People and the Earth's Ecosystems: Human Impacts and Population - PDF

People and the Earth’s Ecosystems Module 2 Human Impacts in the Environment Module Overview: This part of module introduces the major environmental problems that humans have created and considers ways to address these issues. Module Ou...

People and the Earth’s Ecosystems Module 2 Human Impacts in the Environment Module Overview: This part of module introduces the major environmental problems that humans have created and considers ways to address these issues. Module Outcomes: At the end of the lessons, students should be able to: Describe how humanity changes the environment; Describe land conversion for agriculture; and Examine the effects of mining and deforestation to the wildlife.  People and the Earth’s Ecosystems Lesson 1 Human Population Change the Environment Learning Outcomes: Define population ecology. Explain the four factors that produce changes in population size. Summarize the history of human population growth. Define demographics and describe the demographic transition. Explain how highly developed and developing countries differ in population characteristics such as infant mortality rate, total fertility rate, replacement- level fertility, and age structure. Define urbanization and describe trends in the distribution of people in rural and urban areas. Describe some of the problems associated with rapid growth rates in large urban areas. Describe sustainable development and its complexities associated with the concept of sustainable consumption.  People and the Earth’s Ecosystems Abstraction How Do Populations Change in Size? individuals of a given species are part of a larger organization called a population. Population ecology- Branch of biology that deals with the number of individuals of a particular species found in an area and why those numbers increase or decrease over time. (left) A population of blue columbines in Yankee Boy Basin, Colorado. Populations of other flowers are in the background; (right) A herd of impala survey their surroundings. Photographed in Tanzania. growth rate (r) The rate of change (increase or decrease) of a population’s size, expressed in percentage per year. birth rate (b) minus the death rate (d) r=b–d also referred to as natural increase in human populations Dispersal- movement from one region or country to another 2 types of dispersal: immigration (i)- individuals enter a population and increase its size emigration (e)- individuals leave a population and decrease its size 59 | P a g e  People and the Earth’s Ecosystems growth rate (r) of a local population must take into account birth rate (b), death rate (d), immigration (i), and emigration (e) r = (b – d) + (i – e) Maximum Population Growth biotic potential- The maximum rate at which a population could increase under ideal conditions. Factors that influence the biotic potential of a species: the age at which reproduction begins the fraction of the life span during which an individual can reproduce the number of reproductive periods per lifetime the number of ofspring produced during each period of reproduction. life history characteristics determine whether a particular species has a large or a small biotic potential. Generally, larger organisms, such as blue whales and elephants, have the smallest biotic potentials, whereas micro organisms have the greatest biotic potentials Factors that interact to change population size Exponential population growth The accelerating population growth that occurs when optimal conditions allow a constant reproductive rate. Environmental Resistance and Carrying Capacity organisms don’t reproduce indefinitely at their biotic potential because the environment sets limits, which are collectively called environmental resistance. Examples: limited food, water, shelter, and other essential resources, as well as increased disease and predation The environment controls population size: As the population increases, so does environmental resistance, which limits population growth. carrying capacity ( K )- The largest population a particular environment can support sustainably (long term), if there are no changes in that environment. population rarely stabilizes at K (carrying capacity) but its size may temporarily rise higher than K. It will then drop back to, or below, the 60 | P a g e  People and the Earth’s Ecosystems carrying capacity. Sometimes a population that overshoots K will experience a population crash, an abrupt decline from high to low population density when resources are exhausted. When a population influenced by environmental resistance is graphed over a long period, the curve has an S shape (see next figure) The curve shows the population’s initial exponential increase (note the curve’s J shape at the start, when environmental resistance is low). Then the population size levels out as it approaches the carrying capacity of the environment Human Population Patterns Thomas Malthus (1766–1834) a British economist One of the first people to recognize that the human population can’t increase indefinitely was pointed out that human population growth is not always Noted that human population can increase faster than its food supply, he warned that the inevitable consequences of population growth would be famine, disease, and war. Projecting Future Population Numbers zero population growth- The state in which the population remains the same size because the birth rate equals the death rate. estimates vary depending on fertility changes Small differences in fertility, then, produce large differences in population forecasts Demographics of Countries Demographics- The applied branch of sociology that deals with population statistics. infant mortality rate- The number of deaths of infants under age 1 per 1000 live births. Per person GNI PPP- a country’s gross national income (GNI) in purchasing power parity (PPP) divided by its population. It indicates the amount of goods and services an average citizen of that particular country could buy in the United States 61 | P a g e  People and the Earth’s Ecosystems Highly developed moderately developed Less developed countries countries countries have the lowest -have birth rates and have the shortest life birth rates in the infant mortality rates expectancies, the world, low infant higher than those of lowest average per mortality rates and highly developed person GNI PPPs, the have longer life countries, but they are highest birth rates, and expectancies declining the highest infant -medium level of mortality rates industrialization, and their average per person GNI PPPs are lower vs highly developed countries replacement-level fertility- The number of children a couple must produce to “replace” themselves. total fertility rate (TFR)- The average number of children born to each woman. The Demographic Transition- process whereby a country moves from relatively high birth and death rates to relatively low birth and deathrates. Age Structure of Countries Age Structure- The number and proportion of people at each age in a population age structure diagram- presents the number of males and the number of females at each age, from birth to death The age structure diagram of a country with a high growth rate, based on a high fertility rate (Ethiopia or Guatemala)—is shaped like a pyramid 62 | P a g e  People and the Earth’s Ecosystems Declining fertility rates have profound social and economic implications because as fertility rates drop, the percentage of the population that is elderly increases. Population and Urbanization Urbanization- A process whereby people move from rural areas to densely populated cities. The city as a dynamic ecosystem Environmental Problems of Urban Areas Suburban sprawl that encroaches into former forest, wetland, desert, or agricultural land destroys or fragments wildlife habitat. brownfields—areas of abandoned, vacant factories, warehouses, and residential sites that may be contaminated from past uses Air pollution: airborne emissions, including particulate matter (dust), sulfur oxides, carbon oxides, nitrogen oxides, and volatile organic compounds (from automobiles) water flow is affected because they cover the rainfall absorbing soil with buildings and paved roads Contaminated runoff Environmental Benefits of Urbanization well-planned city actually benefits the environment by reducing pollution and preserving rural areas. Compact development- Design of cities in which tall, multiple-unit residential buildings are close to shopping and jobs, and all are connected by public transportation. Urbanization is a worldwide phenomenon. more than 50% of the world population lives in urban areas with populations of 2000 or greater 63 | P a g e  People and the Earth’s Ecosystems Challenges faced by developing countries substandard housing (slums and squatter settlements); poverty; exceptionally high unemployment; heavy pollution; and inadequate or non-existent water, sewage, and waste disposal (left figure). Rapid urban growth also strains school, medical, and transportation systems. Application What is happening in this picture? The photo shows people—mainly displaced/marginalized rural workers—picking through trash at the Smoky Mountain in Payatas landfill in the Manila. They are looking mainly for scraps of plastics and metals that they can sell. What valuable environmental service does such scavenging provide? Do you think this is the result of urbanization and environmental conversion? 64 | P a g e  People and the Earth’s Ecosystems Lesson 2 People and Agriculture Learning Outcomes: Differentiate between undernutrition and overnutrition. Define food insecurity and relate it to human population, poverty, and world hunger. Contrast industrialized agriculture with subsistence agriculture. Describe three kinds of subsistence agriculture. Relate the benefits and problems associated with the green revolution. Describe the environmental impacts of industrialized agriculture, including land degradation and habitat fragmentation.  People and the Earth’s Ecosystems Abstraction World Food Problems  average adult human must consume enough food to get approximately 2600 calories, per day  Undernutrition- a type of malnutrition in which there is an underconsumption of calories or nutrients that leaves the body weakened and susceptible to disease  Overnutrition- a type of malnutrition in which there is an overconsumption of calories that leaves the body susceptible to disease. Millions of children suffer from kwashiorkor, caused by severe protein deficiency. Note the characteristic swollen belly, which results from fluid retention.Photographed in Haiti. Marasmus is progressive emaciation caused by a diet low in both total calories and protein. Symptoms include a pronounced slowing of growth and extreme wasting of muscles. Photographed in Somalia. Globally, millions of adult men and women are hungry. This homeless man is suffering from severe malnutrition and starvation. Photographed in New Delhi, India. Population and World Hunger  food insecurity- The condition in which people live with chronic hunger and malnutrition.  Factors that contribute to food shortage: civil wars and military actions, HIV/AIDS (which has killed or incapacitated much of the agricultural 67 | P a g e  People and the Earth’s Ecosystems  Most farmers in developing countries practice subsistence agriculture  Shifting cultivation - a form of subsistence agriculture in which short periods of cultivation are followed by longer periods of fallow (land being left uncultivated), during which the land reverts to forest. Shifting cultivation supports relatively small populations.  Slash-and-burn agriculture - a type of shifting cultivation that involves clearing small patches of tropical forest to plant crops. Farmers must move from one area of forest to another every 3 years or so.  Nomadic herding, in which livestock is supported by land too arid for successful crop growth, is a similarly land-intensive form of subsistence agriculture. Nomadic herders must continually move their livestock to find adequate food for the animals.  Intercropping- a form of intensive subsistence agriculture that involves growing a variety of plants on the same fi eld simultaneously. When certain crops are grown together, they produce higher yields than when they are grown as monocultures.  Monoculture- is the cultivation of only one type of plant over a large area  Polyculture - a type of intercropping in which several kinds of plants that mature at different times are planted together. Challenges of Agriculture  prime farmland- land that has the soil type, growing conditions, and available water to produce food, forage, fiber, and oilseed crops.  Challenges: decline in prime farmland, coping with declining numbers of domesticated varieties, improving crop and livestock yields, and addressing environmental impacts. Loss of Agricultural Land  prime agricultural land is falling victim to urbanization and suburban sprawl by being converted to parking lots, housing developments, and shopping malls Global Decline in Domesticated Plant and Animal Varieties  A global trend is currently under way to replace the many local varieties of a particular crop or domesticated farm animal with just a few kinds  farmers abandon traditional varieties in favor of more modern ones, which are bred for uniformity and maximum production; great loss in genetic diversity  germplasm Any plant or animal material that may be used in breeding. Increasing Crop Yields  Advances by research scientists since then have dramatically increased food production in highly developed countries  Greater knowledge of plant nutrition has resulted in production of fertilizers that promote high yields.  The use of pesticides to control insects, weeds, and disease-causing organisms has also improved crop yields. 69 | P a g e  People and the Earth’s Ecosystems The Green Revolution  By the middle of the 20th century, serious food shortages occurred in many developing countries coping with growing populations.  The development and introduction during the 1960s of high-yield varieties of wheat and rice to Asian and Latin American countries gave these nations the chance to provide their people with adequate supplies of food  But the high-yield varieties required intensive industrial cultivation methods, including the use of commercial inorganic fertilizers, pesticides, and mechanized machinery, to realize their potential. These agricultural technologies were passed from highly developed nations to developing nations.  (1965) Mexico’s annual wheat production rose to more than 2400 kg (2.65 tons) per hectare.  Indonesia, formerly imported more rice than any other country in the world. Today Indonesia produces enough rice to feed its people and export some. Critics of Green Revolution  green revolution has made developing countries dependent on imported technologies, such as agrochemicals and tractors, at the expense of traditional agriculture.  associated with higher crop production are the high energy costs built into this type of agriculture  environmental problems caused by the intensive use of fertilizers and pesticides.  (1999) International Food Policy Research Institute projected that the world demand for rice, wheat, and corn will increase 40% between 2000 and 2020.  concerted scientific effort to improve crops: genetic engineering  Modern agricultural methods, such as water-effi cient irrigation Increasing Livestock Yields  use of hormones and antibiotics, although controversial, increases animal production. Hormones, usually administered by ear implants, regulate livestock bodily functions and promote faster growth.  low doses of antibiotics to feed for pigs, chickens, and cattle. These animals gain 4 to 5 percent more weight than untreated animals (still continued in United States and many other countries) Environmental Impacts:  Air pollution  Water pollution  pesticide runoff  degradation (of land)- Natural or human-induced reduction in the potential ability of the land to support crops or livestock.  Habitat fragmentation- The breakup of large areas of habitat into small, isolated patches. 70 | P a g e  People and the Earth’s Ecosystems Solutions to Agricultural Problems  Sustainable agriculture- Agricultural methods that maintain soil productivity and a healthy ecological balance while having minimal long-term impacts.  An important goal of sustainable agriculture is to preserve the quality of agricultural soil  Crop rotation, conservation tillage, and contour plowing help control erosion and maintain soil fertility  organic agriculture—use no pesticides  integrated pest management (IPM)- incorporates the limited use of pesticides with pest-controlling biological and cultivation practices  second green revolution -trend away from using intensive techniques that produce high yields and toward methods that focus on long-term sustainability of the soil. Genetic Engineering: A Solution or a Problem?  Genetic engineering- The manipulation of genes (for example, taking a specific gene from one species and placing it into an unrelated species) to produce a particular trait.  has the potential to produce more nutritious food plants that contain all the essential amino acids  has been used to develop more productive farm animals, including rapidly growing hogs and fishes.  greatest potential contribution: the production of vaccines against disease organisms that harm agricultural animals Concerns About Genetically Modified Foods  inserted genes could spread from GM crops to weeds or wild relatives of crop plants and possibly harm natural ecosystems in the process  some consumers might develop food allergies to GM foods 71 | P a g e  People and the Earth’s Ecosystems Lesson 3 Mining and Environment Learning Outcomes: Relate the environmental impacts of mining and refining minerals. Include a brief description of acid mine drainage. Explain how mining lands can be restored. Abstraction Environmental Implication of Mineral Use Effects of mining disturbs large areas of land destroys existing vegetation mined land is particularly prone to erosion wind erosion causing air pollution water erosion polluting nearby waterways and damaging aquatic habitats depletion of the groundwater 74 | P a g e  People and the Earth’s Ecosystems acid mine drainage Pollution caused when sulphuric acid and dangerous dissolved materials such as lead, arsenic, and cadmium wash from mines into nearby lakes and streams. Tailings -usually left in giant piles on the ground or in ponds near the processing plants -contain toxic materials such as cyanide, mercury, and sulfuric acid. -contaminate the air, soil, and water. Smelting plants may emit large quantities of air pollutants, particularly sulfur, during mineral processing. Contaminants in ores include the heavy metals lead, cadmium, arsenic, and zinc. toxic elements may pollute the atmosphere during the smelting process and cause harm to humans. Smelters emit airborne pollutants as well as hazardous liquid and solid wastes that can pollute the soil and water. Depletion of non-renewable energy reserves and production of carbon dioxide and other air pollutants Restoration of Mining Lands When a mine is no longer profitable to operate, the land can be reclaimed, or restored to a seminatural condition (e.g Copper Basin in Tennessee) Reclamation prevents further degradation and erosion of the land, eliminates or neutralizes local sources of toxic pollutants, and makes the land productive for purposes other than mining Restoration also makes such areas visually attractive 75 | P a g e