In short order. Here is how the preservation of the indigenous population of Europe can be saved from the clutches of further ethnic cleansing.
#1 The Navy’s of Europe can arrest and deport, and prevent anywhere from 30%-80% of racist invaders trying to racially replace indigenous Europeans.
#2 Build A modern wall with a sensor network aided by aerial automated monitoring drones. This will keep out 90% of invaders as standalone fixes.
#3 Pass laws that protect the indigenous population of Europe. “Indigenous Protection Laws”
That’s it folks. It is all literally that simple to save earths global ethnic minority population… Europeans.