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Number of Caribou Caribou on Alaskan island: Why the decline after 1940?

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Presentation on theme: "Number of Caribou Caribou on Alaskan island: Why the decline after 1940?"— Presentation transcript:

1 Number of Caribou Caribou on Alaskan island: Why the decline after 1940?

2 Population Regulation and Negative Density-dependence: Population regulation: a limit on the size of a population, called K, the carrying capacity of the environment. Negative Density-dependence: birth rates decrease and death rates increase with increases in population density: b decreases and d increases as N increases. Question: If K is the maximum number of individuals that the environment can support, how can there be an OVERSHOOT?

3 Population Regulation and Negative Density-dependence: When r declines to zero with increasing density, we say that population is regulated and N t+1 = N t = K is called the equilibrium population size or the carrying capacity of the environment. NtNt r 0 K = carrying capacity

4 Population Regulation and Negative Density-dependence: When r declines to zero with increasing density, we say that population is regulated and N t+1 = N t = K is called the carrying capacity. NtNt r 0 When N t < K, then population size increases. When N t > K, then population size decreases. K = carrying capacity

5 Basic Equation for Exponential Growth N t+1 = N t + bN t - dN t = N t + (b - d)N t r = b - d = Intrinsic rate of increase  N = N t+1 – N t = rN t Basic Equation for Logistic Growth  N = N t+1 – N t = rN t {(K – N t )/K} K = Carrying Capacity  N = 0 when K = N t

6 The causes of Negative Density-dependence are: 1. Resource limitation: result of competition between members of the same species. 2. Limited Space for Territories 3. Accumulation of waste products 4. Increase in Predators or Disease

7 Number of Tomatoes per Plant Density of Tomato Plants Resource limitation by competition

8 Number of Tomatoes per Plant Density of Tomato Plants Resource limitation by competition

9 Number of Tomatoes per Plant Density of Tomato Plants Resource limitation by competition: More tomatoes per plant at LOW Density

10 Figure Decreased fecundity at high population densities Crowding reduces reproduction by competition for resources

11 Limited Space for Territories Uniform dispersion of Eagle nests at Lake Monroe caused by territorial behavior.

12 Brewing Beer: Accumulation of waste products: limitation of growth by one’s own excrement 1. Brewing: boiling grains (barley, etc.) to create sugary syrup. 2. Fermenting: inoculate the syrup with yeast and they convert sugars to alcohol. Sugar + Oxygen  CO 2 + lots of energy Sugar  Alcohol + little energy Density- dependence 1 2 Alcohol poisoning: waste product kills the yeast

13 Negative Density-dependence resulting from an Increase in Predators or Disease

14 Time Density N t+1 = N t + r N t ( 1- ) NtKNtK r = 0.8 K = Time Density No Time Lags One Generation Time Lags Overshoot K = 100

15 Time-lags in density dependence cause oscillations in density. Time-lag: Effect of N t on b and d is not reflected immediately as a reduction in r t but rather as a reduction in r t+L, where L is the time lag. Biology of Time Lags: Parent generation passes resources on to offspring generation. In mammals, in the form of mother’s milk; in Daphnia, in the form of nutrients in the eggs.

16 Number of Caribou Caribou on Alaskan island: OVERSHOOT of K

17 Some lab populations don’t follow the logistic model

18 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Historically, K, the carrying capacity has increased with technology: fire, agriculture, use of fossil fuels only in past 100 years. Human Population Growth: J-shaped curve

19 First Oil Well Human Population Growth: J-shaped curve

20 Role of Oil in Human Population Growth 1.More than 80% of the cost of farming is the cost of oil a. cost of running farm equipment. b. pesticides are oil derivatives. c. herbicides are oil derivatives. d. fertilizers are oil and natural gas derivatives. e. transportation of farm produce to market. f. refrigeration and storage. The average item on your plate has travelled 1,700 miles! 2. More than 90% transportation of all kinds uses oil as fuel. 3. Much electricity in the US is made from natural gas.

21 Oil is a Fossil Fuel Algal growth 100 to 150 mya created sediments in oxygen poor regions which were later buried 7,000 to 15,000 feet under shale and other rock by geological processes, where the heat was sufficient to break down their carbon into oil and gas. Result: 1.Oil is only found in certain places. 2.There is no fast way to make more oil. Figure after C. Campbell

22 Discovery of oil in the US peaked in 1930 and Production of oil in US peaked 40 years later in US Consumption of oil has NOT PEAKED, it continues to INCREASE. Peak US Discovery Peak Production Figure after C. Campbell Large Improvements in Oil Technology

23 Discovery of oil in the WORLD peaked in and Production of oil in the WORLD is now peaking years later in WORLD Consumption of oil has NOT PEAKED; it continues to INCREASE. Past discovery by ExxonMobil Figure after C. Campbell

24 Four largest Oil Fields in the World: Ghawar, Saudi Arabia; produces 5.0 million barrels/day. Discovered: 1948 Cantarell, Mexico; produces 2.2 million barrels/day 2004 Discovered: 1976 Burgan, Kuwait produces around 1.4 million barrels/day Discovered: 1938 Da Qing, China; produces 1 million barrels/day Discovered: 1959

25 Mexico: In 2005, Cantarell produced more than 60% of Mexico's oil production. Cantarell is considered the "Ghawar" of Mexico. Discovered: Decline 2006: 13% less productive in 2006 than in Only 1 million barrels/day by Cause of Decline: enhanced production methods that allow faster oil extraction. Largest fields found offshore in the deepwater today produce about 250,000 barrels/day. It will take 4 of them to replace Cantarell.

26 Da Qing, China. Discovered: Decline 2006: 7% less productive in 2006 than in Use of oil is growing in China. It now imports 30% of its oil. It is estimated that by 2010 it will import > 60% of its oil. By 2031, China will use 90 million barrels of oil per day. The entire world uses 88 million barrels of oil per day in 2006.

27 Kuwait: Saturday, November at 08:46 Bloomberg It was an incredible revelation last week that the second largest oil field discovered in the world is exhausted and past its peak output. Yet that is what the Kuwait Oil Company revealed about its Burgan field. “The peak output of the Burgan oil field will now be around 1.7 million barrels* per day, and not the two million barrels per day forecast for the rest of the field's 30 to 40 years of life, Chairman Farouk Al Zanki told Bloomberg.” Note: This field is only 300 miles away from the largest oil field. *: It is only producing 1.4 million barrels a day right now!

28 Official Energy Statistics of US Government: World energy consumption is projected to increase by 71% from 2003 to It took 125 years to use first 1 trillion barrels of oil; Only 30 years to use the 2 nd trillion barrels of oil.

29 Boston Globe, Wednesday, November 14, 2005 New England can expect rolling blackouts this winter if cold weather places unusual demands on the use of natural gas for heat. Many New England electric companies make electricity from natural gas and, if the price of gas increases owing to winter shortages, they may choose to sell their gas on the market instead of using it to produce electricity. There is no law against it.

30 The US, has only 4.7 percent of the world's population but consumes 25 percent of the world's resources and generates 25 to 30 percent of the world's waste. Compared to an average citizen in India, a typical person in the U.S. uses: 50 times more steel 56 times more energy (oil and gas) 170 times more synthetic rubber 250 times more motor fuel 300 times more plastic Each American consumes as much grain as five Kenyans, and as much energy as 35 Indians, 150 Bangladeshis or 500 Ethiopians.

31 P = Annual Oil Production Q = Cummulative (Total) Oil Production to date r NtNt

32 Monday: Cane Toads: An Unnatural History “If Monty Python produced a National Geographic Special it would be Cane Toads!” Sample Exam IV questions from last week’s lectures will be placed on the web. No Discussions next week. In Discussion the week AFTER Thanksgiving, you will be preparing for the next exam by making up Multiple Choice Questions.


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