Have there been any study that document the evidence of the changing ratio of the biomass of different trophic levels?

Question

You would expect a number such as the producers (photosynthetic) biomass to consumers + decomposers biomass ratio is a very important indicator for sustainability. It is also very probable that the ratio has been changed due to human activities (land clearance, animal agriculture etc.) which have resulted in the likes of climate change (which is in a sense just a problem of excessive mineralization (both industrial and biological) relative to immobilization by producers). Have there been any studies that try to calculate and monitor this number? I can't seem to find any.

Answer 1

Hi there! You've touched on a major point of ecology, environmental studies, and sustainability science here. The study that comes to mind is foundational - I've seen it's figures in multiple classes before I even knew the paper existed - and it was published May 21, 2018 by Bar-on, Phillips, and Milo. Here is the citation:

Bar-On, Y. M., Phillips, R., & Milo, R. (2018). The biomass distribution on Earth. Proceedings of the National Academy of Sciences, 115(25), 6506-6511.

This study was the first of its kind, conducting a census of biomass on earth to understand the structure and dynamics of the biosphere. To my knowledge, there are no long-term ecological research studies evaluating biomass distributions like this for the whole planet. Nevertheless, Bar-on, Phillips, and Milo (2018) offer a pre-human biomass estimation in the supplemental materials of their paper. They hold that they have no projection for uncertainty associated with this figure, so it should be considered with caution. Based on their estimates, though, it is likely safe to assume that the ratio of pre-human to extant wild mammal biomass is remarkably small. They found that the global biomass of terrestrial megafauna prior to the Quarternary Megafauna Extinction (QME) was ~0.02 Gt C while the extant biomass of modern livestock is ~0.1 Gt C (5x greater). "Even the biomass of humans alone (~0.05 Gt C) is around twice the size of the biomass of all wild megafauna before the QME event." The supplemental materials are very comprehensive, offering review of 305 additional sources to the manuscript, which had 49 citations. They include review of marine mammal biomass as well as plants.