+

Chapter 25: Extinction and Conservation

Robert E. Ricklefs

The Economy of Nature, Fifth Edition

+ Take note

Be sure to check the readings on the website They will be on the exam

2

+ Human Impact on Earth

The human impact on the earth is substantial: in the year 2000, human population was 6 billion:

we are still growing at the robust rate of 2% per year humans control or indirectly affect much of the

earth’s surface: 35% of land area is used for crops or permanent pastures countless additional hectares are grazed by livestock tropical forests are being felled at 17 million hectares per year

2% of remaining forest is cut per year desertification is a widespread problem, especially in Africa air and water pollution are also widespread

3

+ 4

+ Human impacts on the planet can be reduced.

Negative consequences of human impacts on natural systems are enormous: deterioration of the environment:

will lead to a declining quality of life for all humans already affects the other life forms on the planet

But there is cause for hope: humans can live in a clean and sustaining world,

but only by placing support for our own population into balance with preservation of other species and the ecological processes that nurture us

5

+ Three Lessons from Ecology 1

The science of ecology has much to tell us about living sustainably in a healthy world.

Environmental problems cannot be solved until the human population is brought under control: density-dependent control of the human

population will mean untold suffering we must learn to value individual human

experience over numbers of progeny

6

+ Three Lessons from Ecology 2

Individual consumption of energy, resources, and food produced at higher trophic levels must be reduced: we have already exceeded the capacity of earth

to support the current human population at a level enjoyed by the most affluent societies

we can make contributions to sustainability by: investing in and utilizing energy- and resource- efficient

technologies eating lower on the food chain

7

+ Three Lessons from Ecology 3

Ecosystems should be maintained in as close to their natural state as possible to keep natural processes intact: areas unsuitable for grazing or agriculture should not

be converted to such uses: these areas are best set aside for conservation and

recreation living with nature is always preferable to, and less

costly than, going against it

8

+ Biological diversity is incompletely described. There may be as many as 10 to 30 million species of

plants, animals, and microbes worldwide: only 1,500,000 species have been catalogued although lists are important, they represent only one

approach to the documentation of biological diversity or biodiversity, the many unique attributes of living things

9

+ Proportions of named species…10

+ Components of Biodiversity 1

Ecological diversity: each species has unique attributes and adaptations that

define its place in the ecosystem: plants, for example, vary in:

tolerances of environmental conditions defenses against herbivores growth form strategies for pollination and seed dispersal

11

+ Components of Biodiversity 2

Genetic diversity: crucial to evolutionary responses of organisms to

changing environments has both within- and between-species components

Geographic diversity: each region has different species composition and

diversity endemic species are restricted to small

geographic areas regions with many endemics possess high endemism

12

+ Endemism

Oceanic islands are well known for harboring endemic forms: nearly all native birds, plants, and insects of

isolated islands live nowhere else loss of such island species caused by habitat

destruction, hunting, or alien species means worldwide extinction

humans have caused many extinctions of island endemics

13

+ Be sure to …

Spend some time here: http://biodiversity.moe.gov.lb/

14

+ Value of Biodiversity

Current loss of species is at an all-time high in earth’s history: some estimates place this rate in excess of one species per

day

Why should we be concerned about loss of species? many species are gone already extinction is a natural process

15

+ Moral Responsibility

Extinction raises important moral issues: some feel that because humankind affects all of nature, it is

our moral responsibility to protect nature if morality is intrinsic to life itself:

rights of nonhuman individuals and species are as legitimate as the rights of individuals in human society

Environmental ethics

16

+

“What is a man without the beasts? If all the beasts were gone, men would die from great loneliness of spirit, for whatever happens to the beasts also happens to man.”—Chief Seattle

17

+ Economic Benefits

Individual species have direct economic and recreation values for humankind: food resources game species sources of forest and other natural products drugs and other organic chemicals

about 25% of prescriptions filled in the United States / more than 100 important medicinal drugs / are extracted directly from flowering plants

Assigning economic value to one species – does not address conserving biodiversity in a general sense. Why not?

18

+Economic values of species can cause environmental harm. Policies favoring certain species may harm others:

cultivated species displace other species viewed as having lesser value

predators, such as wolves, are eliminated because of conflicts with livestock operations

overexploitation of resources (such as fisheries) may lead to their demise

19

+ Ecotourism

Some species have high value because they attract tourists, in a practice known as ecotourism: many countries have benefited from the willingness

of tourists to visit game parks and preserves; ecotourism: often brings much-needed foreign currencies into developing

countries is responsible for development of parks and preserves is expanding, but its potential is finite:

people have limited resources to devote to such activities many species and ecosystems are not attractive to ecotourists

20

+ Giving monetary value …21

Chief Seattle: How can you buy or sell the sky, the warmth of the land? The idea is strange to us.If we do not own the freshness of the air and the sparkle of the water, how can you buy them?• Only after the last tree has been cut down, Only after the last river has been poisoned, Only after the last fish has been caught, Only then will you find money cannot be eaten.•~ Cree Prophecy

+ Indication of Environmental QualityIndividual species may have value as

indicators of environmental change: birds of prey declined during the 1950s and

1960s in the United States: this decline was traced to pollution of aquatic

habitats by breakdown products of DDT, which: entered aquatic food chains and were concentrated at

each step in the chain interfered with physiology and reproduction in birds

identification of the problem led to banning of DDT and subsequent recovery of many species

22

+ Broken eggshells in the nest of a brown pelican

23

+Maintenance of Ecosystem Function Diversity may help stabilize ecological systems:

the research of Tilman and Downing has shown that biomass production was less affected by drought on high-diversity plots: with many species present, some can assume key roles

when environmental conditions change such switching is less likely in less diverse systems

24

+ Decrease in plant biomass after event – related to plants species richness before event

25

+ Plant biomass increases w/ number of plant guilds

26

+ Extinction is natural, but its present rate is not. Extinction is of concern because evolutionary

lineages are lost forever. The relatively low rate of natural extinction is called

background extinction: life span of most species in the fossil record is 1 to 10

million years analysis of the fossil record indicates a background

extinction rate of 1 species per year

27

+Other Types of ExtinctionMass extinctions are caused by natural

catastrophes, such as meteor impacts: such bolide impacts are thought to occur at

intervals of 10 to 100 million years: may have been responsible for mass extinctions at the end

of the Paleozoic and Mesozoic eras

Anthropogenic extinctions are caused by humans: such preventable extinctions have brought the

modern extinction rate to far in excess of natural levels

28

+ 29

+ Humans cause extinctions by several mechanisms.Populations disappear because deaths

exceed births over a prolonged period: extinction may be viewed as a failure to adapt

to changing conditions a recent survey has revealed the principal

causes of population decline for endangered U.S. species: habitat reduction and modification (67% of cases) small population size introduction of exotic species overexploitation

30

+ Habitat Reduction and FragmentationHabitat reduction and fragmentation threaten many species: some habitats are reduced or eliminated altogether fragmentation creates a suite of additional

problems: small areas may not be able to support viable populations

of larger species, such as mammals small populations are subject to stochastic local extinction fragmentation increases edges, exposing forest interior

species to increased parasitism and predation species of fragmented habitats may be unable to migrate

with changing climate induced by global warming

31

+ 32

+Atlantic coastal forests of Brazil – reduced to a small fraction

33

+ Fragmented habitats…

…support smaller populations Becomes a biological ‘island’

34

+ Small Population Size

Stochastic extinction is a risk that increases dramatically for the smallest populations.

Reduced genetic variation in small populations may further increase the probability of extinction: founder effects, inbreeding, genetic drift, and

population bottlenecks all pose problems some species, notably the northern elephant

seal, have survived severe population bottlenecks successfully

35

+ Introductions of Exotic Species

Decreases in habitat quality are frequently the consequence of introduced predators, competitors, or disease organisms: many species arrive accidentally and others are

introduced intentionally islands seem to be most vulnerable to introduced

species (Hawaiian Islands have suffered greatly from introduced species)

aquatic systems are also vulnerable to effects of exotics

continental areas are not immune to effects of exotics

36

+ 37

+ 38

+ 39

+ 40

+ 41

+Overexploitation

Many species have succumbed to effects of direct exploitation by humans: efficient hunting and fishing may drive species to

extinction humans have a long history of overexploitation:

arrival of humans in North America was accompanied by rapid extinction of 56 species in 27 genera of large mammals

42

+ Overexploitation: changes the species composition of a community

43

+ 44

+ 45

+ Vulnerability to extinction is poorly understood.

Why some species are more vulnerable to extinction than others is hard to determine.

Some attributes that predispose species to extinction include: species attractive for exploitation species that have evolved in the absence of hunting species that have evolved in the absence of diverse

disease organisms species with limited geographic range, restricted

habitat distribution, and small local population size

46

+ 47

+ 48

+ 49

+ 50

+ 51

+ 52

+ 53

+ Conservation Planning

Successful planning for conservation must include adequate habitat for a self-sustaining population: in practice, conservation planning must consider:

ecological requirements of the species amount of space needed to support a minimum

viable population

54

+Minimum Viable Populations

The minimum viable population (MVP) is the smallest population that can sustain itself in the face of environmental variation.

MVPs must be large enough to remain out of danger from stochastic extinction.

Other minimal attributes include: wide distribution, such that local catastrophes cannot

affect the entire species some degree of population subdivision that can

prevent the spread of disease

55

+More on Conservation Planning

Migrations complicate conservation planning: seasonal movements or different seasonal habitat

needs are difficult to satisfy: the entire Serengeti ecosystem of East Africa is needed to

accommodate seasonal movements of wildlife long-distance migrants may face multiple challenges in

breeding and wintering grounds

It is not feasible to plan for the conservation of every species: focus is increasingly on habitat conservation

56

+What could happen…57

+

Removed the buffalo – exterminated the buffalo (why?) Replaced buffalo grass Planted wheat + cows What happened?

58

+ 59

+ Black Sunday…60

+ Critical Areas for ConservationWhat are the most valuable areas for

conservation of species? the focus is on areas serving as havens for the

largest numbers of species not represented elsewhere: such biodiversity hotspots typically combine local

diversity and endemism in continental areas, the objective is to target habitats and

areas of special biological interest: several small preserves may be more effective than one large

preserve adding more area to preserves becomes increasingly expensive

61

+ 62

+Challenges of Tropical Conservation 1 Many tropical countries have large tracts of uncut

forest and other undisturbed tropical habitats: it may be relatively easy to set aside parks “on paper,” but

many conflicts remain: rapid growth of human populations increased exploitation of forest products illegal or questionable activities of poachers,

squatters, miners, and logging concessions

63

+Challenges of Tropical Conservation 2

The price of conservation is rising worldwide.Conservation must be an international effort,

with wealth of the developed countries shared globally to protect biodiversity: involving local people in the design and management

of parks is especially important: the benefits of conservation must be tangible and

economically compelling

64

+ Design of Nature Preserves 1

Ecological principles derived from the theory of island biogeography can be helpful: the species-area relationship:

larger areas support more species than smaller by: reducing likelihood of stochastic extinction promoting genetic diversity buffering populations against disturbances

the avoidance of edge effects: the effects of habitat alteration extend for some distance

freedom to migrate

65

+ Design of Nature Preserves 2

General recommendations exist for creation of preserves from large expanses of uniform habitat: larger is better than smaller one large area is better than several smaller

that add to the same size corridors connecting isolated areas are

desirable circular areas are better than elongate areas

with more edge

66

+ Design of Nature Preserves 3Several small areas in different habitats may

be more effective than one large area in uniform habitat.

Nature preserves must be designed with the habitat requirements of their inhabitants in mind: migratory needs must be accommodated through

incorporation of diverse habitats linked by corridors roads and pipelines interfering with movements

must be bridged in some fashion

67

+ Check…

http://www.newscientist.com/blog/environment/2008/05/iron-curtain-becomes-nature-haven.html

68

+ Endangered species have been rescued from the brink. The California condor is a success story

with several important lessons: the condor population had dwindled to less than

20 individuals in the 1980s the decision was made to bring the entire

population into a captive breeding program this program has been very successful, highlighting the

important role played by zoological parks the condor can now be released into habitat

preserves purchased expressly for condor conservation

69

+ 70

+ California Condor

Experienced gained through projects like that designed for the California condor will have many benefits: experience gained will benefit similar programs in

the future large tracts of natural habitat have been preserved such projects heighten the public’s awareness of

conservation issues: condor populations are compatible with other land uses

(recreation, hunting, ranching), so long as appropriate precautions are taken

71

+ Condor Conservation

Concessions to condors are neither difficult nor expensive. Making them simply depends on instilling values that acknowledge natural systems as an integral part of the environment of humankind.

72

+ Summary 1

Humankind has an enormous impact on earth and its natural resources. These impacts will continue to grow as the population grows beyond 6 billion.

Resolving the environmental crisis will require cessation of population growth, conservation of energy and resources, and taking ecological values into consideration.

Biodiversity has ecological, genetic, and geographic components.

73

+ Summary 2

The value of species is rooted in moral, aesthetic, and economic considerations. Species also have value as indicators of environmental quality. Diversity may also help stabilize ecosystem function.

Background extinction may be estimated from the fossil record. Mass extinctions are associated with catastrophic events, while anthropogenic extinction has increased dramatically.

74

+ Summary 3Habitat reduction may hasten a population’s

decline toward extinction. Introduction of exotic species is also a substantial cause of extinctions.

Optimal design of nature preserves takes advantage of biodiversity hotspots, and principles elucidated in the theory of island biogeography.

Species may be brought back from the brink of extinction. Such efforts highlight conservation problems and may also conserve natural habitats.

75