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TitleEstuaries naturalness score
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorGIS Unit, Information and Land Services Division, Department of Primary Industries and Water
DescriptionAn index which rates the relative ‘naturalness’ or condition of estuaries based on a selection of input variables.
Input data
Lineage
The condition assessment and subsequently the generation on a Naturalness score (N-score) for estuary was largely based on work undertaken previously by Edgar et al. (1999). Edgar et al. (1999) observed that the magnitudes of two anthropogenic disturbance indices based on benthic macroinvertebrate community data, faunal abundance index (Din) and faunal productivity index (Dip), were highly correlated with human population density within the estuary catchment. Having established this relationship, Edgar et al. (1999) then assessed condition using the surrogates of human population density and broad land tenure (crown land, reserve, etc.) within the catchment to derive a Naturalness score (N-score) (Figure 1).
Figure 1. Flow-chart outlining data inputs from Edgar et al. (1999) and processes used in the condition assessment to derive Naturalness score (N-score).
Estuarine condition was scored relative to the two measures of human population density provided by Edgar et al. (1999); Estuarine Catchment Area (ECA - a measure of the entire upstream catchment) and Estuarine Drainage Area (EDA - a measure of the local drainage area). The maximum value of human population density in the catchment or drainage area was used to derive a condition assessment, based on the human population density classes used by Edgar et al. (1999). These were: >100, 10-100, 0.5-10, 0.05-0.5 and <0.05 per km2. This resulted in 5 increments which were considered to be strongly related to condition and linearly distributed to give indicative N-scores of 0.2, 0.4, 0.6, 0.8 and 1.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
References
Edgar, G.J., Barrett, N.S. and Graddon, D.J. (1999). A Classification of Tasmanian Estuaries and Assessment of their Conservation Significance using Ecological and Physical Attributes, Population and Land Use. Technical Report Series. Number 2. Tasmanian Aquaculture & Fisheries Institute, Hobart, Tasmania. 231 pp.
Column headingES_NSCORE
Type of dataCategorical but was further banded according to Table 1.
Number of classes5 (or 3 according to Table 1).
Assigning values to ecosystem spatial units
An N-score (0.2 = poor condition, 0.4, 0.6, 0.8 or 1 = good condition) was assigned to estuary spatial units as ES_NSCORE according to data collected by Edgar et al. (199) and re-analysed by the CFEV program as described above.
The estuaries spatial data layer has the naturalness data categorised according to Table 1. The categorical data was used for reporting and mapping purposes.
Table 1. Naturalness categories for estuaries.
Category | Min to max values |
Low | 0 to 0.6 |
Medium | >0.6 to 0.85 |
High | >0.85 to 1 |
CFEV assessment framework hierarchy