Exactly my thoughts, they need an army not a A-Team unit.

It may not be quite that simple. Moving an army is no small feat, the logistics required is complicated and could be miserable to try to manage in the Amazon.

If they did manage to get a large enough military force in to catch most of the illegal miners, how much damage would be done to the Amazon just by the army getting in there?

This defeatist take is getting old. Why don't we abolish all police and laws because we can't change anything?