So, considering all of these impending and immediate ecological dangers, which are undoubtedly exacerbated as human numbers continue to rise, what is the human carrying capacity? How many of us can the Earth truly support? Can the Earth continue to support 7 billion of us, not to mention the U.N.'s projected increase, to between 7.8 and 12.5 billion individuals by 2050 (Cohen, 1997)? The answer is very complex, relying on many variables that are subject to change.
At least 65 estimates of the maximum possible human population, ranging from less than one billion to over 1000 billion. These estimates vary so greatly because of the different methods used to calculate them. For example, food is often considered to be the single greatest limiting factor on human population size, so maximum yields and minimum nutrient requirements per person are often incorporated into carrying capacity estimates. However, the calculations get a bit convoluted when we realize that maximum food produced depends on somewhat unpredictable variables such as soil types, water availability, the length of growing seasons, crop requirements, farming technologies, farmer education, transportation of farm inputs and outputs, economic demand of the goods produced, and international politics influencing trade (Cohen, 1997).
Yet another inaccuracy of many carrying capacity approximations arises when we observe that the consumption standards vary by country. For example, the meat choices and quantities are very different from one country to the next, as can be seen in the following figures. Americans acquire about 25% of their calories from animal products, resulting in plant calorie production that is 4 times greater than the minimum amount required for our county, in order to feed both people and livestock (Cohen, 1997).
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To skew matters yet further, some scientists are of the opinion that food is not the primary limiting factor for population, while factors such as nitrogen, phosphorous, land, fresh water, energy, sunlight, diseases, waste management, or climate change may have stronger controls over the size of our population. We must not forget that upon meeting certain natural constraints, humans may adapt and overcome them (Cohen, 1997).
So, it appears that our population limit is determined by a combination of natural limits and human actions, both of which are subject to change, and therefore exceedingly difficult to predict (Cohen, 1997). If we cannot predict these two factors, we are hard pressed to accurately determine our true carrying capacity! What we do know as of now, however, is that improving on sustainability practices- from energy usage to farming to waste management- results in decreased resource consumption per person, and increased resource availability for other members of our population.
This information guides me to, what I believe, is a logical assumption: if any of the aforementioned environmental damages occur at the hands of our species, we are effectively lowering our carrying capacity. An ecology teacher I knew once said: "We may not know the numerical value of the human carrying capacity, but might it already be upon us? In our country alone, prisons are full, schools are understaffed, and some people are, believe it or not, hungry. And let's not forget about the hunger and disease in the developing countries." The following figures depict rates of U.S. prison overfilling, U.S. hunger, and world hunger, respectively.
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While my teacher's observations weren't based on the intensive scientific calculations mentioned above, I share her sentiments- I believe that the state of human welfare today indicates the arrival to (or even surpassing of) our carrying capacity. In the following sections, I will share stories that I believe exemplify the need for an end to human population growth.
Works cited:
Cohen, Joel E. Population, Economics, Environment and Culture: an Introduction to Human Carrying Capacity. Journal of Applied Ecology 34: 1325-1333.
In readin this part of the blog, some ideas have come to mind that I'd like to post for discussion. First is reference to the first Alley video we watched last week, where he discusses the "economic model" of oil and how it suggests that we should invest now in alternate fuels because of the high probibility that we will face the need for them in the near future. I want to try and tie that concept together with fact that you mention that the UN estimates the world population could reach 12.5 billion by 2050. However, that paper was published in 1997, well before the current economic crisis we are experienceing in the united states.
ReplyDeleteI think that there might be a more modern carrying capacity limiting factor, that being money for the united states. I know that in other parts of the world there might be much more free access to the basic necessities which allow populations to grow, such as food. But, if in america citizens are not finding jobs and there is no economic growth, I do not see people having children. It just doesn't make sense. So, in closing, I think that there might be a large economic shift should we decide to move off of fossil fuels, and I think that if we continue to be in a stagnated state without economic growth, there will be no population growth. Because without investment in long term institutions, the numbers of jobs wont be increaseing, so people will still be struggling in america. I am interested to see what parts of the world do experience economic growth over the coming centuries, and what sectors allow them to achieve that.
Overall,
ReplyDeleteGood blog so far. This is really stimulating my interest in the topic. There is good layout and the material is presented well. I can't find any weeknesses in this blog so far. I am interested in reading the rest of it!
Good job!