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Environmental Issues & Problems ENV 150 Guillaume Mauger Schedule for today: Population population in ecosystems: carrying capacity, growth curves, species human population: future projections, resource use, pop. control Review from last week. Ecology as the engineer’s perspective: evaluating ecosystem structure and function • Types of Ecosystems: Biomes • Evolution / Nat. Selection / Adaptation • Characteristics of Sustainable Ecosystems: – – – – Reliance on Solar Nutrient cycling Biodiversity Population Control Quickwrite: Separate page into 2 Columns 1. Service-Learning: – Name the organization you will be working with, and what you will be doing, OR – One sentence on what you want to do, plus: • one list the organizations you have already contacted, and • another list on those you are planning to contact 2. Paper Topic: 1-2 sentences each: – summary of your paper topic – Why it is an important topic/question – How it relates to your service learning Thomas R. Malthus An Essay on the Principle of Population (1798, revised 1826) “It is observed by Dr. [Benjamin] Franklin that there is no bound to the prolific nature of plants or animals but what is made by their crowding and interfering with each other’s means of subsistence.” Thomas R. Malthus Thomas R. Malthus An Essay on the Principle of Population An Essay on the Principle of Population (1798, revised 1826) “… among these effects may be reckoned a very considerable portion of that vice and misery, and of that unequal distribution of the bounties of nature…” Population Change in = Population (1798, revised 1826) “The cause to which I allude is the constant tendency in all animated life to increase beyond the nourishment prepared for it.” Population Growth ( Births + Immigration ) - ( Deaths + Emigration ) Exponential (“J” curve) vs. Logistic (“S” curve) Population Growth Population Growth NOTE: this is an example of stable population growth Exponential (“J” curve) vs. Population Growth Q: Example of “Irruptive” or Malthusian growth Logistic (“S” curve) What causes some species to overshoot/crash and other populations to grow more slowly? Population Growth Q: What causes some species to overshoot/crash and other populations to grow more slowly? … no clear answer, but … Population and species characteristics “opportunists” r-selected species Population and species characteristics “Competitors” k-selected species • Many small offspring (400/yr) • Little - no parental care of offspring • Early reproductive age (3-4 mo.) • Most offspring die before reaching reproductive age • Pioneer species • Generalists • Fewer, larger offspring (2-3 every 2 years) • High parental care of offspring (born blind) • Later reproductive age (4-7 yrs old) • Most offspring survive to reproductive age • Late successional species • Specialists Review Human Population • Carrying Capacity • Sustainable Yield • Natural Capital degradation results from…? World Population Projections Human Population Definitions: Crude Birth Rate = number live births per 1,000 people per year Crude Death Rate = number of deaths per 1,000 people per year Source: UN Dept. of Economic and Social Affairs, “World Population to 2300”, 2009 Human Population Definitions: Total Fertility Rate = average number of children each woman has in her lifetime Replacement Rate = number of children a couple must have to replace themselves (different for different countries). Population Pyramids Male Female Expanding Rapidly Prereproductive ages 0–14 Male Female Expanding Slowly Reproductive ages 15–44 Male Female Male Stable Postreproductive ages 45–85+ Female Declining Demographic transition Birth rate and death rate (number per 1,00 per year) Stage 1 Preindustrial Stage 2 Transitional Stage 3 Industrial World Population Projections Stage 4 Postindustrial Question: Are we overpopulated? Have we exceeded the Earth’s carrying capacity? Can we provide an adequate standard of living to everyone? Was Malthus right? Birth rate Death rate What are specific consequences or solutions? Total population Growth rate over time Low Increasing Very high Decreasing Low Zero Negative Source: UN Dept. of Economic and Social Affairs, “World Population to 2300”, 2009 Video: NOVA Video: Hans Rosling http://www.ted.com/index.php/talks/hans_rosling_shows_the_best _stats_you_ve_ever_seen.html World Population Projections Source: UN Dept. of Economic and Social Affairs, “World Population to 2300”, 2009