A lot of this stuff is up for interpretation.  Your guess is as good as mine.  The actual name of the planet health upgrade is "Emergency Facilities", so it would appear to the space-age equivalent of bomb shelters.

Why would you want to destroy all of the planets infrastructure though, knowing full well that it would create chaos and rioting among the populaceand plus, if you want to take over the planet, it would take alot of resources to restore order and acquire taxes from the population if their all in refugee camps.