Humans in the Biosphere Honors Biology Chapter 6
The Tragedy of the Commons • Areas used by everyone are no one’s responsibility • Leads to misuse; loss of resources
Renewable Resources • Resources can regenerate (living) or • Resources that can be recycled through biogeochemical cycles • Examples • Trees • Water
Renewable resources are NOT necessarily UNLIMITED. • Freshwater is a renewable resource, BUT there are events that CAN make it very limited. For example: • Drought • Pollution
Nonrenewable Resources • Cannot be replenished by natural processes. • Examples: • Fossil fuels
Is a tree population renewable or nonrenewable? • Individual trees are renewable • A population of trees may not be, because the ecosystem they were in may change forever once the trees are gone.
Sustainable Development • Using resources without depleting them • Providing for human needs without causing long-term damage to the environment • Must take into account • Functioning of ecosystems • Human economic systems
Sustainable Development Strategy - Example • Using insects instead pesticides to control pests
Land Resources - Soil • Renewable or not? • Renewable if managed properly
Mismanagement of Soil Resources • Soil Erosion • Wearing away of surface soil by water and wind • Results when land is plowed, and roots that hold soil in place are removed
Mismanagement of Soil Resources • Desertification • Misuse of soil causes once productive areas to become deserts • Dry climate • Farming • Overgrazing • Drought
Forest Resources • Ways in which forest resources are used by people • Building • Burning
Forest Resources • Ways in which forests provide ecological services • Forests as “lungs of the Earth” • Absorb CO2 and release O2 • Store nutrients • Provide habitat and food for organisms • Moderate climate • Limit soil erosion • Protect freshwater supplies
Are Forests Renewable Resources? • Maybe – it depends on the forest • Our temperate deciduous forests seem to come back pretty well after cutting, though not always exactly as they were • Old Growth Forests are NOT renewable • Ancient trees and ecosystems • Will not be replaced by a similar ecosystem if cut • The plants and animals dependent on the anceint trees in the system would die • Even if allowed to come back, the ecosystem would never return to its present state.
Deforestation • Definition: The loss of forests • Deforestation can lead to • Severe soil erosion • Erosion can wash nutrients out of the soil • Grazing or plowing after deforestation can cause permanent changes in the soils that prevent regrowth of trees.
Fishery Resources • Overfishing • Harvesting fish at a rate greater than they can replace themselves by reproduction • 1950 – 1990 • Fish harvest dramatically increased • Fish populations dramatically declined • “Tragedy of the Commons” • Fishing of certain species banned • Some populations have seen recovery
Virginia Example • Menhaden • “breadbasket of the Bay” • favorite foods of striped bass, bluefish, sea trout, tuna and sharks • Menhaden Fishery • one of the most important and productive on the Atlantic coast • providing fish meal, fish oil and fish solubles and bait for other fisheries • More pounds of menhaden are landed each year than any other fish in the United States • Fishery is considered stable along Atlantic coast, BUT may be causing damage in the Bay • Menhaden play a key ecological role in the Bay as an important prey species for top predators such as striped bass, and for their ability to filter the water • the number of juvenile menhaden in the Bay population has been low • A proposal to cap the harvest in Chesapeake Bay is under discussion
Aquaculture • Raising aquatic animals for human consumptions • Good: provides food for people without drawing from natural populations • Disposal of wastes from the aquatic animals can be a source of pollution
Air Resources • Smog • Mixture of chemicals that results in a brown/gray haze in the atmosphere. • Mostly due to • Automobile exhaust • Industrial emissions
Pollutant • A harmful material that can enter the biosphere through the land, air or water. • Pollutants released from burning fossil fuels include: • Carbon dioxide • Nitrates and Sulfates • Particulates
What are particulates • Microscopic particles of ash and dust that can enter the nose mouth and lungs causing health problems
Nitrates and Sulfates • Combine with water vapor in the air • Create Acid Rain • Kills plants by damaging leaves • Change soil chemistry • Change chemistry of standing water ecosystems • Dissolves and releases toxic elements that may be bound up in soil • mercury
Freshwater Resources • People use freshwater for • Drinking • Washing • Watering crops • Industry • Recreation
Pollution Threatens Freshwater Supplies • Improperly discarded chemicals can enter streams and rivers • Wastes discarded on land can seep through soil into groundwater supplies • Sewage containing phosphorus and nitrogen encourages algae growth • Eutrophication • Leads to loss of oxygen when algae decay • Sewage can also spread disease • Though most cities due try to treat sewage before it enters water ways… • Still, animal waste runs off cow pastures, etc.
Protection of Wetlands and the sustainable use of water • Wetlands act to purify water that passes through them • Saving wetlands means cleaner water
Primary use of water in the U.S. • Agriculture • Uses ¾ of freshwater
The Value of Biodiversity - Terms • Biodiversity • Sum total of the genetically based variety of all organisms in the biosphere • Ecosystem diversity • the variety of habitats, communities and ecological processes in the living world • Species diversity • number of different species in the biosphere • Genetic diversity • sum total of all the different forms of genetic information carried by organisms living on Earth
Species Status • Threatened • A species that is likely to become endangered if it is not protected • Endangered • any species which is "in danger of extinction throughout all or a significant portion of its range." • Extinct • a species that no longer exists
Extinction Rate Today • Are we undergoing a mass extinction? • Yes. • Normal extinction rate between 10 and 100 species per year • Remember – this includes all life – bacteria, protists, plants, etc. • Current extinction rate may be as high as 27,000 species per year • What is the cause?
Why is biodiversity of practical value to humans? • Species of many kinds have provided us with foods, industrial products and medicines • Inherent value just of its own merit???
Threats to Biodiversity – Human Impacts • Altering habitats • Hunting species to extinction • Introducing toxins into the environment • Introducing foreign species into a new environment
Habitat Alteration • Natural habitats may be destroyed when land is developed • As habitats disappear, the species that live in them vanish • Habitat fragmentation • The splitting up of ecosystems as developments take up land area • Habitats become biological islands – isolated • The smaller the island, the smaller the number of species and population sizes – the more vulnerable they are.
Demand for Wildlife Products • Demand for animal species products has caused extinction by hunting • Carolina parakeet • Passenger pigeon
Pollution – Biological Magnification • Certain pollutants are NONbiodegradable • When producers take chemicals these into their bodies, they are stored in tissues rather than altered and excreted. • When consumers eat the producers, they consume more concentrated amounts of the chemical • This pattern repeats itself as you move up the food chain and the toxin gets more an more concentrated.
Biological Magnification • Definition: phenomenon in which the concentration of certain compounds in each organism in a food chain increases
DDT and Biological Magnification • Decade After WWII • Pesticide industry promoted the benefits of DDT before the consequences of its use were understood. • By the 1950s scientists learned that: • DDT persists in the environment • DDT is transported by water to areas far from where it is applied • By this time, DDT was already a global problem
DDT and Biological Magnification • Who was affected • Pelicans, ospreys, eagles • Top of the food chain • Affected calcium deposition in eggs – made them weak and easy to crush • Weight of parent while incubating eggs crushed eggs
Other pollutants and biological magnification • PCBs • Great Lakes • Endocrine system problems in lots of animals including humans • Concentration in Herring Gull eggs is 5,000 times greater than in phytoplankton at base of food web
Other Pollutants and Biological Magnification • Mercury • By-product of plastic production • Plastic production and coal power plants • Expelled into rivers/oceans • Bacteria at the bottom mud convert to a more harmful substance • Methyl mercury • Accumulates in tissues of organisms including humans
Introduced / Invasive Species • Species that are introduced into a new environment • May be no natural predators • Reproduce rapidly • Take over habitat • Crowd out native species • Reduce biodiversity in native ecosystems
Zebra mussels • Native to freshwater lakes of southeast Russia • Spread began in 1700s • First discovered in this country in Great Lakes in 1988 • Ballast water from ships probably responsible for introduction