The Earth’s Carrying Capacity: How Much More

Can it Take?By Olivia Winkeler

Carrying Capacity● Has to do with “population pressures” of organisms on an environment● Definition: the maximum quantity of a particular species that its environment

or habitat can support for an unlimited amount of time○ i.e., The relationship between an environment’s resources and the manner in which they are

consumed by a species

What happens when a habitat’s carrying capacity is exceeded?In natural habitats with which humans have not tampered, when a population increases above the environment’s carrying capacity

● Resources available are insufficient to maintain that size population● Population can remain at that level for a short time with the use of stored-up

resources● Eventually, population must fall due to lack of resources

Cont.● If the population excess was far too high, the population decline may occur

rapidly● This results from excessive strain placed on the environment● The effect may be a reduction of population numbers beyond restoring the

population to the carrying capacity● The extinction of a species may result if the devastation of the environment by

overpopulation is too great and resources are depleted too far

For HumansThe situation is different because:

● Humans occupy multiple “habitats” all around the world● Resource consumption varies widely based on multiple factors

○ Affluence, environmental consciousness, location, availability of resources

For example...

● The resource use consequent of a North American or Western European lifestyle cannot be equated to the resource use of a lifestyle of someone living in a remote village in South America or Africa.

● Resource use of an American family living below the poverty line is very different from resource use of a very wealthy American family of the same size

● The carrying capacities for subsistence living and for poor persons is higher than for those who live “comfortably”, using more resources and producing more waste

Resource Usage

Geography and Climate

● Different geographical locations can support more/fewer people than others● This is a result of:

○ Climate○ Fertility (relatively speaking) - ex. Polynesians, Easter Island Rapa Nui and Vikings○ Level of urbanization

■ The extent to which the carrying capacity of an area has already been reduced by human tampering

For humans, resources/carrying capacity influences include:

● Food/basic sustenance (not considering the significant caloric surplus available to most people in developed nations)

● Technologies/tools● Ability to process/get rid of waste● Fuels● Mobilization potential in the event of “major threats” (Postel)● Living space

Ways Humans Have Altered Earth’s Carrying Capacity Already● Depletion of the ozone layer

○ Ability to absorb waste products of respiration

● Agricultural advances/techniques○ GMOs, food production efficiency

● Climate change by anthropological factors○ Droughts○ Flooding/sea level changes

More Projected AlterationsHumans will continue to cause drops in:

● Per capita availability of rangeland● Fish available to catch and eat

○ Rangeland and fish catch together provide a substantial amount of the world’s protein intake

● Per capita area of irrigated land○ Provides area to grow over ⅓ of worldwide food harvest

● Per capita cropland area● Per capita forested land

All of this negatively affects Earth’s carrying capacity

Net Primary Productivity● Defined as the basic energy supply of all organisms living on Earth● During the 20th century, the global human appropriation of terrestrial net

primary productivity doubled ○ As early as 1992, humans consumed 40% of terrestrial net primary productivity○ In 2005, human appropriation of net primary production of all vegetation was 25%

● If humans can maintain the current strides in efficiency, it is estimated that HANPP might only grow to 27–29% by 2050

● An increase in primary bioenergy from additional agricultural biomass could result in an increase of HANPP to 44% by 2050 (Krausmann et. al.)

What is the Earth’s Carrying Capacity for Humans?● Many scientists agree that the Earth will reach its total, adjusted carrying

capacity between the years 2030 and 2060● Predictions for the number of humans the Earth can sustain go up to 14 billion

people - before we run out of food

Technically, we have already exceeded the Earth’s carrying capacity

● Living space○ Close quarters in urban areas, where it is estimated 70% of people will live by 2020

● Fossil fuels

2:08 to 6:04

https://www.youtube.com/watch?v=IFzc3lGF8DY

Solutions1. Reduce the population

2. Reduce resource consumption (become vegans)

3. Double food production

→ Carrying capacity of 10 billion

But then what?

Population ControlThe average number of children being had by families in developed countries is decreasing, but in underdeveloped countries, it is increasing.

● Lack of access to birth control○ Politics○ Economics○ To a smaller extent, religious beliefs

Fertility “Replacement Level”

● 2.1 children per family● Population would never increase

Referenceshttp://eds.b.ebscohost.com/eds/pdfviewer/pdfviewer?sid=2f8a1ebd-8b99-4c41-9d24-b9c87ec42230%40sessionmgr101&vid=2&hid=117

https://populationmatters.org/wp-content/uploads/D20Carryingcapacity.pdf

https://na.unep.net/geas/archive/pdfs/geas_jun_12_carrying_capacity.pdf

http://agrpartners.com/wp-content/uploads/2013/09/AGR-Thought-Piece-Carrying-Capacity1.pdf

http://www.sciencedirect.com/science/article/pii/S0040162513001613?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3690849/

Videohttps://www.youtube.com/watch?v=IFzc3lGF8DY