Human ImpactChapter 5

Loss of Biodiversity Biodiversity—variety of life in an area Tropical regions contain two-thirds of all land

speciesNumber of mammals, for example:

• Canada—163• US—367• Mexico—439

Importance of biodiversity—food webs and ecosystem balance, 02 for humans, diverse diets, clothing and building materials, medicines

Endangered Species in GA

Purple pitcherplant—Sarracenia purpurea

Loggerhead Sea Turtle—Caretta caretta

Black right whale—Eubalaena glacialis

Red-cockaded woodpecker—Picoides borealis

Endangered Species in GA

Loss of Biodiversity

Possible causes—Habitat lossHabitat fragmentationHabitat degradation (by pollution)

Solutions:

Habitat Preservation through…

National and State Parks

W.M.A (Wildlife Management Areas)

Biomagnification

Biomagnification—toxins become more concentrated as it moves up the trophic levels

Example is DDT insecticide (Dichloro-diphenyl-trichloroethane)Collects in fatty (adipose) tissues of

animals

History of DDT Developed and used during WWII-

small tins given to soldiers to combat lice & malaria

Heavily used in US from 1940s to 1970s, even sprayed in public areas to kill mosquitoes

Banned from US in 1972, but continues to be used in other countries

Rachel Carson

DDT a serious problem…decline in bird (top of food chain) populations (thin egg shells)

Silent Spring written by Carson helped to bring about formation of EPA and banning of DDT

Bird populations showed dramatic recovery Even today, traces of DDT have been found

in every organism tested—even in human breast milk throughout world

Land Resource Depletion

What happening? Plowing removes the roots that hold

the soil in place, increasing the rate of soil erosion.

SOIL EROSION – is the wearing away of surface soil by water and wind.

Desertification – the process of turning once productive areas into deserts from a combination of farming, overgrazing, and drought.

Land Resources Why is it a problem?

Soil is a renewable resource, however it can be permanently damaged if mismanaged

What is being done? Contour plowing- fields

plowed across the slope of the land

Leaving stems and roots of the previous year’s crops in place to hold soil.

Planting trees

Land Resource Depletion

Deforestation – loss of forest which leads to severe erosion

Water Resources

What is happening?Pollution such as OIL SPILLS threatens our

water supply. Improperly discarded chemicals can enter

streams and rivers.Domestic sewage entering our water ways

can cause an increase in bacteria growth.Overfishing - fish stocks in many fisheries

are being harvested faster than they reproduce.

Water Resources

Why is this a problem?Fresh water is used daily for everything from

drinking and washing to watering crops and making steel.

Although water is a renewable resource, the total supply of fresh water is limited.

What is being done? Conservation by: drip irrigation and consumer

awareness of conservation

Water Resources (Oceans)

What is happening?– Overfishing - fish stocks

in many fisheries are being harvested faster than they reproduce.

Why is this a problem?– People depend on the

ocean as a major source of protein, both from finfish and from shellfish.

– With the amount of fish caught each year increasing, the fish cannot reproduce fast enough to keep up.

– - Disrupts ecosystem (food web)

Water Resources

What is being done?Limiting the catch of

fish Certain fishing

grounds have been temporarily closed

Aquaculture - farming of aquatic organisms (see picture to right)

Air Resources

What is happening?

–Smog - a mixture of chemicals that occurs as a gray-brown haze in the atmosphere

This is due primarily to automobile exhausts and industrial emissions.

–Pollutant - a harmful material that can enter the biosphere through air, land, or water

The burning of fossil fuels can release pollutants that cause smog and other problems in the atmosphere.

What is Acid Rain and What Causes It?

"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.

Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground; it affects a variety of plants and animals.

Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms.

Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles.

Scientists discovered, and have confirmed, that sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain.

In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal.

Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid.

Air Resource Depletion

Air Resources Why is it a problem?

This leads to toxins that enter the mouth, nose and lungs causing health problems over the long term.

Gases released from the burning of fossil fuels combine with water vapor to form ACID RAIN

Acid rain kills plants and changes the chemistry of soils

What is being done? Technology to control emissions from factory

smokestacks Strict automobile emission standards and clean air

regulations

Global Warming

Global Warming

Some warming is good…if not for the ozone and atmosphere, Earth would be -18˚C (warming is due to greenhouse gases in the atmosphere trapping in heat—see the next slide for a picture)

Estimated increase of 2˚C by end of 21st century

Even 1.3˚C affects polar ice cap melting (sea level could rise 100 m, gradually going in 150 km or more)

Green House Effect

Natural situation in which heat is retained in the earth’s atmosphere by green house gasses (carbon dioxide, methane, water vapor and other gasses).

Sunlight Some heatescapesinto space

Greenhousegases trapsome heat

Atmosphere

Earth’s surface

Global Warming

Global Warming

Why is this a problem?Polar ice caps will continue to melt and

could rise enough to flood some low lying coastal areas.

Storms and other weather disturbances could become more frequent and severe.

Heat favors rodents, weeds, and insects that reproduce and spread quickly.

Ozone Depletion Ozone layer (composed of 03 in

lower stratosphere) Stratospheric Ozone

The stratosphere, or "good" ozone layer extends upward from about 6 to 30 miles and protects life on Earth from the sun's harmful ultraviolet (UV) rays

This natural shield has been gradually depleted by man-made chemicals like chlorofluorocarbons (CFCs). A depleted ozone shield allows more UV from the sun to reach the ground, leading to more cases of skin cancer, cataracts, and other health problems.

Ozone Depletion

Ozone Depletion

Ozone Depletion

Why is this a problem?The ozone layer absorbs a great

deal of harmful UV rays before it reaches the earth’s surface.

As the ozone layer is depleted, UV exposure can cause sunburns, cancer, eye damage and decreases an organism’s resistance to disease.

Ozone Depletion Solutions

Reduce the amount of CFC’s use. Most CFC’s are banned 1987 The Montreal Treaty - -

reduction of CFC’s and eventual ban the CFC production.