Population was a major topic of discussion among biologists 40-50 years ago, and then disappeared from view probably because this was when the right-to-life movement really began to get some traction and any discussion of population would suggest limiting population growth might be a good idea and that in turn would lead to birth control and a reason for continuing to allow abortions. Now the topic has returned and it's been interesting to see my students' reactions to this issue including Garrett Hardin's now classic essays on this topic. If you haven't ever read him, you should. His essays have aged well. Basically they are surprised the problem was so well understood decades ago and it generated no action at all except almost the opposite (e.g., limitations on talking about contraception in sex ed classes and in USA foreign aid). The Phactor was the 2,489,152,594th person alive at the date of my birth (you can find out your number here). Yes, that's right! In my short 6 decades Earth's human population has nearly tripled! The Phactor finds this a very scary and sobering bit of data, and no question about it in the minds of most biologists, human population is beyond the carrying capacity, which is not the same as asking how many people can the Earth support. Carrying capacity is defined in biology as the maximum population size of the species that a given environment can sustain indefinitely. The last word is the problem. Humans alter their own environment and prosper at the expense of natural communities, at the expense of other species and non-renewable resources. So the Earth can and will have to support more people but at great expense to natural communities and other species, and this is not sustainable indefinitely. However, birth rate in many places is falling, so growth is slowing, but not in countries that seem least able to sustain such growth (e.g. sub-Saharan Africa). The worst part is that it is hard to know what to do, individually, collectively, about this problem, and many people deny (it's so fashionable) there even is a problem, and you hate the thought that doing nothing might be the right thing or only thing to be done. Other than those who had only 1 sibling or none (less than 25% of my classes), none of my students planned to have a family as large as the one they grew up in. That's an action, but even that has dire consequences as so many of our social support networks were built upon the assumption of continued growth, and thus become chain letters. Not happy thoughts for a Monday! Your thoughts are welcomed.
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