Re: Total biomass of living individuals

Hi Ian-

That is a gigantic question! To give you an answer, I would need to know the biomass of every major family, genus and species-finding those numbers (if they exist) would be a huge task.

I can, however, answer your question in a general way:

I found a source of some numbers on plant biomass here(see section 11.x). Most plant biomass occurs on land, about 99%. That's because terrestrial plants have to deal with gravity (aquatic plants mostly need to deal with viscosity), and have a lot more biomass tied up in "structure" (e.g. wood). Furthermore, of the terrestrial biomass, 75% is in forests with about 28% of terrestrial plant biomass in tropical rain forests. Tropical forests though, have the highest biodiversity on the planet, with a huge variety of families, genera and species- so that biomass would be partitioned between a large number of groups. Using the numbers given in the table at the bottom of the above page, I calculate the runner up to tropical forests to be boreal forests, at about 25% of terrestrial plant biomass. Boreal forests are not as diverse as tropical forests, being primarily confiers, which are the family Pinacea. That would be my best guess for the most successful family- as for genus or species it's hard to say.

I wasn't able to find any numbers or references to biomasses of animals, so I really can't tell you much about them. Based on what I know, there is a huge biomass of worms, but they are also divided up into many families. As an oceanographer, I can tell you that copepods of the family Calanoida are the biggest animal biomass in the ocean, and there is one species of krill found in the southern ocean called Euphausia superba that has a huge biomass (it dominates the biomass of the ecosystem there). For vertebrates, it's even harder to guess. I'd discount birds in general, because they don't weigh much, and large vertebrates, because there's comparatively fewer of them. Off the top of my head, I'd suggest perhaps rodents (though they are an order: Rodentia), because they're abundant and pretty much ubiquitous. Again as an oceanographer, small pelagic fish like anchovy (family Eugraulidae) or the herrings and sardines (family Clupeidae) which have historically maintained very high biomasses (less so currently, most stocks have been heavily overfished).

Hope that helps!
Rob Campbell, MAD Scientist