Birdlife International 2000 9881 spp of birds 1183 (12%) threatened w/ global extinction

1. Birdlife International 2000 9881 spp of birds 1183 (12%) threatened w/ global extinction 182 Critically endangered 321 Endangered 680 Vulnerable to extinction

2. What causes avian extinction? 64 42 30 28 20 16 Human exploitation Introduced species Habitat loss Historic extinctions Currently threatened

3. One of the most ubiquitous patterns in Ecology is the simple observation that larger areas hold more species. But more than this, there is a consistent quantitative relationship between the 2 variables. Species Power law: S = cAz Area

4. Or, taking the logarithm of both sides: Log (S) = log (c) + z log (A) Log Species (S) Slope = z Log Area (A) Both c and z are taxon-specific, but importantly, z is scale-specific Intercept = c

5. Species-Area Relationships for alpine forest birds and mammals

6. What is the mechanism for such a pattern?

7. What is the mechanism for such a pattern? • A larger area holds more individuals •  more individuals = lower risk of extinction • Why? Allee effects, stochastic fluctuations that reduce an already • small population, lack of rescue effect between multiple • populations • (2) A larger area has greater habitat (or otherwise) diversity and thus • meets the requirements for a greater number of species

8. Two types of Species-Area relationships: continental: z ~ 0.15 Log Species Island: z ~ 0.35 Log Area

9. What does this mean? Continental : z ~ 0.15 Log Species Island: z ~ 0.35 Log Area Small islands have fewer species than a similarly sized block of continent. But as island size gets bigger, this difference in the number of species diminishes, i.e., large islands are effectively continental.

10. WHY?? Log Species Continental Island Relaxation to an Island State Log Area Many species cannot persist as isolated populations on small islands, whereas the same species may persist in contiguous areas where they occur not as isolated populations but as several populations connected to each other via dispersal

11. Understanding the consequences of the loss of area S = cAz Assume c = 100 and an initial area of 1.0 If we lose 90% of the area, how many spp remain? A = 0.1 so… Log Species Log Area

12. Step #1 – loss of endemics S = cAz Assume c = 100 and an initial area of 1.0 We lose 90% of the area, how many spp remain? A = 0.1 so… S = 100(0.1)0.15 S1 = 71 S S1 Log Area

13. Step #2 – relaxation to an island state S = cAz Assume c = 100 and an initial area of 1.0 We lose 90% of the area, how many spp remain? A = 0.1 so… S = 100(0.1)0.35 S2 = 45 S S1 S2 Log Area

14. After Newmark Cons. Bio. 1995 100 Survivorship of mammal population from western parks Percent Surviving 95 90 0 100 Time since Park establishment (yrs)

15. To Summarize: • Loss of Endemics (29%) • Immediate – spp whose entire • geographic range was lost • (2) Relaxation to an island state • (26% of initial spp). 10-100s of • years – avoidable if we act now S S1 S2 Total = 55% Lost S3 Log Area

16. There are some important caveats: • Extinction is not random – Nested subsets • (2) Not every unit area of the planet has the same level • of species Richness – HOTSPOTS

17. Nested subsets - Species fall out of small areas in an orderly and predictable sequence 1 2 3 4 5 6 7 8 Random pattern a a a a a a a a b b b b b b c c c c d d d e e f Completed Nested Pattern 1 2 3 4 5 6 7 8 a a a a a a a a b b b b b b c c c c d d d e e f

18. Bird species on landbridge islands in the New Zealand area (after Diamond 1984) Island Species lg sm

19. Which species are most prone to extinction ?? • Large body size • High residual generation time • Specialization

20. There are some important caveats: • Extinction is not random – Nested subsets. • (2) Not every unit area of the planet has the same level • of species Richness – HOTSPOTS

21. 40 80 160 Latitudinal gradients of species richness – The number of species decreases as you move away from the equator 280 420 600

22. 25 Hotspots have been identified worldwide

23. Mesoamerica Spp: 1,193 Endemics: 251 Brazilian Cerrado Spp: 837 Endemics: 29 Tropical Andes Spp: 1,166 Endemics: 677

24. Indo-Burma Spp: 1170 Endemics: 140 Polynesia/Micronesia Spp: 254 Endemics: 174 Madagascar Spp: 359 Endemics: 199 Wallacea Spp: 697 Endemics: 249

25. Vas. plants 132,000 44% Birds 2746 28% Mammals 1406 29% Herps 5529 45% In only < 2% of the planet Cumulatively they hold an amazingly high proportion of the Earth’s biota:

26. Other problems with Fragmentation....

27. Forest fragmentation in Madison County, WI 1831-1950

28. Area-sensitivity in birds 100 Red-winged Blackbird Percent occurrence versus forest area 80 Mourning Dove 60 40 20 100 Blue jay 80 Northern Flicker 60 40 20 1 2 3 Log Forest Area from Faaborg 1988

29. 100 Kentucky Warbler 80 Ovenbird 60 40 20 1 2 3 Log Forest Area Strongly fragment-adverse species - exact mechanism(s) is unknown - additional factors at work, e.g., paring success declines in small fragments - May actually be beneficial – e.g., if forest edges are hostile, fragment-adverse behavior keeps these species from settling there

30. Time to lose 50% of avian spp as a function of forest area 100 ha forest fragment loses 50% of its bird spp in 15 yrs!!!! Rates of species loss from Amazonian forest fragments. PNAS 100:14069-14073