The weakening of earth?s magnetism is one of the factors believed to be predictive of a pole reversal. That magnetic field reversals have occurred in the past is confirmed in the geological record. What is unclear is how precisely the transition occurs, and what happens to life forms extant at the time of this pole flip.
Does the magnetic field drop to zero gauss? Dire predictions follow upon the heels of this theory. Electronic devices would all be at risk: there may be damage to, or complete loss of, all near-earth-orbiting satellites and possibly the space station itself. Effects on life forms could range from migrating birds losing their sense of direction to immune system decline and even widespread die-off from radiation-induced cancers.
Losing its protective magnetic envelope, the atmosphere would expand and become thinner, possibly leading to altitude sickness near sea level. No longer filtered out, deadly cosmic rays would kill most if, not all, living creatures on the surface. Only those living in deep caves would be safe. This scenario has prompted some to build underground bunkers in hopes of surviving.