1. EXTINCTION & THE BIODIVERSITY CRISIS

2. Biodiversity: All the variety of life, at every level of organization... Genetic diversity Species diversity Ecosystem diversity

3. According to the U.S. Endangered Species Act: – An endangered species is “in danger of becoming extinct throughout all or a significant portion of its range” –A threatened species is “likely to become endangered in the foreseeable future”

4. Extinction: The death of the last surviving individual of a species, population, or gene, locally or globally.

5. The Biodiversity Synthesis Report KEY FINDINGS: Decline in biodiversity due to human activities more rapid in past 50 yrs than at any time in human history Over last 100 yrs, human-caused species extinctions have multiplied ~ 1,000 times 12 % of birds, 23% of mammals, and 32% of amphibians are threatened with extinction

6. Current estimates of species loss range between 10-50% over next 20-50 years. This current rapid decline in biodiversity is known as the “Biodiversity Crisis”

7. What makes a species vulnerable to extinction? Vulnerability to introduced exotics Overexploitation Rarity Habitat loss / Fragmentation

8. Introduced Exotics Species that humans have moved from native locations to new geographic regions In absence of their native competitors, predators, parasites, and pathogens, introduced species may spread rapidly Introduced species that become established in a new habitat usually disrupt the community European Starling

9. Fig. 56-8 (a) Brown tree snake(b) Kudzu Brown tree snake introduced accidentally to Guam has caused extinction of 12 species of birds and 6 species of lizards. Asian plant kudzu introduced by USDA to control erosion; now choking out native plant species.

10. Overexploitation Human harvesting of wild plants or animals at rates exceeding ability of populations of those species to rebound Large organisms with low reproductive rates are especially vulnerable

11. Overexploitation by the fishing industry has greatly reduced populations of some game fish, such as blue-fin tuna World’s fish stocks have been reduced by 90% since the start of industrial fishing

12. Rare species are the most vulnerable to extinction, though common species can also become extinct. Three ways a species can be rare... Rarity

13. 1.

14. Cave Salamander

15. 2.

17. 3.

18. Maned Wolf

19. 4.

20. Proboscis Monkey

21. 5.

22. Hawaiian Hawk

23. 6.

24. Dwarf Naupaka

25. A small population is prone to positive-feedback loops that draw it down an extinction vortex The key factor driving the extinction vortex is loss of the genetic variation necessary to enable evolutionary responses to environmental change

26. Fig. 56-10 Inbreeding Small population Genetic drift Lower reproduction Higher mortality Smaller population Reduction in individual fitness and population adaptability Loss of genetic variability

27. Case Study: The Greater Prairie Chicken and the Extinction Vortex Populations fragmented by agriculture and later found to exhibit decreased fertility Scientists imported genetic variation by transplanting birds from larger populations Population rebounded, confirming that low genetic variation had been causing an extinction vortex

28. Estimates of current rates of extinction worldwide are based primarily on species- area relationships and rates of tropical deforestation. Habitat Loss

29. The fragmentation of habitats into patches that are too small to support populations is a major cause of extinction... Habitat Fragmentation

32. edge effects small area isolation Problems due to fragmentation:

33. Fig. 56-14 (a) Natural edges (b) Edges created by human activity

34. Edge Effects

35. edge effects small area isolation Problems due to fragmentation:

36. Island Biogeography: Species richness on islands depends on island size and distance from mainland. Equilibrium Model Explains variation in species richness on different islands by considering effects of isolation and area on rates of immigration and extinction.

39. Removal Experiment - Mangrove Islands Arthropods removed from islands of equal size, near and far from mainland. Number of species on each island at end of expt matched number at start (at least on near island), though the species differed.

40. Today, the equilibrium model of island biogeography is being applied to conservation issues… The equilibrium species number is dynamic: species composition constantly changes due to immigration and extinction.

41. Smaller fragments have: fewer habitat types fewer species smaller populations higher extinction rates

42. Area-sensitive species with large home ranges are especially vulnerable to small area effects... Spider Monkey White-plumed Antbird Jaguar

43. Isolation Rates of extinction are much higher on islands than on the mainland......problematic if species are not immigrating due to isolation.

44. Bogor Botanical Garden, Java Habitat fragments are habitat “islands”...

45. Habitat (Movement) Corridors: -links between fragmented habitats -allow species movement between habitats A possible solution?

46. Fig. 56-15

47. Advantages of Habitat Corridors - increased species richness - “rescue effect” - maintain genetic variation - altitudinal migration

48. Three-wattled Bellbird - altitudinal migrant

49. Disadvantages of Habitat Corridors - increased disease transmission - increase predation risk - increased spread of fire - reduced genetic variation between fragments

50. Biodiversity ‘Hot Spot’: A relatively small ecosystem with a high concentration of species, many of which are endemics.

51. Equator Terrestrial biodiversity hot spots Marine biodiversity hot spots Hotspots of biodiversity are also hotspots of extinction…

52. Video Topics Population Ecology: life history strategies parental care / fecundity Community Ecology: biodiversity mutualisms, competition, predation Ecosystem Ecology: primary producers (plants) primary, secondary, tertiary consumers water cycle Conservation Biology: hot spot, endemic species, rarity, habitat fragmentation, extinction