Regarding "Ideal Human Population", no one seems to really answer the question, taking into consideration the land needed for houses, stores, roads, animals that need forests to live, water (lakes, ponds) forests for lumber to build these homes, stores etc. what about the farmland needed to raise the cattle, pigs, chickens we need for survival. Land for factories....get my point. All they talk about is land for growing grains. 15 years ago economists and scientist estimated the max human population to be 4 billion...
We are in big trouble, we are destroying the earth more everyday, and we are too egotistical, and stupid to realize it and do something to correct it. Just requiring two children per couple would start reducing the problem. You want more than that... adopt...
Howard - The background of this is that we expect the global population is going to increase by 2-3 billion over the next 50-100 years or so, but we then predict it will level out to some extent. And as the questioner hints in their original question, we also expect we’re going to see population’s increasingly becoming urbanised, part of city dwellers and they’re also going to want to have higher aspirations to lifestyle. So they going to want to increase their meat consumption and that is also not a very effective use of resources.
And then we’ve got planet change that we’ve been hearing about so we’re going to get increased climatic extreme, floods and drought. So the question is, can we sustain the population that we are predicted to see?
Chris - Which is what?
Howard - We’re currently heading towards 10 billion people. So we’re about 6-7 billion at the moment and we’re likely to head towards 10 by the end of this century.
Chris - People say we’re consuming resources at the moment at the rate of two planet earths, not one. So, if you increase our numbers by another 30-50%, which is what that number you’ve just suggested is, that means we’ll be up to three planet earths per person equivalent per year. That’s totally unsustainable, surely?
Howard - It is dangerously unsustainable and that increases the threat upon our natural vegetation because there will be a demand to try to convert more land area into agricultural productive land, so it’s a real threat all the way round. But then you can come back on us and say, well why don’t we control the amount of food we waste? Up to 40 or 60% of the food that is bought in America and in Europe is just thrown away, it’s not consumed. Why don’t we learn to redistribute that food better?
Chris - Isn’t that a short term solution though, Howard? Because if I feed more people, I’ll get more people and we’ll end up at the natural point where we’ve still got a population crisis albeit with a higher number of people ultimately anyway.
Howard - Well, coupled with this increasing population, we expect that there be increased education. There’s going to be an increased awareness that you no longer need to have a huge family to support you in your dotage, as it were, and that actually small families are sustainable and they are realistic. So what we actually need to focus on is education and particularly empowerment of women. This is really important on a world scale to try to get cultural understanding that a huge family is not necessary.
Chris - You’re a plant scientist though. I suspect you would love to see a solution to this problem lie with plants but there have been some people who’ve suggested that, in fact, if the entire world went vegetarian, this would immediately cut our carbon dioxide output by quite a significant amount. Because, if you look at the average westerner, we probably eat our own body weight in meat each year and, if you look at the rearing cycle for meat, we need about three years worth of supply. So, therefore, there’s probably three times as much weight of animals as there is humans so you could immediately translate that into a very dramatic reduction if we all just stopped eating meat but, would we be healthy?
Howard - Yes, indeed. One small step we might care to take is to go vegetarian one or two days a week and this would start to change us to move towards a more sustainable diet, it would be better for our health as well.
Chris - The other possibility is in-vitro meat, isn’t it? We’ve heard in the last couple of years we’ve had the in-vitro burger being made where people grow cells in a dish and make muscle artificially. Apparently, it doesn’t taste too good though!
Howard - It looks pretty horrendous as well!
Chris - Okay, maybe I’ll give that one a miss then!
Maximum human population...
Not sure about the rest of the world, but the UK could be indefinitely sustainable at well above the present quality of life with about 10 - 20% of the present population. There's no problem achieving it: if we pay every woman £500 every 6 months if she isn't pregnant, and abolish all child support payments, the birthrate would surely fall very quickly.
I can't upload the graphs but the model is simple. Divide the population in to "under 20", "working fraction" and "60 - 100" and assume that we die off linearly from 60 to 100. Then if we have a simplfied stable replacement (2 children per female aged 20 - 60) we have 25%, 50% and 25% in each cohort.
A huge population is certainly handy when defending yourself against an aggressor, as Hitler discovered when he invaded Russia and Britain discovered in the Zulu wars. But, it does not necessarily discourage an invader to give it a go.