What happens when the geomagnetic field shifts?

The shifting of the geomagnetic field means that Earth's magnetic poles will switch places. In other words, our magnetic compass's north will point to Antarctica, and the south will be somewhere near Canada. This shifting of geomagnetic poles will affect how devices that operate on magnetism work; our magnetic compass is one such example. Another major issue will be with the life forms that use Earth's magnetic field for navigation. Examples of such life forms are birds, sea turtles, salmon, fish, and so on. They may get lost on their way when this shift happens, but they will ultimately adjust to the new poles. Finally, the weak poles (during this shifting) may leave our planet vulnerable to solar flares and coronal mass ejections, and the planet may experience a higher level of solar radiations.
Please do note that this reversal of polarity is nothing new and has happened many times in Earth's history. In fact, the last polarity shift took place about 780,000 years ago. While the exact effects of polarity shift are not clearly known, we can be sure that life will go on and that polarity reversal will not cause a doomsday.
Hope this helps.