Yonatan Zunger, of Google, writing nearly five years ago, tossed out a fact that's stuck with me since: the response of "large animal" populations to global temperature changes:
"When the biota of a planet get rewritten, the creatures that require the most delicate maintenance die first. This tends to mean really big creatures, that rely on large supplies of their foods; apex predators, which rely on the entire food chain beneath them; and "canary" species like many frogs, which are very sensitive and tend to be the first to die when something is going wrong. Historically, the cutoff for "large creatures" (that tend to not survive extinction events) seems to be in the ballpark of 20 pounds; things bigger than that just require the ecosystem to be too healthy."
That immediately following:
"The last big spike like this was the Paleocene-Eocene Thermal Maximum, about 55 million years ago. Average temperatures rose by 6C over a period of 20,000 years -- which is enough to look like a giant, sharp spike on the history-of-the-entire-planet graph."
We're on track to temperature changes of roughly that order of magnitude, and almost certainly in a far shorter period of time -- a few centuries, perhaps less.
https://plus.google.com/+YonatanZunger/posts/SgzQU5DM3LQ
I think this may be one of the related body-mass / extinction related articles (though it postdate's Yonatan's item):
We are in for a rough ride over the next several hundred years.
The good news, if there is good news, is that the present rate of human induced CO2 injection is not likely to be continued for too much longer.
Of course, it it induces further injections, things may get interesting.
There are carbon-capture devices already extant. Solar-powered. Self-replicating. They're called "plants".
Problem is that 1) you've got to sequester the carbon formed, 2) there's only so much ag productivity (measured in terms of carbon fixation) on the planet, and 3) it is largely spoken for -- humans claim 40% of net primary productivity, the rest of the planet fights over the remaining 60%.
I'd strongly recommend you start sorting out what the environmentalists (or at least ecologists) have been doing for the past century or so. Their models strike me as vastly more sound than those who claim other affiliations.
BAU is not sustainable. The question is which of the other-than-usual tracks we select. Or allow to be selected for us.
Here's what I mean by that: For some species the survivability rate is inverse to the population density- the habitat fills up and a natural equilibrium results. But for other species there is a range of population densities where the survivability rate is positively correlated with population- so the more you have, the better they survive. Any species that moves in large herds is like that- the predators get full, they can't eat any more, and the dent the predators can make on the population is negligible. We are like that too; the more of us there are, the more we can specialize tasks and support each other, and the faster our population increases. (Up to some limit).
Swarming species are more delicate than they look though- passenger pigeons are a good example. Once some external force pushes the population below a certain level, the remainder have a much much harder time surviving. I don't know if people appreciate how easily a good nuclear war could cause the total extinction of humanity- once we lose the big interconnected economy, with all the easy to find resources gone, we could really be f*ed.
In the case of passenger pigeons (now extinct) and locusts (not a species but a behavioural mode of specific species of grasshoppers), the swarming behaviour was a mobile one, essentially a fast-cycle nomadic activity. Swarming for each both provided defence against predation (any predator species were overwhelmed by the number of prey) and against competition: by moving rapidly across landscapes, passenger pigeons and locusts could out-compete other species for food sources (including humans).
If there's a benefit to human-based swarming, it doesn't appear to follow either of these modes. Humans don't swarm in mobs (outside of riots, and there, for similar advantage), but in stationary urbanisations. And the benefits seem to largely be of information flows and interactivity or interdependence.
At the same time, cities have multiple vulnerabilities. They aren't mobile, they require prodigious resources (Los Angeles, as an example, sources water from up to 1,500 miles away, and every city on the planet is dependent on oil which is found in only a few specific high-concentration regions and much of which crosses oceans to arrive), and of waste removal.
So, yes, humans become more effective competitors as they aggregate. Until, perhaps, they don't.
Fly in the ointment and all that.
nuclear war->there are maybe a few people left in bunkers.
If we were to get rid of the nuclear option then both your chain and my chain would not be viable.
Nukes before greenhouses?
Also for anyone to go nuclear there would have to be a strategic goal for that Russia nuking the US won’t really help their food shortage and vice versa.
With big brains and tools, humans can live in a much broader set of environmental conditions than any other species. While it doesn't make us extinction-proof, it makes us pretty hardy. It is hard to imagine what would destroy all the ecological niches that humans could survive in.
I would bet on the humans.
It's because I'm a human being, isn't it.
Or whatever it is that passes for same.
Absolutely not. Most lifeforms simpler than us have an easier time surviving because it is easier for them to reproduce quickly. You're basically ignoring insects, crustaceans, algea, bacteria, most plants, and pretty much everything else.
Sure we're hardy and adaptable when you ignore most of life on earth. And then you want to bet on the only species that has almost purposefully engineered its own demise? Talk about bias...
E.g. if food for small rodents becomes much less available, the expected result is that small rodent species dwindle in population but survive, while some of large predators that need those small rodents may go extinct.
Cockroaches and rats will outlast homo sapiens.