How many animals do we need to save?

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

Extinction Vortex A population of a few individuals cannot survive

Can a number of individuals be set?

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

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

What are the consequences of setting the wrong number? Too high Too low

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

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

Yellowstone area wolf packs 2004 How many wolves should be in Yellowstone NP

How many tigers does the world need? None?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

How many animals do we want to save?

Complex interactions of science, economics, and ethics.

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.

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

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.

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.

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.

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

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

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

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

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

How many animals do we need to save?

Skills needed for the exams:

1. Understand material from lecture. Quizzes can help diagnose. Be self-critical and skeptical. Skills needed for the exams:

1. Understand material from lecture. 2. Be able to apply the information. Skills needed for the exams:

2. Be able to apply the information. Lecture is presented linearly, but applying the information may mean seeing it non- linearly. Skills needed for the exams:

3. Communicate what you know. If I answered your question with what you wrote down, would it make sense? Skills needed for the exams:

1. Understand material from lecture. 2. Be able to apply the information. 3. Communicate what you know. Skills needed for the exams: