How many animals do we need to save?

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How many animals do we need to save?
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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
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A population of a few individuals cannot survive
ExtinctionVortex
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Can a number of individuals be set?
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Can a number of individuals be set? Fewest
number of individuals for an area, but fewest
number for what?
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• Can a number of individuals be set?
• Extreme examples
• Ecotourism want the largest possible population
• Mining or Agriculture would like none or
  somewhere elseNIMBY

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

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

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What are the consequences of setting the wrong
number? Subjective values meets objective science
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How many wolves should be in Yellowstone NP
Yellowstone area wolf packs 2004
http//www.forwolves.org/ralph/historical.html
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How many tigers does the world need? None?
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• What criteria do we use to set limits?
• Money
• Land
• Development

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

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• 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?

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• 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?

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

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

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• 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

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• 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

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

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

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

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• 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

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• 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

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• 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

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How many animals do we want to save?
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How many animals do we want to save? Complex
interactions of science, economics, and ethics.
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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.
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How many animals do we want to save? Sandersons
proposed solution
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How many animals do we want to save? Sandersons
proposed solution Minimum Viable Population-
number of individuals that allows animals to
exist free from human interference.
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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.
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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.
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• How many animals do we want to save?
• Sandersons proposed solution- multilayered
  approach
• Demographic sustainability

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• How many animals do we want to save?
• Sandersons proposed solution- multilayered
  approach
• Demographic Sustainability
• Ecological Functions (includes ability to freely
  evolve)

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• How many animals do we want to save?
• Sandersons proposed solution- multilayered
  approach
• Demographic Sustainability
• Ecological Functions
• Human Use and Interactions

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• How many animals do we want to save?
• Sandersons proposed solution- multilayered
  approach
• Demographic Sustainability
• Ecological Functions
• Human Use and Interactions
• Can we return animals to levels that existed
  before humans had a negative impact?

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

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How many animals do we need to save?