Human Population

Environmental ScienceEnvironmental Science

What is a Population?

• PopulationPopulation- all the members of a - all the members of a certain species in a certain area. certain species in a certain area.

• Human population- All the members Human population- All the members of the human race on Earth.of the human race on Earth.

• Why on Why on ALLALL of Earth? of Earth?– Humans have used technology to adapt Humans have used technology to adapt

and be able to easily move from and be able to easily move from anywhere on Earth to anywhere else.anywhere on Earth to anywhere else.

Population Changes

• Populations grow when the Populations grow when the birth birth raterate is greater than the is greater than the death ratedeath rate..– Birth rate-number of organisms Birth rate-number of organisms

reproduced in a yearreproduced in a year– Death rate- number of organisms that Death rate- number of organisms that

perish in a yearperish in a year

Population Change

• Populations can Populations can decreasedecrease if the if the death rate is greater than the birth death rate is greater than the birth rate.rate.

Limiting Factors to Population Growth

• Limiting Factor-Limiting Factor- Anything that limits Anything that limits how many individuals a certain how many individuals a certain population will havepopulation will have– Food supply-Food supply- If there’s not enough food If there’s not enough food

for every organism to grow and carry out for every organism to grow and carry out life functions, then some organisms will dielife functions, then some organisms will die

– SpaceSpace-If there isn’t enough habitat, some -If there isn’t enough habitat, some organisms will dieorganisms will die

– Predation/Disease- If there are no Predation/Disease- If there are no predators/disease, a population can predators/disease, a population can increaseincrease

White Tail Deer• Around 1900, the white tail deer in NY Around 1900, the white tail deer in NY

population was population was very lowvery low..– Due to almost no habitat, and unregulated Due to almost no habitat, and unregulated

human huntinghuman hunting– Efforts were made to limit huntingEfforts were made to limit hunting– Forest habitats started to increase as Forest habitats started to increase as

agriculture in NY decreasedagriculture in NY decreased• Now, in 2008, the white tail population is Now, in 2008, the white tail population is

enormousenormous– Due to regulated hunting and no natural Due to regulated hunting and no natural

predatorspredators– Abundant food sources and a TON of habitatAbundant food sources and a TON of habitat

Carrying Capacity• Carrying capacity-Carrying capacity- The The

total number of individuals total number of individuals that a certain habitat can that a certain habitat can support and sustain. support and sustain.

• Carrying capacity is based Carrying capacity is based on the on the limiting resourceslimiting resources of a given habitat.of a given habitat.

• When a population When a population exceeds exceeds its carrying its carrying capacity, it will rapidly capacity, it will rapidly decrease (crash) until it is decrease (crash) until it is below the carrying capacitybelow the carrying capacity

Easter Island• The inhabitants of Easter Island were The inhabitants of Easter Island were

so numerous that they used up all of so numerous that they used up all of their resources.their resources.

• When the resources were all gone, When the resources were all gone, many people killed each other for the many people killed each other for the scarce food and water that was left.scarce food and water that was left.

• Other people starved, until the Other people starved, until the population was very, very smallpopulation was very, very small

Human Population Growth

• With the invention of new With the invention of new technologies, the human population technologies, the human population has exploded from just has exploded from just 200 million200 million ~8000 B.C. to ~8000 B.C. to 6.6 billion6.6 billion today. today.

Human Society• Human Society has changed over timeHuman Society has changed over time• Hunter-Gatherer Society-Hunter-Gatherer Society- Humans Humans

lived in small bands and spent most of lived in small bands and spent most of their time looking for foodtheir time looking for food

• Agricultural Society-Agricultural Society- Humans spent Humans spent time in small cities and towns, in one time in small cities and towns, in one place, and spent most of their time place, and spent most of their time growing food.growing food.

• Industrial Society-Industrial Society- Humans live in Humans live in larger communities, but can freely larger communities, but can freely travel, and spent most of their time travel, and spent most of their time pursuing money, rather than food.pursuing money, rather than food.

Human Population Growth• There are three stages of population There are three stages of population

growth:growth:– 1. Pre-agricultural societies: birth rate and 1. Pre-agricultural societies: birth rate and

death rates are high, but close to equal, so death rates are high, but close to equal, so the population the population grows slowlygrows slowly

– 2. Agricultural societies: population size 2. Agricultural societies: population size increasesincreases due to an increase in health care due to an increase in health care resulting in higher birth rates and lower resulting in higher birth rates and lower death rates. death rates.

– 3. Industrial society-Birth rates fall until they 3. Industrial society-Birth rates fall until they are roughly equal to death rates, resulting in are roughly equal to death rates, resulting in zero population growthzero population growth..

Why the changes in population growth?

• AgriculturalAgricultural: population increases : population increases because level of health care increases, because level of health care increases, but the birth rate doesn’t decrease. In an but the birth rate doesn’t decrease. In an agricultural society, children are an asset. agricultural society, children are an asset.

• IndustrialIndustrial: The population levels out and : The population levels out and stops increasing because of advances in stops increasing because of advances in technology, but also because children technology, but also because children become economic liabilities, rather than become economic liabilities, rather than assets.assets.

Population Pyramid

• Population Pyramid: Population Pyramid: a grapha graph showing the number of males and showing the number of males and females in each age group in a females in each age group in a country’s population.country’s population.

Japan

• Japan’s three population pyramids shows Japan’s three population pyramids shows the three kinds of population growth. the three kinds of population growth.

• 1950- 1950- Rapid growthRapid growth, the birth rate is , the birth rate is greater than the death rate.greater than the death rate.

• 2006- 2006- Slowing growthSlowing growth, the birth rate is , the birth rate is greater than the death rate, but not by greater than the death rate, but not by muchmuch

• 2050- 2050- Zero growthZero growth, or negative growth, , or negative growth, the death rate exceeds the birth rate.the death rate exceeds the birth rate.

Japan

Problems with Population Growth

• PollutionPollution- increased - increased people means more people means more pollutionpollution

• ShortageShortage of natural of natural resources- As more resources- As more people consume more people consume more and more, we will run out and more, we will run out of some resourcesof some resources

• SpaceSpace-Where will we put -Where will we put all these people and still all these people and still have lands to support have lands to support them?them?

Solutions?

• We need to consume less!We need to consume less!• Work for a sustainable future.Work for a sustainable future.

– Sustainable- being able to support a Sustainable- being able to support a certain population indefinitelycertain population indefinitely