Population is the members of one species which occupies a given area. When examining population, any species may be examined--humans, dogs or birds--but that species must be identified. In this unit we examine local human population. We need to also specify the environment, or community. This unit, again, focuses on a specific area, New Haven, and the state of Connecticut.
Population is a numbers game. Three things affect the size of the human population for any given area: births, deaths and people moving in and out of the area. As more people reproduce, more children are born and population size keeps increasing. Demographers use birth rates and death rates to determine population size. They find out population numbers by taking the numbers of births or deaths per 1000 persons in the population at the mid-year of any given year. Then the demographers divide the total number of births or deaths per year by the total population at midyear and multiply the results by 1,000. Population experts also use fertility rates to determine population size. A fertility rate is the number of live births per 1,000 women in the reproductive age group (15 to 44 in the United States and up to 49 years in many other countries). For further projections demographers use the total fertility rate, which is a projection of the average number of children a woman will have during her entire reproductive period. (See YNHTI Curriculum Unit: Human Ecology: How It Relates to Population, by Sherree L. Kassuba, Guide Entry to 80.05.07)
Any study of population must be preceded by an understanding of such concepts as community, environment and carrying capacity. A community contains many different interacting species. Species are identified and differentiated by their ability to reproduce only within their own species. The individuals belonging to any one community are said to be a population. The environment is the habitat, both natural and man-made, that support the community.
Carrying capacity is a difficult concept to define, much less comprehend. The carrying capacity concept is critical to ecology and states that an environment--by extension, the earth--has a finite amount of resources. Given this finite environment, the growth of many of its members follows an S-shaped curve where growth slows and eventually stops because of environmental limits. Space and resources are finite, particularly non-renewable resources. This can be illustrated by introducing a few algae into a petri dish. At optimum temperature and with adequate food, algae increase their numbers, slowly at first, then more rapidly , until growth eventually slows and then stops, usually because of waste accumulation. The usefulness of the carrying capacity concept, however, is hotly debated by economists and ecologists because while ecologists see finite resources being depleted, economists see technology increasing the earth's store of resources. New irrigation techniques, for example, have made previously arid, useless land into efficient agricultural land.
One critical fact about carrying capacity that students need to understand is that human choices influence the earth's carrying capacity. Their decisions determine the earth's future. While each students may find it difficult to comprehend that they can affect the whole earth's future, it is imperative the realize their impact. If students indicate they each want two children, the replacement rate, world population would grow to 7.7 billion in 2050 and would level off around 8.4 billion by 2150. Future population size is very sensitive to future levels of average fertility, however. If the average couple had a level of fertility that was one tenth of a child less than replacement rate, population would peak at 7.8 billion in 2050, but would drop to 5.6 billion in 2150. For example, if there are 20 students in the classroom, and each student (10 couples) wants 2 children, an additional 20 children projected, the former scenario prevails; population levels at about 8.4 billion. If, however, the total future children the class elects to have drops by one tenth (2), the latter scenario prevails, and population levels at 5.6 billion. Your 20 students can actually contribute to a future population which can be reduced by more than 2 billion!.
Global overpopulation is a vast, overwhelming concept. Our population is growing at 1.6%. At this rate, given current our current population, humans would number 11 billion by 2025. The earth currently has 5.7 billion people. A billion is an unfathomable number . A billion is 1,000 million or 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10 (109) Students should imagine 2 football field side by side. That area is 100 meters by 100 meters. If you stacked all the people in New Haven on each square meter, you would have a billion or so people. A billion equals four times the 1990 population of the United States.
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When introducing the concept of overpopulation, students, should consider these facts: The United States is the third most populous country in the world following China and India. The U.S. population, currently more than 265 million, is growing by about 2.5 million people each year, making the United States one of the world's fastest-growing industrialized nations. In 1994, there were about 3.95 million births and 2.29 million deaths in the United States, resulting in a net natural increase of nearly 1.7 million more people. Sixty percent of pregnancies and 40 percent of births in the United States are unintended. The Census Bureau projects that in the year 2000, the U.S. population will exceed 275 million, more than double the 1940 population. By 2050, the nation's population is projected to increase by nearly 130 million people -- the equivalent of adding another four states the size of California.
Students cannot begin to understand the numbers associated with overpopulation and its implications until they personalize the "population" concept. Only after student's understand and can empathize with personal and community space and resource limitations, can they extend these concepts and begin to appreciate and comprehend global stresses due to overpopulation.
Activities
A. Overpopulation Obviously Stunts Growth
(*note: start project first week of unit; 8 week discovery)
Objective: Students will measure effects of overpopulation in plants
Materials:
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3 identical seed starter flats
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soil
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water
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light source
Procedure:
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1. Fill seed starter flats with soil. Take care to use the same amount of soil (control.)
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2. Label each flat: A, B, C
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3. In flat A plant one seed in each subdivision (6 to 8 subdivision flats are ideal).
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4. In flat B plant two seeds in each subdivision.
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5. In flat C plant five seeds in each subdivision.
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6. Prepare a chart to measure growth in each flat for eight weeks.
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7. Students propose how much growth they expect from each flat (Flat A will yield 1/2 the height flat in flat B within a month, for example).
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8. Water, using the same amount, twice weekly.
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9. Record plant growth in mm.
Extension: plant will not continue to grow in starter kit. It will die because its demands exceed the carrying capacity of the starter kit. Transplant a few plants from flat A and contrast their growth with those left in the flats.
B. In Your Face: Overpopulation at home, school, play
Objective: Students will record and describe how they are affected by overpopulation at home, school and in their community. They will organize their findings to discover where they feel the effects of overpopulation and for which resources they find most valuable and competitive.
Procedure: Students will keep a log/diary for three days (including one weekend) in which they record any activities which were negatively affected by others in any way. Brainstorm a substantial list with the class which includes examples such as: they had to wait for the bathroom; they couldn't watch TV because Dad was watching; they got stuck in traffic; they couldn't hear their radio because the car next to theirs was too loud; they had to take an undesirable school lunch because first choice was gone. Daily they will record their activities which were affected by others in a format which illustrates where they are most impacted by others.
Example:
Create master list on display board in which all students share how others "ruin their day". Ask students to decide if there is one area in their life that is more "overcrowded". Students compare their findings. Students decide if over population is an issue in their life. List the situations in which they wished there were fewer people. List when they wished there were more people. Compare these lists.
C. How much space do I need anyway?
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Objective: Students will identify all the space and resources they need in a day.
(Save this information for final project)
Procedure: Students will estimate how much space and resources they need. (For a more scientific sample, have students record data for one or two weeks and average the data) This lesson requires previous knowledge of area, calculating area.
At home: Using a yardstick or tape measure, have students measure and record how much living space is in their home. Then have them divide this number of square feet (meters) by the number of residents in the home to calculate their own living space: __________
At school: Students can interview the principal or other professional to discover how many square feet (yards) their school is, and how many students attend their school. By dividing the number of students into the square feet (yards), they will discover their individual space requirement: _________
Commuting/play/travel: Students should estimate how much "free space" they need for activities. It is a fun investment to buy one or two foot/athletic odometers that each student can wear to get a class average of miles spent walking to school, or participating in activities. Students who play sports should include the size of fields required to support their sport. After data is gathered, aggregate the "commuting/recreation" space, divide by total in class and use an average of space for this project: _________
Food: Students should create a blank menu to record all the food they eat in one week. Then estimate how much land is required to provide that food. Remember dairy and meat require almost an acre of land to support livestock. Estimate food space: ________
*note: The Millennium Institute calculates that each person requires approximately 30,000 square feet (.26 hectares) of farmland just to produce enough food and fiber or survival.
Water: Have student keep track of all the water they use in one day. They should consult energy and usage guides on appliances to see how much water these items use. In Water, Water Everywhere, toilet and shower usage are estimated at 12 and 30 gallons respectively. Average American water consumption is estimated at 193 gallons per day. Use student's or Water, Water estimates here: ________
Garbage: Students should measure their household trash daily, using a tape measure and calculating volume: _________ and weight ___________.You should also keep trash in the classroom for one week. What is the total for trash at school? __________
Record your data for individual use in the first column. Multiply individual use by the total number of students in the class for class use. Use town census numbers to estimate resources used by the town. New Haven population (1990): 130,474 (Use http://www.census.gov/main/www/srchtool.html for local census information)
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Current Individual Use
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Class Use
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Town Use
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Home
School
Commute/play
Food
Water
Trash
Do students consider these numbers to be high?
Multiply "Current Individual Use" by 6 billion to discover how much space/resources are needed by people in the world this year. World population is currently growing by over 80 million people each year, and is projected to exceed six billion people in 1998.
D. Space, No problem
Objective : Students will decide if there is enough space on the planet for its population to live comfortably, using a scaled model of available living space.
Procedure: Some growth advocates argue that the world is not overpopulated because its entire population could fit in Jacksonville, Florida. (At one square foot per person.) Draw or tape a three by three foot square on the playground or classroom floor, and place 9 students in it. Consider whether the lifestyle needs of those students can be met in that space. Discuss what other needs those students have beyond room to stand. How large a "footprint" do they need at school, including desk and study space, playground space, bathroom space, lunchroom space, library space, etc.
