Carrying Capacity

1. Carrying Capacity

2. Imagine our planet as a “ global bus ” Suppose thata bus has enough seats for fifty passengers We would all agree that we could crowd a few extra persons on board in an emergency

3. But how many extracould the vehicle accommodate? What if 100 passengers climbed aboard? • or 350? • or 2,748?

4. Clearly at some point a critical system would fail • The engine would overheat • The tires would blow • The axles would break • The transmission would fail or • The engine would blow a gasket

5. In all likelihood, the first system to be affected might bethe restroomat the back of the bus as the amount of waste generated by the passengers overwhelms its capacity to accommodate those wastes

6. Why should we suppose that earth’s biological and ecological machinery is invulnerable?

7. Biologists employ the term Carrying Capacity which is defined as follows The number of members of a population an ecosystem can support over a long period of time without suffering severe or irreparable damage.

8. Since ecosystems are finite in size and resources, each has an upper limit to the population that it can support Each also has an upper limit to its ability to provide food, resources, ecological services, maintain itself, resist damage, and to accept, cleanse, and recycle wastes

9. Limiting Factors There are a variety oflimiting factorsthat play a role in regulating the ultimatesize of a population

10. Limiting Factors can be defined as: • Those things which prevent a population from growing infinitely large.

11. Examples of Limiting Factors • Limited capacity to accept pollution and wastes • Physical damage done to the ecosystem and its components Other examples • Disease • Competition for resources • Predators • Starvation, hunger and limited food supplies

12. Food suppliesare not always the most important limiting factors Sometimes it is physical damage to the environment Elephants, when confined, knock down trees, strip them of vegetation, and trample grasses and groundcover

13. Sometimes wastes are the most important limiting factor An exploding population of yeast cells in grape juice generate poisonous wastes in the form of ethanol

14. A population explosion of algae in a pond can quickly deplete the water of its dissolved O2 catastrophically changing the entire environmentto anoxic conditions that kill most other life forms eutrophication

15. Population explosions of marine dinoflagellates can produce deadly red-tides and fish-kills Each dinoflagellate releases tiny amounts of a poisonous neurotoxic waste into the environment At some point, the environment’s capacity to dissipate, cleanse, and recycle the poisonous wastes is exceeded

16. Human body wastes are unlikelyto affect our entire planet

17. But the collective impacts of allour industrial and societal wastes, Such as • Chlorofluorocarbons • Heavy metals • Acid rain • Nuclear wastes and • Rising levels of greenhouse gases represent significant challengesto earth’s ecological systems

18. Today our population is almost seven billion

19. Are there any “ Warning Lamps ”beginning to light up on the “ global dashboard ” ? • Ozone depletion • Greenhouse gases • Melting ice • Acid precipitation • Hunger and starvation • Deforestation • Disappearing wilderness • Collapsing fisheries/’dead zones’ • Desertification • Mass extinctions of wild plants and animals

20. Dead zone in Gulf of Mexico The large region of low oxygen, high nitrogen water often referred to as the 'Gulf Dead Zone,' shown here, crosses nearly 5,800 square miles of the Gulf of Mexico

21. If all these stresses are occurring now, what will happen as we add three or more additional billions over the next half century?

22. Finally, we are not alone on our global bus

23. Other passengers (species) occupy much of the available seating

24. Today, as more and more human passengersclimb aboard, these other speciesare being displaced at an accelerating rate

25. So just how fast has our species been growing?

26. So what does this look like?

27. Approximate World Population Year 0001 - 1650 = Doubled in 1650 yrs 1650 - 1830 = Doubled in 0180 yrs 1830 - 1930 = Doubled in 0100 yrs 1960 - 2000 = Doubled in 0040 yrs 8000 BC 5 Million 0001 AD 250 Million 1650 AD 500 Million 1831 AD 001Billion 1930 AD002 Billion 1960 AD003 Billion 1975 AD004 Billion 1987 AD005 Billion 1999 AD006 Billion

28. Historical Demographics Approximate World Population Year 8000 BC 5 Million 0001 AD 250 Million 1650 AD 500 Million 1831 AD 001Billion 1930 AD002 Billion 1960 AD003 Billion 1975 AD004 Billion 1987 AD005 Billion 1999 AD006 Billion Do you see any patterns here?How long does it take for our numbers to double?

29. Approximate World Population Year Notice that it took all of human history until 1830 for us to reach our first billion 8000 BC 5 Million 0001 AD 250 Million 1650 AD 500 Million 1831 AD 001 Billion 1930 AD002 Billion 1960 AD003 Billion 1975 AD004 Billion 1987 AD005 Billion 1999 AD006 Billion Just 100 years to reach our second billion And just 30 years to add our third billion

30. Approximate World Population Year 8000 BC 5 Million 0001 AD 250 Million 1650 AD 500 Million 1831 AD 001 Billion 1930 AD002 Billion 1960 AD003 Billion 1975 AD004 Billion 1987 AD005 Billion 1999 AD006 Billion Today we add another billion persons to our population every twelve to fifteen years

31. While nature had all of human history until 1830 to adjust to the impact of our first billion, today we are making the same demands(and more, because we are industrialized) every twelve to fifteen years

32. Billion What about the future? U.N. “medium” assumptions project the following for the decades ahead 2013 7 Billion 2028 8 Billion 2053 9 Billion ?