What Makes Populations and Species Vulnerable?
Brook Milligan
Department of BiologyNew Mexico State University
Las Cruces, New Mexico [email protected]
Fall 2009
Brook Milligan What Makes Populations and Species Vulnerable?
Rarity
What makes populations and species vulnerable?
RarityBut . . .Many types of rarity exist
Examples of rarity
Argyroxiphium macrocephalum (Haleakala silversword):limited to Haleakala Volcano, Maui, Hawaii, but very commonwithin craterSetaria geniculata (knotroot bristlegrass): distributed fromMassachusetts to California, south to Argentina and Chile; notselective regarding habitat, but everywhere sparse; 2 specimensin NM (Hidalgo and Dona Ana Counties)
Brook Milligan What Makes Populations and Species Vulnerable?
Rarity
What makes populations and species vulnerable? RarityBut . . .
Many types of rarity exist
Examples of rarity
Argyroxiphium macrocephalum (Haleakala silversword):limited to Haleakala Volcano, Maui, Hawaii, but very commonwithin craterSetaria geniculata (knotroot bristlegrass): distributed fromMassachusetts to California, south to Argentina and Chile; notselective regarding habitat, but everywhere sparse; 2 specimensin NM (Hidalgo and Dona Ana Counties)
Brook Milligan What Makes Populations and Species Vulnerable?
Rarity
What makes populations and species vulnerable? RarityBut . . .Many types of rarity exist
Examples of rarity
Argyroxiphium macrocephalum (Haleakala silversword):limited to Haleakala Volcano, Maui, Hawaii, but very commonwithin craterSetaria geniculata (knotroot bristlegrass): distributed fromMassachusetts to California, south to Argentina and Chile; notselective regarding habitat, but everywhere sparse; 2 specimensin NM (Hidalgo and Dona Ana Counties)
Brook Milligan What Makes Populations and Species Vulnerable?
Dimensions of Rarity
Geographic distribution
narrowwide
Habitat requirements
restrictedbroad
Local population size
everywhere smallsomewhere large
Brook Milligan What Makes Populations and Species Vulnerable?
British flora survey
160 species categorized by experts
Geographic DistributionWide Narrow
Habitat Specificity Habitat SpecificityLocal Population Size Broad Restricted Broad Restricted
Somewhere large 58 (36%) 71 (44%) 6 (4%) 14 (9%)common
Everywhere small 2 (1%) 6 (4%) 0 (0%) 3 (2%)
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
narrow geographic rangeone or a few populationssmall population sizespecialized niche requirementsrestriction to rare habitatlow population density
Correlates of rarity
Direct human exploitation
Correlated effects of human-induced habitat alteration
Evolutionary indications
Complex habitat requirements
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
large home rangelarge body sizeineffective dispersers
Direct human exploitation
Correlated effects of human-induced habitat alteration
Evolutionary indications
Complex habitat requirements
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
Direct human exploitation
subject to human hunting or harvesting
Correlated effects of human-induced habitat alteration
Evolutionary indications
Complex habitat requirements
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
Direct human exploitation
Correlated effects of human-induced habitat alteration
aggregate permanently or temporarilycharacteristic of stable, pristine environmentsno prior contact with humans
Evolutionary indications
Complex habitat requirements
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
Direct human exploitation
Correlated effects of human-induced habitat alteration
Evolutionary indications
low genetic variabilityrelated to extinct or threatened species
Complex habitat requirements
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
Direct human exploitation
Correlated effects of human-induced habitat alteration
Evolutionary indications
Complex habitat requirements
seasonal migrants
Immediate indicators
Brook Milligan What Makes Populations and Species Vulnerable?
Factors inreasing vulnernability
Rarity
Correlates of rarity
Direct human exploitation
Correlated effects of human-induced habitat alteration
Evolutionary indications
Complex habitat requirements
Immediate indicators
declining population size
Brook Milligan What Makes Populations and Species Vulnerable?
International Union for the Conservation of Nature (IUCN)system
Categories of species
Categories applicable to worldwide status
extinctextinct in the wildcritically endangeredendangeredvulnerablenear threatenedleast concern: include widespread and abundant speciesdata deficientnot evaluated
Additional categories applicable to regional status
regionally extinctnot applicable: species not occuring naturally in a region or arare migrant
Brook Milligan What Makes Populations and Species Vulnerable?
Distribution of Species
Total IUCN Red List: 41,415 species
Extinct: 785 species
Extinct in the wild: 65 species
Endangered and vulnerable: 16,306 species
critically endangeredendangeredvulnerable
Brook Milligan What Makes Populations and Species Vulnerable?
Status of Major Taxonomic Groups
Endangered and vulnerable species
Mammals: 25%
Birds: 12.5%
Amphibians: 33%
Assessed plants: 70%
Brook Milligan What Makes Populations and Species Vulnerable?
IUCN Evaluation criteria
Population size: total number of mature individuals
Geographic range: total geographic area (B) currently alive(D)
Population dynamics
observable decline in numbers of individuals (A)predicted decline in numbers of individuals (C)extinction probability: probability of extinction within aspecified time or number of generations (E)
rarely used, but correlated with other factorshow to calculate: PVA methods upcoming
Brook Milligan What Makes Populations and Species Vulnerable?
IUCN Red List Criteria v3.1
IUCN Red List Criteria v3.1A. Populationsize B. Geographic C. Declining D. Pop. E. Extinction
Category reduction1 range pop. size size probability
% km2 indiv. indiv. % Years Gen.Critically endangered ≥80–90 <10-100 <250 <50 ≥50 10 3Endangered ≥50–70 <500–5,000 <2,500 <250 ≥20 20 5Vulnerable ≥30–50 <2,000–20,000 <10,000 <1000 ≥10 100Source: http://data.iucn.org/themes/ssc/redlists/RLcats2001booklet.html1. Reduction over 10 years or 3 generations.
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Major agricultural pest in 1870s
$200 million in crop damage between 1873 and 1877 inColorado, Nebraska and other states“Greatest concentration of animals” (The Guinness Book ofWorld Records)
A swarm of Rocky Mountain locusts that flew overNebraska on July 20–30, 1874, covered an areaestimated at 198,000 square miles (almost twice thesize of Colorado). The swarm must have containedat least 12.5 trillion insects with a total weight of27.5 million tons.
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Major agricultural pest in 1870s
$200 million in crop damage between 1873 and 1877 inColorado, Nebraska and other states
“Greatest concentration of animals” (The Guinness Book ofWorld Records)
A swarm of Rocky Mountain locusts that flew overNebraska on July 20–30, 1874, covered an areaestimated at 198,000 square miles (almost twice thesize of Colorado). The swarm must have containedat least 12.5 trillion insects with a total weight of27.5 million tons.
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Major agricultural pest in 1870s
$200 million in crop damage between 1873 and 1877 inColorado, Nebraska and other states
“Greatest concentration of animals” (The Guinness Book ofWorld Records)
A swarm of Rocky Mountain locusts that flew overNebraska on July 20–30, 1874, covered an areaestimated at 198,000 square miles (almost twice thesize of Colorado). The swarm must have containedat least 12.5 trillion insects with a total weight of27.5 million tons.
Brook Milligan What Makes Populations and Species Vulnerable?
Rocky Mountain Locust Distribution
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Current status
Now (virtually?) extinct
Historical causes
Permanent and migratory phases of life cycle
Waves of expansion from Rockies to plains
Vulnerable because of habitat limitation in permanentbreeding grounds: riparian regions in Rocky Mountains ofColorado
Conservation status
Rare or not?
Conserve or not?
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Current status
Now (virtually?) extinct
Historical causes
Permanent and migratory phases of life cycle
Waves of expansion from Rockies to plains
Vulnerable because of habitat limitation in permanentbreeding grounds: riparian regions in Rocky Mountains ofColorado
Conservation status
Rare or not?
Conserve or not?
Brook Milligan What Makes Populations and Species Vulnerable?
Case study: Rocky Mountain locust (Melanophus spretus)
Current status
Now (virtually?) extinct
Historical causes
Permanent and migratory phases of life cycle
Waves of expansion from Rockies to plains
Vulnerable because of habitat limitation in permanentbreeding grounds: riparian regions in Rocky Mountains ofColorado
Conservation status
Rare or not?
Conserve or not?
Brook Milligan What Makes Populations and Species Vulnerable?