53 communities text

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Community Ecology

• Overview: What Is a Community?

• A biological community

– Is an assemblage of populations of various species living close enough for potential interaction


• The various animals and plants surrounding this watering hole

– Are all members of a savanna community in southern Africa

Figure 53.1


• Concept 53.1: A community’s interactions include competition, predation, herbivory, symbiosis, and disease

• Populations are linked by interspecific interactions

– That affect the survival and reproduction of the species engaged in the interaction


• Interspecific interactions

– Can have differing effects on the populations involved

Table 53.1


Competition

• Interspecific competition

– Occurs when species compete for a particular resource that is in short supply

• Strong competition can lead to competitive exclusion

– The local elimination of one of the two competing species


The Competitive Exclusion Principle

• The competitive exclusion principle

– States that two species competing for the same limiting resources cannot coexist in the same place


Ecological Niches

• The ecological niche

– Is the total of an organism’s use of the biotic and abiotic resources in its environment


• The niche concept allows restatement of the competitive exclusion principle

– Two species cannot coexist in a community if their niches are identical


• However, ecologically similar species can coexist in a community

– If there are one or more significant difference in their niches

When Connell removed Balanus from the lower strata, the Chthamalus population spread into that area.

The spread of Chthamalus when Balanus was removed indicates that competitive exclusion makes the realizedniche of Chthamalus much smaller than its fundamental niche.

RESULTS

CONCLUSION

Ocean

Ecologist Joseph Connell studied two barnacle speciesBalanus balanoides and Chthamalus stellatus that have a stratified distribution on rocks along the coast of Scotland.

EXPERIMENT

In nature, Balanus fails to survive high on the rocks because it isunable to resist desiccation (drying out) during low tides. Its realized niche is therefore similar to its fundamental niche. In contrast, Chthamalus is usually concentrated on the upper strata of rocks. To determine the fundamental of niche of Chthamalus, Connell removed Balanus from the lower strata.

Low tide

High tide

Chthamalusfundamental niche

Chthamalusrealized niche

Low tide

High tideChthamalus

Balanusrealized niche

Balanus

Ocean

Figure 53.2


• As a result of competition

– A species’ fundamental niche may be different from its realized niche


A. insolitususually percheson shady branches.

A. distichus perches on fence posts and

other sunny surfaces.

A. distichus

A. ricordii

A. insolitus

A. christophei

A. cybotes

A. etheridgei

A. alinigar

Figure 53.3

Resource Partitioning

• Resource partitioning is the differentiation of niches

– That enables similar species to coexist in a community


G. fortis

Beak depth (mm)

G. fuliginosa

Beak depth

Los Hermanos

Daphne

Santa María, San Cristóbal

Sympatric populations

G. fuliginosa, allopatric

G. fortis, allopatric

Per

cent

ages

of

indi

vidu

als

in e

ach

size

cla

ss

40

20

0

40

20

0

40

20

0

8 10 12 14 16

Figure 53.4

Character Displacement

• In character displacement

– There is a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species


Predation

• Predation refers to an interaction

– Where one species, the predator, kills and eats the other, the prey


• Feeding adaptations of predators include

– Claws, teeth, fangs, stingers, and poison

• Animals also display

– A great variety of defensive adaptations


• Cryptic coloration, or camouflage

– Makes prey difficult to spot

Figure 53.5


• Aposematic coloration

– Warns predators to stay away from prey

Figure 53.6


• In some cases, one prey species

– May gain significant protection by mimicking the appearance of another


• In Batesian mimicry

– A palatable or harmless species mimics an unpalatable or harmful model

(a) Hawkmoth larva

(b) Green parrot snake

Figure 53.7a, b


• In Müllerian mimicry

– Two or more unpalatable species resemble each other

(a) Cuckoo bee

(b) Yellow jacketFigure 53.8a, b


Herbivory

• Herbivory, the process in which an herbivore eats parts of a plant

– Has led to the evolution of plant mechanical and chemical defenses and consequent adaptations by herbivores


Parasitism

• In parasitism, one organism, the parasite

– Derives its nourishment from another organism, its host, which is harmed in the process


• Parasitism exerts substantial influence on populations

– And the structure of communities


Disease

• The effects of disease on populations and communities

– Is similar to that of parasites


• Pathogens, disease-causing agents

– Are typically bacteria, viruses, or protists


Mutualism

• Mutualistic symbiosis, or mutualism

– Is an interspecific interaction that benefits both species

Figure 53.9


Commensalism

• In commensalism

– One species benefits and the other is not affected

Figure 53.10


• Commensal interactions have been difficult to document in nature

– Because any close association between species likely affects both species


Interspecific Interactions and Adaptation

• Evidence for coevolution

– Which involves reciprocal genetic change by interacting populations, is scarce


• However, generalized adaptation of organisms to other organisms in their environment

– Is a fundamental feature of life


• Concept 53.2: Dominant and keystone species exert strong controls on community structure

• In general, a small number of species in a community

– Exert strong control on that community’s structure


Species Diversity

• The species diversity of a community

– Is the variety of different kinds of organisms that make up the community

– Has two components


• Species richness

– Is the total number of different species in the community

• Relative abundance

– Is the proportion each species represents of the total individuals in the community


• Two different communities

– Can have the same species richness, but a different relative abundance

Community 1A: 25% B: 25% C: 25% D: 25%

Community 2A: 80% B: 5% C: 5% D: 10%

D

C

BA

Figure 53.11


• A community with an even species abundance

– Is more diverse than one in which one or two species are abundant and the remainder rare


Trophic Structure

• Trophic structure

– Is the feeding relationships between organisms in a community

– Is a key factor in community dynamics


• Food chainsQuaternary consumers

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

Carnivore

Carnivore

Carnivore

Herbivore

Plant

Carnivore

Carnivore

Carnivore

Zooplankton

Phytoplankton

A terrestrial food chain A marine food chainFigure 53.12

– Link the trophic levels from producers to top carnivores


Food Webs

• A food web Humans

Baleen whales

Crab-eater seals

Birds Fishes Squids

Leopardseals

Elephant seals

Smaller toothed whales

Sperm whales

Carnivorous plankton

Euphausids (krill)

Copepods

Phyto-plankton

Figure 53.13

– Is a branching food chain with complex trophic interactions


• Food webs can be simplified

– By isolating a portion of a community that interacts very little with the rest of the community

Sea nettle

Fish larvae

ZooplanktonFish eggs

Juvenile striped bass

Figure 53.14


Limits on Food Chain Length

• Each food chain in a food web

– Is usually only a few links long

• There are two hypotheses

– That attempt to explain food chain length


• The energetic hypothesis suggests that the length of a food chain

– Is limited by the inefficiency of energy transfer along the chain


• The dynamic stability hypothesis

– Proposes that long food chains are less stable than short ones


• Most of the available data

– Support the energetic hypothesis

High (control)

Medium Low

Productivity

No. of species

No. of trophic links

Num

ber

of

spec

ies

Num

ber

of

trop

hic

links

0

1

2

3

4

5

6

0

1

2

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5

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Figure 53.15


Species with a Large Impact

• Certain species have an especially large impact on the structure of entire communities

– Either because they are highly abundant or because they play a pivotal role in community dynamics


Dominant Species

• Dominant species

– Are those species in a community that are most abundant or have the highest biomass

– Exert powerful control over the occurrence and distribution of other species


• One hypothesis suggests that dominant species

– Are most competitive in exploiting limited resources

• Another hypothesis for dominant species success

– Is that they are most successful at avoiding predators


Keystone Species

• Keystone species

– Are not necessarily abundant in a community

– Exert strong control on a community by their ecological roles, or niches


• Field studies of sea stars

– Exhibit their role as a keystone species in intertidal communities

Figure 53.16a,b

(a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates.

With Pisaster (control)

Without Pisaster (experimental)

Num

ber

of s

peci

es

pres

ent

0

5

10

15

20

1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73

(b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.


• Observation of sea otter populations and their predation

Figure 53.17Food chain beforekiller whale involve-ment in chain

(a) Sea otter abundance

(b) Sea urchin biomass

(c) Total kelp density

Num

ber

per

0.25

m2

1972 1985 1989 1993 19970

2

468

10

0

100

200

300

400

Gra

ms

per

0.25

m2

Ott

er n

umbe

r (%

max

. co

unt)

0

40

20

60

80

100

Year

Food chain after killerwhales started preyingon otters

– Shows the effect the otters haveon ocean communities


Ecosystem “Engineers” (Foundation Species)

• Some organisms exert their influence

– By causing physical changes in the environment that affect community structure


• Beaver dams

– Can transform landscapes on a very large scale

Figure 53.18


• Some foundation species act as facilitators

– That have positive effects on the survival and reproduction of some of the other species in the community

Figure 53.19

Salt marsh with Juncus (foreground)

With Juncus

Without Juncus

Nu

mb

er

of

pla

nt

spe

cie

s

0

2

4

6

8

Conditions


Bottom-Up and Top-Down Controls

• The bottom-up model of community organization

– Proposes a unidirectional influence from lower to higher trophic levels

• In this case, the presence or absence of abiotic nutrients

– Determines community structure, including the abundance of primary producers


• The top-down model of community organization

– Proposes that control comes from the trophic level above

• In this case, predators control herbivores

– Which in turn control primary producers


• Long-term experiment studies have shown

– That communities can shift periodically from bottom-up to top-down

Figure 53.20

0 100 200 300 400

Rainfall (mm)

0

25

50

75

100

Per

cen

tag

e o

f he

rbac

eous

pla

nt c

over


• Pollution

– Can affect community dynamics

• But through biomanipulation

– Polluted communities can be restored

Fish

Zooplankton

Algae

Abundant

Rare

RareAbundant

Abundant

Rare

Polluted State Restored State


• Concept 53.3: Disturbance influences species diversity and composition

• Decades ago, most ecologists favored the traditional view

– That communities are in a state of equilibrium


• However, a recent emphasis on change has led to a nonequilibrium model

– Which describes communities as constantly changing after being buffeted by disturbances


What Is Disturbance?

• A disturbance

– Is an event that changes a community

– Removes organisms from a community

– Alters resource availability


• Fire

– Is a significant disturbance in most terrestrial ecosystems

– Is often a necessity in some communities

(a) Before a controlled burn.A prairie that has not burned forseveral years has a high propor-tion of detritus (dead grass).

(b) During the burn. The detritus serves as fuel for fires.

(c) After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

Figure 53.21a–c


• The intermediate disturbance hypothesis

– Suggests that moderate levels of disturbance can foster higher species diversity than low levels of disturbance


• The large-scale fire in Yellowstone National Park in 1988

– Demonstrated that communities can often respond very rapidly to a massive disturbance

Figure 53.22a, b

(a) Soon after fire. As this photo taken soon after the fire shows, the burn left a patchy landscape. Note the unburned trees in the distance.

(b) One year after fire. This photo of the same general area taken the following year indicates how rapidly the community began to recover. A variety of herbaceous plants, different from those in the former forest, cover the ground.


Human Disturbance

• Humans

– Are the most widespread agents of disturbance


• Human disturbance to communities

– Usually reduces species diversity

• Humans also prevent some naturally occurring disturbances

– Which can be important to community structure


Ecological Succession

• Ecological succession

– Is the sequence of community and ecosystem changes after a disturbance


• Primary succession

– Occurs where no soil exists when succession begins

• Secondary succession

– Begins in an area where soil remains after a disturbance


• Early-arriving species

– May facilitate the appearance of later species by making the environment more favorable

– May inhibit establishment of later species

– May tolerate later species but have no impact on their establishment


McBride glacier retreating

0 5 10

Miles

GlacierBay

Pleasant Is.

Johns HopkinsGl.

Reid Gl.

GrandPacific Gl.

Canada

Alaska

1940 1912

1899

1879

18791949

1879

1935

1760

17801830

1860

1913

1911

18921900

1879

1907 19481931

1941

1948

Cas

emen

t Gl.

McB

ride

Gl.

Plateau Gl.

Muir G

l.

Riggs G

l.

• Retreating glaciers

– Provide a valuable field-research opportunity on succession

Figure 53.23


• Succession on the moraines in Glacier Bay, Alaska

– Follows a predictable pattern of change in vegetation and soil characteristics

Figure 53.24a–d

(b) Dryas stage

(c) Spruce stage

(d) Nitrogen fixation by Dryas and alder increases the soil nitrogen content.

Soi

l nitr

ogen

(g/

m2)

Successional stagePioneer Dryas Alder Spruce

0

10

20

30

40

50

60

(a) Pioneer stage, with fireweed dominant


• Concept 53.4: Biogeographic factors affect community diversity

• Two key factors correlated with a community’s species diversity

– Are its geographic location and its size


Equatorial-Polar Gradients

• The two key factors in equatorial-polar gradients of species richness

– Are probably evolutionary history and climate


• Species richness generally declines along an equatorial-polar gradient

– And is especially great in the tropics

• The greater age of tropical environments

– May account for the greater species richness


• Climate

– Is likely the primary cause of the latitudinal gradient in biodiversity


• The two main climatic factors correlated with biodiversity

– Are solar energy input and water availability

(b) Vertebrates

500 1,000 1,500 2,000

Potential evapotranspiration (mm/yr)

10

50

100

200

Ver

tebr

ate

spec

ies

richn

ess

(log

scal

e)

1

100 300 500 700 900 1,100

180

160

140

120

100

80

60

40

20

0

Tre

e sp

ecie

s ric

hnes

s

(a) TreesActual evapotranspiration (mm/yr)

Figure 53.25a, b


Area Effects

• The species-area curve quantifies the idea that

– All other factors being equal, the larger the geographic area of a community, the greater the number of species


• A species-area curve of North American breeding birds

– Supports this idea

Area (acres)

1 10 100 103 104 105 106 107 108 109 1010

Nu

mb

er

of

spe

cie

s (lo

g s

cale

)

1

10

100

1,000

Figure 53.26


Island Equilibrium Model

• Species richness on islands

– Depends on island size, distance from the mainland, immigration, and extinction


Figure 53.27a–c

• The equilibrium model of island biogeography maintains that

– Species richness on an ecological island levels off at some dynamic equilibrium point

Number of species on island

(a) Immigration and extinction rates. The equilibrium number of species on anisland represents a balance between the immigration of new species and theextinction of species already there.

(b) Effect of island size. Large islands may ultimately have a larger equilibrium num-ber of species than small islands because immigration rates tend to be higher and extinction rates lower on large islands.

Number of species on island Number of species on island

(c) Effect of distance from mainland. Near islands tend to have largerequilibrium numbers of species thanfar islands because immigration ratesto near islands are higher and extinctionrates lower.

Equilibrium number Small island Large island Far island Near island

Imm

igration

Extin

ctio

n

Extin

ctio

n

Imm

igration

Extin

ctio

n

Imm

igration

(small island)

(larg

e is

land)

(large island)

(sm

all

isla

nd) Imm

igration

Extin

ctio

n

Imm

igration

(far island)

(near i

sland)

(near island) (far i

slan

d)

Extinctio

n

Rat

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imm

igra

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or e

xtin

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Rat

e of

imm

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or e

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Rat

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imm

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or e

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n


• Studies of species richness on the Galápagos Islands

– Support the prediction that species richness increases with island size

The results of the study showed that plant species richness increased with island size, supporting the species-area theory.

FIELD STUDY

RESULTS

Ecologists Robert MacArthur and E. O. Wilson studied the number of plant species on the Galápagos Islands, which vary greatly in size, in relation to the area of each island.

CONCLUSION

200

100

50

25

10

0

Area of island (mi2) (log scale)

Num

ber

of p

lant

spe

cies

(lo

g sc

ale)

0.1 1 10 100 1,000

5

400

Figure 53.28


• Concept 53.5: Contrasting views of community structure are the subject of continuing debate

• Two different views on community structure

– Emerged among ecologists in the 1920s and 1930s


Integrated and Individualistic Hypotheses

• The integrated hypothesis of community structure

– Describes a community as an assemblage of closely linked species, locked into association by mandatory biotic interactions


• The individualistic hypothesis of community structure

– Proposes that communities are loosely organized associations of independently distributed species with the same abiotic requirements


• The integrated hypothesis

– Predicts that the presence or absence of particular species depends on the presence or absence of other species

Pop

ulat

ion

dens

ities

of

indi

vidu

al

spec

ies

Environmental gradient(such as temperature or moisture)

(a) Integrated hypothesis. Communities are discrete groupings of particular species that are closely interdependent and nearly always occur together.Figure 53.29a


• The individualistic hypothesis

– Predicts that each species is distributed according to its tolerance ranges for abiotic factors

Pop

ulat

ion

dens

ities

of

indi

vidu

al

spec

ies

Environmental gradient(such as temperature or moisture)

(b) Individualistic hypothesis. Species are independently distributed along gradients and a community is simply the assemblage of species that occupy the same area because of similar abiotic needs. Figure 53.29b


• In most actual cases the composition of communities

– Seems to change continuously, with each species more or less independently distributed

Num

ber

of

plan

tspe

r he

ctar

e

Wet Moisture gradient Dry

(c) Trees in the Santa Catalina Mountains. The distribution of tree species at one elevation in the Santa Catalina Mountains of Arizona supports the individualistic hypothesis. Each tree species has an independent distribution along the gradient, apparently conforming to its tolerance for moisture, and the species that live together at any point along the gradient have similar physical requirements. Because the vegetation changes continuously along the gradient, it is impossible to delimit sharp boundaries for the communities.

0

200

400

600

Figure 53.29c


Rivet and Redundancy Models

• The rivet model of communities

– Suggests that all species in a community are linked together in a tight web of interactions

– Also states that the loss of even a single species has strong repercussions for the community


• The redundancy model of communities

– Proposes that if a species is lost from a community, other species will fill the gap


• It is important to keep in mind that community hypotheses and models

– Represent extremes, and that most communities probably lie somewhere in the middle


PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 54Chapter 54

Ecosystems


• Overview: Ecosystems, Energy, and Matter

• An ecosystem consists of all the organisms living in a community

– As well as all the abiotic factors with which they interact


• Ecosystems can range from a microcosm, such as an aquarium

– To a large area such as a lake or forest

Figure 54.1


• Regardless of an ecosystem’s size

– Its dynamics involve two main processes: energy flow and chemical cycling

• Energy flows through ecosystems

– While matter cycles within them


• Concept 54.1: Ecosystem ecology emphasizes energy flow and chemical cycling

• Ecosystem ecologists view ecosystems

– As transformers of energy and processors of matter


Ecosystems and Physical Laws

• The laws of physics and chemistry apply to ecosystems

– Particularly in regard to the flow of energy

• Energy is conserved

– But degraded to heat during ecosystem processes


Trophic Relationships

• Energy and nutrients pass from primary producers (autotrophs)

– To primary consumers (herbivores) and then to secondary consumers (carnivores)


• Energy flows through an ecosystem

– Entering as light and exiting as heat

Figure 54.2

Microorganismsand other

detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow


• Nutrients cycle within an ecosystem


Decomposition

• Decomposition

– Connects all trophic levels


• Detritivores, mainly bacteria and fungi, recycle essential chemical elements

– By decomposing organic material and returning elements to inorganic reservoirs

Figure 54.3


• Concept 54.2: Physical and chemical factors limit primary production in ecosystems

• Primary production in an ecosystem

– Is the amount of light energy converted to chemical energy by autotrophs during a given time period


Ecosystem Energy Budgets

• The extent of photosynthetic production

– Sets the spending limit for the energy budget of the entire ecosystem


The Global Energy Budget

• The amount of solar radiation reaching the surface of the Earth

– Limits the photosynthetic output of ecosystems

• Only a small fraction of solar energy

– Actually strikes photosynthetic organisms


Gross and Net Primary Production

• Total primary production in an ecosystem

– Is known as that ecosystem’s gross primary production (GPP)

• Not all of this production

– Is stored as organic material in the growing plants


• Net primary production (NPP)

– Is equal to GPP minus the energy used by the primary producers for respiration

• Only NPP

– Is available to consumers


• Different ecosystems vary considerably in their net primary production

– And in their contribution to the total NPP on Earth

Lake and stream

Open ocean

Continental shelf

Estuary

Algal beds and reefs

Upwelling zones

Extreme desert, rock, sand, ice

Desert and semidesert scrub

Tropical rain forest

Savanna

Cultivated land

Boreal forest (taiga)

Temperate grassland

Tundra

Tropical seasonal forestTemperate deciduous forest

Temperate evergreen forest

Swamp and marsh

Woodland and shrubland

0 10 20 30 40 50 60 0 500 1,000 1,500 2,000 2,500 0 5 10 15 20 25

Percentage of Earth’s netprimary production

Key

Marine

Freshwater (on continents)

Terrestrial

5.2

0.3

0.1

0.1

4.7

3.53.3

2.9

2.7

2.41.8

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7.99.1

9.6

5.4

3.50.6

7.1

4.9

3.8

2.3

0.3

65.0 24.4

Figure 54.4a–c

Percentage of Earth’ssurface area

(a) Average net primaryproduction (g/m2/yr)(b) (c)


• Overall, terrestrial ecosystems

– Contribute about two-thirds of global NPP and marine ecosystems about one-third

Figure 54.5

180 120W 60W 0 60E 120E 180

North Pole

60N

30N

Equator

30S

60S

South Pole


Primary Production in Marine and Freshwater Ecosystems

• In marine and freshwater ecosystems

– Both light and nutrients are important in controlling primary production


Light Limitation

• The depth of light penetration

– Affects primary production throughout the photic zone of an ocean or lake


Nutrient Limitation

• More than light, nutrients limit primary production

– Both in different geographic regions of the ocean and in lakes


• A limiting nutrient is the element that must be added

– In order for production to increase in a particular area

• Nitrogen and phosphorous

– Are typically the nutrients that most often limit marine production


• Nutrient enrichment experiments

– Confirmed that nitrogen was limiting phytoplankton growth in an area of the ocean

EXPERIMENT Pollution from duck farms concentrated near Moriches Bay adds both nitrogen and phosphorus to the coastal water off Long Island. Researchers cultured the phytoplankton Nannochloris atomus with water collected from several bays.

Figure 54.6

Coast of Long Island, New York. The numbers on the map indicate the data collection stations.

Long Island

Great South Bay

Shinnecock Bay

Moriches Bay

Atlantic Ocean

30 21

1915

1154

2


Figure 54.6

(a) Phytoplankton biomass and phosphorus concentration (b) Phytoplankton response to nutrient enrichment

GreatSouth Bay

MorichesBay

ShinnecockBay

Startingalgal

density

2 4 5 11 30 15 19 21

30

24

18

12

6

0

Unenriched control

Ammonium enrichedPhosphate enriched

Station number

Ph

yto

pla

nkt

on

(mill

ion

s o

f ce

lls p

er

mL

)

87

6

5

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2

1

02 4 5 11 3015 19 21

87

6

54

32

1

0

Ino

rga

nic

ph

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rus

(g

ato

ms/

L)

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on

(mill

ion

s o

f ce

lls/m

L)

Station number

CONCLUSION Since adding phosphorus, which was already in rich supply, had no effect on Nannochloris growth, whereas adding nitrogen increased algal density dramatically, researchers concluded that nitrogen was the nutrient limiting phytoplankton growth in this ecosystem.

Phytoplankton

Inorganicphosphorus

RESULTS Phytoplankton abundance parallels the abundance of phosphorus in the water (a). Nitrogen, however, is immediately taken up by algae, and no free nitrogen is measured in the coastal waters. The addition of ammonium (NH4

) caused heavy phytoplankton growth in bay water, but the addition of phosphate (PO4

3) did not induce algal growth (b).


• Experiments in another ocean region

– Showed that iron limited primary production

Table 54.1


• The addition of large amounts of nutrients to lakes

– Has a wide range of ecological impacts


• In some areas, sewage runoff

– Has caused eutrophication of lakes, which can lead to the eventual loss of most fish species from the lakes

Figure 54.7


Primary Production in Terrestrial and Wetland Ecosystems

• In terrestrial and wetland ecosystems climatic factors

– Such as temperature and moisture, affect primary production on a large geographic scale


• The contrast between wet and dry climates

– Can be represented by a measure called actual evapotranspiration


• Actual evapotranspiration

– Is the amount of water annually transpired by plants and evaporated from a landscape

– Is related to net primary production

Figure 54.8Actual evapotranspiration (mm H2O/yr)

Tropical forest

Temperate forest

Mountain coniferous forest

Temperate grassland

Arctic tundra

Desertshrubland

Net

prim

ary

prod

uctio

n (g

/m2 /

yr)

1,000

2,000

3,000

0500 1,000 1,5000


• On a more local scale

– A soil nutrient is often the limiting factor in primary production

Figure 54.9

EXPERIMENT Over the summer of 1980, researchers added phosphorus to some experimental plots in the salt marsh, nitrogento other plots, and both phosphorus and nitrogen to others. Some plots were left unfertilized as controls.

RESULTS

Experimental plots receiving just phosphorus (P) do not outproduce the unfertilized control plots.

CONCLUSION

Live

, ab

ove-

grou

nd b

iom

ass

(g d

ry w

t/m

2)

Adding nitrogen (N) boosts net primaryproduction.

300

250

200

150

100

50

0June July August 1980

N P

N only

Control

P only

These nutrient enrichment experiments confirmed that nitrogen was the nutrient limiting plant growth in this salt marsh.


• Concept 54.3: Energy transfer between trophic levels is usually less than 20% efficient

• The secondary production of an ecosystem

– Is the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period of time


Production Efficiency

• When a caterpillar feeds on a plant leaf

– Only about one-sixth of the energy in the leaf is used for secondary production

Figure 54.10

Plant materialeaten by caterpillar

Cellularrespiration

Growth (new biomass)

Feces100 J

33 J

200 J

67 J


• The production efficiency of an organism

– Is the fraction of energy stored in food that is not used for respiration


Trophic Efficiency and Ecological Pyramids

• Trophic efficiency

– Is the percentage of production transferred from one trophic level to the next

– Usually ranges from 5% to 20%


Pyramids of Production

• This loss of energy with each transfer in a food chain

– Can be represented by a pyramid of net production

Figure 54.11

Tertiaryconsumers

Secondaryconsumers

Primaryconsumers

Primaryproducers

1,000,000 J of sunlight

10 J

100 J

1,000 J

10,000 J


Pyramids of Biomass

• One important ecological consequence of low trophic efficiencies

– Can be represented in a biomass pyramid


• Most biomass pyramids

– Show a sharp decrease at successively higher trophic levels

Figure 54.12a

(a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as illustrated by data froma bog at Silver Springs, Florida.

Trophic level Dry weight(g/m2)

Primary producers

Tertiary consumers

Secondary consumers

Primary consumers

1.5

11

37809


• Certain aquatic ecosystems

– Have inverted biomass pyramids

Figire 54.12b

Trophic level

Primary producers (phytoplankton)

Primary consumers (zooplankton)

(b) In some aquatic ecosystems, such as the English Channel, a small standing crop of primary producers (phytoplankton)supports a larger standing crop of primary consumers (zooplankton).

Dry weight(g/m2)

21

4


Pyramids of Numbers

• A pyramid of numbers

– Represents the number of individual organisms in each trophic level

Figure 54.13

Trophic level Number of individual organisms

Primary producers

Tertiary consumers

Secondary consumers

Primary consumers

3

354,904

708,624

5,842,424


• The dynamics of energy flow through ecosystems

– Have important implications for the human population

• Eating meat

– Is a relatively inefficient way of tapping photosynthetic production


• Worldwide agriculture could successfully feed many more people

– If humans all fed more efficiently, eating only plant material

Figure 54.14

Trophic level

Secondaryconsumers

Primaryconsumers

Primaryproducers


The Green World Hypothesis

• According to the green world hypothesis

– Terrestrial herbivores consume relatively little plant biomass because they are held in check by a variety of factors


• Most terrestrial ecosystems

– Have large standing crops despite the large numbers of herbivores

Figure 54.15


• The green world hypothesis proposes several factors that keep herbivores in check

– Plants have defenses against herbivores

– Nutrients, not energy supply, usually limit herbivores

– Abiotic factors limit herbivores

– Intraspecific competition can limit herbivore numbers

– Interspecific interactions check herbivore densities


• Concept 54.4: Biological and geochemical processes move nutrients between organic and inorganic parts of the ecosystem

• Life on Earth

– Depends on the recycling of essential chemical elements

• Nutrient circuits that cycle matter through an ecosystem

– Involve both biotic and abiotic components and are often called biogeochemical cycles


A General Model of Chemical Cycling

• Gaseous forms of carbon, oxygen, sulfur, and nitrogen

– Occur in the atmosphere and cycle globally

• Less mobile elements, including phosphorous, potassium, and calcium

– Cycle on a more local level


• A general model of nutrient cycling

– Includes the main reservoirs of elements and the processes that transfer elements between reservoirs

Figure 54.16

Organicmaterialsavailable

as nutrients

Livingorganisms,detritus

Organicmaterials

unavailableas nutrients

Coal, oil,peat

Inorganicmaterialsavailable

as nutrients

Inorganicmaterials

unavailableas nutrients

Atmosphere,soil, water

Mineralsin rocksFormation of

sedimentary rock

Weathering,erosion

Respiration,decomposition,excretion

Burningof fossil fuels

Fossilization

Reservoir a Reservoir b

Reservoir c Reservoir d

Assimilation, photosynthesis


• All elements

– Cycle between organic and inorganic reservoirs


Biogeochemical Cycles

• The water cycle and the carbon cycle

Figure 54.17

Transportover land

Solar energy

Net movement ofwater vapor by wind

Precipitationover ocean

Evaporationfrom ocean

Evapotranspirationfrom land

Precipitationover land

Percolationthroughsoil

Runoff andgroundwater

CO2 in atmosphere

Photosynthesis

Cellularrespiration

Burning offossil fuelsand wood

Higher-levelconsumersPrimary

consumers

DetritusCarbon compounds in water

Decomposition

THE WATER CYCLE THE CARBON CYCLE


• Water moves in a global cycle

– Driven by solar energy

• The carbon cycle

– Reflects the reciprocal processes of photosynthesis and cellular respiration


• The nitrogen cycle and the phosphorous cycle

Figure 54.17

N2 in atmosphere

Denitrifyingbacteria

Nitrifyingbacteria

Nitrifyingbacteria

Nitrification

Nitrogen-fixingsoil bacteria

Nitrogen-fixingbacteria in rootnodules of legumes

Decomposers

Ammonification

Assimilation

NH3 NH4+

NO3

NO2

Rain

Plants

Consumption

Decomposition

Geologicuplift

Weatheringof rocks

Runoff

SedimentationPlant uptakeof PO4

3

Soil

Leaching

THE NITROGEN CYCLE THE PHOSPHORUS CYCLE


• Most of the nitrogen cycling in natural ecosystems

– Involves local cycles between organisms and soil or water

• The phosphorus cycle

– Is relatively localized


Decomposition and Nutrient Cycling Rates

• Decomposers (detritivores) play a key role

– In the general pattern of chemical cycling

Figure 54.18

Consumers

Producers

Nutrientsavailable

to producers

Abioticreservoir

Geologicprocesses

Decomposers


• The rates at which nutrients cycle in different ecosystems

– Are extremely variable, mostly as a result of differences in rates of decomposition


Vegetation and Nutrient Cycling: The Hubbard Brook Experimental Forest

• Nutrient cycling

– Is strongly regulated by vegetation


• Long-term ecological research projects

– Monitor ecosystem dynamics over relatively long periods of time

• The Hubbard Brook Experimental Forest

– Has been used to study nutrient cycling in a forest ecosystem since 1963


• The research team constructed a dam on the site

– To monitor water and mineral loss

Figure 54.19a

(a) Concrete dams and weirs built across streams at the bottom of watersheds enabled researchers to monitor the outflow of water and nutrients from the ecosystem.


• In one experiment, the trees in one valley were cut down

– And the valley was sprayed with herbicides

Figure 54.19b(b) One watershed was clear cut to study the effects of the loss

of vegetation on drainage and nutrient cycling.


• Net losses of water and minerals were studied

– And found to be greater than in an undisturbed area

• These results showed how human activity

– Can affect ecosystems

Figure 54.19c(c) The concentration of nitrate in runoff from the deforested watershed was 60 times

greater than in a control (unlogged) watershed.

Nitr

ate

co

nce

ntr

atio

n in

ru

no

ff(m

g/L

)

Deforested

Control

Completion oftree cutting

1965 1966 1967 1968

80.0

60.0

40.0

20.0

4.0

3.02.0

1.0

0


• Concept 54.5: The human population is disrupting chemical cycles throughout the biosphere

• As the human population has grown in size

– Our activities have disrupted the trophic structure, energy flow, and chemical cycling of ecosystems in most parts of the world


Nutrient Enrichment

• In addition to transporting nutrients from one location to another

– Humans have added entirely new materials, some of them toxins, to ecosystems


Agriculture and Nitrogen Cycling

• Agriculture constantly removes nutrients from ecosystems

– That would ordinarily be cycled back into the soil

Figure 54.20


• Nitrogen is the main nutrient lost through agriculture

– Thus, agriculture has a great impact on the nitrogen cycle

• Industrially produced fertilizer is typically used to replace lost nitrogen

– But the effects on an ecosystem can be harmful


Contamination of Aquatic Ecosystems

• The critical load for a nutrient

– Is the amount of that nutrient that can be absorbed by plants in an ecosystem without damaging it


• When excess nutrients are added to an ecosystem, the critical load is exceeded

– And the remaining nutrients can contaminate groundwater and freshwater and marine ecosystems


• Sewage runoff contaminates freshwater ecosystems

– Causing cultural eutrophication, excessive algal growth, which can cause significant harm to these ecosystems


Acid Precipitation

• Combustion of fossil fuels

– Is the main cause of acid precipitation


• North American and European ecosystems downwind from industrial regions

– Have been damaged by rain and snow containing nitric and sulfuric acid

Figure 54.21

4.6

4.64.3

4.14.3

4.6

4.64.3

Europe

North America


• By the year 2000

– The entire contiguous United States was affected by acid precipitation

Figure 54.22

Field pH5.35.2–5.35.1–5.25.0–5.14.9–5.04.8–4.94.7–4.84.6–4.74.5–4.64.4–4.54.3–4.44.3


• Environmental regulations and new industrial technologies

– Have allowed many developed countries to reduce sulfur dioxide emissions in the past 30 years


Toxins in the Environment

• Humans release an immense variety of toxic chemicals

– Including thousands of synthetics previously unknown to nature

• One of the reasons such toxins are so harmful

– Is that they become more concentrated in successive trophic levels of a food web


• In biological magnification

– Toxins concentrate at higher trophic levels because at these levels biomass tends to be lower

Figure 54.23

Con

cent

ratio

n of

PC

Bs

Herringgull eggs124 ppm

Zooplankton 0.123 ppm

Phytoplankton 0.025 ppm

Lake trout 4.83 ppm

Smelt 1.04 ppm


• In some cases, harmful substances

– Persist for long periods of time in an ecosystem and continue to cause harm


Atmospheric Carbon Dioxide

• One pressing problem caused by human activities

– Is the rising level of atmospheric carbon dioxide


Rising Atmospheric CO2

• Due to the increased burning of fossil fuels and other human activities

– The concentration of atmospheric CO2 has been steadily increasing

Figure 54.24

CO

2 c

onc

en

trat

ion

(pp

m)

390

380

370

360

350

340

330

320

310

3001960 1965 1970 1975 1980 1985 1990 1995 2000 2005

1.05

0.90

0.75

0.60

0.45

0.30

0.15

0

0.15

0.30

0.45

Te

mp

era

ture

va

ria

tion

(

C)

Temperature

CO2

Year


How Elevated CO2 Affects Forest Ecology: The FACTS-I Experiment

• The FACTS-I experiment is testing how elevated CO2

– Influences tree growth, carbon concentration in soils, and other factors over a ten-year period

Figure 54.25


The Greenhouse Effect and Global Warming

• The greenhouse effect is caused by atmospheric CO2

– But is necessary to keep the surface of the Earth at a habitable temperature


• Increased levels of atmospheric CO2 are magnifying the greenhouse effect

– Which could cause global warming and significant climatic change


Depletion of Atmospheric Ozone

• Life on Earth is protected from the damaging effects of UV radiation

– By a protective layer or ozone molecules present in the atmosphere


• Satellite studies of the atmosphere

– Suggest that the ozone layer has been gradually thinning since 1975

Figure 54.26

Ozo

ne la

yer

thic

knes

s (D

obso

n un

its)

Year (Average for the month of October)

350

300

250

200

150

100

50

01955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005


• The destruction of atmospheric ozone

– Probably results from chlorine-releasing pollutants produced by human activity

Figure 54.27

1

2

3

Chlorine from CFCs interacts with ozone (O3),forming chlorine monoxide (ClO) and oxygen (O2).

Two ClO molecules react, forming chlorine peroxide (Cl2O2).

Sunlight causes Cl2O2 to break down into O2 and free chlorine atoms. The chlorine atoms can begin the cycle again.

Sunlight

Chlorine O3

O2

ClO

ClO

Cl2O2

O2

Chlorine atoms


• Scientists first described an “ozone hole”

– Over Antarctica in 1985; it has increased in size as ozone depletion has increased

Figure 54.28a, b

(a) October 1979 (b) October 2000


PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

Chapter 55Chapter 55

Conservation Biology and Restoration Ecology


• Overview: The Biodiversity Crisis

– Conservation biology integrates the following fields to conserve biological diversity at all levels

– Ecology

– Evolutionary biology

– Physiology

– Molecular biology

– Genetics

– Behavioral ecology


• Restoration ecology applies ecological principles

– In an effort to return degraded ecosystems to conditions as similar as possible to their natural state


• Tropical forests

– Contain some of the greatest concentrations of species

– Are being destroyed at an alarming rate

Figure 55.1


• Throughout the biosphere, human activities

– Are altering ecosystem processes on which we and other species depend


• Concept 55.1: Human activities threaten Earth’s biodiversity

• Rates of species extinction

– Are difficult to determine under natural conditions

• The current rate of species extinction is high

– And is largely a result of ecosystem degradation by humans

• Humans are threatening Earth’s biodiversity


The Three Levels of Biodiversity

• Biodiversity has three main components

– Genetic diversity

– Species diversity

– Ecosystem diversity

Genetic diversity in a vole population

Species diversity in a coastal redwood ecosystem

Community and ecosystem diversityacross the landscape of an entire regionFigure 55.2


Genetic Diversity

• Genetic diversity comprises

– The genetic variation within a population

– The genetic variation between populations


Species Diversity

• Species diversity

– Is the variety of species in an ecosystem or throughout the biosphere


• An endangered species

– Is one that is in danger of becoming extinct throughout its range

• Threatened species

– Are those that are considered likely to become endangered in the foreseeable future


• Conservation biologists are concerned about species loss

– Because of a number of alarming statistics regarding extinction and biodiversity


• Harvard biologist E. O. Wilson has identified the Hundred Heartbeat Club

– Species that number fewer than 100 individuals and are only that many heartbeats from extinction

(a) Philippine eagle

(b) Chinese river dolphin

(c) Javan rhinocerosFigure 55.3a–c


Ecosystem Diversity

• Ecosystem diversity

– Identifies the variety of ecosystems in the biosphere

– Is being affected by human activity


Biodiversity and Human Welfare

• Human biophilia

– Allows us to recognize the value of biodiversity for its own sake

• Species diversity

– Brings humans many practical benefits


Benefits of Species and Genetic Diversity

• Many pharmaceuticals

– Contain substances originally derived from plants

Figure 55.4


• The loss of species

– Also means the loss of genes and genetic diversity

• The enormous genetic diversity of organisms on Earth

– Has the potential for great human benefit


Ecosystem Services

• Ecosystem services encompass all the processes

– Through which natural ecosystems and the species they contain help sustain human life on Earth


• Ecosystem services include

– Purification of air and water

– Detoxification and decomposition of wastes

– Cycling of nutrients

– Moderation of weather extremes

– And many others


Four Major Threats to Biodiversity

• Most species loss can be traced to four major threats

– Habitat destruction

– Introduced species

– Overexploitation

– Disruption of “interaction networks”


Habitat Destruction

• Human alteration of habitat

– Is the single greatest threat to biodiversity throughout the biosphere

• Massive destruction of habitat

– Has been brought about by many types of human activity


• Many natural landscapes have been broken up

– Fragmenting habitat into small patches

Figure 55.5


• In almost all cases

– Habitat fragmentation and destruction leads to loss of biodiversity


Introduced Species

• Introduced species

– Are those that humans move from the species’ native locations to new geographic regions


• Introduced species that gain a foothold in a new habitat

– Usually disrupt their adopted community(a) Brown tree snake, introduced to Guam in cargo

(b) Introduced kudzu thriving in South CarolinaFigure 55.6a, b


Overexploitation

• Overexploitation refers generally to the human harvesting of wild plants or animals

– At rates exceeding the ability of populations of those species to rebound


• The fishing industry

– Has caused significant reduction in populations of certain game fish

Figure 55.7


Disruption of Interaction Networks

• The extermination of keystone species by humans

– Can lead to major changes in the structure of communities

Figure 55.8


• Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitat

• Biologists focusing on conservation at the population and species levels

– Follow two main approaches


Small-Population Approach

• Conservation biologists who adopt the small-population approach

– Study the processes that can cause very small populations finally to become extinct


The Extinction Vortex

• A small population is prone to positive-feedback loops

– That draw the population down an extinction vortex

Smallpopulation

InbreedingGenetic

drift

Lower reproduction

Higher mortality

Loss ofgenetic

variabilityReduction inindividual

fitness andpopulationadaptability

Smallerpopulation

Figure 55.9


• The key factor driving the extinction vortex

– Is the loss of the genetic variation necessary to enable evolutionary responses to environmental change


Case Study: The Greater Prairie Chicken and the Extinction Vortex

• Populations of the greater prairie chicken

– Were fragmented by agriculture and later found to exhibit decreased fertility


• As a test of the extinction vortex hypothesis

– Scientists imported genetic variation by transplanting birds from larger populations


• The declining population rebounded

– Confirming that it had been on its way down an extinction vortex

EXPRIMENT Researchers observed that the population collapse of the greater prairie chicken was mirrored in a reduction in fertility, as measured by the hatching rate of eggs. Comparison of DNA samples from the Jasper County, Illinois, population with DNA from feathers in museum specimens showed that genetic variation had declined in the study population. In 1992, researchers began experimental translocations of prairie chickens from Minnesota, Kansas, and Nebraska in an attempt to increase genetic variation.

RESULTS After translocation (blue arrow), the viability of eggs rapidly improved, and the population rebounded.

CONCLUSION The researchers concluded that lack of genetic variation had started the Jasper County population of prairie chickens down the extinction vortex.

Num

ber

of m

ale

bird

s

(a) Population dynamics

(b) Hatching rate

200

150

100

50

01970 1975 1980 1985 1990 1995 2000

Year

Egg

s ha

tche

d (%

)

100

90

80

70

60

50

40

301970-74 1975-79 1980-84 1985-89 1990 1993-97

Years

Figure 55.10


Minimum Viable Population Size

• The minimum viable population (MVP)

– Is the minimum population size at which a species is able to sustain its numbers and survive


• A population viability analysis (PVA)

– Predicts a population’s chances for survival over a particular time

– Factors in the MVP of a population


Effective Population Size

• A meaningful estimate of MVP

– Requires a researcher to determine the effective population size, which is based on the breeding size of a population


Case Study: Analysis of Grizzly Bear Populations

• One of the first population viability analyses

– Was conducted as part of a long-term study of grizzly bears in Yellowstone National Park

Figure 55.11


• This study has shown that the grizzly bear population

– Has grown substantially in the past 20 yearsN

umb

er o

f in

div

idua

ls

150

100

50

01973 1982 1991 2000

Females with cubs

Cubs

YearFigure 55.12


Declining-Population Approach

• The declining-population approach

– Focuses on threatened and endangered populations that show a downward trend, regardless of population size

– Emphasizes the environmental factors that caused a population to decline in the first place


Steps for Analysis and Intervention

• The declining-population approach

– Requires that population declines be evaluated on a case-by-case basis

– Involves a step-by-step proactive conservation strategy


Case Study: Decline of the Red-Cockaded Woodpecker

• Red-cockaded woodpeckers

– Require specific habitat factors for survival

– Had been forced into decline by habitat destruction

(a) A red-cockaded woodpecker perches at the entrance to its nest site in a longleaf pine.

(b) Forest that can sustain red-cockaded woodpeckers has low undergrowth.

(c) Forest that cannot sustain red-cockaded woodpeckers has high, dense undergrowth that impacts the woodpeckers’ access to feeding grounds.Figure 55.13a–c


• In a study where breeding cavities were constructed

– New breeding groups formed only in these sites

• On the basis of this experiment

– A combination of habitat maintenance and excavation of new breeding cavities has enabled a once-endangered species to rebound


Weighing Conflicting Demands

• Conserving species often requires resolving conflicts

– Between the habitat needs of endangered species and human demands


• Concept 55.3: Landscape and regional conservation aim to sustain entire biotas

• In recent years, conservation biology

– Has attempted to sustain the biodiversity of entire communities, ecosystems, and landscapes


• One goal of landscape ecology, of which ecosystem management is part

– Is to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planning


Landscape Structure and Biodiversity

• The structure of a landscape

– Can strongly influence biodiversity


Fragmentation and Edges

• The boundaries, or edges, between ecosystems

– Are defining features of landscapes

(a) Natural edges. Grasslands give way to forest ecosystems in Yellowstone National Park.

(b) Edges created by human activity. Pronounced edges (roads) surround clear-cuts in this photograph of a heavily logged rain forest in Malaysia.Figure 55.14a, b


• As habitat fragmentation increases

– And edges become more extensive, biodiversity tends to decrease


• Research on fragmented forests has led to the discovery of two groups of species

– Those that live in forest edge habitats and those that live in the forest interior

Figure 55.15


Corridors That Connect Habitat Fragments

• A movement corridor

– Is a narrow strip of quality habitat connecting otherwise isolated patches


• In areas of heavy human use

– Artificial corridors are sometimes constructed

Figure 55.16


• Movement corridors

– Promote dispersal and help sustain populations


Establishing Protected Areas

• Conservation biologists are applying their understanding of ecological dynamics

– In establishing protected areas to slow the loss of biodiversity


• Much of the focus on establishing protected areas

– Has been on hot spots of biological diversity


Finding Biodiversity Hot Spots

• A biodiversity hot spot is a relatively small area

– With an exceptional concentration of endemic species and a large number of endangered and threatened species

Terrestrial biodiversity hot spots

Equator

Figure 55.17


• Biodiversity hot spots are obviously good choices for nature reserves

– But identifying them is not always easy


Philosophy of Nature Reserves

• Nature reserves are biodiversity islands

– In a sea of habitat degraded to varying degrees by human activity

• One argument for extensive reserves

– Is that large, far-ranging animals with low-density populations require extensive habitats


• In some cases

– The size of reserves is smaller than the actual area needed to sustain a population

Biotic boundary forshort-term survival;MVP is 50 individuals.

Biotic boundary forlong-term survival;MVP is 500 individuals.

Grand TetonNational Park

Wyo

min

g

Idah

o

43

42

41

40

0 50 100

Kilometers

Snake R.

Yellowstone National Park

Shoshone R.

Montana

Wyoming

Montana

Idaho

Mad

ison

R.

Gal

latin

R.

Yellowstone R.

Figure 55.18


Zoned Reserves

• The zoned reserve model recognizes that conservation efforts

– Often involve working in landscapes that are largely human dominated


• Zoned reserves

– Are often established as “conservation areas”

(a) Boundaries of the zoned reserves are indicated by black outlines.

(b) Local schoolchildren marvel at the diversity of life in one of Costa Rica’s reserves.

Nicaragua

CostaRica

Pan

amaNational park land

Buffer zone

PACIFIC OCEAN

CARIBBEAN SEA

Figure 55.19a, b


• Some zoned reserves in the Fiji islands are closed to fishing

– Which actually helps to improve fishing success in nearby areas

Figure 55.20


• Concept 55.4: Restoration ecology attempts to restore degraded ecosystems to a more natural state

• The larger the area disturbed

– The longer the time that is required for recovery


• Whether a disturbance is natural or caused by humans

– Seems to make little difference in this size-time relationship

Rec

over

y tim

e (y

ears

)(lo

g sc

ale)

104

1,000

100

10

1

103 102 101 1 10 100 1,000 104

Natural disasters

Human-caused disasters

Natural OR human-caused disasters

Meteorstrike

Groundwaterexploitation

Industrialpollution

Urbanization Salination

Modernagriculture Flood

Volcaniceruption

Acidrain

Forestfire

Nuclearbomb

Tsunami

Oilspill

Slash& burn

Land-slide

Treefall

Lightningstrike

Spatial scale (km2)(log scale)

Figure 55.21


• One of the basic assumptions of restoration ecology

– Is that most environmental damage is reversible

• Two key strategies in restoration ecology

– Are bioremediation and augmentation of ecosystem processes


Bioremediation

• Bioremediation

– Is the use of living organisms to detoxify ecosystems


Biological Augmentation

• Biological augmentation

– Uses organisms to add essential materials to a degraded ecosystem


Exploring Restoration

• The newness and complexity of restoration ecology

– Require scientists to consider alternative solutions and adjust approaches based on experience


• Exploring restoration worldwide

Truckee River, Nevada. Kissimmee River, Florida.

Equator

Figure 55.22


Tropical dry forest, Costa Rica. Succulent Karoo, South Africa.

Rhine River, Europe. Coastal Japan.Figure 55.22


• Concept 55.5: Sustainable development seeks to improve the human condition while conserving biodiversity

• Facing increasing loss and fragmentation of habitats

– How can we best manage Earth’s resources?


Sustainable Biosphere Initiative

• The goal of this initiative is to define and acquire the basic ecological information necessary

– For the intelligent and responsible development, management, and conservation of Earth’s resources


Case Study: Sustainable Development in Costa Rica

• Costa Rica’s success in conserving tropical biodiversity

– Has involved partnerships between the government, other organizations, and private citizens


• Human living conditions in Costa Rica

– Have improved along with ecological conservationIn

fan

t m

ort

alit

y (p

er

1,0

00

live

birt

hs)

200

150

100

50

01900 1950 2000

80

70

60

50

40

30

Year

Life expectancyInfant mortality

Life

exp

ect

an

cy (

yea

rs)

Figure 55.23


Biophilia and the Future of the Biosphere

• Our modern lives

– Are very different from those of early humans who hunted and gathered and painted on cave walls

(a) Detail of animals in a Paleolithic mural, Lascaux, FranceFigure 55.24a


• But our behavior

– Reflects remnants of our ancestral attachment to nature and the diversity of life, the concept of biophilia

(b) Biologist Carlos Rivera Gonzales examining a tiny tree frog in PeruFigure 55.24b


• Our innate sense of connection to nature

– May eventually motivate a realignment of our environmental priorities

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