6-1A Changing Landscape -the activities of humans can affect the biosphere Ex. - can wipe out native species through the introduction of non-native species (predators) - settlers to an area can introduce disease A.Earth as an Island -all organisms on earth, including humans. share limited resources -with increases in human population, there is increasing demands on the earths resources B.Human Activities that have affected the biosphere -humans are the most important source of environmental change on the planet activities include: 1.hunting and gathering - historically, the primary means of survival - many people were nomadic and lived and traveled in small groups Ways they changed the earth: - built dams (diverted water) - burned grasslands (for the growth of certain plants) - caused the extinction of many animals (wooly mammoth, saber tooth tiger) -today, small groups in parts of the world supplement their diet through subsistence hunting Ex. tribes in New Guinea; make few demands on the environment when taking meat of wild animals -may use newer forms of technology for hunting; guns, snowmobiles (Alaskan tribes), or manufactured tools 2.Agriculture - began 11,000 years ago at the end of the ice age - spread of agriculture supplied people with a dependable supply of food - this lead to larger settlements (towns and cities) and the development of government, laws, and writing a. domestication of animals - farmers began to keep herds of domesticated animals (sheep, goats, cows, pigs, dogs, etc.) - the animals provided the humans with hides, meat, milk, wool, and companionship - the animals also did work - a disadvantage was the overgrazing by herbivores which changed grassland ecosystems, eroded soils, and placed demands on water supplies b.from traditional to modern agriculture :-world exploration -exchange of foods (influenced farming all over the world) 1800:-technological advances in irrigation -new crop varieties -invention of farm machines (increased crop yields) c.The Green Revolution s fast growing populations strained worlds food supply - new farming practices were introduced which increased yields of many crops including rice and wheat (global food production has more than doubled in the past 50 years) Ex. new plant varieties called miracle strains were developed which improved harvests Monoculture method was used whereby one large field was planted with one crop year after year These methods also created problems: -depleted energy and water supplies -pest species can reproduce on a large scale in monocultures; farmers must use pesticides -fertilizer use interferes with food webs and biogeochemical cycles C.Industrial Growth and Urban Development -Industrial Revolution (1800s) led to industrial productivity and scientific knowledge that gave us the conveniences of modern life -Cities and industries grew rapidly and cheaply (led to pollution from discarded wastes) -Cities became crowded growth of suburbs across the American landscape (suburban sprawl) and a higher standard of living 6-2Renewable and Nonrenewable Resources A.The Tragedy of the Commons -the notion that any resource that was open to everyone (air, oceans) will eventually be destroyed because everyone can use the resource but no one is responsible for preserving it (tragedy) Environmental Resources can be classified into two types: 1.Renewable -can regenerate and are replaceable -not unlimited; drought or overuse may limit water Ex. trees 2.Nonrenewable -one that cannot be replaced by natural processes Ex. coal, oil, and natural gas (fossil fuels) B.Sustainable Use -a way of using natural resources in a way that does not deplete them -a system that operates without harm to the ecological resources on which it depends EX. We can manage unwanted species by understanding their interactions with other organisms; the ladybug is used as a biological pest control instead of pesticides C.Land Resources -provides space for cities and suburbs -provides raw materials for industry -important for soil in which crops grow; misuse can lead to soil erosion and desertification -soil erosion and desertification can be prevented by contour plowing and by leaving stems and roots of previous years crop in place and by planting rye rather than leaving the soil unprotected Desertification D.Forest Resources -important for wood products, fuel, cooking and heating -removes CO2 and produces O2 -stores nutrients, provides habitats and food for organisms -moderates climate -controls soil erosion Effects of deforestation -severe erosion -permanent changes (chemical) to local soils and microclimate preventing re-growth of trees Forest management strategies -harvest of mature trees to promote the growth of younger ones -breeding of new and faster growing trees that produce high quality wood E.Ocean Resources -fishing industry has increased to the point where fish stocks in fisheries are harvested before they have time to reproduce (overfishing) -has affected cod, anchovies, halibut, Atlantic herring, salmon, Alaskan king crab Fish management strategies -limit catch of fish population affected by overfishing -close some fishing regions temporarily to give them time to recover -aquaculture (farming of aquatic organisms) to obtain animal protein; must be managed properly to avoid pollution from fish wastes F.Air Resources Pollutant a harmful chemical that enters the biosphere through land, air, or water Smog a pollutant that is the result of automobile exhaust and industrial emissions Burning of fossil fuels releases acidic gasses containing nitrogen and sulfur into the atmosphere combine with water vapor form droplets of nitric and sulfuric acid drift and then fall to the earth as rain (acid rain) Acid rain kills plants, changes soil chemistry and standing water ecosystem chemistry, may dissolve and release toxic elements (mercury) from soil which can then enter the biosphere. G.Water Resources -water supplies must be protected from pollution and an ever-growing demand from society Ways pollutants threaten water supplies -improperly discarded chemicals can enter streams and rivers -land wastes can seep into soil and enter underground water supplies that we tap with wells -domestic sewage can encourage growth of algae and bacteria in aquatic habitats -microorganisms in sewage can spread disease ***most sewage is treated to make it environmentally safe Water management strategies -protect the natural systems involved in the water cycle -water conservation in homes, industry, and agriculture 6-3Biodiversity -the sum total of the genetically based variety of all organisms in the biosphere -one of the earths greatest natural resources Ecosystem diversity -the variety of habitats, communities, and ecological processes in the living world Species diversity -the number of different species in the biosphere Genetic diversity - the sum total of all the different forms of genetic information carried by all organisms living today ****Important to keep biodiversity intact; loss results in loss of valuable resources to the biosphere and humankind B.Threats to Biodiversity -human activity alters habitats reducing biodiversity Ex. hunting species to extinction Introducing toxic compounds into food webs bringing foreign species to new environments - the above alters ecosystems and may contribute to endangered species (at risk of extinction) or extinction itself - genetic diversity decreases as populations become endangered making them more vulnerable to extinction C.Habitat Alteration and Fragmentation habitat fragmentation -occurs when habitats are destroyed and their species disappear and when land development splits ecosystems into pieces D.Demand for Wildlife Products -historically, has pushed some animal species towards extinction Ex. Carolina parakeet feathers Other species fur, meat, hides, medicinal properties (horns and gallbladders) -laws have been enacted to ban international trade on products from endangered species E.Pollution DDT -a pesticide that builds up in tissues of organisms -non-biodegradable ( it is not broken down by metabolic processes) -results in biological magnification as DDT concentration increases in organism at higher trophic levels in a food chain or web -biological magnification affects the whole food web, but those at the top are at greatest risk (especially fish-eating birds) Biological Magnification Effects of DDT (dichlorodiphenyltrichloroethane) -eggs of fish-eating birds become fragile and do not survive intact -1970s; DDT usage was banned in the US F.Introduced Species -invasive species; harmless plants and animals inadvertently introduced into new habitats that reproduce rapidly -the new habitats lack predators or parasites to control their growth Ex. Zebra mussels - an aquatic pest introduced in the 1980s that spread through the Great Lakes and some major rivers Zebra Muscles G.Conserving Biodiversity 1.Conservation -the wise management of natural resources Strategies for Conservation a.managing individual species to keep them from becoming extinct Ex. zoos; breeding programs b.protecting ecosystems by preserving habitats, wildlife, and biodiversity Ex. parks, reserves, marine sanctuaries Challenges in Conservation a. protecting biodiversity in countries that are unable to do so Ex. tropical rainforest destruction - located in developing countries where seeing to the needs of the human population outweighs conservation goals b. setting up a hot-spot strategy to locate problem areas and list priorities 6-4Charting a Course For the Future Two types of global change are of concern: 1.Ozone depletion Ozone layer a concentration of ozone gas km above the earths surface -absorbs harmful UV radiation from sunlight before it reaches earth (global sunscreen) -1970s; evidence of ozone thinning over Antarctica which has been growing larger -by 1995, there was evidence of a hole over the Arctic which had expanded to cover some parts of the US -ozone depletion is caused by chlorofluorocarbons (CFCs); a propellant in aerosol cans; acts as a catalyst that allows UV light to break apart ozone molecules in the colder atmospheres (polar zones) -CFC use is being phased out in US and other countries 2.Global Warming -increase in average temperature of the biosphere -global temperatures have increased 0.5 degrees Celsius in the past 120 years -temperatures between 1980 and 2000 rose faster than in the last 100 years -has affected the polar ice caps (melting); could be totally melted within the next 50 years -the hypothesis is that human activity has caused global warming by adding CO2 and other greenhouse gasses to the atmosphere causing it to retain more heat -other scientists believe it is part of natural variations in climate Possible Effects of Global Warming a.Rising sea levels leading to flooding of low-lying coastal areas b.More frequent and more severe weather disturbances c.Climate and weather changes will affect ecosystems and geographic distribution of species d.Certain species will be favored; insects, rodents, weeds e.Warmer temperatures will increase geographic distribution of disease-carrying species (mosquitoes) Effects of Global Warming D.The Value of a Healthy Biosphere 1.Provides us with raw materials for foods, medicines, and other products 2.Temperature control, water purification, soil formation etc. (See Fig 6-22, pg. 160)