PoISONING PLANET EARTH PoLLUTION AND OTHER ENVIRONMENTAL HAZARDS A farmer in Vaudreuil Haiti works in a cornfield on June 30 2009 Thony Belizaire AFP Getty Images are therefore usually said to be more stable than simple ecosystems A field of corn has only one dominant species the corn plant and is a very simple ecosystem It is easily destroyed by drought insects disease or overuse A forest may remain relatively unchanged by weather that would destroy a nearby field of corn because I2
PoLLUTION A GLOBAL CRISIS OL These passenger pigeons were painted by the famous American natu ralist and bird expert John James Audubon 1985 1851 before they became extinct Buyenlarge Archive Photos Getty Images 13
PoisoNING PLANET EARTH PoLLUTION AND OTHER ENVIRONMENTAL HAZARDS the forest is characterized by greater diver sity of plants and animals Its complexity gives it stability Every environmental system has a car rying capacity for an optimum or most desirable population of any particular spe cies within it Sudden changes in the relative population of a particular species can begin a kind of chain reaction among other elements of the ecosystem For example eliminating a species of insect by using massive quantities of a chemical pesticide also may eliminate a bird species that depends upon the insect as a source of food Such human activities have caused the extinction of a number of plant and animal species For example overhunting caused the extinction of the passenger pigeon The last known survivor of the species died at the Cincinnati Zoo in 1914 Less than a century earlier the passenger pigeon popu lation had totaled at least 3 billion Excessive hunting or infringement upon natural habi tats is endangering many other species The great whales the California condor and the black footed ferret are among the endan gered animals Endangered plants include snakeroot the western lily and the green pitcher plant 14
PoLLUTION A GLOBAL CRISIS PoPULATION GROWTH AND ENVIRONMENTAL ABUSE The reduction of the Earth's resources has been closely linked to the rise in human population For many thousands of years people lived in relative harmony with their surroundings Population sizes were small and life supporting tools were simple Most of the energy needed for work was provided by the worker and animals Since about 1650 however the human population has increased dramatically The problems of overcrowding multiply as an ever increasing number of people are added to the world's population each year The rate of growth of the world s popula tion has finally begun to slow to slightly more than 1 percent after reaching an all time high of more than 2 percent in the early 1960s In 2007 there were more than 6 6 billion people on the planet The United Nations predicts that by the year 2050 almost 9 2 bil lion people will be living on Earth almost four times the number of people living on Earth in 1950 The booming human population is con centrated more and more in large urban areas Many cities now have millions of inhabitants 15
