Humans in the Biosphere

1. Humans in the Biosphere Chapter 6

2. 6-1 A Changing Landscape • Hawaii as an analogy for the Earth • Land was limited/finite • Native people were original conservationists: for each palm cut down, replaced with two • Prohibited fishing during fish reproductive season

3. A Changing Landscape • Settlers changed the practices of centuries • Cleared vast areas to grow sugar cane • Used large amounts of fresh water for agriculture • Hawaii today • Native species of animals scarce • Drinking water restricted • Once common fish now rare

4. Earth as an Island • Earth has a limited resource base • Knowledge of interactions- energy flow, chemical cycling, climate, population-limiting factors- allow us to save ourselves by making predictions

5. Human Activities • Human activities can change local and global environments • Among human activities that affect the biosphere are hunting and gathering, agriculture, industry, and urban development

6. Hunting & Gathering • First humans probably caused a mass extinction in North America 12,000 ya – woolly mammoths, zebras, yaks, saber-toothed cats • Today, still a few hunter/gatherer groups in world. Most use some form of technology, such as manufactured tools or guns.

7. Agriculture • By end of last Ice Age (11,000 ya) humans began to farm- wheat, rice, potatoes. Why? • Stable & predictable food supply • Larger settlements • Development of government, laws, writing

8. Traditional toModern Agriculture • Machinery aided social development – seed drill, plow • World exploration led to exchange of crops • Large-scale irrigation in dry areas increased yield & allowed deserts to become breadbaskets • As specialized techniques developed, farming became a monoculture, with chemical fertilizers and pesticides.

9. The Green Revolution • In mid-1900s, despite agricultural advances, many food shortages occurred. • Result was “miracle strains” of wheat, corn; monoculture;chemical fertilizers. • In 20 years, Mexico increase wheat production 10X; India & China produced enough to feed their own people • World food production doubled.

10. Challenges for the Future • Monoculture leads to problems with pests and diseases • Chemical pesticides can damage beneficial insects (pollinators),contaminate water supplies, and accumulate in the environment. • Not enough fresh water for irrigation e.g., Midwest & West depends on Ogalla aquifer, which may dry up in 20-40 years at present rate of replenishment

11. Industrial Growth & Urban Development • For years, cities discarded industrial wastes & pollutants into air, water, & soil without concern • Urban sprawl developed consumes farmland & natural habitats, as well as producing stress on environment • Can we learn to control these harmful effects of human activity while preserving- or even improving- our standard of living?

12. 6-2 Renewable & Nonrenewable Resources • “The tragedy of the commons” • Free and accessible resources may eventually be destroyed. There is no one responsible for preserving it. • Land Resources • Forest Resources • Fishery Resources • Air Resources • Freshwater Resources

13. Classifying Resources • Renewable resources can regenerate if they are alive, or can be replenished by biochemical cycles if they are nonliving. • Nonrenewable resources cannot be replenished by natural processes. • Classification depends on context. A single tree is renewable; a population of trees may not be.

14. Sustainable Development • Sustainable development is a way of using natural resources without depleting them. • Must take two views into account: • The functioning of ecosystems • The ways that human economic systems operate.

15. Land Resources • “Land” includes space as well as soil. • Soil is a mixture of decayed matter (humus), minerals, sand, clay and silt (from bedrock).

16. Land Resources • Plowing removes roots which holds soil in place. This increases the rate of soil erosion by water and wind. • Desertification: caused by a combo of farming, overgrazing, and drought. • Solutions: contour plowing, leaving previous year’s stems & roots, planting a field with rye rather than naked.

17. Forest Resources • Wood necessary for many people for homes, paper, fuel in heating & cooking. • Living forests often called “lungs of the Earth”- remove CO2 and produce O2. • Forests also • Store nutrients • Provide habitats • Provide food • Moderate climate • Limit soil erosion • Protect freshwater supplies

18. Forest Resources • Is it renewable? Depends on type of forest. • Temperate softwood forests of Northeast: renewable. Been logged at least once and have regrown naturally. • Alaska and Pacific Northwest are old-growth hardwood forests: never been cut. Takes 100s of years to re-grow, so nonrenewable.

19. Forest Resources • Deforestation can lead to • Severe erosionas soil is exposed to heavy rain • Nutrients in topsoil are washed away • Grazing and plowing that follows can cause permanent changes in soil, making it brick-like and hard • Solutions: • Harvest selectively- leaving younger • Foresters also maintaintree farms • Tree geneticists engineer faster-growing, high-quality wood

20. Fishery Resources • Example of Chesapeake Bay and river’s watershed: both saltwater & freshwater in estuaries. Has striped bass, American shad, crabs, oysters. • Overfishing example: between 1950 and 1990 fish catch grew from 19 million tons to 90 million tons. By the 1990s cod and haddock facing extinction.

21. Fishery Resources • Sustainable development: Data gathered by ecologists has helped to create guidelines for commercial fishing. Specifies how many and what size fish can be caught. Loss of jobs occurred in short term, but fish populations are recovering. • Aquaculture: raising of aquatic animals for human consumption. Can pollute water and damage aquatic ecosystems.

22. Air Resources • Smog is caused by pollutants which enter biosphere through land, air or water. • Can be caused by burning of fossil fuels which release nitrogen & sulfur compounds, causing acid rain. • Kills plants • Changes chemistry of soils • Releases toxic elements like mercury from soil

23. Freshwater Resources • Although water is a renewable resource, the total supply of freshwater is limited. • Threat of pollution • Improperly discarded chemicals can enter streams and rivers • Wastes can seep into underground water supplies and wells • Domestic sewage contains N and P which encourage algae & bacteria growth • Disease can spread to humans & animals- now most cities treat wastewater

24. Freshwater Resources • ¾ of all water consumed in this country is used in agriculture • Drip irrigation delivers water directly to plant roots- no runoff!

25. 6-3 Biodiversity • Biodiversity = The sum total of the genetically-based variety of all organisms in this biosphere. • Ecosystem diversity: includes habitats, communities, and ecological processes • Species diversity:the number of different species in the biosphere (currently 1.5 million- only millions more to go!) • Genetic diversity: The sum total of all the different forms of genetic info carried by all organisms

26. Biodiversity • Biodiversity is one of Earth’s greatest natural resources. Species of many kinds have provided us with • Foods • Industrial products • Medicines • Painkillers, antibiotics, heart drugs, antidepressants, anticancer drugs

27. Threats to Biodiversity • 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. • Can lead to endangered species and extinction

28. Habitat Alteration • As habitats disappear, the species that live in those habitats vanish. • Development can split ecosystems into pieces, becoming biological islands – habitat fragmentation

29. Demand for Wildlife Products • Toxic compounds can accumulate in the tissues of organisms. When carnivores eat herbivores which consumed toxic compounds, the substance is concentrated further, called biological magnification. • Top level carnivores are at highest risk, though all of food web will be affected. • Example: DDT and eagle eggs

30. Introduced Species • Introduced into new habitats, invasive species that were harmless in their native habitats reproduce rapidly because their new habitat lacks the parasites and predators that control their population “back home”. • Example: zebra mussels, purple loosestrife

31. Conserving Biodiversity • Conservation: the wise management of natural resources, including the preservation of habitats and wildlife • Today, conservation efforts focus on protecting entire ecosystems as well as single species

32. Conserving Biodiversity • Protecting an ecosystem will ensure that the natural habitats and the interactions of many different species are preserved at the same time. • National parks & forests • Marine sanctuaries • Hunting & fishing regulations

33. 6-4 Charting a Course for the Future • Researchers are gathering data to monitor and evaluate the effects of human activities on important systems in the biosphere. • Ozone layer – continually monitored • Global climate systems – evaluate change

34. Ozone Depletion • O3 • Absorbs UV radiation that can cause cancer, damage eyes, reduce resistance to disease • 1970s- discovered hole in ozone layer – most likely triggered by CFCs., Since CFC ban hole is getting smaller (very slow deterioration of molecule)

35. Global Climate Change • Strong evidence shows that the climate patterns are changing from usual cycles. • Evidence of global warming due to human activity? Or part of a longterm cycle? • Effects of global warming could be flooding of coastal regions, droughts and extreme heat in summer, new organisms thriving and old ones becoming extinct.

36. The Value of a Healthy Biosphere • Human society depends on healthy, diverse, and productive ecosystems because of the environmental and economic benefits they provide. • The biosphere is strong. Humans are clever. We can both adapt.