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Conservation Biology. 22 Conservation Biology. Case Study: Can Birds and Bombs Coexist? Conservation Biology Declining Biodiversity Threats to Biodiversity Approaches to Conservation Ranking Species for Protection Case Study Revisited Connections in Nature : Some Burning Questions.

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22 conservation biology
22 Conservation Biology
  • Case Study: Can Birds and Bombs Coexist?
  • Conservation Biology
  • Declining Biodiversity
  • Threats to Biodiversity
  • Approaches to Conservation
  • Ranking Species for Protection
  • Case Study Revisited
  • Connections in Nature: Some Burning Questions
case study can birds and bombs coexist
Case Study: Can Birds and Bombs Coexist?

Decades of bombing at Fort Bragg have inadvertently protected thousands of acres of longleaf pine savanna, and helped save the endangered red-cockaded woodpecker.

Figure 22.1 The Red-Cockaded Woodpecker: An Endangered Species


As the human population has grown, and we have cut, plowed, drained, and dammed, we have destroyed the habitat of many species.

These changes have given rise to a biodiversity crisis.

The Red List of Threatened Species, compiled by the World Conservation Union, lists 16,118 species as threatened with extinction.



Observe, measure, and communicate

Changes in species abundances, distributions, and biological traits that have resulted from human activities.

conservation biology9
Conservation Biology

Concept 22.1: Conservation biology is an integrative discipline that applies the principles of ecology to the conservation of biodiversity.

  • Studies maintenance, loss, and restoration of biodiversity
  • Decisions require several biological disciplines, and law, political science, economics and sociology.
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Conservation Biology

Biodiversity provides hundreds of domesticated and wild species for





building materials,

and decorative items.

conservation biology11
Conservation Biology

Ecosystem services — natural processes that sustain life, such as water purification, soil formation and maintenance, pollination of crops, climate regulation, and flood control.

conservation biology13
Conservation Biology

Many ecologists, such as Dan Janzen, have chosen to speak up, and even refocus their research programs, as they have come to understand the irreversible consequences of the biodiversity crises.

E. O. Wilson began writing about biodiversity and its importance, to bring the issues into the public eye.

declining biodiversity
Declining Biodiversity

Alwyn Gentry devoted his life to identifying, classifying, and mapping the immense diversity of plants in Central and South America.

He was an eyewitness to plant species extinctions as deforestation rapidly destroyed habitat.

Concept 22.2: Biodiversity is declining globally, and Earth’s biota is becoming increasingly homogenized.

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Declining Biodiversity

Current extinction rate estimation relies on:

The species–area relationship.

Changes in the threat status of species (e.g., shift from endangered to critically endangered).

Rates of population decline or range contraction of common species.

declining biodiversity23
Declining Biodiversity

The greatest “losers” among native species tend to be specialists with adaptations that resulted from evolution in a particular place.

The “winners” tend to be generalists with less stringent habitat requirements.

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Declining Biodiversity

The spread of introduced species and native generalists, coupled with decline of native specialists, is leading to taxonomic homogenization of Earth’s biota.

threats to biodiversity
Threats to Biodiversity

Understanding the causes of biodiversity losses is the first step toward reversing them.

For any given species, multiple factors are likely to contribute to decline and extinction.

Concept 22.3: The primary threats to biodiversity are habitat loss and degradation, invasive species, and overexploitation.

threats to biodiversity28
Threats to Biodiversity

Habitat degradation—changes that reduce quality of the habitat for many, but not all, species.

Habitat fragmentation—breaking up of continuous habitat into habitat patches amid a human-dominated landscape.

Habitat loss—conversion of an ecosystem to another use.

threats to biodiversity30
Threats to Biodiversity

Invasive species—non-native, introduced species that sustain growing populations and have large effects on communities.

Of particular concern are invasive species that impact native endangered species.

threats to biodiversity31
Threats to Biodiversity

Example: Zebra mussels have had negative impacts on the freshwater mussels in the order Unionoida.

North America has a third of the world’s Unionoida.

Many species are endemic, and rare, and were already threatened by poor water quality and habitat loss.

threats to biodiversity32
Threats to Biodiversity

The Nile perch was introduced into Lake Victoria in Africa in the early 1960s.

After about 15 years, population size increased, as the native endemic cichlid species declined. As many as 200 cichlid species may have gone extinct.

Before the introduction, cichlids made up 80% of the biomass in the lake; the Nile perch now accounts for 80% of the biomass.

threats to biodiversity34
Threats to Biodiversity

Road-building increases accessibility and facilitates overharvesting, as does the widespread availability of guns.

13 million mammals are killed each year in the Amazon rainforests by hunters.

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Threats to Biodiversity

Overfishing in the oceans has led to declines in top predators, and other species.

Every ton of fish caught by commercial trawlers = 1 to 4 tons of bycatch.

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Threats to Biodiversity

Disease can also contribute to species decline.

Extinction of the Tasmanian wolf in the 1930s was hastened by a disease; Tasmanian devil faces a similar threat.

In North America, decline of the black-footed ferret is worsened by canine distemper.

approaches to conservation
Approaches to Conservation

Should conservation focus on habitat preservation or understanding the biology of threatened species?

The U.S. Endangered Species Act mandates the identification and protection of critical habitat.

Concept 22.4: Conservation biologists use many tools and work at multiple scales to manage declining populations.

approaches to conservation40
Approaches to Conservation

There are two approaches to conservation planning:

Fine-filter (genes/populations/species).

Coarse-filter (landscape/ecosystem/ habitat)—emphasis on maintaining ecosystem processes; protects many species at once.

approaches to conservation41
Approaches to Conservation

Small populations


genetic drift and inbreeding

loss of genetic variability and fixation of deleterious alleles.

approaches to conservation42
Approaches to Conservation

Cheetahs = extremely low diversity.

Low sperm counts

Poor reproductive success (wild and captive)

Genetic bottleneck in the Pleistocene


Figure 22.15 Molecular Genetic Can Identify the Origin of Organisms Intercepted in Illegal Trade

approaches to conservation44
Approaches to Conservation


Population viability analysis (PVA) allows ecologists to assess extinction risks and evaluate management options.

The probabilities of population persistence are calculated under various scenarios.

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Approaches to Conservation

PVA is used to:

Assess risk of extinction of a population.

Identify particularly vulnerable age or stage classes.

Determine how many organisms needed to establish a new population.

Determine what might be a safe number of animals or plants to harvest.


Figure 22.16 Ex Situ Conservation Efforts Can Rescue Species from the Brink of Extinction

approaches to conservation47
Approaches to Conservation

The ESA currently protects 1,300 native species.

It also regulates trade in endangered species as a result of an international treaty, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

ranking species for protection
Ranking Species for Protection

How do we allocate limited resources for species protection?

Do we protect all threatened species, or only ones with large ecological roles?

Which habitats are most critical to protect?

Concept 22.5: Prioritizing species helps maximize the biodiversity that can be protected with limited resources.

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Ranking Species for Protection

The World Conservation Union began assessments of conservation status in 1963 with the red-listing process.

The Nature Conservancy established the Natural Heritage Program (now NatureServe) in the early 1970s to assess conservation status of American species.

ranking species for protection52
Ranking Species for Protection

A flagship species is a charismatic organism that people will want to give protection to, such as the giant panda.

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Ranking Species for Protection

Umbrella species—selected with the assumption that protection of its habitat will serve as an “umbrella” to protect many other species with similar habitat requirements.

They usually have large ranges (grizzly bear) or specialized habitats (red-cockaded woodpecker), or are easy to count (butterflies).

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Ranking Species for Protection

Several focal species are selected for their different ecological requirements or susceptibility to different threats.

By thus casting a broader net, we improve the chances of protecting regional biodiversity.