I see why you'd ask, but I think huge amounts of fertilizer are also moved, which are not biomass until incorporated in plant growth.

Also natural ecosystems (in balance) would normalize biomass to some extent. A pond with algae can easily replace some algae that you take, because it grows to fill the pond. Thus, if you expose the surface water, you give an opportunity for replacement growth that wouldn't have existed. That biomass primarily comes from water and carbon dioxide in the air that gets converted.