land shark; land speculator
A person or company that aggressively buys up small plots of land, often using coercive tactics, to assemble a larger site for development. The term carries a negative, predatory connotation.
It seems land sharks are operating behind the scenes in that area.
I was pressured by a land speculator to sell my land.
Compound of 地上げ (land assembly, from 地 'land' + 上げ 'raising') and 屋 (suffix for a person or business). The term emerged during Japan's bubble economy era.