Ch 24: Human Population, Planetary Resources, &

Conservation

Human Population

• Growth rate of a population is determined by difference in birthrate and death rate.

• Growth rate peaked at 2% in 1965 & current world growth rate is 1.3%

Two Types of Countries

• More Developed Countries (MDC’s)– Population growth is modest

(overall 0.1%)– Good standard of living

• Less Developed Countries (LDC’s)– Population growth is dramatic– Majority of people live in

poverty

Growth & the Environment

• Biotic potential – the maximum growth rate under ideal conditions

• Environmental resistance – declines growth rate because of limiting factors

• Carrying capacity – maximum population that the environment can support for an indefinite period

Human Use of Resources & Pollution

• Resource – anything from the biotic or abiotic environment that helps meet the needs of survival.

• Two types of resources– Nonrenewable – limited in supply– Renewable – not limited in supply

• Pollution – any alteration of the environment in an undesirable way

Limited Resources• Land & human Habitation

– Beaches – at least 40% of the world’s population lives near the coast and this leads to beach erosion and loss of marine habitats.

– Semiarid land – human habitation can lead to desertification (which is conversion of semiarid land to desert like conditions) from allowing animals to overgraze the land.

– Tropical Rain Forest – human habitation can lead to deforestation (removal of trees and then habitats for native organisms)

Limited Resources

• Water - Freshwater is available as surface water & aquifers.

– Build dams – to increase supply but may not be useful for long• Lose water due to seepage into underlying rock beds.• Salt left behind due to evaporation and agricultural runoff increase salinity

and can make the a river’s water unusable further downstream• Hold back less water over time due to sediment buildup

– Aquifers – people remove water at a rate that cannot be sustained and leads to sinkholes and saltwater intrusion

– 70 % of all freshwater is used to irrigate crops, but farmers could use drip irrigation to reduce water use by 50%

Limited Resources

• Food – Farming - supply of food has been increased due to modern

farming methods, but these methods can be harmful:• Planting a few genetic varieties• Heavy use of fertilizers, pesticides, and herbicides • Generous Irrigation• Excessive fuel consumption

– Domestic Livestock• Large portion of farming goes to feed livestock

– For every 1lb of meat, they use 10 lbs of grain

• Injection of growth hormones & antibiotics

Limited Resources

• Energy– Nonrenewable Sources

• 75% of the worlds energy supply come from fossil fuels that will eventually run out

• Fossil fuels produce greenhouse gases that affect global warming.

– Renewable Sources• Hydropower – converts falling water into

electricity• Geothermal Energy – getting hot

temperature from the earth’s crusts and converting the heat into steam

• Wind Power – using a windmill to create energy

• Solar Energy – taking energy from the sun, storing it, and then converting it to electricity.

Limited Resources

• Minerals– Non-metallic – Sand, Gravel, & Phosphate

– Metallic – Aluminum, Copper, Iron, Lead, & Gold

• Strip mining – An invasive way to obtain minerals, which can lead to whole mountaintops being destroyed. This leads to ruined habitats and wildlife as well as cause toxic waste to be deposited in nearby streams and rivers.

Hazardous Waste

• In addition, to using up our resources, we are depleting the available resources by dumping hazardous wastes.

– Biological magnification – accumulation of synthetic organic chemicals that becomes concentrated at higher trophic levels.

Loss of Biodiverstiy

• Biodiversity – variety of life on Earth, described by the # of different species and their abundance.

• We are losing our biodiversity, because of:– Habitat Loss

– Alien Species – introduction of nonnative species

– Pollution• Acid Rain• Global Warming • Ozone Depletion• Synthetic organic chemicals

– Overexploitation – occurs when a number of individuals are taken from the wild

– Disease – from exposure to domestic animals and their pathogens

Examples of Species Loss

Indirect Values of Biodiversity

• Biogeochemical Cycles

• Waste disposal via decomposers

• Provision of fresh water via “sponge effect”

• Prevention of soil erosion

• Regulation of climate by reducing CO2

• Ecotourism

Direct Value of Biodiversity

• Medicinal value– Rosy Periwinkle – leukemia &

Hodgkin– Armadillo - leprosy– Horseshoe crabs – substance that

makes pacemakers, implants, prosthetic devices free of bacteria

• Agricultural value– Available wild strains– Biological pest control

• Consumptive use value– Fish– Wild Game– Fruit & Vegetables– Rubber

Unsustainable vs. Sustainable Society