1). There isn't one for big mammals any more. The majority of the ecosystem is locked up in plants and bacteria. For example fungi outweigh all _animals_ by roughly 6 times. Bacteria by 30 times and plants by 200 times.

2). We're the major drivers in the processes that used to limit biomass on the planet. The nitrogen cycle is dominated by humans [0] where depending on how you measure it we've done something between doubling it and increasing it by an order of magnitude. The same is true for all the other limiting cycles. By comparison the carbon cycle has been barely touched.

3). Mammals are rather big and we don't like big things trying to eat us/step on us. Mammal global mass has been decreasing since the last ice age when we figured out how to hunt mammoths to extinction and 8,000BC when we domesticated goats.

[0] https://en.wikipedia.org/wiki/Human_impact_on_the_nitrogen_c...

Plants, reptiles, amphibians, insects, marsupials, fish, bacteria, algae, fungus, etc.

Unfortunately there barely is.

I also wonder this. Some thoughts:

1) Life is remarkably adaptive. 2) There probably won't be much longer.