1. science
2. biology
3. zoology
4. endangered species

6
Global Interactions 2: Second Edition
unit 1.1
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At the beginning of the twentieth century there were 1.6 billion
people on earth and while pollution and environmental
degradation were common, the problems were generally local.
The world still seemed vast, and large areas remained virtually
untouched by human activity. Just over 100 years later the
world’s population has grown to more than 6 billion and the
environmental problems that have resulted from this rapid
growth now affect the whole planet. Whole ecosystems are at risk;
agricultural and urban developments have degraded the planet
and altered its atmosphere. As habitats are destroyed, the species
of plants and animals that depend on them become extinct.
These problems can only worsen as the world’s population
grows to an estimated 10 billion by 2050, and the size of the
global economy grows to at least five times its present size. Can
this rate of population and economic growth be sustained? What
about the countries of the developing world where millions of
people still don’t have an acceptable standard of living? Do they
have a right to the same standard of living as we in the developed
world have? Can this be achieved without further environmental
degradation? These are the questions that must be answered if
we are to sustainably manage and protect the global environment,
its habitats and biological diversity.
It should not be assumed that human impact on the
biophysical environment is a relatively recent event. For many
thousands of years many indigenous peoples behaved in ways
that transformed ecosystems and led to the extinction of many
species. Such impacts were, however, usually followed by long
periods of environmental stability during which the biophysical
environment adjusted to the human impact. Some experts
argue that the earth’s ecosystems are in fact ‘human artefacts’:
ecosystems modified by thousands of years of human use.
Ecosystems at
Risk: An Overview
Earth provides enough to satisfy every
man’s need, but not every man’s greed.
Mahatma Gandhi, Indian independence leader
We do not inherit the earth from our
ancestors, we borrow it from our children.
Native American proverb
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Analyse the biophysical interactions that lead to diverse
ecosystems and their functioning.
Explain the factors that place ecosystems at risk.
Account for the vulnerability and resilience of ecosystems.
Compare and contrast the vulnerability and resilience of
two ecosystems at risk.
Outline the natural and human-induced modifications that
cause stress in ecosystems.
Explain why it is important to manage and protect
ecosystems.
Evaluate the traditional and contemporary management
strategies used to protect ecosystems.
extended responses
exam-style questions
Ecosystems at Risk: An Overview
7
Newly discovered arboreal, jungle-dwelling kangaroo.
6.2 ERUGIF
Scientists don’t have to venture
into space to discover new worlds.
In late 2005, a team of Indonesian,
Australian and US scientists spent
nearly a month in the Foja Mountains
on the western side of New Guinea
(the part of the island belonging
to Indonesia) surveying the area’s
wildlife and plants. Within minutes
of arriving in the area, the scientists
encountered a bizarre, orange-faced
honeyeater bird. It proved to be a
new bird species; the first discovered
in New Guinea since 1939.
On the second day the scientists
made another amazing discovery
when a male and female Berlepsch’s
six-wired bird of paradise came
into their camp to perform a mating
dance. Until then the homeland of
this ‘lost’ bird had been unknown. It
was the first time Western scientists
had even seen an adult male of this
species.
Another surprise for the scientists
was their discovery of the goldenmantled tree kangaroo. The animal
is the rarest arboreal (tree-dwelling),
jungle-dwelling kangaroo in the
world. This was the first time this
mammal was found in Indonesia,
making it only the second site in the
world where the species is known
to exist.
‘Lost World’:
treasure trove of new
species found in
Indonesian New Guinea
unit 1.1
8
Global Interactions 2: Second Edition
abiotic the non-living components of ecosystems,
such as light, soil, water and air.
aquatic ecosystem a water-based ecosystem, such
as a pond, lake or ocean.
autotrophic organism an organism that
manufactures its own food from sunlight, water
and minerals; also known as a producer organism.
benchmark a standard reference point used in a
study for comparison.
bioaccumulation a process whereby toxic chemicals
are concentrated at successively higher trophic
levels within the food chain.
biodiversity the variety of species and the genetic
variability among individuals within each species.
biome the biological components of an ecosystem.
biotic the organisms that make up the living parts
of ecosystems.
carnivore a meat-eating animal.
community a group of interdependent organisms
living together in a common environment and
interacting with one another.
decomposer an organism that feeds by breaking
down the dead organic matter in an ecosystem.
Examples include bacteria, mushrooms and
fungi. Most chemicals are returned to the soil and
groundwater for reuse by autotrophic organisms.
desertification the process of turning non-desert
lands into desert by poor management of the
ecosystem. It is usually caused by a combination
of overgrazing, soil erosion, prolonged drought and
perhaps climatic change.
dynamic equilibrium a situation in which stability is
achieved in an ecosystem.
ecology the study of organisms and their
relationship to one another and their surroundings.
ecosphere the ecosystem of the planet; the totality
of all ecosystems.
ecosystem the dynamic complex of plant, animal
and micro-organism communities and their nonliving environment as a functional unit.
ecotone the transition zone where one type of
ecosystem blends into another. It usually contains
many of the plant and animal species found in
both ecosystems and sometimes those not found
in either.
existence value the amount of money that people
are prepared to spend or forgo in order to keep
an ecosystem (or species within an ecosystem)
in existence.
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food chain a series of organisms, each eating or
decomposing the preceding one.
food web a network of interconnected food chains.
genetic engineering the science of manipulating the
DNA of organisms to modify organisms.
habitat the environment of a living organism.
herbivore an organism that consumes plants as its
only source of food.
heterotrophic organism a consumer organism that
is unable to make its own food.
interdependence the dependence of organisms
within a habitat on each other for the survival of
their species.
leaching the removal, by water, of minerals from the
upper layers of a soil to the lower layers.
monoculture an environment where one plant
species dominates totally.
nutrients elements or compounds needed for the
survival, growth and reproduction of a plant or
animal.
omnivore an organism that consumes both plants
and animals as a source of food.
option value the money that people are prepared
to pay in order to interact with an ecosystem or
species.
permafrost permanently frozen soils; usually found
in tundra ecosystems.
phytoplankton small, drifting plants, mostly algae,
found in aquatic ecosystems.
predator an organism that captures and feeds on
another species.
producer organism see autotrophic organism.
productivity the rate at which biological matter
(biomass) is produced by an ecosystem or part of
an ecosystem.
species all organisms of the same kind that are
potentially capable of breeding and producing
fertile offspring.
technosphere a sphere of technological influence,
created by people, which overwhelms natural
ecosystems.
terrestrial to do with the land.
xerophytic plants that exist on extremely small
amounts of water.
zooplankton small, floating herbivores that feed on
phytoplankton.
glossary
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6.2 ERUGIF
Temperature
Temperate
scrub or
grassland
Tropical
rainforest
Desert
very hot
Tropical scrub
forest or
grassland
Monsoon
forest
Subtropical
rainforest
s
Precipitation and temperature interact to determine characteristics of ecosystems.
This graph demonstrates how the variability of this relationship results in a wide variety
of ecosystems.
FIGURE 1.1.1
below freezing
Tundra
Northern
coniferous
forests
Temperate
broad-leaved
and mixed
forest
Temperate
rainforest
Climate regions and major terrestrial
ecosysystems
Polar
5000 mm
It is important to note that the components of any ecosystem can vary
naturally or as a result of human intervention. Each variation will, in
Variations in ecosystems
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Ecology is the science that examines the interactions between organisms
and their living (biotic) and non-living (abiotic) environment. The key
word in this definition is interactions. Groups of organisms and their
biophysical environment interact and exchange matter and energy.
Collectively, they form an ecological system or ecosystem. Consequently,
we refer to ecosystems as being dynamic; this means that they are
constantly changing and adapting.
By identifying characteristic patterns of interaction it is possible to
distinguish different types of ecosystem. An ecosystem is, therefore,
defined as an identifiable system of interdependent relationships
between living organisms and their biophysical environment.
Ecosystems are systems through which incoming solar energy
is captured and channelled through a hierarchy of life forms. Each
ecosystem has its own characteristic plant and animal community.
Plants, both on land and in the sea, convert sunlight (via a process
known as photosynthesis) into storable—and edible—chemical energy.
Animals feed on these plants and on other animals. The quest for food
is the central organising principle within ecosystems.
An important feature of ecosystems is the set of processes by which
nutrients are retained and recycled. Living things do not create new
matter. Instead, they recycle nutrients obtained from air, soil, water and
other organisms, using solar energy to build and maintain themselves.
What is an ecosystem?
Ecosystems and their functioning
high
Precipitation
low
6.2 ERUGIF
Ecosystems at risk: An Overview
9
Marya Mannes
The earth we abuse and the living things we kill will,
in the end, take their revenge; for in exploiting their
presence we are diminishing our future.
The requirement for ecologically sustainable
developments has become more widely
accepted. As a result, there is growing
demand for consultants to assist developers
and governments create developments that
are environmentally friendly. Typical areas
these consultants work in are:
addressing soil erosion
recording, mapping and preserving native
flora and fauna
developing strategies to deal with climate
change
dealing with demographic (population)
changes.
Several universities now offer degrees
specialising in environmental consultancy.
Environmental consultant
geojobs
Fungi are an example of recyclers that ensure
nutrients are returned to an ecosystem.
FIGURE 1.1.2
unit 1.1
Tropical scrub forest
Colombo
Mosul
Darwin
Global Interactions 2: Second Edition
Climate strongly affected by altitude
12
Cold all year
Hot dry summer, mild wet winter
Warm to mild summer, cool
to cold and dry winter
Cold most months
with a short summer
Warm to mild summer,
cool to cold winter, wet all year
Singapore
Harbin
Mountains
Tundra
Polar (ice cap)
Warm to mild months, dry in winter
Warm to mild months, wet all year
Hot all year, rainy most months
but with a definite dry season
Hot and mostly dry all year;
unreliable rainfall
Hot and dry all year; unreliable rainfall
Hot and rainy most of the year
Hot and rainy all year
Tropic of Capricorn
Equator
In Salah
Palermo
Gronfjörden
Mediterranean type
vegetation (temperate scrub)
Tropic of Cancer
Arctic Circle
Tropical rainforest
Desert
Temperate broad-leaved and
mixed forest: open woodland
Tropical grassland (savanna)
Temperate grassland: some
areas have widely spaced trees
Monsoon forest
Northern coniferous forest
Tropic of Capricorn
Equator
Tropic of Cancer
Arctic Circle
FIGURE 1.1.6
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Worldwide climatic patterns.
0
6.2 ERUGIF
1000 2000 km
Belo Horizonte
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FIGURE 1.1.7
Churchill
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6.2 ERUGIF
1000 2000 km
The world’s major terrestrial ecosystems.
0
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TABLE 1.1.1
Covered with ice and snow for much of the year; permanently frozen subsoil; 1–3 month
growing season
Treeless; shrubby or mat-like vegetation
Most extensive in Northern Hemisphere
Tundra
Mountain
Ecosystems at Risk: An Overview
13
Source: Australian Academy of Science, Environmental Science
Increasing altitude produces a decrease in temperature, similar to the effect of
increasing latitude
Vegetation types vary with altitude; beyond a certain height, trees do not grow and the
vegetation resembles tundra
Warm and humid; frequent rain; average temperature is 25°C all year; no true seasons;
little change in day length; growth throughout the year; infertile clay soil
Closed canopy; little understorey; large number of plant species (great diversity)
competing for available light; trees often have large trunks and buttressed roots; many
epiphytes (plants that grow on other plants) and vines; little leaf litter
In the tropics but with distinct wet and dry seasons
Trees less closely spaced than in rainforest; many trees shed their leaves in the dry
season
Monsoon forest
Tropical rainforest
Rainfall not abundant; high evaporation
Thorny shrubs and trees
Grades into tropical grassland and savanna
Low rainfall but seasonal heavy storms can occur; frequent fires; thin soil
Grasses with scattered clumps of trees, grading into either open plain or woodland
Very little rain; true desert has less than 100 mm precipitation per year and arid
areas less than 250 mm; high summer daytime temperatures (often >37°C); large
temperature difference between day and night
Widely scattered shrubs; water-conserving plants and non-drought-adapted ephemerals
(grow and set seed quickly on rare occasions when water is available); some very dry,
sandy deserts have almost no plant growth
Generally located between 20° and 35° north and south of the Equator
Long, hot, dry summers; mild winters with reliable rainfall; growth often stops in
summer drought
Open forest with stunted tree growth; woodland and shrubland; many bushes and
shrubs; tough evergreen leaves that are often spiny
Known as chaparral in North America, matorral in Chile and maquis in the
Mediterranean area; also found in parts of southern Western Australia and parts of
South Africa
Tropical scrub forest
Tropical grassland (savanna)
Desert
Mediterranean-type vegetation
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Temperate broad-leaved
and mixed forest
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Erratic rainfall; fires occur
Dominated by grasses and annuals (plants that complete their life cycle and set seed
within a single growing season)
Often exploited for grazing sheep and cattle
Temperate grassland
Warm, mild growing season that varies with latitude; moderate precipitation evenly
distributed throughout year; large seasonal differences and changes in day length;
rich topsoil
Some trees evergreen, some deciduous; well-developed understorey
Long winters with a thick cover of snow; summer short but with long, often warm, days;
3–4 month growing season
Dominated by conifer trees; thick layer of needles on the ground
Occurs on large continental land masses
Northern coniferous
forest (taiga)
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Permanent ice cap, in places up to 5 km deep
No plant growth; no animal life away from coast
Characteristics
Polar
Ecosystem
Characteristics of major terrestrial ecosystems
unit 1.1
54
Global Interactions 2: Second Edition
R.W.B. Carter, coastal geomorphologist
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migrating dune a dune that is created when a
blowout is extended by continued destruction of
the dune system. They move inland, covering the
landscape with sand.
parabolic dune a dune created by blowouts. These
are dunes that take on a ‘U’ shape as they move
back through the dune system.
parallel dunes the lines of dunes that lie behind the
foredune. They form in lines that run parallel to the
beach. Also known as transverse dunes.
prevailing wind the most common direction from
which the wind blows in a given area.
saltation the transportation of particles in a
current of wind (or water) by a series of bouncing
movements.
sand grains of weathered rock, sometimes mixed
with crushed shell.
seres each stage in plant succession as a plant
community develops at a particular site.
suspension particles of sand carried along by the
wind, often well above the ground.
swale a trough or depression that develops between
two adjacent dunes.
washout water washing over the dune system from
inland lakes and water courses.
wave a movement of energy through water caused
by the frictional drag of wind blowing across the
surface of a body of water. The development of the
wave involves the transfer of energy from the wind
to the water’s surface.
Coastal dunes are large accumulations of sand located immediately
behind the active beach zone. They are formed when sand is deposited
onto the shore by wave action, dries out and is blown to the back of the
beach. This process is referred to as accretion.
On coasts where there is relatively little wave action and a large
tidal range, extensive areas of tidal flats are exposed at low tide. As
the tide retreats, the sand dries out and is exposed to the wind. Over
time, prevailing winds shape the sand into a system of dunes. The
dune systems found along the North Sea coasts of Denmark, Belgium,
Germany and the Netherlands were formed under such conditions.
On coasts where the tidal range is relatively small, sand is delivered
to the beach by wave action. The dunes formed under such conditions
rely more heavily on a combination of wave and wind action. Dune
systems formed under such conditions are found along the south-east
and west coasts of Australia, the west coast of Africa and parts of the
east and west coasts of North America.
In some parts of the world, sand has been accumulating since the
Pleistocene period. This is the geological period dating from about
What are coastal dunes?
accretion the growth of a dune due to the buildup
of sand.
aeolian transport the movement of material, such
as sand, by wind.
beach an accumulation of sediment acting as the
boundary between the land and sea.
beach nourishment the artificial replenishment of
beach sand.
berm the first component of the dune system.
It lies closest to the water’s edge and is created
by waves piling up sand. It is sometimes referred
to as an incipient dune.
blowout the movement of sand inland, often
resulting from a disturbance to the dune
vegetation.
coastal dunes exposed shoreline systems of
one or more sand ridges derived from material
transported by wind and waves.
current the flow or movement of a large body of
water in an ocean. The movement is caused by
prevailing winds, the earth’s rotation and the
distribution of the continental land masses.
Dune Care a community based action group that
aims to preserve, protect and rehabilitate coastal
dune ecosystems.
foredune the coastal dune or line of dunes that is
found behind the berm. Foredunes are subject
to erosion and their form and composition are
constantly changing. Also known as a frontal dune.
longshore drift the movement of sediment by
currents running parallel to the shore.
Of all the coastal ecosystems, sand dunes have
suffered the greatest degree of human pressure.
Many sand dunes have been irreversibly altered
through the activities of [people], both by accident
and design.
glossary
Coastal dunes are found on all the world’s continental land masses, with
the exception of Antarctica. They form wherever there is sand available
for their construction.
Sand—grains of weathered rock—can be classified as very coarse
(with a diameter of 1–2 mm), coarse (0.6–1 mm), medium (0.2–0.6 mm)
and very fine (0.06–2 mm). Windblown desert sand is usually finer than
beach sand. Beaches generally obtain their sand from rivers flowing to
the sea and from the wearing away of cliffs.
In some coastal areas other forms of coastal sediments dominate.
In the south-east of England, for example, the primary sediment type
is shingle. These are rounded, waterworn stones, which have been
eroded from the surrounding cliffs. In such circumstances dunes do not
have the opportunity to develop. The source of coastal sediments is,
therefore, very important in determining whether sand is available for
the construction of coastal sand dunes.
The other significant factor is wind. It is the single most important
factor in determining the shape and extent of coastal dunes. Dunes are
most likely to develop in coastal regions that experience strong onshore
prevailing winds. For this reason the most extensive dune ecosystems
Spatial distribution and dimensions
of coastal dune ecosystems
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2 million years ago to the end of the last Ice Age, about 10 000 years ago.
These ancient sand deposits have, over time, developed into enormous
dune fields that have significantly altered the topography of the land.
Massive dune fields, with dunes stretching back many kilometres
from the beach, often develop in areas where arid lands are found
adjacent to the coast. Desert dunes, which are formed by the wind
shifting dry sands, sometimes merge with the coastal dunes formed by
the landward movement of beach sands. Such dune fields are found
along the coasts bordering the Sahara Desert in North Africa and along
Western Australia’s northern coastline. These dunes can grow to vast
heights and can be several kilometres in length. (See figure 1.2.1.)
6.2 ERUGIF
Coastal Dunes
55
G. Soucie, environmentalist
The real conflict of the beach is not between sea
and shore, for there is only a lover’s quarrel, but
between man and nature. On the beach, nature has
achieved a dynamic equilibrium that is alien to man
and his static sense of equilibrium.
Massive dune fields have developed along the arid
coast of northern Western Australia.
FIGURE 1.2.1
Geographers study natural hazards and
the impact that these can have on the
environment and communities. Emergency
managers are trained to find ways to reduce
the risks of natural hazards and to protect
communities that are in hazard-prone areas.
Emergency manager
geojobs
unit 1.2
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58
Global Interactions 2: Second Edition
In November 1970 a massive storm surge and
cyclone hit the coast of India and Bangladesh
and was responsible for as many as 300 000
deaths.
did you know?
storm surge a very high tide created by a
combination of a king tide (the highest tide in
a tidal cycle) and a large storm.
>
Much of the sediment used for dune building comes
from the erosion of headlands and other coastal
features.
FIGURE1.2.6
2.6
FIGURE
1 Interpreting diagrams Examine figure 1.2.3.
Describe the relationship between wind
velocity and the rate of aeolian transport.
Explain what this indicates about the role of
wind in dune construction.
2 Writing task Write a report outlining the role
of weather in the development of coastal
dune systems.
3 Writing task Study the Geofocus box ‘Aeolian
transport’.
a Study figure 1.2.4. Write a brief report on
the ways wind transports sand.
b Write a paragraph explaining the terms
saltation and critical velocity.
c Distinguish between the processes of
surface creep and suspension.
working geographically
1 Define and explain the term aeolian transport.
2 Outline the factors that affect the rate of
aeolian transport.
understanding the text
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Hydrological processes are those that involve water, which is one of the
most important agents of change on earth. Along coasts it is a critical
factor in determining the nature of coastlines. River systems transport
sediment to the coast, where it is distributed by longshore drift and
ocean currents. Waves erode cliffs and headlands, providing additional
sediment. (See figure 1.2.6.) Storm waves cause damage to beaches, but
constructive waves rebuild them.
Wind-induced waves play a particularly important role in the
development of coastal dunes. Waves transport the sand that is needed
for dune construction and they create change in dune systems by
attacking them during storms.
During periods of relatively calm weather, waves bring sand from
offshore deposits (such as offshore bars) and deposit it onto beaches.
This sand is then available for the wind to transport it into the dune
system. In periods of severe and unstable weather, storms create large
and powerful waves that strike the coast with such force that they
remove sand from beaches and the foredune area. In very severe storms
the waves may attack the dune system, creating washovers. (These
events are examined in more detail on page XXX.)
In addition to the action of waves there is a range of other hydrosphererelated processes that impact on coastal dunes. The effect of currents is
very important, particularly the process of longshore drift.
The importance of longshore drift lies in its role as a transporter of
sediment. Sediment, which is produced or deposited in one part of the
coastal system, is transported to other locations within the system by
the process of longshore drift. This allows dunes and other sedimentbased landforms to develop in areas some distance from the source of
coastal sediments.
Queensland’s Fraser Island, a vast island made entirely of sand,
demonstrates this point. Some of the sand that makes up the island and
its huge dune system is derived from sandstone deposits found in the
Sydney region. Longshore drift and ocean currents have transported the
sand northwards along Australia’s eastern coastline.
Rainfall is another important factor in the development of coastal
dunes. While rainfall infiltrates sand dunes with relative ease, heavy
downpours can produce runoff, which erodes the sandy surface,
exposing it to the wind. Another important change caused by rainfall is
the development of dune lakes. These lakes form in low-lying areas of
the dune system. Fraser Island has a large number of dune lakes.
Hydrological processes
Precipitation
Levels of precipitation (rainfall) are also important in determining the
nature and extent of the vegetation binding the sand together. Areas
with regular rainfall are more likely to have a vegetation profile. Areas
with low or irregular rainfall are likely to remain unstable and support
little vegetation growth.
Temperature
Temperature plays an important role in determining the rate at which
beach sand dries and the extent and type of vegetation that grows in
an area. As mentioned above, vegetation plays an important role in
determining the rate of aeolian transport. The temperature also affects
the functioning of ocean currents. These currents may have the potential
to move sediment long distances or to cause beaches to be eroded or
built up.
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FIGURE 1.2.7
6.2 ERUGIF
B
Sand is not uniform. Its chemical and mineral composition varies
greatly from place to place. This is because sands have been derived
from different types of rock. The chemical and mineral composition
of sands is very important in determining the nature of coastal dune
ecosystems.
Composition of sands
A Chandeleur Islands in 2001. The extensive dune system is visible. B Chandeleur
Islands following Hurricane Katrina in 2005.
A
The Chandeleur Islands are a collection of low-lying islands
off the coast of New Orleans, in the southern United States.
An extensive dune system is found on the islands and a
unique ecosystem had developed over a long period of time.
This part of the US coastline is very susceptible to
hurricane activity, with several large hurricanes striking
the islands since 2000: Hurricane Lili (2002), Hurricane
Ivan (2004) and Hurricane Dennis (2005). However, it was
Hurricane Katrina in August 2005 that caused the most
damage to the dune system.
geofocus
Coastal Dunes
59
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1 Outline the role of hydrological processes
in the formation of coastal sand dunes.
2 Explain the contribution of longshore drift
to the development of coastal dunes.
3 Explain the processes involved in the
development of dune lakes and swales.
4 Define the term ponding. Why is it so
significant to the dune environment?
understanding the text
Figure 1.2.7A show the Chandeleur Islands in 2001.
As can be seen, a large dune system is located around
the edges of the islands. Figure 1.2.7B is taken in the
days following Hurricane Katrina. As is clear, the
whole dune system has been destroyed by a
massive storm surge that has engulfed much
of the islands.
Impact of Hurricane Katrina on the
Chandeleur Islands
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In times of heavy rainfall, surface runoff accumulates in a swale,
which is a trough or shallow depression between the crests of coastal
dunes. Eventually the sand becomes saturated and the water table rises.
With the return of warmer weather, the swale dries out and the water
table retreats. By this time, however, much of the protective vegetation
has drowned and the sand is now left exposed. This causes a migrating
dune to form and begin moving away from the now dry lake.
In some locations, notably on Fraser Island, dunes may form across
the mouth of a valley. If a stream runs through the valley, ponding may
occur: the dunes, acting like a dam, hold back the stream’s water and
so a lake is formed. Such lakes tend to be semipermanent (or in some
places permanent) and cause a major change in the local environment,
encouraging different flora and fauna to colonise the affected area.
unit 1.2