleared landscapes (i.e. Mitchell landscapes),
including the percent native vegetation cleared, is available from the VIS Classification database. Follow
the Overcleared Landscapes Quick Guide to export the data.
Step 2. Determine the patch size area for each Mitchell landscape
Use GIS to determine the patch size area for each Mitchell landscape. If there are multiple patches within
one Mitchell landscape, use the largest patch for that landscape. Enter the patch size area for each
Mitchell landscape into the credit calculator.
Step 3. Determine the patch size score for each Mitchell landscape
Use Table 18 in Appendix 5 of the FBA to determine the patch size score for each Mitchell landscape using
the corresponding patch size class and percent native vegetation cleared. The credit calculator will
automatically generate the score for each Mitchell landscape.
Step 4. Determine the final patch size score
The final patch size score is calculated by averaging the patch size scores for each Mitchell landscape.
The credit calculator will automatically average these scores.
5. Assessing the change in area to perimeter ratio
Step 1. Calculate area and perimeter of each patch
Use GIS to calculate the area (m 2, not ha) and perimeter (m) of each separate patch >1 ha within the buffer
zone that will be impacted by development, i.e. intersected, modified or removed by development. Treat
each patch of vegetation >1 ha as a separate patch, i.e. disregard the gap requirement as per patch size
definition in the FBA. For a linear shaped development this zone extends 550 m from each side of the
centreline of the development and therefore includes the development footprint. For a multiple
fragmentation development, the buffer zone extends from the boundary of the development footprint and
therefore does not include the development footprint.
Step 2. Calculate the total area and total perimeter length before development
Calculate the total current area (m2) and total current perimeter length (m) of all the patch areas (>1 ha)
that will be impacted by the development. This provides the total area and total perimeter length before the
development.
Step 3. Determine the current area to perimeter ratio (before development)
Calculate the current area to perimeter ratio by dividing the total current area (m2) by the total current
perimeter length (m). Enter this value into ‘Area/Perimeter ratio – Before development’ in the credit
calculator, using a whole number.
Step 4. Determine the future area and perimeter lengths of patches after development
For each patch size identified in Step 1, use GIS to determine the future area (m 2) and future perimeter (m)
after development. This includes all new and existing edges created by the impact of development and for
this purpose both the area of new and existing patches can be <1 ha and distance to other vegetation (as
per definition of patch size in the FBA) is irrelevant. Therefore, all new and existing patches that are
created after development are counted within this calculation. Calculate the total future area (m 2) and
future perimeter length (m) of all new and existing patches.
Step 5. Determine the future area to perimeter ratio (after development)
Calculate the future area to perimeter ratio by dividing the total future area (m 2) by the total future
perimeter length (m). Enter this value into the area to perimeter ratio after development in the credit
calculator using a whole number.
Step 6. Determine the proportional change in area to perimeter ratio
Use the following equation to determine the proportional change in area to perimeter ratio:
𝐹𝑢𝑡𝑢𝑟𝑒 𝑎𝑟𝑒𝑎 𝑡𝑜 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑟𝑎𝑡𝑖𝑜 (𝑓𝑟𝑜𝑚 𝑆𝑡𝑒𝑝 5) – 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑎𝑟𝑒𝑎 𝑡𝑜 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑟𝑎𝑡𝑖𝑜 (𝑓𝑟𝑜𝑚 𝑆𝑡𝑒𝑝 3)
× 100%
𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑎𝑟𝑒𝑎 𝑡𝑜 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑟𝑎𝑡𝑖𝑜
Note, the proportional change in area to perimeter ratio will be automatically generated by the credit
calculator.
Step 7. Determine the score for the proportional change in area to perimeter ratio
Use Table 19 in Appendix 5 of the FBA to determine the corresponding score for the proportional change
in the area to perimeter ratio. This will be automatically generated by the credit calculator.
Note, if the proportional change in area to perimeter ratio is a negative value (i.e. the future area to
perimeter ratio is less than the current area to perimeter ratio) then the credit calculator will return a value
of zero and the area to perimeter ratio score will be calculated as zero.
Published by:
Office of Environment and Heritage NSW
Email: [email protected]
Website: www.environment.nsw.gov.au
OEH 2015/0460
July 2015