The Earths carrying capacity is simply put as, the max population that can continuously live on earth. As a calculation, carrying capacity is the total area of habitable earth divided by the area of land required for each person to live. The problem is calculating the land required for each person to live. This calculation requires you to consider energy consumption, food consumption and waste just for starters. Finding the current energy consumption or livestock consumption is not hard however predicting how much livestock the earth can hold or how much land can be used for crops is very difficult. From the graph below you can see that estimating how much corn you can yield per acre is hard. Estimating the carrying capacity would require you to also determine how much land would be dedicated to growing corn.
Figure 1 comes from
Although it is hard to determine exactly what the earths carrying capacity is scientists can make an educated guess based on history. Unfortunately the guesses range from 1 to 20 billion and no real consensuses can be made.
It is possible to say that we currently consume a lot of fossil fuels. According to Earth trends in the graph shown 80% of the energy we consume are nonrenewable fossil fuels. This means that the source of %80 of our energy will run out and must be replaced by another source. Changes must be made to ensure that our children will have the energy necessary to live as great a life as we do. Energy information administration estimates that we could run out of oil in 2112. 2112 is a long ways away and it is even longer before we will run out of coal but if we ignore the issue we are just hurting our future generations. We are in desperate need of innovations to help us create reliable renewable energy sources.
Figure 2
Sources:
http://earthtrends.wri.org/
http://dieoff.org/page112.htmhttp://earthtrends.wri.org/
http://en.wikipedia.org/wiki/Carrying_capacity