Present Day Extinctions. Past Mass Extinctions

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1 Geography Dr. B. Holzman Present Day Extinctions I. Extinctions in recent time A) human population increase B) natural selection II. Who gets it A) r-selected vs. K-selected species B) loss of habitat C) loss of range III. Human Impacts Past Mass Extinctions Climate changes led to other changes 1

2 Geography Dr. B. Holzman PLEISTOCENE MEGAFAUNA Global Warming EXTINCTION Extinction is a biological reality: It is a process of Evolution. It is estimated that about one fourth of the species of birds and mammals that have become extinct since 1600 A.D. may have died out naturally. 2

3 Geography Dr. B. Holzman Mammals 1600 A.D: 4226 living species of mammals since then 120 have become extinct Africa Quagga Birds 1600 A.D living species of birds since then. 162 have become extinct Species can become extinct or endangered because of several human impacts: Excessive exploitation: hunting Introduced species: invasion Environmental contaminants: pollution Habitat Destruction and Change: this is the biggest contributor to current extinctions without replacement 3

4 Geography Dr. B. Holzman CLASS Critically endangered endangered threatened vulnerable Total extinct Mammals Birds Reptiles Amphibs Insects Other The following listed native fish and wildlife are threatened with extinction in the US. Mammals: Indiana Bat - Myotis sodalis Delmarva Peninsula Fox Squirrel - Sciurus niger cinereus Timber Wolf - Canis lupus lycaon Red Wolf - Canis niger San Joaquin Kit Fox - Vulpes macrotis mutica Grizzly Bear - Ursus horribilis Black-Footed Ferret - Mustela nigripes Florida Panther - Felis concolor coryi Caribbean Monk Seal - Monachus tropicalis Guadalupe Fur Seal - Arctocephalus philippi townsendi Florida Manatee or Florida Sea Cow - Trichechus manatus latirostris Key Deer - Odocoileus virginianus clavium Sonoran Pronghorn - Antilocapra americana sonoriensis Loss of habitat 4

5 Geography Dr. B. Holzman Between 1980 and 1995 Africa lost 10.5 percent of its forest cover, Latin America 9.7 percent, and Asia 6.4 percent. But developed areas managed to increase their forest cover; Europe by around 4 percent. Loss of range A cat is about the worst mammal there is on the bluebird trail," Domestic cats are responsible for 33 bird going extinct since the 1600s 5

6 Geography Dr. B. Holzman Who gets it? Depends on species strategy and human perception Exponential and Logistic Growth Population size (N) K Population size (N) Time (t) Exponential Growth Time (t) Logistic Growth Number of reindeer 2,000 1,500 1, Number of sheep (millions) Year Year K selected larger adults fewer young parental care slower maturity slow rate of increase long gestation adapted to limited fluctuation in environment greater survivability thermoregulation immune system longer lifespan stable populations Examples: 6

7 Geography Dr. B. Holzman r- strategy small adults many young little - no parental care early maturity little to no immune system short gestation short lifespan vulnerable to environmental change population unstable Boom and Bust cycle examples: Characteristics of Species affecting survival Endangered Large size Predator Narrow habitat tolerances Valuable fur, oil, hide,etc Restricted distribution Lives largely in international waters Migrates across international boundaries Reproduction in one or two vast aggregates Long gestation period Small litters Intolerance of the presence of humans Dangerous to humans, livestock, etc Safe Small size Grazer, scavenger, insectivore Wide habitat tolerances Not a source of natural products Broad distribution Lives largely in one country Reproduction by solitary pairs or in many small aggregates Short gestation period Big litters and quick maturation Tolerance of humans Perceived as harmless Adaptive Population 1-2 MYA 2-10 Million 8000 BC- 1A.D Million 1 A.D A.D. 750 Million Billion Billion Billion Billion Billion. Current population: 6.5 billion 7

8 Geography Dr. B. Holzman Human Impact Human population 3.75 MYA East Africa (Australopithecus) 2 MYA (4?) Species of Hominids 3 Australopithecus 1 Homo habilis 1.75 MYA A. boisei, A. robustus Homo erectus 1 MYA Homo sapien Homo neanderthal Recent Homo sapien sapien H. sapien sapien made it to the New 20 KYA (although there is archeological evidence to suggest that humans were in South America prior to this time) Human Impact Domestication of plants and animals: Earliest domestication is thought to have been cereals (wheat, barley): 11-9KYA Simultaneous cultivation may have occurred 8

9 Geography Dr. B. Holzman Early Domestication Origins of some cultivated plants: SW Asia: millet, soybean, radish, tea, peach, apricot, orange, lemon C. Asia: spinach, onion, garlic, almond, pear, apple India/S.E. Asia: rice, sugar cane, cotton, banana Mexico/S. America: maize, cotton, red pepper, agave S. America: tomato, potato, tobacco, peanut, pineapple 9

10 Geography Dr. B. Holzman Human Impact Agriculture leads to food surplus which leads to increased population Increased population leads to increase use of resources (pollution, sedimentation of waterways, local loss of species) Industrial Revolution :

11 Geography Dr. B. Holzman Increased technological innovation increases life span quality of life and use of resources Stage 1 Preiindustrial Stage 2 Transindustrial Stage 3 Industrial Stage 4 Postindustrial Birth rate and death rate (number per 1,000 per year) Birth rate Death rate Total population 0 Low Increasing Growth Very high Decreasing Low Zero Negative growth rate growth rate growth rate growth rate growth rate growth rate growth rate Time High Relative population size Low Green Revolution: Gene Revolution: 1960s 2000s World Population Growth,

12 Geography Dr. B. Holzman Human Impacts on Ecosystems Habitat degradation and fragmentation Ecosystem simplification Predator elimination Introduction of non-native species Over-harvesting renewable resources Interference with ecological systems Easter Island 12

13 Geography Dr. B. Holzman In the end we will conserve only what we love, We will love only what we understand and we will understand only what we are taught. Baba Dioum (Senegal) 13

14 Geography Dr. B. Holzman Be safe! I hope you have the time of your life.. FINAL EXAM TUESDAY December 19 8:30 14