Critiques of these estimates

Critics of estimates based on species-area relationships have pointed out that $>$ 95% of the eastern forests in North America were cut while only 4 bird species went extinct⁵. How can we account for this apparent discrepancy [12]?

• The region was not simultaneously deforested. As agriculture moved westward, forest reclaimed abandoned fields. Forests always covered $>$ 50% of the land area.

  
  

  $$0.5^{0.25} = 0.84$$
  
  

  16% or 25-26 out of $\approx$160 forest species should have gone extinct.

• May not have been enough time for extinction. Species-area relationship is an equilibrium expectation.

  Committed to extinction versus actually extinct

• Only 28 of the 160 species are restricted to eastern forests. The rest are widely distributed elsewhere and would have persisted there. They could have later moved back into eastern forests.

  
  

  $$(0.5^{0.25})(28) = 23.5 \qquad ,$$
  
  

  i.e., 23-24 of the 28 species should have persisted. Only 4-5 should have gone extinct, which is about what we saw.

• We lost few bird species from eastern North American forests because we had few endemics to lose.