Existing comment:
Nigel E. Stork (University of Melbourne)
Various slides:
What traits make species more extinction prone?
- Large body size
- Small (restricted) ranges
- Low fecundity
- Higher trophic level
- High specificity to another organism
- Low physiological/behavioral adaptability
Extinctions over the geological time frame:
- At least 96% of extinctions occurred outside major mass extension events.
- Background rate of one extinction/million species/year (E/MSY) (May, Lawton & Stork 1995)
Global Extinctions:
- 2-3 million years wave of extinctions of megafauna due to emergence of hominids
- Half of the world's megafauna (>45 kilos) extinct -- particularly in Australia, Eurasia, Americas, Madagascar
- Over last 1,000 years, massive loss of ratites and other birds on Pacific and other oceanic islands
- Loss of amphibians due to disease and climate change
- Overall, about 300 vertebrates recorded as globally extinct in the last century -- 0.4% of vertebrates since year 1600 - 50 E/MSY
Extinction rates in birds:
- Background rate of 1 species extinction/million species/year (E/MSY) (May et al 1995)
- Pimm et al PNAS 2006:
--- 1.3% of birds extinct since 1500 = 26 E/MSY
--- But three factors increase rate:
----- Numbers known extinctions before 1800 is increasing
----- Taxonomy increasing numbers
----- Some species are probably extinct
--- Therefore corrected rate = 100 E/MSY
--- Predict end of 21st Century rate = 1,000 E/MSY
- But recognize birds poor predictors of other taxa
What does this mean for global insect extinction rates?
(1) 1% of birds and mammals extinct since 1600
(2) This suggests 0.14% extinctions for insects.
(3) Assuming 8 million insect species on Earth then approximately 11-24,000 have gone extinct since 1600
(4) Even if all those are lost in last 50 years, then this is equivalent to 5-10 a week (not 100 a day)!
(5) Smith et al suggest 12-55 fold increase in extinction rates for birds and mammals over next 300 years
(6) RER would suggest 1.7-7.7% insect extinction over next 300 years
(7) Equivalent to 100-500,000 insect species.
Summary:
- Global extinction rates largely based on species-area relationship.
- Loss or change of habitat does not automatically translate into species extinctions
- Global extinction of species much rarer than widely thought.
- Most confined to islands.
- Mostly a phenomenon of vertebrates
- Extinction threats vary for different taxa
- Some groups may be much less threatened -- "Relative extinction rates"
- Co-extinctions probably also rare |