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Module 2: Human Impacts in the Environment

• This module introduces significant environmental problems caused by humans and explores potential solutions.
• Students will be able to describe how humanity changes the environment, describe land conversion for agriculture, and examine the effects of mining and deforestation on the wildlife.

Lesson 1: Human Population Change the Environment

• Students will be able to 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.
• Students will be able to 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.
• Students will be able to 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, and describe sustainable development and its complexities associated with the concept of sustainable consumption.

How Populations Change in Size

• Individuals of a species are part of a larger organization called a population.
• Population ecology is a branch of biology studying the number of individuals of a particular species in an area.
• Growth rate (r) is the rate of change (increase or decrease) of a population's size, expressed in percentage per year.
• Growth rate calculation: birth rate (b) minus the death rate (d), where r = b – d; often referred to as natural increase when discussing human populations
• Dispersal is the movement from one region or country to another.
• Immigration (i) refers to individuals entering a population, increasing its size.
• Emigration (e) refers to individuals leaving a population, decreasing its size.
• It is important to note that the Growth Rate (r) of a local population takes into account birth rate (b), death rate (d), immigration (i), and emigration (e) where r = (b − d) + (i – e)

Maximum Population Growth

• Biotic potential is the maximum rate at which a population could increase under ideal conditions.
• Factors that influence the biotic potential of a species include 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, and the number of offspring produced during each period of reproduction.
• Life history characteristics determine whether a particular species has a large or small biotic potential.
• Larger organisms generally have the smallest biotic potentials, whereas microorganisms have the greatest biotic potentials

Exponential Population Growth

• Accelerating population growth occurs when optimal conditions allow a constant reproductive rate.

Environmental Resistance and Carrying Capacity

• Organisms do not reproduce indefinitely at their biotic potential due to environmental limits, collectively called environmental resistance (e.g., limited food, water, shelter, increased disease and predation).
• As the population increases, so does environmental resistance, limiting population growth.
• Carrying capacity (K) is the largest population a particular environment can support sustainably, long term, if there are no changes in that environment.
• Population size may temporarily rise higher than K, then drop back to, or below, the carrying capacity.
• Populations that overshoot K can experience a population crash, which is an abrupt decline from high to low population density when resources are exhausted.
• Populations influenced by environmental resistance graphed over time form an S-shaped curve
• The curve shows the population's initial exponential increase (J shape at the start, when environmental resistance is low) the population size levels out as it approaches the carrying capacity of the environment

Thomas Malthus

• Thomas Malthus (1766–1834) was a British economist who recognized that human population couldn't increase indefinitely and pointed out that human population growth is not always beneficial.
• He noted that human population can increase faster than its food supply, and warned of famine, disease, and war as inevitable consequences of unsustainable population growth..

Projecting Future Population Numbers

• Zero population growth is the state in which the population remains the same size because the birth rate equals the death rate.
• Estimates vary depending on fertility changes and small differences in fertility produce large differences in population forecasts.

Demographics of Countries

• Demographics is the applied branch of sociology that deals with population statistics.
• Infant mortality rate represents the number of deaths of infants under age 1 per 1000 live births.
• Per-person GNI PPP indicates the amount of goods and services an average citizen of a particular country could buy in the United States.
• Replacement-level fertility is the number of children a couple must produce to "replace" themselves.
• Total fertility rate (TFR) is the average number of children born to each woman.
• The Demographic Transition is a process whereby a country moves from relatively high birth and death rates to relatively low birth and death rates.
• Age Structure is the number and proportion of people at each age in a population.
• An age-structure diagram shows the number of males and the number of females at each age, from birth to death.

Highly Developed Countries

• These countries have the lowest birth rates in the world, low infant mortality rates, and longer life expectancies.

Moderately Developed Countries

• They have birth and infant mortality rates higher than highly developed countries but are declining and posses a medium level of industrialization, with average per-person GNI PPPs lower than highly developed countries

Less Developed Countries

• Shortest life expectancies, lowest average per-person GNI PPPs, highest birth rates, and highest infant mortality rates characterize these countries

Population and Urbanization

• Urbanization is a process whereby people move from rural areas to densely populated cities.
• Suburban sprawl into former natural or agricultural areas destroys wildlife habitat.
• Environmental problems in urban areas include brownfields, air pollution, covered water flow, and contaminated runoff.

Environmental Benefits of Urbanization

• Well-planned cities can benefit the environment by reducing pollution and preserving rural areas.
• Compact development, characterized by tall, multiple-unit residential buildings near shopping and jobs and connected by public transit, is part of the solution.
• Urbanization is a worldwide phenomenon, with more than 50% of the world population living in urban areas with populations of 2000 or greater.

Challenges Faced by Developing Countries

• Include substandard housing (slums and squatter settlements), poverty, high unemployment, heavy pollution, and inadequate or non-existent infrastructure.

Lesson 2: People and Agriculture

• Students will be able to differentiate between undernutrition and overnutrition, define food insecurity and relate it to human population, poverty, and world hunger, contrast industrialized agriculture with subsistence agriculture.
• Students will also be able to describe three kinds of subsistence agriculture, relate the benefits and problems associated with the green revolution, and describe the environmental impacts of industrialized agriculture, including land degradation and habitat fragmentation.

World Food Problems

• An average adult human must consume enough food to get approximately 2600 calories per day
• Undernutrition is malnutrition from underconsumption of calories or nutrients
• Overnutrition is malnutrition from overconsumption of calories

Population and World Hunger

• Food insecurity refers to 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 workforce), and drought

Subsistence Agriculture

• Most farmers in developing countries practice this Agriculture.
• Shifting cultivation is a form of subsistence agriculture with short cultivation periods followed by longer fallow periods; supports relatively small populations.
• Slash-and-burn is a type of shifting cultivation involving clearing small tropical forest patches; farmers must move frequently.
• Nomadic herding relies on livestock supported by arid land; herders must continually move livestock to find food.
• Intensive subsistence agriculture that grows multiple plants on the same field.
• Monoculture involves the cultivation of only one type of plant over a large area, while polyculture is a type of intercropping in which crops mature at different times are planted together.

Challenges of Agriculture

• Prime farmland is land with appropriate soil, conditions, and water for crops.
• Challenges include decline in prime farmland + a shortage of domesticated varieties.

Global Decline in Domesticated Plant and Animal Varieties

• There is currently a trend where many local varieties of a domesticated farm animal or crop animal are being replaced with just a few kinds.

Increasing Crop Yields

• Increased yields can be achieved by using pesticides, fertilizers, and understanding plant nutrition.

The Green Revolution

• By the middle of the 20th century, serious food shortages occurred in many developing countries coping with growing populations.
• Development and introduction during the the 60's gave high rates of wheat and rice to Asian and Latin American countries and gave these nations the ability to potentially provide sufficient food to their people.
• The high-yield varieties required intensive industrial cultivation methods of commercial inorganic fertilizers, pesticides, and mechanized machinery passed from highly developed to developing nations.

Critics of Green Revolution

• It has made developing countries dependent on imported technologies that require agrochemicals and tractors, at the expense of traditional agriculture and are associated often with high costs as a result.
• Environmental problems are caused by fertilizer/pesticide intensive use

Increasing Livestock Yields

• Use of hormones and antibiotics increases animal production.
• Use of antibiotics, although controversial, can also increase the bodily functions and growth of animals.

Environmental Impacts of Intensive Cultivation

• Air and water pollution, pesticide runoff, land degradation, and habitat fragmentation.

Solutions to Agricultural Problems

• Sustainable agriculture maintains soil productivity and provides for the ecological health so to have minimal long-term impacts.

Genetic Engineering

• Genetic engineering involves gene manipulation to produce a specific trait.
• There is the potential for increased food output and vaccines but some concerns are that inserted genes could spread from GM crops to weeds/wild relatives or that natural ecosystems will become harmed and that allergies could develop in a population.

Lesson 3: Mining and Environment

• Students will be able to relate the environmental impacts of mining and refining minerals, including a brief description of acid mine drainage, and explain how mining lands can be restored.

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, and depletion of the groundwater

Acid Mine Drainage

• Pollution caused when sulphuric acid and dangerous dissolved materials wash from mines into nearby lakes and streams.

Tailings

• Tailings are usually left in giant piles on the ground or in ponds near the processing plants
• They contain toxic materials such as cyanide, mercury, and sulfuric acid and contaminate the air, soil, and water.

Restoration of Mining Lands

• When a mine is no longer profitable to operate, the land can be reclaimed, or restored to a seminatural condition.
• Reclamation prevents further degradation and erosion of the land and eliminates or neutralizes local sources of toxic pollutants and makes the land productive for purposes other than mining.
• Restoration makes such areas visually attractive.