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TitleImpacts adjacent to saltmarshes sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which rates the relative condition of saltmarshes according to impacts (i.e. land disturbance, stock grazing, drainage disturbance and lack of or poor vegetation) surrounding the saltmarsh.
Input data
Lineage
An analysis of impacts adjacent to saltmarshes was undertaken using an expert rule system (see ‘Assigning values to ecosystem spatial units’ below). Information on expert rules systems can be found in Appendix 3 of the CFEV Project Technical Report. Inputs to this expert rule system were land disturbance adjacent (calculated using an expert rule system), grazing adjacent, drainage disturbance adjacent and adjacent vegetation (calculated using an expert rule system). The impacts not calculated using an expert rules system were assessed by inspecting aerial photographs and were scored between 0 (disturbed) and 1 (pristine) according to the details in Table 1.
Table 1. Summary of input variables assessed using aerial photographs for impacts adjacent to saltmarshes condition variable. Scores indicate condition, (0 - degraded, 1 - pristine).
Variables | Unit | Other comments |
Grazing | Present (0) or absent (1) | Apparent grazing inferred from context i.e. local knowledge, evidence of horses, cattle tracks, or if adjacent to farm and no evidence of fences. |
Drainage disturbance | 1 – absent, 0.5 – little, 0.25 – moderate, 0 – extensive | Presence/extent of drainage channels, realignment of natural drainage. |
Of the impacts assessed for the adjacent impacts to the saltmarsh sub-index, drainage disturbance was considered by experts to have the greatest influence on the overall impacts adjacent to saltmarshes score. Land disturbance adjacent and adjacent vegetation were equally weighted and grazing adjacent was weighted as having the least impact on the overall score. The impacts adjacent to saltmarshes condition variable was used in the overall saltmarsh N-score expert rule system, along with the impacts within saltmarshes variable.
The method for assigning an impacts adjacent to saltmarshes sub-index score to the saltmarsh spatial units is provided below.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
Column headingSM_IMADJ
Type of dataContinuous but has been converted to categorical format (see Table 3).
Number of classes3
Assigning values to ecosystem spatial units
An impacts adjacent to saltmarshes sub-index score (0 = poor condition – 1 = good condition) was assigned to saltmarsh spatial units as SM_IMADJ using the expert rule system shown as a definition table in Table 2 (e.g. if the saltmarsh has a HIGH score for adjacent drainage, HIGH score for adjacent grazing, HIGH score for adjacent land disturbance and a LOW score for adjacent vegetation condition, then assign a score of 0.8). Using fuzzy logic enables input data and output results to be continuous rather than categorical as implied here (i.e. inputs and output data can range on a continuous scale between 0 and 1, and the process of executing the expert rule system will determine its membership as being HIGH or LOW) (refer to Appendix 3 of the CFEV Project Technical Report for more information on expert rules systems).
Table 2. Expert rules system definition table for the impacts adjacent to saltmarshes sub-index for saltmarshes.
Drainage disturbance adjacent (SM_DRADJ) | Grazing adjacent (SM_GRADJ) | Land disturbance adjacent (SM_LDADJ) | Vegetation adjacent (SM_VGADJ) | Impacts adjacent to saltmarshes score (SM_IMADJ) |
H | H | H | H | 1 |
H | H | H | L | 0.8 |
H | H | L | H | 0.8 |
H | H | L | L | 0.6 |
H | L | H | H | 0.9 |
H | L | H | L | 0.7 |
H | L | L | H | 0.7 |
H | L | L | L | 0.5 |
L | H | H | H | 0.5 |
L | H | H | L | 0.3 |
L | H | L | H | 0.3 |
L | H | L | L | 0.1 |
L | L | H | H | 0.4 |
L | L | H | L | 0.2 |
L | L | L | H | 0.2 |
L | L | L | L | 0 |
The saltmarsh spatial data layer has the continuous impacts adjacent to saltmarshes sub-index data categorised according to Table 3. The categorical data was used for reporting and mapping purposes.
Table 3. Impacts adjacent saltmarshes sub-index categories for saltmarshes.
Category | Min to max values |
1 | 0 to <0.2 |
2 | 0.2 to <0.8 |
3 | 0.8 to 1 |
CFEV assessment framework hierarchy