Really? Are you talking about the landmines in Croatia that weren't fully cleared after the 1990s Balkan war? People were actually providing maps with the approximate locations of the fields so they can be safely bypassed.
You make it sound like Europe is planting mines to keep migrants out. If the reaction of a small minority of European countries (2-3) seems exaggerated when faced with over 1 million (!) immigrants, then the fact that over 7000 people [0] were killed at the US-Mexico border just over the past 20 years should really shock you to the core.
[0] https://en.wikipedia.org/wiki/Migrant_deaths_along_the_Mexic...