Will a sudden change in the orientation of earth's magnetic poles have catastrophic consequences for migrating species?
Let's hope.Indeed, the researchers I spoke with all thought that organisms would be able to adjust to an acute weakening or even complete reversal of the magnetic field. "My gut reaction is it's not going to have an impact," says Frank Paladino, the Indiana-Purdue University leatherback researcher whose project I was visiting that night in 1993.
History seems to back this up. There is no firm evidence that the many magnetic field reversals that have taken place throughout our planet's history (see When Compasses Point South) have coincided with or triggered extinctions. Reversals take hundreds if not thousands of years to complete, and because for any one type of animal that represents hundreds or thousands of generations, species have time to accommodate to the change. Moreover, Kirschvink notes that even if the main dipole field were to collapse—an event that can last for up to 10,000 years during a reversal—residual fields 5 or 10 percent as strong as the main field would remain on the surface, and animals would be able to use those quite well for migration.