How many species?

1. How many species? • 5 - 9 million non-bacterial species estimated • Some estimates have ranged up to 100 million because of potential insect diversity • 1.5 million cataloged, but many are only descriptions or a museum specimen • Will we count them before they go extinct?

3. Extinctions versus identification

4. Extinction versus identification • At current rate of identification, if there are 5 million species, then most will have been described by the year 2220 • If extinction rates are as high as 5% per decade, then regardless of how many species exist on Earth, more than half will be extinct within 150 years, 2164 • At the rates considered more realistic (i.e., <1% per decade) the rate of species description greatly outpaces extinction rates whether there are 2 or 10 million species on Earth.

5. The challenges of counting • Taxonomic skills are necessary to find and identify new species • New species are routinely discovered • Speciation is occurring in some taxa • Extinctions need to be verified • Extinction debt • Historical and future trends • Causes of present-day biodiversity decline

6. New species get counted when they are identified… • 30,000 to 40,000 taxonomists worldwide • 16,000 new species identified per year • However, overall there are fewer species being described per taxonomist, suggesting that it may already be harder to discover new species Relatively large, conspicuous species are still being discovered in remote or poorly studied areas. Shown are (a) an undescribed jay species from the Amazon basin, (b) a recently discovered fruit bat and (c) monitor lizard from the Philippines

8. Speciation occurring in some taxa… • Associated with plant hybridization • More new plant species have come into existence in Europe over past three centuries than documented as becoming extinct over same period, even though most new hybrid-origin species likely to remain undetected. • Current speciation rates are unusually high and they could be higher than during or after previous mass extinctions.

9. While other taxa are declining…

10. Large regions in all continents have lost 50% or more of the populations of the evaluated mammals.

15. When do you conclude a species is extinct? • Of all the mammalian species thought to have become extinct since the year 1500, about one-third have at some stage been rediscovered. • How long should you continue to look?

16. Extinction is not necessarily easy to conclude. Sometimes species thought to be extinct are still present in small isolated populations

19. Extinction debt • Challenges counting of species • Defined as the lock in of future extinction of species due to human impacts that occurred at some earlier point in time. • Time delay between human impact and extinction

20. Human-caused extinctions

21. Human-caused extinctions • Lose between 1-5% of species per year • Current rates of extinction are 100 to 1,000 times natural background levels

24. Multiple dispersals out of Africa 3 First pulse - 120,000 ya into Middle East and south Asia Second pulse 60,000 ya – into these regions and around the world

25. Pleistocene megafaunal extinctions in the Americas (15,000 - 12,000 years ago) • Fossil evidence rapid extinctions coinciding with migration of humans into NA • Naïve fauna: overkill hypothesis: keystone herbivores • Climate change also played a role • Dire wolf, American lion lost in extinction cascade after their prey reduced

27. Giant sloth dung

28. 80% of megafauna went extinct with arrival of humans in Central and South America.

30. Australian megafaunal extinctions (45,000 -50,000 years ago) • Human hunting implicated: timed with arrival of Aboriginals into Australia. Loss of large herbivores and then loss of large predators

31. Thylacoleo, a marsupial lion Two species of Protemnodon

32. Contemporary extinction • There is evidence that contemporary extinctions, while very high, have not been as high as some had predicted, for several reasons: • Effective conservation efforts • Species persisting in secondary habitats and anthropogenic land covers • Distinctive patterns to extinctions in the Anthropocene • Faunal homogenization • Faunal size bias

34. Comparison of species richness among wildlife parks. Color code: yellow = 1896–1950, green = 1950–2013. Species richness (the number of species) higher today. Why?

35. Biotic homogenization • Increased numbers of species locally due to human-aided dispersal of generalist species • Locally unique specialist species decline • Increased alpha diversity but declining beta diversity

36. Faunal size bias • Defaunation in the Anthropocene is size-specific • Selective impact on large-bodied mammals and birds – size determines susceptibility to extinction

37. Anthropocene mechanisms that can contribute to exinction • What are the top two contributors to extinction, either locally, or globally: • Invasive species • Habitat change • Overexploitation • Pollution • Climate change • Disease

41. Habitat fragmentation results in island systems

42. Habitat fragmentation results in island systems

43. Mammalian displacement in movement as a function of human footprint As human impacts grow, mammals (and other animals, are restricted to smaller and smaller habitats

45. As island size decreases: • Extinction rate increases • Resources become limited • Distances between island increases • Organisms cannot come in contact with a mate

46. Theory of Island Biogeography (1967)

47. SLOSS (Single large versus several small) debate

48. Road planning and design will shape biodiversity trends • Accelerating rates of road construction, mainly in tropical and subtropical regions • 2 billion autos by 2030

49. Road expansion accelerates economic growth, but… • Benefits have to be weighed against impacts on biodiversity • Good: rural roads that link farmers to urban markets can have positive impact on economic growth • Bad: Poorly built or designed roads on floodplains or steep terrain can cause erosion and cascading effects on fisheries, agriculture, and tourism