HUMAN IMPACT ON ECOSYSTEMS HUMAN POPULATION GROWTH AND

HUMAN IMPACT ON ECOSYSTEMS

HUMAN POPULATION GROWTH AND NATURAL RESOURCES • Earth’s human population continues to grow • Earth’s carrying capacity • Technology and human population

GROWTH OF THE HUMAN POPULATION • Humans first reached North America at least 12, 000 years ago, crossing the land bridge between Siberia and Alaska • Humans spread throughout North American and South America • About 2, 000 years ago 130 million people on Earth • 1650 500 million

GROWTH OF THE HUMAN POPULATION • Since then, average global birthrate has remained near 30 births per 1000 people/year • The death rate has fallen steadily with improvement in medical care and sanitation • 2002 death rate 9 deaths per 1000 people/year • The world’s population continues to grow!

GROWTH OF THE HUMAN POPULATION • World’s population exceeded 6 billion in October 1999 • About 260, 000 people are added to the world population every day, or 180 people/minute • The global rate of population growth has been declining • Projected to stabilize by 2050 at 9. 7 billion

THE GROWING HUMAN POPULATION EXERTS PRESSURES ON EARTH’S NATURAL RESOURCES • Nonrenewable resource: natural resource that is used more quickly than it can be formed • Renewable resource: resource that replenishes itself quickly enough so that it will not be used faster than it can be produced

EFFECTIVE MANAGEMENT OF EARTH’S RESOURCES WILL MEET THE NEEDS OF THE FUTURE • Ecological footprint: amount of land necessary to produce and maintain enough food, water, shelter, energy, and waste

AIR QUALITY • Pollution: anything that is added to the environment and has a negative affect on the environment or its organisms • Smog: air pollution in which gases released from burning fossil fuels form a fog when they react with sunlight • Particulate: microscopic bits of dust, metal, and unburned fuel produced by industrial processes

ACID RAIN • Precipitation – p. H below normal – Unusually high concentration of sulfuric or nitric acids • Often a result of chemical pollution of the air: – Automobile exhausts – Burning of fossil fuels

WHAT IS THE IMPACT OF ACID RAIN? • Rainwater and some soils are naturally acidic • The acidity added by human activity is having a dramatic effect • USA and Canada thousands of lakes are “dying” as their p. H levels fall far below 5. 0 • Forests in the eastern USA and southern Canada are being damaged • The symbiotic fungi in tree roots cannot survive

THE OZONE LAYER • O 3, a protective shield in the upper atmosphere • 1985 disintegration of the ozone layer was evident from satellite imagery back to 1978 • The ozone hole continued to grow larger • Allowed for more UV radiation to reach the Earth’s surface • Increase chances of skin cancer, cataracts, etc.

WHAT IS DESTROYING OZONE? • Chlorofluorocarbons (CFCs): • Hydrocarbons in which some or all of the hydrogen atoms are replaced by chlorine and fluorine • Invented in the 1920 s, used in coolants for refrigerators and air conditioners and in cleaning solvents • Use is restricted because they destroy the ozone • High in the atmosphere, UV radiation from the sun is able to break the stable bonds of CFCs • The free chlorine atoms enter a series of reactions that destroy ozone

AIR POLLUTION IS CHANGING EARTH’S BIOSPHERE

GREENHOUSE EFFECT • The warming of the surface of Earth and the lower atmosphere • A result of carbon dioxide and water vapor; which absorb and reradiate infrared radiation

GLOBAL WARMING • The average global temperature has been steadily increasing for more than a century, particularly since the 1950 s • Global warming is often followed by centuries of cold • Sunspot cycles may contribute to these cyclical changes in global temperature • Human activity is significantly contributing to global warming in modern times

WATER QUALITY • Water pollution affects ecosystems • Indicator species: species whose presence in an ecosystem gives clues about the conditions of that ecosystem

BIOLOGICAL MAGNIFICATION • The accumulation of increasingly large amounts of toxic substances within each successive link of the food chain • Examples: DDT, pesticides

THREATS TO BIODIVERSITY • Preserving biodiversity is important to the future of the biosphere • Loss of habitat eliminates species – Habitat fragmentation: process by which part of an organism’s preferred habitat range becomes inaccessible • Introduced species can disrupt stable relationships in an ecosystem – Introduced species: species that is not native and was brought to an area as a result of human activities

THREATS TO BIODIVERSITY • Effects on native species • Economic damage

LOSS OF RESOURCES • Nonrenewable resources are being consumed or destroyed at alarming rates – Extinction of species – Loss of topsoil – Ground-water pollution and depletion

EXTINCTION OF SPECIES • ½ the world’s tropical rainforests have been burned to make pasture or farmland in the last 50 years • No one knows how many species are being lost • As a species disappear, so do our chances to learn about them and to learn about their possible benefits

LOSS OF TOPSOIL • The USA is one of the most productive agricultural countries on Earth, largely because of its fertile soils • The topsoil cannot be replaced and it is being lost at a rate of several cm/decade • Since 1950 the world has lost 1/3 of its topsoil, primarily because of human activity

GROUND-WATER POLLUTION & DEPLETION • Aquifer: A porous rock that stores and allows the flow of ground-water • Water seeps into aquifers too slowly to replace the large amount of water being withdrawn • There is not much effort to conserve ground water • Large amounts are wasted on watering lawns, washing cars, leaky and inefficient faucets and toilets

GROUND-WATER POLLUTION & DEPLETION • A great deal of ground water is being polluted by irresponsible disposal of chemical wastes • Once pollution enters the ground water, there is no effective way to remove it

CONSERVATION • Sustainable development manages resources for present and future generations – Rotation – Fishing gear review – Harvest reduction – Fishing bans

CONSERVATION PRACTICES FOCUS ON A FEW SPECIES BUT BENEFIT ENTIRE ECOSYSTEMS • Umbrella species: species whose being protected under the Endangered Species Act leads to the preservation of its habitat and all the other organisms in its community

PROTECTING EARTH’S RESOURCES HELPS PROTECT OUR FUTURE • Protecting natural resources • A sustainable Earth • A worldwide effort is needed! • Early 1990 s international agreement to stop CFC production • The release of many dangerous industrial and agricultural chemicals has been restricted in the USA • Efforts to reduce pollution: Clean Air Act of 1990

WHAT CAN YOU DO? • Conserve energy by walking, riding a bike, or taking public transportation • Do a resource-and energy-use inventory of your home • Learn about the environment • Recycle newspapers, aluminum products, glass and plastic • Create rich soil by making your own compost heap from leaves, grass and fruit peelings