It won't be permanent, it'll just be noticeable in evolutionary time. Think K-T or End Permian events not the collapse of the magnetosphere. Mind you that's really bad. Like, I'm comparing this to the death of the non-avian dinosaurs and an event called the great dying, with our best case scenario being an extinction event more reminiscent of those demarking minor change in evolutionary era, it's really fucking bad. But there's reasonable hope that a small spattering of species of various types (except megafauna, we're fucked) will survive and adapt.