There is ten tonnes per square metre of matter shielding between each square metre of Earth's surface and the Karman Line. That is orders of magnitude more shielding against cosmic rays than even fragile complex slow-breeding critters like us require.

Magnetospheric shielding is only directly important if you're in orbit.

(It protects out upper atmosphere from erosion of light fractions by the solar wind, which is very important but a separate problem).