Global famine? Give me a break.
That would require the failure of multiple crop species extending across thousands of miles. It's never happened in human history on that scale.
Why would it now? Yes, losing all the Cavendish bananas would be really bad. But why would a superbug that takes out all the bananas have any effect on the corn, wheat, etc growing down the road?
The biodiversity issue is intraspecies not interspecies.
Simply, copies.
If a superbug is able to destroy all the world's bananas, it would grow in population 1 million fold to do so. A bacteria or virus with a million times as many members will evolve a million times as quickly.
Given such, a species jump wouldn't be hard to do. And after the first couple, the superbug would likely start to tailer itself to genes that many plant species share, making the next jumps even easier.
Thing is, I'm pretty sure that ants and humans are only a few times further apart than potatoes and corn are. (Monocots and Dicots split ~140-150 Myr ago [0], Arthropoda and Chordata about ~1000 Myr ago [1]) (I initially thought the Monocots/Dicots split was further back... looks like a closer comparison would be to marsupials, diverging ~170 Myr ago)
There are already lots of viruses at scale that don't become superbugs and randomly jump the species barrier.
A species entirely made up of genetic clones is what this whole thread is about. I'm surprised you missed this.
This isn't Pandemic - there is no neural or neural analog on viruses - hell we couldn't even do that with networked nanomachines.
It would be far more plauisble for all housecats in the world to coordinate and plan the conquest of humanity as they at least have the ability to think and communicate.
I just think, on average, an individual virus particle will mutate at a certain rate. If there are a million times the population, a virus as a whole will then mutate 1 million times faster. So, if a certain virus would given a certain mutation, would jump to another species, and that had a certain chance to do so, then that same virus with 1 million times its normal population would have 1 million times the chance to do so.
That's about as spelled out and basic I'm able to make it.