The more naive have talked about wildlife rushing madly ahead of advancing glaciers of the last ice age. It is true that the geographic ranges of many plants and animals changed drastically with the changing climates, but hardly at a pace requiring panic. When you come to think about it, many plants, anyway, had to move slowly. They certainly can't pick up their roots and dash away.
Information on migration rates from the Chihuahuan Desert is pretty
scanty, but data from fossil pollen in the eastern part of North America reveals
ballpark figures that should be roughly applicable here. Generally speaking, trees
require considerable time to mature to seed-bearing size. Thus a seed sprouting a short
distance beyond its parent requires years before any of its seeds can produce a further
advance. Movement northward of beech, oak, and hickory at the end of the ice age, when
temperatures were warming rapidly, was estimated to average about 650, 1150, and 650 to
820 feet per year. Why, even cold molasses ought to be able to move that fast!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.