Human Population & Environmental Impact

Human Populations World population clock Population graph It is predicted that the human population will reach almost 9.5 billion people by 2050 Do you think we will have reached our carrying capacity by then? Is the human race getting ready for a population crash? What determines the human population impact on the environment?

Human Population A little History: 1. Hunters/gatherers. – Small communities that could support themselves. – Usually moved around following the herds. 2. Rise of agriculture. – People started to farm, grow crops to feed themselves and others – Somewhat settled communities and villages, controlled by the seasons. – Larger families to support the labor needs of the crops. – Major increase in the human population. 3. Industrial revolution. – Improvements to food supply, health care, living conditions – More city dwellings, to keep workers closer to the factory. – Rapid increase in human population. 4. Technology age (today) – Rate of population has steadied or decreased in wealthy countries, ie US, Canada, Europe – Increase in city populations. – High health care, food supply/nutrition, increased living conditions. – Education and world awareness have increased.

Reproductive strategies K-selected: Characterized by larger sized organisms that live at or near the carrying capacity for their species. – Few offspring, with higher survival rate – Spend larger amounts of energy on parental care where most offspring survive. Characteristics of k-selected species: – Long life span with slower maturity rate, maturing at a late age. – High parental care and protection – Adapted to stable environment – Lives in later succession stages – Niche specialists – Predators – Regulated by internal factors – Higher trophic level – Ex: humans, trees, elephants

Reproductive Strategies R-Selected: Characterized by smaller sized organisms with high populations exceeding carrying capacity and end up crashing the population (j- curve). – Rapid reproduction rate, shorter life span – Spends larger amounts of energy on producing offspring, but not in parental care and protection. Characteristics of r-selected species: – Many offspring with rapid growth and early maturity. – Adapted to unstable environment – Pioneers and colonizers, early succession stages – Niche generalists – Prey – Regulated by mainly external factors – Lower trophic levels – Ex: fish, annual plants, bacteria

Human Population Impact on the environment: Increase in resource use – Especially non-renewable resources like coal, oil Produces more wastes – Pollutes the environment – Places to put the wastes as area of nonliving people decreases Less space for other species to survive if there are larger cities and more people.

Malthus The Malthus Hypothesis: Thomas Malthus –  lived  expressed a pessimistic view on the dangers of overpopulation growth.  He claimed that food supply was the main limiting factor that could contribute  to pop growth.  pop growth grew exponentially (2,4,8,16…) while food supply grew  arithmetically (2,4,6,8…).  Law of diminishing returns – over cultivation of land Limitations:  too simplistic a theory  a shortage of food is just one possible explanation, when only the poor go  hungry  unequal distribution of resources is greater cause  Increase in Technology is far greater than Malthus predicted.

Boserup Ester Boserup’s Theory: Ester Boserup – 1965  A danish economist – “necessity if the mother of invention”  Asserted that any increase in a population will demand an increase in food supply therefore the technology to create more food will become available.  Based on her research in various land use systems  Innovation and shifting in cultivation methods will increase the production of food. Limitations:  Based on a “closed” community, but immigration and emigration are too common.  Too difficult to test due to immigration and emigration because of overpopulation in certain areas.

Survivorship Curves How to predict the survivorship fate of a group of individuals by knowing at what age individuals died. Can represent the mortality patterns of a population over a period of time. Where the patterns stay relatively consistent for each species.

Graph 1 – typical K-select R-select Rare

Graph 2 - Actual