Definitions of terms used in the IUCN Categories & Criteria

1. Definitions of terms used in the IUCN Categories & Criteria Continuing Decline

2. Continuing Decline Definition A recent, current or projected future decline (which may be smooth, irregular or sporadic) which is liable to continue unless remedial measures are taken.

3. Continuing Decline • Continuing declines are used in two ways in the IUCN Red List Criteria: • Continuing decline at any rate – used in criteria B and C2, where the taxon has already been characterized by restricted ranges or population size. • A quantitative estimated continuing decline – used in criterion C1. For criterion C, continuing decline is meant to apply to decline occurring now or that is very likely to occur in the near future. The timeframe for rate of continuing decline is specified in criterion C1 for each category : CR – 25% over 3 years or 1 generation (whichever is longer) EN – 20% over 5 years or 2 generations (whichever is longer) VU – 10% over 10 years or 3 generations (whichever is longer)

4. Continuing Decline Estimating rate of decline Rate of decline over long generation times may be estimated from data over shorter time frames. Often this will involve fitting a model of decline over the available data and extrapolating to the longer time period. Note that this involves assumptions about the decline rate remaining constant, or increasing, or decreasing relative to the observed time interval. These assumptions must be justified with reference to threatening processes, life history or other relevant factors. The above also applies for estimating rates of reduction for criterion A.