Earth Science: Geology, the Environment, and the Universe

Chapter 24: The Mesozoic and Cenozoic Eras

Problem of the Week

To Be or Not to Be: The Sixth Extinction

The Key information in the problem was taken from information in the reference websites below.

1. Mass Extinctions of the Phanerozoic
   *Good short explanations of most widely accepted of mass extinctions and mass extinctions in general.


2. The Sixth Extinction
   (National Geographic)


3. The Hall of Biodiversity: The Sixth Extinction
   (American Museum of Natural History)


4. The Sixth Extinction....
   by Richard Leakey and Roger Lewin (Doubleday, 1995)


5. Timing and Rate of the KT Extinction; What Else Died Out?
   By Pete Goddard

Answers:

1. To find the amount of time it will take for 85% of the known, named species to become extinct at the rate currently believed to be occurring, you can use the following train of thought


• If you are losing 30,000 and gaining 10,000 each year, then you are losing 20,000 species each year.


• 85% of 1.7 million is found by multiplying 0.85 times 1.7 million which is 1.445 million. The remaining amount is 0.255 million (15%) – this is the amount that needs to be remaining.


• Let y be the number of years that it takes to get to lose this many species.
  -20y = 1.4445 million
  -Divide both sides of the equation by 20
  -y = 72.25 years
  


• In this amount of time, the number of named species will be 0.255 million so 85% of the species will be extinct.



If you want a more specific time, you could change the 0.25 years to months. 1/4 of a year is 3 months.

72 years and 3 months.

2. The Cenozoic, or current extinction, is occurring at a much faster rate than the Cretaceous extinction did (thousands of years). Scientists estimate that in 100 years 50% of the currently known species will be extinct. Our estimate above, has it occurring even faster.