Exam II

Conservation Law, Restoration, Conservation Genetics, Structured Decision Making

Evolution of conservation law in the U.S.

Conservation laws in the U.S. are influenced by several very different philosophies

Preservation

preserving wildness for the sake of the wildness

Dates for Preservation:
1854
1870’s
1872
1892

1854: Henry David Thoreau publishes Walden, which describes a deep appreciation for living with nature
1870’s: John muir begins publishing essays on “oneness with the earth” and the spiritual purity of nature
1872: Yellowstone National Park becomes the first National Park
1892: Sierra Club is formed

John Muir

Believed indigenous people were “primitives” obstructing the nation’s destiny. Leading to the removal and killing of native peoples in Yellowstone and Glacier National Parks.

Conservation

intelligent use of natural resources to sustain yield of resources for future generations

Dates for Conservation:
1887
1891
1901-1909
1905

1887: The first North American conservation organization is formed, the Boone and Crocket Club
1891: The Yellowstone Timberland Reserve (now the Shoshone National Forest) becomes the first “National Forest”
1901-1909: Pres. Theodore Roosevelt ushers in a “new conservationism”
1905: Pres. Roosevelt creates the United States Forest Service

Early conservationists

Believed that indigenous people impeded the progress of the nation and forcibly removed and killed Native Americans

Environmentalism

human health is dependent on a healthy environment and natural resources

Dates of Environmentalism:
1945
1954
1962

1945: Bombing of Hiroshima and Nagasaki brings public awareness to the dangers of radiation
1954: Hydrogen bomb testing on Bikini Atoll reveals the extreme toxicity of radioactive fallout
1962: Rachel Carson publishes Silent Spring on the dangers of DDT

Major developments in the 1960’s-1980’s (mostly out of the Environmental movement)

1964: Pres. Lyndon B. Johnson signs the Wilderness Act, which creates the National Wildlife Refuge system

1970: Clean Air Act

1972: Water Pollution Control Act — amended in 1977 to become the Clean Water Act

1973: Endangered Species Act

1974: Safe Drinking Water Act

1976: Resource Conservation and Recovery Act

1980: Superfund Act

National Park System (P, C, or E)

Preservationist

National Forest Service (P, C, or E)

Conservationist

Clean Air Act (P, C, or E)

Environmental

Clean Water Act (P, C, or E)

Environmental

National Wildlife Refuges (P, C, or E)

Preservationist/Conservationist

National Marine Sanctuaries (for fishing) (P, C, or E)

Conservationist (some preservationist)

Endangered Species Act (P, C, or E)

Environmental

State Park (P, C, or E)

Preservationist

Wildlife Management Area (P, C, or E)

Conservationist

National Monument (P, C, or E)

Preservationist

What other types of legislation can protect biodiversity

1. import/export laws

2. laws that encourage land management

What threatens biodiversity?

1. Habitat loss/fragmentation → pollution

2. overexploitation

3. introduced species

The Endangered Species Act (ESA) 1973

The main function is to identify and protect species that are threatened with extinction

What does the ESA do?

1. Government agencies must consult with the USFWS or NOAA on any activity that might affect listed species

2. Prevents “take” of listed species on private land, trade in listed species, and damage to their habitats

3. Requires agencies to develop recovery plans for listed species

4. Recovery plans need to include explicit recovery goals (e.g., the population size at which the species can be removed from the list), as well as devising a strategy for achieving recovery

Criticisms of the ESA

1. It costs too much

   • loss of income from land that is protected

   • direct cost of recovering species → millions of dollars

2. It limits growth

3. Interferes with landowner rights

4. Cannot help all species

National Environmental Policy Act (1970)

The main function is to promote the enhancement of the human environment. It required federal agencies to assess the environmental effects of their proposed actions prior to making decisions.

NEPA

Requires federal agencies to produce an environmental impact system for any actions likely to have significant effects on the environment.

• Can be VERY long (thousands of pages)

• Must be completed BEFORE the project starts

• Must have public comment

If the agency isn’t sure if an action will have significant environmental effects they can conduct an environmental assessment to determine if it will.

What is restoration?

The process of intentionally altering a site to establish a defined, indigenous, historic ecosystem. The goal of this process is to emulate the structure, function, diversity and dynamics of the specific ecosystem."

Why do we restore?

1. Make the ecosystem like it once was

2. Reduce or remove the need for active management

3. Improve sustainability

4. Improve ecological integrity

5. Imrpove ecological resilience

Approaches to restoration

1. Don’t do anything

2. Reclamation

3. Rehabilitation

4. Partial restoration

5. Complete restoration

Don’t do anything

e.g., allowing a grassland to become a forest, or a secondary forest, or a secondary to become an old-growth forest

Reclamation

alleviating problems to increase the productivity, biodiversity, and ecosystem functionality of land, even if the resulting ecosystem is very different from the historic ecosystem

• typically done following severe degradation (e.g., strip mining, landfill, bulldozing)

• non-native vegetation may be planted when non-native plant communities are better than no plant community

Rehabilitation

a step from reclamation, this process makes an attempt to restore the historic ecosystem but is severely limited often due to logistics/feasibility

Partial restoration

restoration of some but not all of the historic ecosystem

• most common

Complete restoration

total restoration of the historic ecosystem

• very difficult

Steps for restoration — part 1

1. Assess a need for action

   • inventory and describe

   • do we need a clean-up? or restoration?

2. Identify and prioritize goals and objectives

3. Conduct an experiment!

Steps for restoration — part 2

1. Assess a need for action

   • inventory and describe

   • do we need a clean-up? or restoration?

2. Identify and prioritize goals and objectives

3. Conduct an experiment!

4. Following analysis of results, commence adaptive management

Inner learning loop 1

small changes to strategies and plans are made in response to learning in between major plannings reviewsI

Inner learning loop 2

Aspects of monitoring are refined in between planning reviews

Inner learning loop 3

Aspects of implementation are refined in between planning reviews in response to monitoring

Outer learning cycle

Long-term goals, plans, and action are reviewed and modified in response to learnings

Scale is a major limitation restoration

• most restoration efforts are small and site-specific

• many restoration needs are broad and long-term

Multi-pronged appraoch to conservation

• Nature reserves (with varying levels of use) that have been restored or maintained at a suitable level of “wildness”, following by adaptive management

• sustainable use of human-occupied land, often involving some degree of restoration then adaptive management

What does sustainable use of human-occupied land look like?

Working with communities and individual landowners to develop more sustainable approaches to balance human life and ecosystem health

Examples of human-occupied land

• fish ladders on dams

• devices to limit bycatch on boats

• green/blue spaces in urban centers

• night lighting regulations

• agriculture

  • wetlands and prairies are often targeted bc of their rich soil and apparent “worthlessness” for humans

Example of agriculture & conservation 

shade grown money

“Sharing” land between agriculture and conservation creates tradeoffs

• using less chemicals, or modifying agriculture to meet the needs of wildlife often results in a reduction in yield (at least in the short-term)

  • e.g., shade coffee: yield is lower with less sun

• with a growing human population, can we afford to decrease yield?

Land sharing

modify methods to benefit wildlife

• typically, incentive (payment, tax benefit) programs are created to encourage farmers to take this approach

• this approach basically amounts to paying farmers to farm inefficiently

Land sparing

farm as intensively as possible on less land

• in theory this would allow more land to be set aside for biodiversity

• to date, most studies suggest that land sparing is the better approach

• BUT sparing only works if land is truly protected and not just used for more agriculture or urbanization

land sharing vs. land sparing

Both approaches could be used in tandem if we can identify ways to increase wildlife use of farmland that does not reduce crop yield

Conservation Genetics

a combination of ecology, molecular biology, mathematical modeling and evolutionary taxonomy

using genetic theory and techniques to reduce the risk of extinction

Genetic problems are more likely in small populations. WHY?

low genetic variation → inbreeding

Inbreeding

in small populations, individuals are more likely to be related and mate with close relatives

(causes inbreeding depression and decreased adaptive potential)

Inbreeding depression

reduced fitness of offspring

• increased probability that offspring will be homozygous for a deleterious recessive gene

Adaptive potential

reduced genetic (and thus phenotypic) variation for selection to act upon

this is especially important given the current fast pace of environmental changes

homozygous

having two copies of the same allele for a gene

heterozygous

having two different alleles of a gene

genetic drift

a random (neutral) process that leads to changes in the genetic makeup of a population

DIFFERENT from natural selection

has a stronger effect on small populations, causing a loss of genetic variation

Negative effects of genetic drift

decreases adaptive potential by eroding genetic variation

increases relatedness, which can increase the risk of inbreeding depression

Why is genetic drift stronger in small populations?

In small populations, only a few individuals carry a single allele, increasing the likelihood that the allele will be lost over each generation

Heterozygosity

the probability that an individual will be heterozygous for a given gene/locus

heterozygosity example

H > 0.85

you have a > 85% chance of being a heterozygote

What can heterozygosity tell us?

• indicator for population genetic variability

  • high heterozygosity = a lot of genetic variability

• heterozygosity can also tell us about the structure and history of a population

  • if the observed heterozygosity is lower than expected, it could be due to historic inbreeding (or maybe bottleneck)

  • if heterozygosity is higher than expected, two previously isolated population may have mixed recently

Census population size (N)

the actual population size observed by counting

Effective population size (Ne)

a theoretical measure of how many individuals are contributing their genes to the next generation* sexual

What factors might cause Ne to be smaller than N?

• sexual selection (not everyone might reproduce) — some get more matings

• sex ration skew (may have 50 males but only 2 females)

• environmental conditions to cause skipping of breeding events

• age structure of population (more very old or young who can’t reproduce)

• fluctuations in population size

Effective population size (Ne) is intimately tied to heterozygosity

The change in heterozygosity between generations due to drift can be determined using this formula:

H_t+1 = [1-(1/(2N_e))] * H_t

H_t+1 = [1-(1/(2N_e))] * H_t

H_t = heterozygosity in the current time

H_t+1 = heterozygosity in the next (t+1) generation

N_e = effective population size

Heterozygosity calculation example:
Let’s assume initial heterozygosity of 0.85 (human estimate), and an effective population size of 5

= [1-(1/2×5)]*0.85 = 0.765

Heterozygosity calculation example p2:

Next, let’s assume the same initial heterozygosity (0.85), but an effective population size of 5000

= [1-(1/2×5000)]*0.85 = 0.849915

Heterozygosity calculation example p3:

How about an effective population size of 500,000?

= [1-(1/2×500000)]*0.85 = 0.84999915

Notes about heterozygosity

(1-1/(2Ne)) must always be less than one (bc Ne is always positive, so you will always subtract a positive number from 1)

So, heterozygosity will always decline due to drift

Does genetic variation always decline?

NO!! If drift is the only process affecting genetic variation, then there will always be a decline, but other processes also other.

What evolutionary processes could increase genetic variation?

• natural selection

• mutations

• migrations (easiest to manipulate)

Other processes that increase genetic variation in a population

mutation and immigration

mutation

mutation rate is relatively low

in large populations, the mutation rate can counterbalance the very small losses due to drift

immigration

even relatively low rates of immigration (1 or 2 individuals per generation) can be enough to counter the effects of drift

So how big do populations need to be?
how would we answer this?

real population studies and statistical modeling (MVP/PVA)

Data from real populations for minimum population sizes

Studies of real populations suggest at least a few hundred individuals, but it probably depends on the species

• some species can last for a long time with very small populations

• in most cases, at least a few 100 individuals are needed for a population to last > 100 years

• but there are not many long-term data sets. so these estimates may not be very good

MVP

a minimal viable population, the smallest population having a 99% chance of remaining extant for 1000 years

any thorough assessment of population viability or MVP needs to consider each of these things — a target population size should be one that is large enough to withstand the worst conditions

Difference sources population vulnerability

• demographic 

• environmental 

• genetic stochasticity

• natural catastrophes

Minimum viable population size rule of thumb

estimates based on minimum viable population analyses led to the “50/500 rule”

• Ne of 50 needed for short-term avoidance of inbreeding

• Ne of 500 needed for long-term avoidance of negative effects of drift

• Widely misinterpreted (not used as much)

  • Ne was assumed to equal census population

  • Focused on 50 not 500

Population Viability Analysis estimates (statistical model)

estimates based on population viability analysis

• one vertebrate study found that the mean minimum viable population size was about 7300 adults, while the median was about 5800 adults

• the minimum population size was larger for species that have been studied for a long time, probably because long term studies do a better job of describing variability

  • this suggests that estimates based on short-term studies are probably underestimates of the true minimum viable population

Minimum population size — summary

Each of these techniques yielded different estimates (a couple hundred, 500, ~7000)

Overall, studies suggest we need at least several 100, and perhaps several 1000 individuals. But there’s a lot of variation between species/populations

• with no other information, this rule of thumb might be an OK starting point

• but it would be much better to collect the data needed to investigate the species’ individuals case

summary

It is valuable to view management as an experiment (questions)

a) What are the management goals/objectives?

b) What are possible management actions?

c) What are the consequences of those actions?