Download Chap.19 Extinction, conservation and restoration

Extinction,
Conservation and
Restoration
Chap.19
Ecology 2000
目錄
• 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.
2
Chap.19 conservation & restoration
目錄
• 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.
3
Chap.19 conservation & restoration
目錄
• 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.
4
Chap.19 conservation & restoration
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.
5
Chap.19 conservation & restoration
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.
6
Chap.19 conservation & restoration
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.
7
Chap.19 conservation & restoration
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.
8
Chap.19 conservation & restoration
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.
9
Chap.19 conservation & restoration
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.
10
Chap.19 conservation & restoration
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 pseudoextinctions.
• (2) a species may cease to exist, in which
case its disappearance from the fossil
record is a case of true extinction.
11
Chap.19 conservation & restoration
Causes of Extinction
• 範例： 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.
12
Chap.19 conservation & restoration
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.
13
Chap.19 conservation & restoration
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.
14
Chap.19 conservation & restoration
Introduced organisms
• Introduced organisms often wreak havoc
on local, native species.
• 範例：
– Nile perch引入 Lake Victoria
– brown tree snake意外引入關島，造成許多本土鳥類
滅絕。
– 夏威夷的外來種入侵，許多特有鳥類和蝸牛滅絕。
連帶造成一些植物滅絕。
15
Chap.19 conservation & restoration
Habitat loss
• Habitat loss may cause extinction by wiping
out suitable places to live.
16
Chap.19 conservation & restoration
Economic pressure
• Economic
pressures may
accelerate the
natural process
of extinction.
• (Fig 19-1)
17
Chap.19 conservation & restoration
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
18
Chap.19 conservation & restoration
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.
19
Chap.19 conservation & restoration
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
20
Chap.19 conservation & restoration
sizes.
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, b=d, and the rate of
change of the population, dN/dt = 0.
21
Chap.19 conservation & restoration
P0(t) =
[ bt / (1 + bt) ] ，
族群愈小，滅
絕機率愈大。
22
Fig. 19-5 Changes in the probability of extinction
with increasing population size, N, for three
Chap.19 conservation & restoration
different time periods
N
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
[ (K
c
- a)/c - lnK
]
– where c = 2r/V - 1 and V is the variance in the
intrinsic rate of increase, r.
23
Chap.19 conservation & restoration
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)
24
Chap.19 conservation & restoration
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 > V
(upper line) and r < V (lower line).
25
Chap.19 conservation & restoration
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.
26
Chap.19 conservation & restoration
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.
27
Chap.19 conservation & restoration
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
28
Chap.19 conservation & restoration
The Shiny
cowbird
expanded its
range in the
islands
(stage I), the
house wren
has become
extinct (E)
on several
island (stage
III).
29
階段 I
絕跡
亞種
階段 II
階段 III
Fig. 19-8 Distribution patterns and taxonomic differentiation
of several birds in the Lesser Antilles, illustrating
Chap.19
restoration
progressive stages of
theconservation
taxon&cycle.
30
Chap.19 conservation & restoration
31
Fig. 19-9 Relative indices of population density
and ecological distribution of songbirds in the
Chap.19 conservation & restoration
West Indies as a function
of stage of taxon cycle.
32
Chap.19 conservation & restoration
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.
33
Chap.19 conservation & restoration
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.
34
Chap.19 conservation & restoration
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.
35
Chap.19 conservation & restoration
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.
36
Chap.19 conservation & restoration
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.
37
Chap.19 conservation & restoration
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.
38
Chap.19 conservation & restoration
Fig. 19-10 The woodland caribou (Rangifer tarandus caribou)
39
Chap.19 conservation & restoration
The dashed line indicates the southern extent of
the main range of the species.
殘餘
再引入
Fig. 19-11 Distribution of the woodland caribou in southern
Ontario, Canada.
40
Chap.19 conservation & restoration
經費足夠
棲息地有無
可以再引入
Fig. 19-12 Flowchart of the
planning process involved
in the reintroduction of the
woodland caribou.
41
Chap.19 conservation & restoration
19.8 Managing genetic diversity is an essential
part of conservation and restoration.
範例
• 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.
42
Chap.19 conservation & restoration
尚存的
過期的
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.
43
Chap.19 conservation & restoration
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.
44
Chap.19 conservation & restoration
Captive breeding in animals
• The Florida panther (豹), for examples, is
now represented by fewer than 50 cats in
southern Florida.
• The black-booted ferret(貂) , California
condor(兀鷹) , and red wolf(狼) are other
such examples.
• Only hope for the preservation of such
species is through captive breeding
programs.
45
Chap.19 conservation & restoration
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.
46
Chap.19 conservation & restoration
The antelopes as a example
• When antelopes(羚羊)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.
47
Chap.19 conservation & restoration
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.
48
Chap.19 conservation & restoration
19.9 Restoration often involves the
reintroduction of species.
範例：reintroduction of the swift fox(狐狸) 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)
49
Chap.19 conservation & restoration
Fig. 19-14 Ranges of the swift
fox and kit fox.
Candidate reintroduction
sites are number 1 through 4.
50
Chap.19 conservation & restoration
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.
51
Chap.19 conservation & restoration
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.
52
Chap.19 conservation & restoration
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.
53
Chap.19 conservation & restoration
Suggested readings (I)
• Burney, D. A. 1993. Recent animal extinctions: Recipes for
disaster. American Scientist 81:240-251.
• Caro, T. M., and M. K. Laurenson. 1994. Ecological and
genetic factors in conservation: A cautionary tale. Science
263:485-486.
• Ceballos, G., and J. H. Brown. 1995. Global patterns of
mammalian diversity, endemism, and endangerment.
Conservation Biology 9:559-568.
• 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 268:1231-1232.
• Glen, W. 1990. What killed the dinosaurs? American
Scientist 78:354-370.
54
Chap.19 conservation & restoration
Suggested readings (II)
• Hansen, A. J., T. A. Spies, F. J. Swanson, and J. L.
Ohmann. 1991. Conserving biodiversity in managed
forests. BioScience 41:382-392.
• Mills, L. S., M. E. Soule, and D. F. Doak. 1993. The
keystone-species concept in ecology and conservation.
BioScience 43:219-224.
• Myers, J. P., et al. 1987. Conservation strategy for
migratory species. American Scientist 75:18-26.
• Redford, K. H. 1992. The empty forest. BioScience 42:412422.
• Robinson, S. K., et al. 1995. Regional forest fragmentation
and the nesting success of migratory birds. Science
267:1987-1990.
55
Chap.19 conservation & restoration
Suggested readings (III)
• Rolston, H., III. 1985. Duties to endangered species.
BioScience 35:718-726.
• Simons, T., S. K. Sherrod, M. W. Collopy, and M. A.
Jenkins. 1988. Restoring the bald eagle. American
Scientist 76:252-260.
• Soule, M. E. 1985. What is conservation biology?
BioScience 35:727-734.
• Timan, D., and J. A. Downing. 1994. Biodiversity and
stability in grasslands. Nature 367:363-365.
• Westman, W. E. 1990. Managing for biodiversity.
BioScience 40L26-33.
56
Chap.19 conservation & restoration
問題與討論
 請提出問題！
57
Chap.19 conservation & restoration