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Examining Mass Extinctions (Earth System Succession (Hull 2015)…
Examining Mass Extinctions
What happens DURING mass extinctions?
During actual mass extinction
hundres yr - kyr - hundreds kyr at most
period of mass species death
occur very
rapidly
Post-Extinction
Recovery
chaotic as new norm emerges
diversity
remains low
gradually increases over ???
disequilibrium - out of equilibrium
Equilibrium Period
Recovery completed
new diversity norm
normal rules of evolution apply again
Post extinction norm emerges from recovery disequilibrium
Recovery response/timescale VARIES GREATLY
Analysing Mass Extinctions
Analyse individually
pre-extinction norm
- species and envmt
during
- mass death & life in aftermath
post-extinction norm
- emerges from diseq
Difficult to analyse
shortlived nature
of actual mass extinction events
geological record difficult
to investigate MEs
poor presevation on kyr basis
Today
Are we experiencing a mass extinction ?
Are we in flux period after mass extinction ?
Earth System Succession
(Hull 2015)
Equilibrium Before
normal evolution & change
Disequilibrium
during mass extinction
most of recovery
chaos as Earth system & diversity are in flux
rapid extinction drives large-scale change in Earth system
Equilibrium After
new norm emerges from recovery disequilibrium
may differ from equilibrium before
each mass extinction drives one succession of Earth system change
Pre-extinction - Transition (m.e.) - Flux (recovery)- Post stability
What happens AFTER mass extinctions?
Extinctions & recoveries have variable tempos
tempo varies unpredictably between me events
makes modelling difficult - concerning today
New norm can emerge in different ways
3 Possible Recovery Tempos
initial high diversity
sudden extinction
1) quick recovery
to high diversity
2) slow recovery
- diversity remains low for long time
3) in-between
- moderate pace recovery