UtardSource?
I mean there is no definite number but I did recall reading that many scientists believe it is between 4-6 billion people. "When a species lives within its carrying capacity, it does not degrade the resources on which it depends. While degrading our resources (e.g. through topsoil erosion and the pumping of underground water for irrigation faster than its renewed) we produce enough food globally to feed our population of 6.6 billion, but an estimated 600-800 million people are undernourished"
https://books.google.com/books?id=xBGffKNfsq8C&pg=PA29&lpg=PA29&dq=world%27s+carrying+capacity+4+billion&source=bl&ots=5JsGacFRMW&sig=7mO6WcP3UrPTiB-9kUYoFYUv40g&hl=en&sa=X&ei=ln1oVfmoHqTHsQSvnoCIDQ&ved=0CGIQ6AEwCQ#v=onepage&q=world's%20carrying%20capacity%204%20billion&f=false
Fact of the matter is we are degrading natural resources at an exponential rate, so be definition we are already over our carrying capacity.
"However, consider that there is only 12 million square miles (7.68 billion acres) of arable land on the planet.
And, ignore for a moment that arable land is being lost at a rate of 38,610 square miles per year.
That is, lets assume no arable land is being lost for the next 33 years. Then . . .
In 2006, there was 1.15 acres of arable land per person, world-wide (i.e. 7.68 billion acres / 6.68 billion people).
By 2039, there may be only 0.59 acres of arable land per person, world-wide (i.e. 7.68 billion acres / 13 billion people)."
http://one-simple-idea.com/Environment1.htm
If it takes 1 acre of arable land to sustain 1 human, and if we factor in the fact that we are already past 7 billion, than just by the numbers we are at if not over carrying capacity.
Of course technology will increase our production of food, but with a expanding population and shrinking arable land area we will soon be limited to how much we can produce.
And thats not even factoring diseases such as blight and its effect on crops. Ever watch Interstellar? That's where we are actually heading. By reducing the variety of crops we grow we are making them more susceptible to diseases that could wipe out the whole species of crop.
SalmonellaFunYou know as well as I do that the earth will reach its carrying capacity in the next 100 years or so. When this happens, I'll be glad to not be around because it will be followed by a small period where we have too many people and not enough resources because people continued to reproduce. After a while though, people will begin to only have children that they can support and it will level off around a pleasant 10 billion
Lol 10 billion if every human were to become vegetarian and we devoted the entirety of earths 3.5 billion acres of arable land to growing grains strictly for humans. In reality that much grain would only feed 2.5 billion omnivores considering how much has to go to feeding livestock. Now if everyone lived like Americans the earths carrying capacity would only be 2.2 billion (3.3x the substance level of food, 250x sustenance level of water)