It's not about the raw number of people, it's more about how old and aging they are. Age distribution is the key factor. 1 billion 60 year olds is not the same as 1 billion 20 year olds.
They are occupying the space left behind by human activity. Chemicals will only create more resistant strains just like it did with Amaranth. The reason these plants are successful is the horrendous landscaping traditions especially in new developments. The use of chemicals only reinforces these plants. Basically what's happening is these strains are put under so much pressure in the urban environment that they becomes "super-weeds" and then invade the rest of the landscape. It might be too late to do anything about it now.
Good stuff. It would've been nice if there ever was an actual "Next Step" tensor that once multiplied (or some other operation) by any tensor representing current state, would give you the next state. That was my initial thinking when I read "Using Linear Algebra".
My understanding is that incinerators don't just release the output. The exhaust is pumped back into the system and dealt with somehow. The extent to which the release is "dealt with" is the tricky part.
