[suprjami]

Except this pest is so numerous they over-eat an area, ruining that area and starving all other grazing animals, then starve themselves so they must expand to conquer other areas or die out themselves. Here they're expanding.

You use the word "ecosystem" so you must realise it's a system which requires balance, not just blindly saying "don't kill this animal".

The people behind these culls are nature conservationists considering the entire ecosystem and all its participants, not moronic hunters eradicating a species for trophies or sport.