Chapter 13: Biodiversity

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• Chapter 13 Biodiversity
• In this chapter the following topics will be
  covered
• Biodiversity and the species concept
• Benefits of biodiversity
• Humans threaten biodiversity
• Biodiversity protection and Endangered Species
  Act
• Ecosystem management and captive breeding
  programs

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• Biodiversity and the Species Concept
• What Is Biodiversity?
• Three kinds of biodiversity
• - Genetic diversity measure of the variety of
  different
• versions of the same genes within individual
  species.
• - Species diversity describes the number of
  different kinds of
• organisms within individual communities or
  ecosystems.
• - Ecological diversity assesses the richness
  and complexity
• of a biological community, including the number
  of niches,
• trophic levels, and ecological processes that
  capture energy,
• sustain food webs, and recycle materials within
  this system.

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• What Are Species?
• Underlying the commonly used definition of a
  species is the idea that reproductive isolation
  caused by geography, physiology, or behavior
  prevents groups of otherwise similar organisms
  from exchanging genes, and therefore, gives them
  separate identities and evolutionary histories.
• Problems exist with species definitions
  based on reproductive isolation.
• - Mating between species occurs in nature and
  may produce
• fertile offspring.
• - Difficulty in determining whether two groups
  that live in
• different places are capable of interbreeding.
• Species identification, therefore, is often
  based on morphological characteristics.
• Determining whether similar groups of
  organisms can be considered separate species is
  highly subjective.
• DNA sequencing technology is revolutionizing
  biological taxonomy.

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• How Many Species Are There?
• The 1.4 million species presently known
  represent only a small fraction of the total
  number that exist.
• Taxonomists estimate that there may be
  somewhere between 3 and 50 million different
  species alive today.
• About 70 of all known species are
  invertebrates.
• Of all of the world's species, only 10 to 15
  percent live in North America and Europe.
• The centers of greatest biodiversity tend to
  be in the tropics, especially tropical
  rainforests and coral reefs.

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Table 13.1. -- Approximate numbers of known
living species by taxonomic group Bacteria and
cyanobacteria 5,000 Protozoa
(single-celled animals) 31,000 Algae
(single-celled plants) 27,000 Fungi (molds,
mushrooms) 45,000 Multi-cellular plants
250,000 Sponges
5,000 Jellyfish, corals, anemones 10,000
Flatworms (tapeworms, flukes) 12,000
Roundworms (nematodes, hookworms) 12,000
Earthworms and leeches 12,000 Clams,
snails, slugs, squids, octopuses 70,000
Insects 750,000 Mites,
ticks, spiders, crabs, shrimp, centipedes,
120,000 and other non-insect arthropods
Starfish, sea urchins 6,000 Fish and
sharks 22,000 Amphibians 4,000
Reptiles 6,000 Birds 9,000
Mammals 4,000 TOTAL
1,400,000
















Total
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• How Do We Benefit from Biodiversity?
• Food
• All of our food comes from other organisms.
• Plants can contribute to our food supply
  either as they are or as a
• source of genetic material to improve domestic
  crops.
• Unfortunately, overgrazing, forest clearing,
  conversion of natural
• landscapes to agriculture, and other forms of
  disturbance are destroying potentially valuable
  food species and their genes.

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• Drugs and Medicines
• Living organisms provide us with many useful
  drugs and medicines
• - More than half of all prescriptions contain
  some natural products.
• - The value of pharmaceutical products derived
  from Third
• World plants, animals, and microbes is estimated
  to be more
• than 30 billion/year.
• Pharmaceutical companies are actively
  prospecting for useful
• products in many tropical countries.

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• Ecological Benefits
• Many processes all depend on the
  biodiversity of life.
• - Soil formation
• - Waste disposal
• - Air and water purification
• - Nutrient cycling
• - Solar energy absorption
• - Management of biogeochemical and hydrological
  cycles
• Controversy exists about the role of
  biodiversity in ecosystem
• stability.
• Dramatic effects can result from removing
  seemingly
• insignificant members of biological communities
  (e.g. pest control).

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• Aesthetic and Cultural Benefits
• The diversity of life on this planet brings
  us many aesthetic and
• cultural benefits (e.g. hunting, fishing,
  camping, hiking, wildlife watching, and other
  outdoor activities).
• In some cultures, nature carries spiritual
  connotations.
• Nature appreciation is economically
  important.
• - The U.S. Fish and Wildlife Service estimates
  that Americans
• spend 104 billion every year on
  wildlife-related recreation. - Ecotourism can
  be a good form of sustainable economic
  development.
• Many people believe in existence value which
  is simply knowing
• that a species exists is reason enough to protect
  and preserve it.
• Many religious groups have called for
  protecting nature because it is
• God's creation.

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• What Threatens Biodiversity?
• Extinction the elimination of a species is a
  normal process of the
• natural world.
• Human impacts on populations and ecosystems
  have accelerated the
• rate of extinction.
• Natural Causes of Extinction
• More than 99 of all species that ever
  existed are now extinct.
• Most species were gone long before humans
  came on the scene.
• Periodically, mass extinctions have wiped
  out vast numbers of
• species and even whole families.
• - Disappearance of dinosaurs during the
  Cretaceous period
• - During the Permian period about
  two-thirds of all marine species
• and nearly half of all plant and animal
  families died out.
• - Current theories suggest that these
  catastrophes were caused by
• climate changes.

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• Human-Caused Reductions in Biodiversity
• Between 1600 A.D. and 1850, human activities
  appear to have been responsible for extermination
  of two or three species per decade.
• Some estimates suggest that we are losing
  species at thousands of times natural rates.
• Habitat Destruction
• - Biggest reason for the current increase in
  extinctions is habitat
• loss.
• - Habitat fragmentation divides populations
  into isolated groups.
• - Destruction of forests, wetlands, and other
  biologically rich
• ecosystems threatens to eliminate thousands or
  even millions of
• species.

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• Hunting and Fishing
• - Overharvesting is responsible for depletion
  of many species
• - Passenger pigeon - hunting and habitat
  destruction.
• - American Bison - harvested for their hides
  or tongues.
• - Whales - blubber was highly prized as a
  source of oil.
• - Fish stocks - at least three-quarters of all
  commercial
• oceanic species are over-harvested (e.g. shark,
  billfish,
• shrimp, orange roughy, groupers, groundfishes,
  sea
• scallops, bluefin tuna, and red snapper).

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• Commercial Products and Live Specimens
• - In addition to harvesting species for food,
  we also obtain a
• variety of valuable commercial products from
  nature
• - Some forms of commercial exploitation are
  highly destructive
• Despite bans on trade in products
  from endangered
• species, smuggling of furs, hides, horns, live
  specimens, and folk medicines amount to
  millions of dollars/year.
• - Developing countries with the richest
  biodiversity are the main
• sources of wild animals.
• - Profits to be made in wildlife smuggling are
  enormous.
• - Elephants, killed for their ivory tusks, are
  an important example
• of the problems and complexities of wildlife
  trade.
• In 1980, there were about 1.3
  million African elephants
• a decade later only half were left.
• - In contrast, South African has been very
  successful in
• conserving elephants.
• Herds have had to be thinned regularly to
  keep them
• from destroying their habitat.
• - Plants are also threatened by overharvesting
  (e.g. wild ginseng
• and cactus).

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• Predator and Pest Control
• - Some animal populations have been greatly
  reduced or
• exterminated because they are regarded as
  dangerous to
• humans or livestock or because they compete
  with our use of
• resources.
• Some animals are deliberately
  trapped, poisoned, or
• shot (e.g. coyotes).
• Some animals are killed unintentionally by
  poisoned
• bait or misplaced traps.

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• Exotic organisms
• - Organisms introduced into habitats where they
  are not native.
• - One of the greatest threats to
  native biodiversity.
• - Many examples of exotic organisms
  exist.
• Kudzu vine - smothers everything
  in its path, kills trees,
• pulls down utility lines.
• Leafy spurge - reduces carrying
  capacity of the western
• range because cattle can't eat it and it
  crowds out native
• grasses and forbes.
• Purple loosestrife - it crowds
  out indigenous vegetation and reduces
  biodiversity in wetlands.
• Zebra mussels - have reached
  enormous densities
• covering fish spawning beds, smothering
  native
• mollusks in all the Great
  Lakes.
• Round goby - devours the eggs
  and fry of any species that shares their
  territory. One benefit is that this species
  voraciously eat zebra mussels.
• Asian long-horned beetles - the
  larvae burrow into living tree trunks where
  they cut off sap flow between leaves and roots.
• - America also sends exotic species
  to other places.

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• Diseases
• - Disease organisms, or pathogens, may be
  considered predators.
• - The balance between pathogen and
  host does not exist when it
• is introduced into a new environment
  resulting in an epidemic.
• American chestnut and the
  introduction of fungal blight by China.
• Trout and the exotic microorganism called
  Myxobolus cerebralis.
• Pollution
• - Toxic pollutants can have disastrous effects
  on local
• populations.
• Pesticide-linked declines of
  fish-eating birds and falcons
• in the 1970s.
• Declines of marine mammals, alligators, and
  fish suggest complex interrelations between
  pollution and health.
• Lead poisoning in
  bottom-feeding waterfowl, swans, and cranes
  that ingest spent shotgun pellets that fall into
  lakes and marshes. Scavengers, such as
  condors and bald eagles, eat birds and
  mammals that have ingested lead shot.

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• Genetic Assimilation
• - Rare and endangered species may be threatened
  by genetic assimilation because they
  crossbreed with closely related species that
  are more numerous or more vigorous.
• - Opportunistic plants or animals introduced
  into a habitat may genetically overwhelm
  local populations.

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• Endangered Species Management and Biodiversity
  Protection
• Parks, wildlife refuges, nature preserves,
  zoos, and restoration
• programs have been established to protect nature
  and rebuild depleted populations.

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• Hunting and Fishing Laws
• By the 1890s most states had enacted some
  hunting and fishing
• restrictions.
• - Idea behind these restrictions was to conserve
  the resource for
• future human use rather than to preserve
  wildlife for its own sake.
• The wildlife regulations and refuges
  established since that time have
• been remarkably successful for many species.
• - White-tailed deer have increased from half a
  million at the turn
• of the century to 14 million today.
• - Wild turkeys and wood ducks were
  nearly all gone fifty years
• ago, but through restoration efforts have
  been restored to several million each.

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• Endangered Species Act
• Committee on the Status of Endangered
  Wildlife in Canada was established in 1976.
• U.S. Endangered Species Act (ESA) was
  established in 1973.
• Endangered species those considered in
  imminent danger of extinction.
• Threatened species those that are likely to
  become endangered, at least locally.
• Vulnerable species those that are naturally
  rare or have been locally depleted by human
• activities to a level that puts them at risk.
• Sought to identify all endangered species
  and populations and to save as much biodiversity
  as
• possible, regardless of its usefulness to humans.
  
• Regulates a wide range of activities
  involving endangered species.
• - Taking (harassing, harming, pursuing etc...)
  either accidentally or on purpose.
• - Importing into or exporting out of
  the United States.
• - Possessing, selling, transporting,
  or shipping.
• - Selling or offering for sale any
  endangered species.
• Violators of ESA are subject to fines up to
  100,000 and one year imprisonment.
• Currently, the United States has 1500
  species on its endangered and threatened species
  list
• and about 500 candidate species waiting to be
  considered.
• - Although invertebrates make up about
  three-quarters of all known species, they
• account for only 9 percent of those deemed
  worthy of protection.

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Table 13.4 -- Endangered and threatened species,
U.S. and foreign, listed by USFWS
Mammals 331 Birds 267
Reptiles 112 Amphibians 22
Fish 113 Invertebrates 135
Plants 520 Source Data from United States
Fish and Wildlife Service, 1999


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• Recovery Plans
• Once a species is listed as endangered, the
  Fish and Wildlife Service is required to
• prepare a recovery plan detailing how populations
  will be rebuilt to sustainable levels.
• The United States currently spends about
  150 million per year on endangered
• species protection and recovery.
• Some recovery plans have been very
  successful.
• - American alligators - Florida alone estimates
  that it has at least 1 million.
• - Bald eagles - in 1999 were declared recovered
  and removed from the list.
• Opponents of the ESA have tried to require
  that economic costs and benefits be
• incorporated into endangered species planning.
• - An important example is that of the northern
  spotted owl whose protection
• depends on preserving old-growth forest in the
  Pacific Northwest. Economists
• estimate that saving a population of 1600 to
  2400 owls would cost 33 billion,
• with most of the losses borne by local companies
  and residents of Washington
• and Oregon.
• - An even more costly recovery program may be
  required for Columbia River
• salmon and steelhead endangered by hydropower
  dams and water storage
• reservoirs that block their migration to the sea.

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• Private Land and Critical Habitat
• Private land is essential in endangered
  species protection.
• Eighty percent of the habitat for more than
  half of all listed species is on nonpublic
• property.
• Many people are resistant to restrictions on
  how they use their own property to
• protect what they perceive to be insignificant or
  worthless organisms.
• - This is particularly true when the land
  has potential for economic
• development.
• Habitat conservation plans (HCP) landowners
  are allowed to harvest resources or
• build on part of their land as long as the
  species benefits overall.
• - Purpose of HCPs is to try and to avoid
  controversy's like the northern
• spotted owl.
• - About 250 HCPs have been approved and 200
  more are in progress.
• Total of 7 million ha of land
  are covered by these plans.
• - Scientists and environmentalists often are
  critical of HCPs, claiming these
• plans often are based more on politics than
  biology.

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• Reauthorizing the Endangered Species Act
• The ESA officially expired in 1992.
• Since then, Congress has debated many
  alternative proposals from
• outright elimination to substantial strengthening
  of the act.
• Proposals for a new ESA generally fall into
  one of two general
• categories.
• - Environmentalists encourage an ecosystem and
  habitat protection approach rather than
  focusing on individual
• species.
• - ESA opponents want to allow
  exceptions to critical habitat designation.
  Under their proposals, only the least costly,
  most cost effective or least burdensome
  measures would be taken to protect endangered
  organisms.

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• Minimum Viable Populations
• A critical question in all recovery programs
  is the minimum population size
• required for long-term viability of rare and
  endangered species.
• A small number of individuals can undergo
  catastrophic declines due to
• environmental change, genetic problems, or simple
  random events when isolated in a limited
  geographic range.
• - Described as island biogeography in the work
  of R. H. MacArthur and E.O.
• Wilson in 1967 who proposed that species
  diversity is a balance between colonization
  and extinction rates.
• An island far from a population
  source has a lower rate of
• colonization than a nearer island because it
  is harder to reach.
• A large island can support more individuals
  of a given species and
• is less likely to suffer extinction due to
  natural catastrophes, genetic
• problems, or demographic uncertainty - the
  chance that all members
• of a single generation will be of the same
  sex.

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• For many species loss of genetic diversity
  causes a variety of harmful effects that
• limit adaptability, reproduction, and species
  survival.
• - Founder effect occurs when a few individuals
  establish a new population.
• - Demographic bottleneck arises when
  only a few individuals survive some
• catastrophe.
• - Genetic drift reduction in gene
  frequency in a population due to unequal
• reproductive success.
• - Inbreeding mating of closely
  related individuals which can result in random,
• recessive, and deleterious mutations.
• Not all species are harmed by the lack of
  genetic diversity (e.g. the northern
• elephant seal)

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• Habitat Protection
• A growing number of scientists, land
  managers, policymakers, and developers have
• been making the case that it is time to focus on
  a rational, continent-wide preservation of
  ecosystems that support maximum biological
  diversity rather than a
• species-by-species battle for the rarest or most
  popular organisms.
• A leader of this new form of conservation is
  J. Michael Scott, who was the project
• leader of the California condor recovery program
  in the mid-1980s and had spent ten years working
  on endangered species in Hawaii.
• - Scott discovered that even Hawaii has
  many vegetation types completely
• outside of natural preserves.
• - The gaps between protected areas may
  contain more endangered species than are
  preserved within them.
• - Gap analysis approach in which
  conservationists and wildlife managers look
  for unprotected landscapes that are rich
  in species.
• Conservation biologist, R.E. Grumbine
  suggests four remanagement principles for
• protecting biodiversity in a large-scale,
  long-range approach.
• - Protect enough habitat for viable
  populations of all native species in a given
• region.
• - Manage at regional scales large
  enough to accommodate natural disturbances.
• - Plan over a period of centuries so
  that species and ecosystems may continue to
  evolve.
• - Allow for human use and occupancy at
  levels that do not result in significant
• ecological degradation.

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• International Wildlife Treaties
• The 1975 Convention on International Trade
  in Endangered Species
• (CITES) was a significant step toward worldwide
  protection of endangered flora and fauna.
• - Regulated trade in living specimens and
  products derived from
• listed species.
• - Species are still smuggled out of countries
  where they are
• threatened or endangered and documents are
  made to appear
• they have come from areas where the species
  are still common.
• - Difficult to regulate in developing countries
  where wildlife is
• disappearing most rapidly.

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• Zoos, Botanical Gardens, and Captive Breeding
  Programs
• Records of wildlife and exotic plant
  collections date back to the
• beginning of history.
• In some places low-life circuses and seedy
  roadside tourist
• attractions still exhibit sad collections of
  animals in cramped,
• unhealthy cages.
• In developed countries, cruel and callous
  conditions have been
• eliminated by animal welfare laws.
• Most modern zoos and wildlife parks now keep
  animals in clean and
• humane conditions.
• Many animals living will live longer and
  raise more young than they
• would in the wild.
• Valuable genetic traits are preserved in
  repositories such as botanical
• gardens for rare and endangered plant species.
• - May be reintroduced into native habitats
  after being cultivated
• in these gardens.

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• New Zoos and Game Parks
• Large enclosures, realistic terrain, and
  multi-species groupings allow
• more normal social behavior and encourage
  reproduction.
• Under these new conditions, zoos can be
  important places for
• scientific research in wildlife biology.
• Today in the United States some 150
  municipal zoos provide the
• only experience that people will ever have with
  wild animals.
• 110 million visitors per year learn about
  nature through visits to
• zoos.

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• Captive Breeding and Species Survival Plans
• Most mammals in North American zoos are now
  produced by
• captive breeding programs.
• These programs have limitations in that not
  all animals reproduce
• well in captivity.
• Worldwide, zoos house about 500,000
  individual animals, but only
• about 900 species total.
• - Few of these animals are maintained in
  populations large
• enough to preserve the species indefinitely
  if wild
• populations were lost.
• To reduce genetic problems, zoos often
  exchange animals or ship
• individuals long distances to be bred.

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• Saving Rare Species in the Wild
• The Minnesota Zoo and the Ujung Kulon
  National Park in
• Indonesia are trying to save the world's few
  remaining
• Javanese rhinos in their native habitat rather
  than bring them back to the zoo.