Ch. 27 – Human Impact on Earth Resources

1. Ch. 27 – Human Impact on Earth Resources As any population increases, its demand for natural resources increases as well. Any type of organis can have an impact on its environment if its population becomes large enough. A population growth is the increase in the size of a population over time. An initial population is small until the number of reproductive adults increases. This will cause the population of that organism to increase rapidly if there are enough resources to continue the growth. Exponential Growth – a pattern of growth in which a population grows faster as it increases in size. This causes a population explosion. Fig. 27-3 (pg. 713)

2. Most populations wouldn’t be able to continue in an exponential growth pattern because of the lack of resources. • What organisms may have a higher success rate? How about lower? • Carrying capacity – the number of organisms that any given environment can support. • If a population hasn’t reached its carrying capacity there will continue to be more births than deaths. • Once the carrying capacity is reached then the population is at equilibrium an the number of births and deaths equal out.

3. Density-independent factors – are environmental factors that affect population growth. • Ex. Droughts, floods, storms, pollution • These factors affect any population regardless of size. • Density-dependent factors – increasingly affect a population as the population’s size increases. • Ex. Disease, parasites, and lack of food. • Human Population Growth is still in the exponential growth stage and may continue to grow for at least another 50 years. • It hasn’t reached its carrying capacity. • The current rate of growth clearly cannot continue forever. A demand for resources will continue to increase steadily.

4. Human Impact on Land Resources • An average person in North America consumes a renewable yield of approximately 12 acres of forest and farmland. • Mining by surface and subsurface has big affects on the environment. The government requires mining companies to restore the ground to its original contours and replant vegetation in the process of reclamation. • Biodiversity (wide variety of species) is important in maintaining a stable ecosystem for organisms to live in. • Monocultures of one specific crop makes it easy for farmers but provides risks in the form of plant specific diseases, pests, and fungi.

5. Pesticides are helpful to farmers by eliminating insects, but there are drawbacks. • A lot of pesticides kill pollinating and decomposers (beneficial) insects. • Insects reproduce quickly which cause them to build resistance to pesticides. • The runoff and wind may carry pesticides to rivers, lakes, streams which causes harm to other organisms. • Crop rotation is an excellent way for farmers to keep topsoil fertile. Instead of adding artificial fertilizers • Farmers rotate their crops with clover, alfalfa, or other crops that are great nitrogen fixers and put nutrients back into the ground.

6. A big reason topsoil is lost is due to deforestation – the clearing of forested land. • 70% of North American’s live in a urban or suburban area. • The expansion of urban areas has a huge effect on the environment. The effect is a loss of natural habitats for a balanced environment. • A lot of the global warming increase may be due to expansions of urban areas. • This wipes out plants for release of oxygen. • Pavement reflects more light & less rainfall is absorbed. • More greenhouse gases are released. • More solid wastes produced. • These wastes are leaking from landfill as toxins.

7. Lots of techniques have been implemented to decrease the hazards caused from urban expansion. • Barriers for landfills. • Wetlands are recognized and protected. • Contaminated soils are removed and toxic chemicals are destroyed from the soils with heat. • Bioremediation is a technique to treat contaminated soils with bacteria that eat toxic materials and convert them to less-harmful substances.

8. Human Impact on Air Resources • Smog – photochemical haze triggered by solar radiation reacting with hydrocarbons and nitrogen oxides (car exhausts). • Ozone is the major chemical (3 oxygen atoms) in smog. • Ozone is helpful in the upper atmosphere for filtering out harmful U.V. light. • When ozone combines with air pollutants it harmful to eyes, noses, throats, lungs, and plants. • Pollution can be in the form of particulate matter. Dust, pollen, ash, and asbestos fibers. • They cause breathing difficulties and lung diseases.

9. Humans have a major effect on air pollution with global warming, ozone depletion, and acid precipitation. • Global Warming occurs from greenhouse effect, in which the average surface temperature increases. • This is largely due to the burning of fossil fuels, which produce carbon dioxide as a bi-product. • Since the Industrial Revolution (1850s) humans have been burning fossil fuels consistantly. • Fig. 27-18 (pg.725) • This could cause major effects on climate patterns. • Glaciers melting and flooding shore lines, plant and animal species may not adapt well. • Could this be a trend or are humans causing drastic climatic changes.

10. CFCs from human uses was the cause of ozone depletion since the 1980s. • Acid precipitation – precipitation with a pH less than 5. • Forms when sulfur dioxide and nitrogen oxides combine with atmospheric moisture. • Coal generated by power plants produce acid forming gases. Scrubbers are added to the power plants to reduce the pollutants. • The acid rain affects surface waters of aquatic ecosystems and plants and animals. The acid rain also damages stone buildings, statues, metal structures, and especial limestone structures.

11. Human Impact on Water Resources • Freshwater is used by humans in several ways – bathing, drinking, cooking, and washing. • 378 billion liters of water was used per day in 1995. • The greatest demand on water comes from industry, including power plants that use water for cooling purposes. • Water Pollution • Point Sources – generated pollution from a single point of origin, such as a sewage-treatment plant or an industrial site • Nonpoint Sources – generated from widely spread areas, such as runoff from pesticides, fertilizers, roads, parking lots, etc.

12. The Safe Drinking Water Act (1974) and the Clean Water Act (1972). These laws made water safer and cleaner for the ecosystem and human consumption. They helped reduce water pollution. • Water Conservation • Efficient irrigation practices, landscaping plants, improving delivery systems, raise water rates, recycle cooling water & waste water for industries. • Fix leaky pipes, toilets, faucets, etc. • Efficient showerheads, toilets, outdoor watering, etc.