The CLIMEX model uses growth-related indices and stress indices to estimate the potential for growth and survival of a population of a species at a given location, and integrates the indices into the Ecoclimatic Index. Understanding these indices makes their use and interpretation of CLIMEX easier and removes some of the guesswork from prediction and analysis (Sutherst et al.1995).

Growth-related indices relating to seasonal activity patterns and relative abundance are:

These indices are estimated weekly, except for the Annual Growth Index.

Annual stress indices, relating to conditions during the unfavourable season that limit the geographical distribution, are:

Ecoclimatic Index (EI)

The Ecoclimatic Index (EI), scaled between 0 and 100, integrates growth and stress indices on an annual basis to give a single measure of the potential of a given location to support permanent populations of a species at various levels of abundance (Sutherst and Maywald 1985). The index provides simple, concise information on which to base policy decisions.

EI is derived as the annual mean of weekly values of GI (this determines the potential for the population to increase) reduced by the stress indices:

EI = GI_A x SI x SX

where:
                 52
GI_A = 100 ( S GI_W ) / 52
                W=1

GI_W = TI x MI x DI x LI

SI = (1-CS/100)(1-DS/100) (1-HS/100)(1-WS/100)

SX = (1-CDX/100) (1-CWX/100)(1-HDX/100)(1-HWX/100)

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