Chap.19 Extinction, Conservation and Restoration

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Chap.19 Extinction, Conservation and Restoration

• Ecology 2000

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• 19.1 Extinction is a natural process that
  expresses the failure of species to adapt.
• 19.2 The risk of extinction is affected by
  population size, geographic range, age structure
  and spatial arrangement.
• 19.3 Body size, longevity, and population size
  interact to affect the risk of extinction.

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• 19.4 Patterns of distribution among and within
  islands suggest that extinction may result from a
  decrease in competitive ability.
• 19.5 When conservation is no longer possible,
  restoration is sometimes an option.
• 19.6 The metapopulation concept is central to
  conservation biology.

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• 19.7 Recovery plans are based on the life history
  characteristics of the endangered species.
• 19.8 Managing genetic diversity is an essential
  part of conservation and restoration.
• 19.9 Restoration often involves the
  reintroduction of species.

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19.1Extinction is a natural process that
expresses the failure of species to adapt.

• Extinction is a natural process that expresses
  the failure of species to adapt.
• In 1810, the American ornithologist Alexander
  Wilson observed an immense flock of passenger
  pigeons in the Ohio river Valley.
• Wilson estimated that there were more than 2
  billion birds.
• With its extinction on September 1, 1914, the
  passenger pigeon joined a growing list of species
  that have vanished from the Earth.

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Extinction

• It has been estimated that 99.9 of all species
  that have ever lived are now extinct.
• The several million species of plants and animals
  living today are derived from a small fraction of
  those alive at any time in the distant past.
• At least three times in the past 570 million
  years the earth has experienced a series of
  extinction so devastating that 50 or more of the
  species on earth disappeared.

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The first mass extinction

• The first occurred about 245 million years ago at
  the end of the Paleozoic era(Permian period), at
  a time coinciding with great geologic upheaval
  associated with the movement of continental
  landmasses.
• It is estimated that about 90 of the earth's
  species were exterminated during this time.

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The second and the third mass extinction

• The second occurred about 65 million years ago,
  at the end of the age of the dinosaurs, the
  Mesozoic era (Cretaceous period).
• Over half of all the species on earth, including
  the dinosaurs, went extinct during this time.
• A third mass extinction is now under way, one
  that is primarily the result of the activities of
  humankind.

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Types of Extinction

• Background extinction reflects the fact that as
  ecosystems change, some species disappear and
  others take their places. This turnover of
  species, which occurs at a relatively low rate,
  appears to be a normal characteristic of the
  natural world.
• Mass extinction refers to the dying off of large
  numbers of species as a result of natural
  catastrophes.

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Anthropogenic extinction

• Anthropogenic extinction is extinction caused by
  humans. It is similar to mass extinction in the
  number of taxa affected and in its global
  dimensions and catastrophic nature.

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Psudo- vs. true extinction

• Disappearances may occur in two ways.
• (1) species may evolve sufficiently that
  individuals are no longer recognized as belonging
  to the same taxon as their ancestors and are
  given a different scientific name. This is
  referred to as pseudo-extinctions.
• (2) a species may cease to exist, in which case
  its disappearance from the fossil record is a
  case of true extinction.

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Causes of Extinction

• ?? heath hen (Tympanuchus cupido)
• At the time of the arrival of Europeans in North
  America, the heath hen was distributed throughout
  much of the area of New England and south into
  Virginia.
• It was fairly common and abundant throughout its
  range.
• Hunting pressure and habitat alteration increased
  dramatically with the arrival of the Europeans,
  and by the early 1900s, the heath hen was
  restricted to one place, Martha's Vineyard.

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The extinction of heath hen

• Concern about the survival of the species
  resulted in the establishment of a protected
  refuge in 1907, and the population began to
  increase.
• A disastrous fire during the nesting season
  destroyed many nests, and a subsequent
  predation pressure, followed by an outbreak of
  disease, reduced the population to a handful of
  individuals by 1920.
• The last individual died in 1932.

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Anthropogenic climate changes

• Anthropogenic climate changes may raise
  temperatures between 2oC and 6oC sometime during
  the 21st century.
• This is equal to the warming of the earth's
  climate since the last glaciation, only it is
  happening 50 times faster.
• It is likely to cause the worldwide extinction of
  many species, particularly plants.

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Introduced organisms

• Introduced organisms often wreak havoc on local,
  native species.
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• Nile perch?? Lake Victoria
• brown tree snake??????,???????????
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Habitat loss

• Habitat loss may cause extinction by wiping out
  suitable places to live.

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Economic pressure

• Economic pressures may accelerate the natural
  process of extinction.
• (Fig 19-1)

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Fig. 19-2 The amount of ivory harvested from
African elephants increased dramatically in the
1970s and 1980s, contributing to the decline of
elephant populations during the same time period
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19.2 The risk of extinction is affected by
population size, geographic range, age structure
and spatial arrangement.
Fig. 19-3 Probability of extinction per year as a
function of population size for 39 populations of
birds of the British Isles. As population size
increases, the probability of extinction
decreases.
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Fig. 19-4 Percentage of species going extinct
through time(millions of years) among late
Cretaceous bivalves and gastropods having
geographic distributions of three different sizes.
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Probability of extinction

• When a population is at equilibrium, the
  probability of extinction at a particular time,
  P0(t), may be given as
• P0(t) bt / (1 bt) N,
• where b is the birth rate and N is the population
  size.
• At equilibrium, the birth rate and the death
  rate, d, are equal, bd, and the rate of change
  of the population, dN/dt 0.

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P0(t) bt / (1 bt) N,
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Fig. 19-5 Changes in the probability of
extinction with increasing population size, N,
for three different time periods
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persistence time

• We may think of extinction in terms of the time
  to extinction or persistence time, which is
  generally taken to be the time that elapses
  between the colonization of a site and
  extinction.
• The average time to extinction, T
• T 2/Vc (Kc - a)/c - lnK
• where c 2r/V - 1 and V is the variance in the
  intrinsic rate of increase, r.

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The parameter c decreases as the variance
increases with respect to r.
Fig. 19-6 Relationship between the c 2r/V - 1
and the variance, V. (r 0.2)
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A small population with carrying capacity K1 and
a low V, indicating low environmental
stochasticity, may have a longer time to
extinction.
Fig. 19-7 Lande's model of time to extinction for
r gt V (upper line) and r lt V (lower line).
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Age and spatial structure

• Populations of similar size are likely to differ
  in demographic characteristics such as age
  structure and sex ratio. These characteristics
  can influence the probability of extinction.
• The spatial structure of a population can also
  influence the likelihood of extinction.
• Both age and spatial population structure could
  buffer a population from extinction.

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19.3 Body size, longevity, and population size
interact to affect the risk of extinction.

• The rate at which the population returns to its
  equilibrium is referred t as the resilience of
  the population.
• Pimm (1991) Longevity and body size
• In cases in which population are small, all else
  being equal, large, long-lived animals may be
  exposed to less risk of extinction than small,
  short-lived species.
• In situations in which population are large,
  small, short-lived species should be at an
  advantage owing to their greater resilience.

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19.4 Patterns of distribution among and within
islands suggest that extinction may result from a
decrease in competitive ability.

• Immigrants to islands appear to be excellent
  competitors initially.
• Species that colonize islands are usually
  abundant and widespread on the mainland these
  qualities make good colonizers.
• After an immigrant population becomes established
  on an island, however, its competitive ability
  appears to wane its distribution among habitats
  becomes restricted, and local population
  densities decrease. These trends eventually can
  lead to extinction. Taxon cycle

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The Shiny cowbird expanded its range in the
islands (stage I), the house wren has become
extinct (E) on several island (stage III).
?? I
??
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?? II
?? III
Fig. 19-8 Distribution patterns and taxonomic
differentiation of several birds in the Lesser
Antilles, illustrating progressive stages of the
taxon cycle.
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Fig. 19-9 Relative indices of population density
and ecological distribution of songbirds in the
West Indies as a function of stage of taxon cycle.
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New species and new cycle

• A large number of existing species can evolve
  faster than the new species can adapt to meet
  their evolutionary challenge.
• On the other side, the species may again increase
  and begin a new cycle of expansion throughout the
  island.
• This has occurred many times in the birds
  populations within the West Indies.

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19.5 When conservation is no longer possible,
restoration is sometimes an option.

• Restoration involves not only scientific work,
  but also organization, communication, and the
  necessity of working within the relevant
  political and social establishment.
• Restoration ecology should focuses on restoring
  whole habitats and their consituent biological
  communities, rather than on single populations.

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19.6 The metapopulation concept is central to
conservation biology.

• Habitat fragmentation related to human
  development and expansion is a major reason for
  the decline of many endangered species.
• Thus one of the most daunting challenges of
  conservation efforts is to understand the
  dynamics of spatially structured populations.

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Conservation biology

• The metapopulation and landscape concepts have
  helped shaped the approach to this challenge in
  recent years.
• Theory of island biogeography (chap. 29)
• One aspect of the dynamics of wildlife reserves
  that has received considerable attention is the
  concept of habitat corridors, which are often in
  strips or narrow lanes that connect patches.

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19.7 Recovery plans are based on the life history
characteristics of the endangered species.

• The Endangered Species Act of the United Sates
  requires that a recovery plan be developed for
  each species placed on the endangered species
  list.
• Typically, these plans are prepared by teams of
  ecologists and others, such as representative of
  industry or governmental agencies.

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Recovery plan

• The recovery plan includes an analysis of the
  predicament of the species and proposes
  strategies for its recovery.
• The plan also usually includes an analysis of the
  costs and benefits of the preservation of the
  species.
• The scientific foundation of the plan is based on
  the natural history of the species.

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Fig. 19-10 The woodland caribou (Rangifer
tarandus caribou)
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The dashed line indicates the southern extent of
the main range of the species.
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Fig. 19-11 Distribution of the woodland caribou
in southern Ontario, Canada.
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Fig. 19-12 Flowchart of the planning process
involved in the reintroduction of the woodland
caribou.
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19.8 Managing genetic diversity is an essential
part of conservation and restoration.

• ??
• The lakeside daisy is found in only three small
  populations, two in Ontario and one in northern
  Ohio near Lake Erie (Fig. 19-13)
• The Illinois populations had disappeared by the
  early 1970s. No viable seeds were produced by
  these plants during 1970s, and some of the plants
  were moved to gardens for preservation and study.

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A few remaining living individuals in Illinois
populations, but they cannot produce seeds, their
population is essentially extinct.
Fig. 19-13 Distribution of populations of the
rare and threatened lakeside daisy.
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Restoration plan of daisy

• The restoration plan for the lakeside daisy
  called for the establishment of two populations,
  each having a minimum viable population size of
  about 1,000 plants, a number determined by
  population viability analysis and life history
  study.
• It was estimated that this population size would
  buffer the plats against loss of genetic
  variation.

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Captive breeding in animals

• The Florida panther (?), for examples, is now
  represented by fewer than 50 cats in southern
  Florida.
• The black-booted ferret(?) , California
  condor(??) , and red wolf(?) are other such
  examples.
• Only hope for the preservation of such species is
  through captive breeding programs.

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Captive breeding program

• The success of a captive breeding program depends
  on the preservation of all aspects of behavior
  and physiology that are unique to the species.
• One of the most challenging goals is to maintain,
  even enhance genetic variation in the population.

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The antelopes as a example

• When antelopes(??)are started in the wild, they
  turn quickly away from the disturbance and sprint
  in the opposite direction for some distance, then
  stop and reexamine the situation.
• The behavior is not adaptive in the confinement
  of a zoo, however, where an antelope may sprint
  directly into a fence or wall and suffer great
  injury.

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Captive vs natural evolution

• In zoos, there will be a consequent evolution of
  the antelope herd away from the natural behavior.
  
• If reintroduced into the wild, these animals
  would be expected to fare poorly.
• Considerable effort has been expended to develop
  techniques to minimize such nonadaptive genetic
  change.

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19.9 Restoration often involves the
reintroduction of species.

• ??reintroduction of the swift fox(??) to
  Canadian prairies
• The fox disappeared from Canada in the early
  1930s, and its range has retreated southward
  since that time, owing primarily to the
  destruction of the prairie ecosystem resulting
  from agriculture and development.
• Currently distribution (Fig. 19-14)

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Fig. 19-14 Ranges of the swift fox and kit fox.
Candidate reintroduction sites are number 1
through 4.
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Soft vs hard release

• Two types of release strategies were used.
• Animals were transported the release site and
  placed in pens constructed in the prairie. The
  foxes were held in the pens for several months
  until they bred, after which the adults and young
  were released into the wild.
• This type of release strategy is called a soft
  release.

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Hard release

• Foxes were simply transported from the captive
  breeding area or from source populations to the
  reintroduction site, where they were released.
• This strategy is known as a hard release.
• There appeared to by no difference in survival
  between the two release methods.

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No difference
One of the major concerns of those interested in
conservation is the maintenance of
biodiversity. The principles of ecological
diversity will be discussed in detail in Part 6
as part of our discussion of community ecology.
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Suggested readings (I)

• Burney, D. A. 1993. Recent animal extinctions
  Recipes for disaster. American Scientist
  81240-251.
• Caro, T. M., and M. K. Laurenson. 1994.
  Ecological and genetic factors in conservation A
  cautionary tale. Science 263485-486.
• Ceballos, G., and J. H. Brown. 1995. Global
  patterns of mammalian diversity, endemism, and
  endangerment. Conservation Biology 9559-568.
• Eisner, T., J. Lubchenco, E. O. Wilson, D. S.
  Wilcove, and M. J. Bean. 1995. Building a
  scientifically sound policy for protecting
  endangered species. Science 2681231-1232.
• Glen, W. 1990. What killed the dinosaurs?
  American Scientist 78354-370.

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Suggested readings (II)

• Hansen, A. J., T. A. Spies, F. J. Swanson, and J.
  L. Ohmann. 1991. Conserving biodiversity in
  managed forests. BioScience 41382-392.
• Mills, L. S., M. E. Soule, and D. F. Doak. 1993.
  The keystone-species concept in ecology and
  conservation. BioScience 43219-224.
• Myers, J. P., et al. 1987. Conservation strategy
  for migratory species. American Scientist
  7518-26.
• Redford, K. H. 1992. The empty forest. BioScience
  42412-422.
• Robinson, S. K., et al. 1995. Regional forest
  fragmentation and the nesting success of
  migratory birds. Science 2671987-1990.

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Suggested readings (III)

• Rolston, H., III. 1985. Duties to endangered
  species. BioScience 35718-726.
• Simons, T., S. K. Sherrod, M. W. Collopy, and M.
  A. Jenkins. 1988. Restoring the bald eagle.
  American Scientist 76252-260.
• Soule, M. E. 1985. What is conservation biology?
  BioScience 35727-734.
• Timan, D., and J. A. Downing. 1994. Biodiversity
  and stability in grasslands. Nature 367363-365.
• Westman, W. E. 1990. Managing for biodiversity.
  BioScience 40L26-33.

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