Chapter 6 – Humans in the Biosphere

6-1 A Changing Landscape

Earth as an island – we need to need to see how models can be used to make predictions about complex systems… Hawaii pg 139

Among human activities that affect the biosphere are

- hunting and gathering – decreases natural species in certain areas; has caused major mass extinctions

- agriculture – created dependable food source… villages settled… habitat destruction, introduced species, pest control, irrigation

- industry – machines and factories use fossil fuels (coal, oil, natural gas)

- urban development – discarded wastes… pollution, movement to suburbs… habitat destruction

American artist Chris Jordan recreated Seurat’s masterpiece with digital images of 106,000 aluminum cans - the number used in the US every thirty seconds!

6-2 Renewable and nonrenewable resources

Tragedy of the commons – idea that any resource that is free and accessible may eventually be destroyed.

Renewable resource – can regenerate or be replenished by a chemical cycle; trees, water

Nonrenewable resources – cannot be replenished by natural processes; fossil fuels burn and energy is given off

*** a population of trees may be nonrenewable if ecosystem changes

Sustainable development – use ecological studies to see how we are impacting the environment in order to save resources

Land resources – soil can be permanently damaged- soil erosion and desertification occur when humans change environment… contour plowing and leaving in roots can help

Forest resources – used for materials, oxygen, habitats, and food

- deforestation can lead to erosion and loss of habitats

Fishery resources – oceans and lakes provide a lot of food – aquaculture

- overfishing is an example of the tragedy of the commons

Air resources – cities produce smog, a pollutant from the burning of fossil fuels that can cause health problems

-acid rain – nitric and sulfuric acids with a high pH which can kill plants and animals

Formation of Acid Rain

Emissions to AtmosphereNitrogen oxidesSulfur dioxide

Chemical TransformationNitric acid

Sulfuric acid

PrecipitationAcid rain, fog,snow, and mist

Dry Fallout

Condensation

particulates, gases

Industry Transportation Ore smelting Power generation

Freshwater resources – pollution threatens water supplies; improperly discarded chemicals, domestic sewage

6-3 Biodiversity

Biodiversity = the sum total of the genetically based variety of all organisms in the biosphere

- one of Earth’s greatest natural resources.

Species of many kinds have provided us with foods, industrial products, and medicines – including painkillers, antibiotics, heart drugs, antidepressants, and anticancer drugs.

Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species to new environments.

Species Diversity

Pollution – DDT, a pesticide, became more concentrated as it moved up the food web… biological magnification

Biological Magnification of DDTFish-Eating Birds

Magnification ofDDT Concentration

10,000,000

100,000

10,000

1,000,000

1

1000

LargeFish

Small Fish

Zooplankton

Producers

Water

Introduced species – humans transport plants and animals around the world that take over a new habitat

Conserving Biodiversity

- managing endangered species, protecting habitats, fishing regulations

Sustainable Agriculture

Cover CropsLegumes, grasses, and othercover crops recycle soil nutrients,reduce fertilizer need, andprevent weed growth.

Controlled GrazingBy managing graze periods and herddensities, farmers can improve nutrientcycling, increase the effectiveness ofprecipitation, and increase the carryingcapacity of pastures.

Biological Pest ControlThe use of predators and parasitesto control destructive insectsminimizes pesticide use as well ascrop damage

Contour PlowingContour plowing reduces soil erosion from land runoff. On hilly areas, plowing is done across the hill rather than straight up and down.

Crop RotationDifferent crops use and replenish different nutrients. By rotating crops, the loss of important plant nutrientsis decreased.

A B C

Yr. 1

Yr. 2

Yr. 3

corn

corn

corn

alfalfa

alfalfa

alfalfa

oats

oats

alfalfa (plowed in)

6-4 Charting a Course for the Future

Ozone depletion – ozone layer absorbs harmful ultraviolet radiation; evidence exists that chlorofluorocarbons, CFCs, could damage the ozone layer; use of most CFCs are banned in US

Global Climate Change – increase in the average temperature of the Biosphere; some scientists attribute this to human activities and the burning of fossil fuels… CO2

Ecosystem Services

Solar energy

Production of oxygen

Storage and recycling of nutrients

Regulation of climate

Purification of water and air

Storage and distribution offresh water

Food production

Nursery habits for wildlife

Detoxification of human andindustrial wasteNatural pest and disease control

Management of soil erosionand runoff

How does everything fit?