Conservation 2- extinction rates

Conservation 2- extinction rates

1. Why is there concern?

   • 1. Iconic historical examples
     • Dodo
       • Adults hunted for by Dutch sailors from ca. 1590
       • Eggs and clicks eaten by introduced pigs and monkeys
       • Extinct by 1690
     • Great Auk
       • Flightless seabird
       • Huge numbers: Canada, Scotland, Iceland and Norway
       • Hunted
         • Meat
         • Oil
         • Feathers
         • Bait
       • Rare-- fetched great prices
       • Last captured 1884
     • Thylacine
       • Large Marsupial carnivore
       • Complaints of sheep killing- 1824--- hunted vigorously
       • Died in captivity in 1936
   • 2. Global environmental change
     • Deforestation-- Amazon Basin
     • Big 4 drivers of past extinction
       • Extirpation
       • Over-exploitation
       • Invasive species
       • Habitat loss
     • Climate change-- likely to be a problem in the future
   • 3. High profile species and global biodiversity indices in decline--- living planet index

2. Where's the evidence and why the mismatch?

   • 1. Time lag in recording and designating species as extinct
     • 50 year rule- not declared extinct until no one has seen one for 50 years
     • Yangtze river dolphin
       • Probably extinct since 2007
       • Only listed as critically endangered
     • Christmas Island Pipistrelle
   • 2. Unrecorded extinctions
     • DW steadman
       • Used subfossil evidence
       • Polynesians eliminated ca.2000 species of flightless rail from Poacific Islands in past 4000 years
       • 8000 species of bird in total
     • Relationship between arrival of humans and recent extinction of birds on Pacific islands
       • Longer occupied islands have a lower proportion of recorded recent extinctions
       • Higher proportion of unrecorded extinctions longer ago
       • More recently colonised islands have 'excess species'
       • Hawaii-- occupied 1500 years ago-- 80% currently extinct or endangered
     • Two historical waves of extinction
       • New Zealand
         • Extinction rate after arrival of polynesians-- similar to that after arrival of Europeans
         • 900 AD- 125 species
         • 1769-- only 89 species left--- arrival of Europeans
         • Moas-- hunted for food-- extinct by mid- 18th cen
       • Extinctions closer to home- Canary Islands
         • giant tortoises used to inhabit canary islands-- extinctions followed the colinisations of both pre-Europeans and Europeans
         • Dune Shearwater-- Arrival of Guanches
         • Lava Shearwater-- arrival of Europeans
   • 3. Many species are moving towards extinction

3. Predicting future extinction rates

   • 1. Species area relationships
     • Based on established relationships between land and species richness
     • Can reverse species- area accumulation curve-- can extrapolated backwards to calculate expected species loss and habitat degradation
     • Resulted in extinction rates of 5-30%
     • Not really reliable- Extinction debt
       • Species committed to extinction through habitat loss but not yet extinct during equilibrium period
       • Area needed to remove the last individual of a species is much larger than the area needed to encounter first species
       • Impact of habitat loss on rates of extinction have been over-estimated
     • Species richness in degraded and secondary tropical forests
       • Wide range of taxa-- >90% of species in primary forest were also present in logged forest- including species of conservation concern
       • Similar patterns in secondary forests-- abandoned pastures
       • 75% of species still present present even after 1 or 2 rounds of logging
         • 1st round of logging-- some adverse effects
         • 2nd round of logging-- no additional effect
   • 2. Rates estimated from empirical data on actual extintions
     • Stuart Pimm--- Globally recent extinctions of birds are 100 times higher than background rates
     • Predicted 1500 times higher than background rates by end of 21st century
     • Estimates are highly influenced by Pacific islands--- unlikely to be representative
   • 3. Estimation from Red lists of Species
     • Number of species that have changed status from threatened to probably extinct
     • 300- 400 years-- Estimated time required for 50% of species to go extinct-- assume rate doesn't change
     • Barnosky
       • 6th mass extinction would be 240 to 540 years
       • But all threatened species would have to become extinct in next 100 years
       • Rate of extinction would have to remain at 75%
       • BIG IF!!!

4. Influence of climate change-Hawaiian honeycreepers

   • Culex pipiens introduction followed by epidemic of avian malaria and pox
   • All lowland endemics of honeycreepers (24 species, 80% of species) now extinct, but some species still present in uplands
   • Malarial parasites have a minimum temp requirement to complete development of vector-- but with climate change highland temp might increase to above the threshold needed to complete development of vector-- final 20% at risk