Indicator 15.5.1 Red List Index

Indicator 15.5.1: Red List Index -Species included in the Red Book

The Index of Species included in the Red Book is calculated at a given moment through several steps: 1) first, multiplying the number of species from each category of the list with a risk degree (varying from 1 for those "under the extinction risk” to 5 for those "extinct” or "extinct in the wild”) ; 2) summing up the obtained values; 3) the obtained result is divided to the maximum score of threat, which represents the total number of species multiplied by weight attributed to the category of "extinct species”; 4). this final value is subsided from 1 to obtain the value of the Red List Index.

The formula for calculating the indicator needs:

1) for exactly the same set of species to be included in all periods of time

2) the only changes of categories of the Red List to be the ones which result from genuine improvement of deterioration of the status (meaning, excluding the changes resulted from knowledge improvement or taxonomy review)

3) species with missing data are excluded.

Score

RLIt = 1 - [(Ss Wc (t, s) / (WEX * N)]

where:

Wc (t, s) – risk degree for category (c) at the moment (t) for species (the degree of "critically endangered” = 4, "endangered” = 3, "vulnerable” = 2, "extinction risk”= 1, ”the lowest risk”= 0. The "critically endangered" species are determined as 'possibly extinct' or 'possibly extinct in the wild' have a degree – 5 ;

WEX = 5, the degree attributed to "extinct species” or "extinct in the wild”; and N is the total number of assessed species, except for those assessed as missing data in the current period, and those considered to be „extinct” in the year when the set of species was assessed for the first time.

1. Calculation of the index - every 4 years

2. Updating the list on certain species - annually