Chapter 16Human Impact on Ecosystems

Earth’s Resources Natural Resources

– Part of natural environment used by humans

– Include soil, water, crops, wildlife, oil, gas, minerals

– Wilderness and recreation areas Renewable resources

– Materials that can be replenished or recycled by natural processes

– Oxygen, nitrogen, plants, animals, soil, water

Earth’s resources Nonrenewable resources

– Available in limited amounts and cannot be replaced or recycled by natural processes

– Metals, minerals, topsoil Fossil fuels and petroleum products

– Substances made from remains of organisms buried for millions of years

– Nonrenewable

Earth’s resources Extinct organisms

– Disappearance of a species– Last 20 years, 30 species of

plants/animals have disappeared from US

– Humans mainly responsible– Destruction of habitat, hunting, housing

developments, destruction of forests for farmland

When demand exceeds supply

Greater population, greater demand for resources– Need food, water, living space, clothing,

transportation, etc.– Increases prices, may cause shortages

Ecological footprint Amount of land necessary to produce

and maintain enough food and water, shelter, energy, and waste

Depends on the amount and efficiency of the use of resources and the toxicity level of wastes produced

Ecological footprint (2006)

Land resources Topsoil needs to be replenished with

humus and moisture Agriculture increases the rate of soil

erosion or desertification Contour plowing or leaving

roots/stems from previous crops prevents erosion and enriches soils

Forest Resources Temperate forests are renewable,

new seedlings are planted after logging and trees grow back

Old growth forests may lose some species during deforestation due to erosion or over-grazing of the areas

Old growth forests should be selectively logged and replanted

Fishery Resources Fish feed a large number of people

on Earth Over fishing will deplete the fish

populations before they can be replenished by reproduction

Laws are being implemented to control fishing in certain areas of the oceans and during certain seasons

Pollution Waste products usually recycled by natural

processes that exist in excess Can be in the form of microscopic

particles, waste from factories/sewers, household chemicals poured down sinks

Cause contamination of different parts of the environment– Air – Water– Land

Humans burn fuel To heat homes and businesses Power planes, cars, buses, trains Produce electricity Manufacturing and industry All release particulates All release air pollutants

– CO2, CO, nitrogen oxides, sulfur oxides, hydrocarbons: make smog

Acid rain Air pollutants react with water and

oxygen in light to make sulfuric acid and nitric acid

Pollutants come from coal-burning factories and car exhaust

Non-polluted rain has a pH of 5.6-5.7 Rain with pH lower than 5.6 is acid

Effects of acid rain Leaches calcium, potassium, and

other nutrients from soil (decreases nutrients)

Leads to death of trees and damage to plant tissues

Interferes with nitrogen fixation (by bacteria)

Severely effects lakes’ ecosystems

Ozone depletion Ozone prevents harmful UV radiation

from damaging living organisms Ozone is thinning due to

– Air pollutants– CFCs

Legislation (2000) is in effect to decrease the release of CFCs and to recycle existing CFCs

Greenhouse effect Gases in atmosphere keep heat close

to earth Prevents some heat from escaping

into space; Earth stays too warm Main gas involved is CO2

World temperature change/CO2 levels

Global warming Trend of increasing global

temperatures In the last 100 years, the average

global temperature has increased 0.74 C (major changes in temperature usually occur over tens of thousands of years)

Current evidence includes for severe types of weather (flooding, stronger tropical storms, etc.)

Water Pollution Water covers over 2/3 of Earth 3% is freshwater Only .1% is available for organisms

– Drinking, growth, carry away waste Polluted by waterborne diseases

– Cholera, dysentery, hepatitis Polluted by inorganic substances

– Fertilizers, sediments, heated water

Water pollution Comes from runoff from farmland and

cities Added nutrients and chemicals in runoff

lands in water supplies (rivers, lakes) and stimulates plant and algae growth (decreases oxygen levels)

Severely alters many ecosystems Ecosystem health is studied through

indicator species– Species that come in direct contact with the

water / pollutants of the ecosystem

Biomagnification Pollutants that are water soluble and

picked up by organisms are excreted with wastes

Pollutants that are fat soluble build up in the tissues of organisms

With biomagnification, pollutants move up the food chain, accumulating in higher concentrations in predatory animals

Biodiversity Sum of all genetic variety Provides food, industrial products,

medicines Human activity threatens biodiversity

by– Reducing habitats– Over hunting– Introducing toxic substances into food

chains– Introducing new species into foreign

areas

Land pollution Solid wastes found in landfills or

burned Average American produces 1.8 kg of

solid waste daily Not broken down by decay (buried in

landfills=no oxygen)

Habitat Habitat must be managed, not

destroyed, in order to preserve biodiversity

Organisms must have access to their range

Habitat fragmentation is caused by a barrier that prevents organisms from accessing their entire habitat range (such as large highways)

Introduced species These are species brought into an

area as a result of human actions Also called non-native or invasive

species Compete with native or natural

organisms for resources Often damaging to the ecosystem

and can result in extinction of native plant/animals

Sustainable development Using Earth’s resources without

depleting them Does not cause long-term

environmental harm Using natural means to take care of

problems; ex: using insects to get rid of insect pests (ladybugs eat aphids)

Preservation Keeping natural resources from harm

and destruction Yosemite Grant of 1864 was the first

to protect natural areas from development

Develop parks, refuges to balance recreations and the protection of natural resources

Conservation Planned management of natural

areas to prevent destruction or exploitation

EPA (1970), Clean Air Act (1970), Clean Water Act (1972), Endangered Species Act (1973)– Bald Eagles: 791 pairs 1973; 6500 pairs

2000 Recovery programs

– Help threatened or endangered species– Release them back to natural habitats