Chapter 6: Humans in the Biosphere

1. Chapter 6: Humans in the Biosphere

2. Section 6.1 – A Changing Landscape • Like all organisms, humans participate in food webs and chemical cycles. • We depend on these ecological life-support systems to provide breathable air, drinkable water, and fertile soil for farming. • In addition, ecosystem processes provide us with “services” such as storage and recycling of nutrients. • Ecologists refer to these necessities as “ecosystem goods and services” because they have real value to us as individuals and societies. • Among human activities that affect the biosphere are hunting and gathering, agriculture, industry, and urban development.

3. Hunting & Gathering • For most of human history, our ancestors obtained food by hunting and gathering. • Today, groups of people in scattered parts of the world still follow the hunter-gatherer way of life. • These people make relatively few demands on the environment. • However, most of them use some form of technology, such as guns, snowmobiles, or manufactured tools.

4. Agriculture • Humans slowly transitioned from hunting and gathering to the practice of farming or agriculture. • In addition to growing crops, people began raising livestock such as sheep, goats, cows, pigs, and horses. • Farming continued to develop and transition from horse and plows to machinery. • With the development of machinery, irrigation, fertilizers, and pesticides, farmers also transitioned to monoculture farming, in which large fields are planted with a single variety year after year.

5. The Green Revolution • By the middle of the 20th Century, despite agricultural advances, there were food shortages in many parts of the world. • Scientists and plant breeders developed highly productive “miracle strains” of crop seeds. • Chemical fertilizers and pesticides were used to increase productivity. • This effort came to be called the green revolution because it greatly increased the world’s food supply. • There are still challenges today for world agriculture: increasing human population, insects and pests, resistance in pests, enough water for irrigation, loss of farmland, etc.

6. Industrial Growth & Development • Human society and its impact on the biosphere were transformed by the Industrial Revolution, which added machines and factories to civilization during the 1800s. • Provided humans with modern homes, clothing, electronic devices, automobiles, large-scale agriculture, etc. • Today, both industries and suburban growth produce wastes, pollute air, water, and soil, consume farmland and natural habitats, and place additional stress on wildlife populations and on the biosphere’s life-support systems.

7. Industrial growth Urban development Hunting and gathering Agriculture Green revolution Extinctions of large animals Increased pollution High standard of living Monoculture use Food supply Pesticide use Human Activities that have changed the biosphere include may have once caused often relies on the methods of the have resulted in which increased

8. Section 6.2 – Renewable & Nonrenewable Resources • Environmental goods and services may be classified as either renewable or nonrenewable. • Renewable resources can regenerate if they are alive or can be replenished by biochemical cycles if they are nonliving. • However, a renewable resource is not necessarily unlimited. Ex: freshwater, wind, sunlight, trees • A nonrenewable resource is one that cannot be replenished by natural processes. Ex: fossil fuels

9. Sustainable Development • How can we provide for our needs while maintaining ecosystem goods and services that are renewable? • Sustainable development is a way of using natural resources without depleting them and of providing for human needs without causing long-term environmental harm. • Human activities can affect the quality and supply of renewable resources such as land, forests, fisheries, air, and fresh water.

10. Sustainable Agriculture Cover Crops Legumes, grasses, and other cover crops recycle soil nutrients, reduce fertilizer need, and prevent weed growth. Controlled Grazing By managing graze periods and herd densities, farmers can improve nutrient cycling, increase the effectiveness of precipitation, and increase the carrying capacity of pastures. Biological Pest Control The use of predators and parasites to control destructive insects minimizes pesticide use as well as crop damage A B C Yr. 1 Contour Plowing Contour plowing reduces soil erosion from land runoff. On hilly areas, plowing is done across the hill rather than straight up and down. Crop Rotation Different crops use and replenish different nutrients. By rotating crops, the loss of important plant nutrients is decreased. oats alfalfa corn Yr. 2 alfalfa (plowed in) corn alfalfa Yr. 3 oats alfalfa corn

11. Land Resources • Land is a resource that provides space for human communities and raw materials for industry. • Land also includes the soils in which crops are grown, and if managed properly, is a renewable resource. • Soil can be permanently damaged if not managed properly. • Plowing land removes the roots that hold soil in place, and increases the rate of soil erosion, which is the wearing away of surface soil by water and wind. • In parts of the world with dry climates, a combination of farming, overgrazing, and drought can turn once-productive areas into deserts in a process known as desertification.

12. Forest Resources • Earth’s forests are an important resource for the products they provide (wood, paper, etc.), in addition to providing habitats and food for organisms, and for being the “lungs of the Earth.” • Loss of forests, or deforestation, can lead to severe erosion, loss of habitats, and increase the amount of carbon dioxide in the air. • Methods in forest management are helping to maintain and preserve present forests, while helping to replenish cut forests. • Tree geneticists are also breeding new, faster-growing tree varieties that produce high quality wood to meet human demands.

13. Fishery Resources • Fishes and other aquatic animals are a valuable source of food for humans. • Overfishing, or harvesting fish faster than they can be replaced by reproduction is greatly reducing the world’s fish populations. • There are now regulations and guidelines that specify how many fish, and what size can be caught in various parts of the oceans. • Aquaculture, the raising of aquatic animals for human consumption is also helping to sustain fish resources.

14. Growth of Fish Catch World Fish Catch World Fish Catch per Person Amount of Fish per Person (kilograms) Total Catch (million tons) Year Year

15. Air Resources • The condition of the air we breathe affects people’s health. • The preservation of air quality remains a challenge for modern society. • Pollutants are harmful materials that can enter the biosphere through the land, air, or water. • A typical problem in big cities is the pollutant known as smog, which is a mixture of chemicals that occurs as a gray-brown haze in the atmosphere.

16. The burning of fossil fuels in automobiles and industrial factories releases nitrogen and sulfur compounds into the atmosphere where these compounds combine with water vapor and fall to the earth as acid rain. • Acid rain kills plants, damages soil quality, and harms aquatic animals and their eggs. It also has harmful effects on humans.

17. The Formation of Acid Rain Chemical Transformation Nitric acid Sulfuric acid Condensation Emissions to Atmosphere Nitrogen oxides Sulfur dioxide Dry Fallout Precipitation Acid rain, fog, snow, and mist particulates, gases Industry Transportation Ore smelting Power generation

18. Freshwater Resources • Americans use billions of liters of fresh water daily. • The amount of freshwater is limited. • Pollution threatens our water supplies. • One way of ensuring the sustainable use of water resources is to protect the natural systems involved in the water cycle. Ex: wetlands, rivers and lakes • Water conservation is also important.

19. Section 6.3 - Biodiversity • Biodiversity is the sum of all the different organisms in the biosphere. • Ecosystem diversity includes the variety of habitats, communities, and ecological processes in the living world. • Species diversity is the number of different species in the biosphere. (increases as you move toward equator) • Genetic diversity is the sum of all the different forms of genetic information carried by all organisms living on Earth today.

20. Species Diversity Insects 54.4% Protists Other Animals 4.2% 19.7% Plants 18% Bacteria Fungi 0.3% 3.4%

21. The Value of Biodiversity • Biodiversity is 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.

22. 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.

23. When the population of a species is likely to become endangered, it is said to be a threatened species. • A species is considered to be an endangered species when its numbers become so low that extinction is possible. • Extinction is the disappearance of a species when the last of its members dies. • Threatened  Endangered  Extinct • The endangered species actwas passed in 1973 to protect organisms on the threatened or endangered species lists. • Also, establishment of national and state parks.

24. Habitat Alteration • When land is developed, natural habitats may be destroyed. • Habitats supply organisms’ needs and they are a limited resource. • The animals who live in these habitats must learn new behaviors in order to survive in these new environments. • As habitats disappear, the species that live in those habitats also vanish. • Land development also splits ecosystems into pieces. This process is called habitat fragmentation. • The remaining smaller “islands” can support few species, and they are more vulnerable to disturbances.

25. Demand for Wildlife Products • Throughout human history, humans have pushed some animal species to extinction by hunting them for food or other products.

26. Pollution • Many forms of pollution can threaten biodiversity. • A famous example: DDT • DDT was a cheap and effective widely used pesticide. When it was sprayed on crops, it drained into rivers and streams at low, harmless concentrations. • However, DDT is nonbiodegradable, which means that it cannot be broken down by metabolic processes in living organisms. • Also, when consumed or picked up by organisms, they do not eliminate it from their bodies, so it accumulates.

27. When aquatic plants pick up DDT from the water, the pesticide is stored in their tissues. • When herbivores eat those plants, they too store DDT. • Because an herbivore eats many plants, the DDT becomes concentrated to levels 10x higher than levels found in the plants. • When carnivores eat herbivores, the toxic substance is concentrated further. • Biological magnification is a process in which concentration of harmful substances increase in organisms at higher trophic levels in a food chain or food web.

28. Biological Magnification of DDT Magnification of DDT Concentration Fish-Eating Birds 10,000,000 Large Fish 1,000,000 100,000 Small Fish 10,000 Zooplankton 1000 Producers Water 1

29. The wide-spread spraying of DDT over many years had threatened populations of many species, including fish-eating birds, like the osprey, brown pelican, and bald eagles. • One effect of DDT was to make eggs of these birds so fragile that the eggs could not survive intact. • By the early 1970’s, DDT was banned in the U.S. and most other countries. • In the years since, these birds have had a successful recovery and the bald eagle has actually been taken off of the endangered species list.

30. Introduced Species • Humans transport around the world, either accidentally or intentionally, seemingly harmless plants and animals. • Introduced into new habitats, these organisms often become invasive species that reproduce rapidly. • Invasive species increase their populations because their new habitat lacks the parasites and predators that control their population “back home.”

31. Zebra Mussels: An Invasive Species

32. Conserving Biodiversity • Most people would like to preserve Earth’s biodiversity for future generations. • In ecology, the term conservation is used to describe 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. Protecting an ecosystem will ensure that the natural habitats and the interactions of many different species are preserved at the same time. • Efforts include: zoos, captive breeding programs, national parks, forests, and other protected areas, marine sanctuaries, endangered species act, Earth Day, etc.

33. Section 6.4 – Charting a Course for the Future • For most of human history, environmental change was insignificant. • However, in the last 100 years, the human population has increased exponentially. • Today, much of the Earth’s land surface has been altered by human activity. • Researchers are gathering data to monitor and evaluate the effects of human activities on important systems in the biosphere: 1) The Ozone Layer 2) The Global Climate System

34. Ozone Depletion • Between 20-50 km above Earth’s surface the atmosphere contains an ozone layer. • The ozone layer acts as a protective shield or global sunscreen, which absorbs a good deal of harmful UV radiation from sunlight. • UV rays can damage living tissues, cause cancer, and decrease an organism’s resistance to disease.

35. During the 1970’s, scientists found evidence from satellite data that the ozone layer was in trouble. An ozone hole appeared over Antarctica. • Scientists showed that gases called chlorofluorocarbons (CFCs) were damaging the ozone layer. • CFCs were widely used in aerosol cans, coolants in refrigerators and air conditioners and the production of plastic foams. • Today CFCs are banned and current data predicts that the ozone holes should shrink and disappear within 50 years.

36. The Value of a Healthy Biosphere • Ecosystems provide many services to us, and are also a reservoir of organisms that might one day provide us with new medicines and foods. • Biologists are concerned that human activities might affect these ecosystems in unexpected or harmful ways. • What can we do to help??? • Conserve water • Plant trees • Reuse and recycle • Properly dispose of chemicals & hazardous waste • Remember, the biosphere is strong and humans are clever. Both humans and natural ecosystems can work together (coexist), and adapt to change.

37. Ecosystem Services Solar energy Production of oxygen Storage and recycling of nutrients Regulation of climate Purification of water and air Storage and distribution of fresh water Food production Nursery habits for wildlife Detoxification of human and industrial waste Natural pest and disease control Management of soil erosion and runoff