The biome that is most at risk due to over-harvest of organisms might be the

Marine biome.  
The marine biome is the greatest biome on the planet as they and cover an extends that can be estimated to be around 70% of the earth. It incorporates five fundamental seas: the Pacific, Atlantic, Indian, Arctic, and Southern, and numerous littler Gulfs and Bays. Marine areas are generally exceptionally salty

Water also has a high specific heat capacity or resistance to temperature change, and it's a polar solvent, which means it dissolves things well. This quality allows for the existence of life on Earth because it prevents bodies of water, including oceans, from freezing over.

That my opinion though