458 estimating extinction risk (the iucn criteria) fish 458; lecture 24

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45 8 Estimating Extinction Risk (the IUCN criteria) Fish 458; Lecture 24

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Page 1: 458 Estimating Extinction Risk (the IUCN criteria) Fish 458; Lecture 24

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Estimating Extinction Risk(the IUCN criteria)

Fish 458; Lecture 24

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Identifying Species at Risk of Extinction – The IUCN

Framework The IUCN Red List characterizes all

species (plants and animals) into various categories of risk of extinction.

The same framework is applied to all organisms irrespective of their biology and exploitation history (implies a need to scale biological quantities – e.g. by generation time).

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Goals for IUCN Listing Provide scientifically-based information

on the status of species at the global level.

Draw attention to the magnitude and importance of threatened biodiversity.

Influence national and international policy and decision makers.

Provide information to guide actions to conserve biological diversity.

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Summary Statistics Threatened Species (of those evaluated*)

Total (41%: 3155+723 of 9474) Mammalia (57%: 1130+87 of 2133) Aves (56%: 1183 +3 of 2123)’ Elasmobranchii (41%: 39+0 of 95)

Number of threatened species by country USA (998; 131 fishes) Australia (524; 44 fishes)

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A History of the Listing Process

Qualitative until 1994. 1994 = First quantitative

framework (used for the 1996 Red List).

2000 = Revision to the 1994 framework.

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Basic framework (2000 model)

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The threatened categories Critically Endangered (“considered

to be facing an extremely high risk of extinction in the wild”).

Endangered (“considered to be facing a very high risk of extinction in the wild”).

Vulnerable (“considered to be facing a high risk of extinction in the wild”).

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The criteria

A. Reduction in population size B. Small geographic rangeC. Small population size and

decliningD. Very small population sizeE. Quantitative estimate of

extinction risk

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The basic structure

Criteria CR EN VU

A Value Value Value

B Value Value Value

C Value Value Value

D Value Value Value

E Value Value Value

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How to use the system Rank the species against each of the

criteria (note that there are separate thresholds for each criterion / category of risk).

Set the final category to the highest level of risk.

This process has been computerized (RAMAS).

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The A criterion (mature individuals)

Direct observation. An index of abundance. Decline in the area of occupancy,

extent of occurrence / quality of habitat.

Actual or potential levels of exploitation Effects of introduced taxa, pollutants,

etc.

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The A Criterion (past reductions)

“Observed, estimated, inferred or suspected” reduction over 10 years or three generations of [90%, 70%,50%] and causes ceased,

understood and reversible; [80%, 50%, 30%] and causes not

ceased, not understood, or may not be reversible

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The A criterion (future reductions)

Projected reduction over any 10 year or three generation period of [80%, 50%, 30%].

Can include the past and future. Reduction may not have ceased,

not be understood, or may not be reversible.

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Defining Space in the System Extent of occurrence: “area contained

within the shortest continuous boundary which encompasses the present occurrence of a taxon”.

Extent of occupancy: “smallest area essential at any stage to the survival of the population” (e.g. breeding area).

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Criterion B (Geographic range)

Extent of occurrence less than [100km², 5000km², 20000km²] and two of: Severely fragmented or at a single location

(CR) / no more than 5 locations (EN) / no more than 10 locations (VU);

Continuing decline; Extreme fluctuations

Extent of occupancy less than [10km², 500km², 2000km²] and two sub-criteria.

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Criterion C(Small size and declining)

Population size less than [250,5000,10000] and either: Continuing decline at least [25% within three

years or one generation, 20% within five years or two generations, 10% within 10 years or three generations]

Continuing decline and No subpopulation larger than [50, 250, 1000]

individuals; At least [90%, 95%, 100%] of individuals in one

subpopulation; Extreme fluctuations.

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Criterion D(Very small population size)

Critically endangered: 50 mature individuals.

Endangered: 250 mature individuals.

Vulnerable: 1000 mature individuals OR very restricted area of occupancy (<20km²) or number of locations (5 or less).

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Criterion E(Quantitative analysis)

Probability of extinction in the wild is at least 50% within 10 years or three

generations (CR). 20% within 20 years or five

generations (EN). 10% within 100 years (VU).

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Overview of Success Very widely used internationally. Does not require much data. Generally easy to understand and

apply. Can be applied across a wide

range of taxa (e.g. insects to trees).

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Problems with the Framework-I

Specifying thresholds The thresholds are only “roughly”

comparable. The original intent was for the thresholds to

be consistent with the E criterion but this has changed over time.

The thresholds for the A criterion in particular (and the use of “inferred” / “suspected” declines) have been controversial (e.g. listing of Atlantic cod).

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Problems with the Framework-II

Fishes!1996 Red List “The quantitative criterion (A1abd) for the threatened categories may not be appropriate for assessing the risk of extinction for some species, particularly those with high reproductive potential, fast growth and broad geographic ranges. Many of these species have high potential for population maintenance under high levels of mortality, and such species might form the basis for fisheries…”

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Problems with the Framework-III

The decline criterion. “Managed” species. “Long-lived” species (three generations can be

several thousand years for some trees). Should criteria E over-rule? The criteria are “broad brush” and should not

“overrule” more sophisticated analyses. Many fish species would have being threatened or endangered at some time.

How to incorporate “precaution”. No use of “ecological knowledge”.

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Areas of Disagreement African elephants; Some fish species (cod); Marine turtles (Flatback, Olive Ridley,

Green); Crocodiles.

[Note all are species subject to harvest.]

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Readings IUCN Web site: www.iucn.org Mace and Lande (1991):

Conservation Biology 5:148-157. Mace et al. (1992) Species 19:16-

22. Mace and Stuart (1994) Species

22: 13-24