I'm not sure why you're so hostile toward this idea... I know basically nothing about ecology, but it seems relatively straightforward to think of reasons to s

I'm not sure why you're so hostile toward this idea... I know basically nothing about ecology, but it seems relatively straightforward to think of reasons to study biomass. Think about food chains. Food is energy is biomass (as you mention). At a basic level: if you know that a certain ratio of biomass is needed (or expected) between two stages in a chain, then you can keep tabs on one of those stages, and when you see biomass decreasing, it's a signal that the food chain might be soon disrupted. In a food chain, the number of animals seems mostly irrelevant (except in cases of near-extinction), but the total energy is highly relevant.