[crpatino]

It would be a "modest increase" if we had spare carrying capacity. Instead, what we have now is a situation that is going from bad to worse, but since the crisis is unfolding in slow motion, most people do not recognize it as such; after all, most people alive today have either never seen what a good situation looks like, or where too young to grasp the meaning of the changes they observed back then.

The (human) carrying capacity of Earth was estimated to be around 2 billion, which was surpased sometime in the late 1920's. Contrary to other comments here, that does not mean that after you hit population 2,000,000,0001 we all die (we clearly did not). Instead, what it means is that given the technological level we had at that time, we'd consume renewable resourses faster than they can renew themselves, and we'd also produce waste faster than the environment can degrade it. Otherwise, more than 2B people would cause environmental degradation, which would itself reduce the carrying capacity in the long term.

Please note this definition is tied with humans technological level. It is not set in stone, since we have some degree of control over our impact in the environment, and we have the ability to use the same resources in a more efficient way. The big tragedy of 20th century is that this fact was not recognized but for a handful of theorists, and therefore it was not a political and economic goal to explicitly manage the carrying capacity of Earth. As of 2016, the situation is still the same.

By example, we gained a bunch of technologies that allows us to do the same stuff more efficiently. Given explicit economic incentives, we might have... maybe doubled our carrying capacity (CC=4B). Unfortunatelly, because this was not a goal itself, we engaged in a buch of economic practices that negated much of this benefits, so if we are generous these might have been reduced by half (e.g. CC=3B). Also given that population growth was not arrested back in the 1970's, but only slowed down, the carrying capacity has not improved at all (CC=2B).

Currently, environmental degradation is going in overdrive. We have lost a lot of time, and the resources we need to make an orderly transition are already commited to keep the system going. Population will go down, one way or the other. I don't believe in a single sharp die off many apocalyptic thinkers profetize, but adding and extra 1.6B mouths to feed will make the downward tendency of the curve more steeper than it needs to be.

[hx87]

A couple of questions about your numbers:

> was estimated to be around 2 billion

By whom? A source would be nice, which is why I generally refrain from using passive tense when stating facts.

> Also given that population growth was not arrested back in the 1970's, but only slowed down, the carrying capacity has not improved at all

How exactly does population growth affect carrying capacity? If I have a car with 7 seats, its passenger capacity is the same whether I have no passengers or 6 passengers. If population is an intrinsic factor in carrying capacity, then whatever definition of carrying capacity you are using is inadequate.

[crpatino]

Ok, this are complex questions... but I will try to address them as best as I can.

1. The guy who first came with the 2 Billion figure in the 1920s was the scientist Raymond Pearl, though the copncept of 'carrying capacity' as we understand it today did not exist. Pearl's work was for the most part statistic/economic; It was Eugine Odum who later picked up that earlier work in the 1950s and applied it to the ecology concept of 'carrying capacity' which was independently developed by the observation of animals in natural environments. You can check the standard form in Odum's textbook "Fundamentals of Ecology".

The problem with the original formulation for Carrying Capacity is that it is assumed to be fixed, because animal behavior is governed mostly by insticts. Humans, even if ultimately subject to the Laws of Nature, can show much wider variations in behavior due to culture, availability of technology and many other factors. According to the wikipedia page, UN has several estimations of current carrying capacity, and they vary widely (From 4 to 11B) depending on each researcher biases and methodology.

I personally assume that the results in the higher end of the spectrum come from cornucopians that fail to take into account the economic and political presures that get in the way of implementing the (theoretically) optimal solutions, and therefore assume that actual carrying capacity is closer to the 4-5B range... but then, it's my own bias speaking there.

2. Other concept you can take from Odum is that long term carrying capacity can be eroded by organisims that happen to find a short term way to reproduce beyond the current carrying capacity of the ecosystem they belong to. This is what I was talking about in my previous msg, though I admit it sounds a bit convoluted and ranty in retrospective.

If you have a 7 seat car and you usually drive around with 10 or more people on it, (or with merely 5 fraternity bros that usually behave like baboons on meth) someone is eventually going to break one of the seats - probably the copilot one, which happens to be the least robust one. Then, you end up with a 6 seat car, at least for the lenght of the time that it takes you to fix it. And if you do not fix the seat but keep driving around with the same people on board, you are going to break another seat, and another.

[hx87]

Thanks for the background info, and I think you have a good point about carrying capacity degradation. I don't think "degradation" is a single variable though--it's a trade off current well-being, future well-being, and for a lack of a better word, "nature". We can absolutely provide a high standard of living for 9-11 billion people, but to do so we have to discard our desire to "preserve" the world as it is and actively take control of it to a far greater extent than we do now, i.e. large scale geoengineering.