there is certainly something going on, I note the lack of leaves on any of the trees - the ant problem may be bigger than you think - the scene looks quite intimadatory, good job you're a mercenary, what other weapons do you have at hand?
It's a plastic shed, so a flamethrower, while otherwise a perfectly sensible option, might be risky in this specific case.
Temporarily remove the shed, remove all soil to 1m depth, send it away for incineration. Buy all new sterile soil, it will probably need helicopter delivery due to the lack of access.
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