1. How many animals do we need to save?

2. How Many Animals Do We Want to Save? The Many Ways of Setting Population Target Levels for Conservation ERIC W. SANDERSON November 2006 / Vol. 56 No. 11 BioScience 911

3. Extinction Vortex A population of a few individuals cannot survive

4. Can a number of individuals be set?

5. Fewest number of individuals for an area, but fewest number for what?

6. Can a number of individuals be set? Extreme examples: Ecotourism want the largest possible population Mining or Agriculture would like none or somewhere else…NIMBY

7. What are the consequences of setting the wrong number?

8. Too high Too low

9. Can a number of individuals be set? Scientists are reluctant to set a specific number Policymakers want information from scientists

10. What are the consequences of setting the wrong number? Subjective values meets objective science

11. http://www.forwolves.org/ralph/historical.html Yellowstone area wolf packs 2004 How many wolves should be in Yellowstone NP

12. How many tigers does the world need? None?

13. What criteria do we use to set limits? Money Land Development

14. What criteria do we use to set limits? Money Land Development Who benefits? Animals- what is the minimum number for sustainable survivalAnimals- what is the minimum number for sustainable survival

15. What criteria do we use to set limits? Money Land Development Who benefits? Animals- what is the minimum number for sustainable survivalAnimals- what is the minimum number for sustainable survival Ecosystem- What is the minimum number to maintain a healthy ecosystem?Ecosystem- What is the minimum number to maintain a healthy ecosystem?

17. What criteria do we use to set limits? Money Land Development Who benefits? Animals- what is the minimum number for sustainable survivalAnimals- what is the minimum number for sustainable survival Ecosystem- What is the minimum number to maintain a healthy ecosystem?Ecosystem- What is the minimum number to maintain a healthy ecosystem? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?

18. Who benefits? Animals- what is the minimum number for sustainable survival?Animals- what is the minimum number for sustainable survival?  Genetic Diversity Genetic Diversity

19. Who benefits? Ecosystem- What is the minimum number to maintain a healthy ecosystem?Ecosystem- What is the minimum number to maintain a healthy ecosystem?  Density may be more important than total number Density may be more important than total number

20. Who benefits? Ecosystem- What is the minimum number to maintain a healthy ecosystem?Ecosystem- What is the minimum number to maintain a healthy ecosystem?  Density may be more important than total number Density may be more important than total number  Manage population and monitor effects on ecosystem Manage population and monitor effects on ecosystem

21. Who benefits? Ecosystem- What is the minimum number to maintain a healthy ecosystem?Ecosystem- What is the minimum number to maintain a healthy ecosystem?  Density may be more important than total number Density may be more important than total number  Manage population and monitor effects on ecosystem Manage population and monitor effects on ecosystem  Some species may be used to monitor health of overall ecosystem Some species may be used to monitor health of overall ecosystem

23. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos

24. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos  Ecotourism/Tourism Ecotourism/Tourism

25. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos  Ecotourism/Tourism Ecotourism/Tourism  Harvest sustainable population Harvest sustainable population

26. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos  Ecotourism/Tourism Ecotourism/Tourism  Harvest sustainable population Harvest sustainable population  Ecosystem benefits- seed dispersal, pollinators, nutrient recycling Ecosystem benefits- seed dispersal, pollinators, nutrient recycling

27. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos  Ecotourism/Tourism Ecotourism/Tourism  Harvest sustainable population Harvest sustainable population  Ecosystem benefits- seed dispersal, pollinators, nutrient recycling Ecosystem benefits- seed dispersal, pollinators, nutrient recycling These functions cannot practically or economically be carried out by humans

29. Who benefits? Humans- How many do we need to derive some beneifit?Humans- How many do we need to derive some beneifit?  Total eradication may be goal- mosquitos Total eradication may be goal- mosquitos  Ecotourism/Tourism Ecotourism/Tourism  Harvest sustainable population Harvest sustainable population  Ecosystem benefits Ecosystem benefits  Cultural, Aesthetic, Spiritual Cultural, Aesthetic, Spiritual

30. How many animals do we want to save?

31. Complex interactions of science, economics, and ethics.

32. How many animals do we want to save? Complex interactions of science, economics, and ethics. If a number is set, it may stay static as conditions change.

33. How many animals do we want to save? Sanderson’s proposed solution:

34. How many animals do we want to save? Sanderson’s proposed solution: Minimum Viable Population- number of individuals that allows animals to exist free from human interference.

35. How many animals do we want to save? Most of human history includes critical and profound interactions with other organisms. That is now diminished or gone.

36. How many animals do we want to save? Most of human history includes critical and profound interactions with other organisms. That is now diminished or gone.

37. How many animals do we want to save? Sanderson’s proposed solution- multilayered approach: 1.Demographic sustainabilityDemographic sustainability

38. How many animals do we want to save? Sanderson’s proposed solution- multilayered approach: 1.Demographic SustainabilityDemographic Sustainability 2.Ecological Functions (includes ability to freely evolve)Ecological Functions (includes ability to freely evolve)

39. How many animals do we want to save? Sanderson’s proposed solution- multilayered approach: 1.Demographic SustainabilityDemographic Sustainability 2.Ecological FunctionsEcological Functions 3.Human Use and InteractionsHuman Use and Interactions

40. How many animals do we want to save? Sanderson’s proposed solution- multilayered approach: 1.Demographic SustainabilityDemographic Sustainability 2.Ecological FunctionsEcological Functions 3.Human Use and InteractionsHuman Use and Interactions 4.Can we return animals to levels that existed before humans had a negative impact?Can we return animals to levels that existed before humans had a negative impact?

41. Instead of a single number…A number for each level can be determined. How many animals do we want to save? 1.Demographic SustainabilityDemographic Sustainability 2.Ecological FunctionsEcological Functions 3.Human Use and InteractionsHuman Use and Interactions 4.Can we return animals to levels that existed before humans had a negative impact?Can we return animals to levels that existed before humans had a negative impact?

42. How many animals do we need to save?