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Environmental Systems > Threats to Biodiversity > Flashcards

Threats to Biodiversity Flashcards

1
Q

How many species are there in the world?

A

A conservative estimate = 7million

Most are terrestrial animals
2/3 in tropics

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2
Q

What proportion of tropical rainforests have been cleared by humans?

A
  • 50% tropical rainforest has been cleared by humans

- Many countries have no primary forest left

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3
Q

How many species have been described and named?

A

Only between 1.4million and 1.8million

Mostly smaller organisms that haven’t been found e.g. insects, fungi, bacteria

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4
Q

What is extinction and is it a natural process?

A

Extinction : when a species ceases to exist after the last individual in that species dies

It is a natural process // eventually all species become extinct
Most mammals have a species lifespan of 1 million years

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5
Q

What does biologist E.O Wilson think about the current extinction rate?

A

E.O Wilson thinks that:

  • current rate of extinction is 1000x background rate
  • 30-50% of species could be extinct within 100 years
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6
Q

Why do biodiversity hotspots have greater rates of extinction?

A
  • 50% of flora + fauna are in one of the 30 hotspots which together make up only 2% of the land area on Earth
  • These areas are very vulnerable to habitat loss + many species within them are endemic
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7
Q

With a more complex food web, is an ecosystem more or less resilient?

A

> The more complex a food web, the more resilient it is to the loss of one species or reduction in its population size
If one type of prey // food source // predator is lost, others will fill the gap left

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8
Q

Why are communities in young ecosystems that are undergoing succession more vulnerable ?

A
  • When flora+fauna colonise bare land, there are few species at first
  • Species diversity increases w time until a climax community is reached when species composition is stable
  • So communities in young ecosystems undergoing succession may be more vulnerable than those in more resilient + stable older ones
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9
Q

How can the presence of limiting factors accelerate the process of extinction?

A
  • Difficult for organisms to get enough raw materials for growth e.g. water is limiting in a desert
  • Any change that makes it even harder may result in species disappearing
  • If abiotic factors required for life are in abundance (water, light, nutrients) the system is more likely to manage if one is reduced
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10
Q

What is inertia of an ecosystem?

A

Inertia is the property of an ecosystem to resist change when subjected to a disruptive force.

It is key to helping planners know which site will resist change // recover most quickly

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11
Q

What are natural hazards?

A

Naturally occurring events that may have a negative impact on environments (+humans)

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12
Q

What are environmental disasters?

A
  • caused by human activity
  • e.g. loss of tropical rainforest on massive scale
  • e.g. oils spills
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13
Q

What is the major cause of loss of biodiversity and give 3 examples?

A

Loss of Habitat

  • In Philippines, Vietnam, Sri Lanka, Bangladesh (high human pops.) most wildlife habitat + primary forest lost
  • Mediterranean // only 10% original forest cover remains
  • In Madagascar by 2020, predicted only protected moist forest area left // home to lemurs + other endemic species which could become extinct
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14
Q

What is fragmentation of habitat?

A
  • A large area is divided up into a patchwork of fragments
  • Separated from each other by roads, towns, fences, fields etc…
  • Fragments are isolated in a degraded landscape + act as islands
  • Higher edge to area ratios as fragments get smaller
  • Greater fluctuations of light, temp + humidity at edge than middle
  • Invasion of habitat by pests // humans increases + spread of disease increases
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15
Q

What is pollution?

A

Pollution caused by human activities can degrade or destroy habitats + make the unsuitable to support the range of species that a pristine ecosystem can support

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16
Q

Name two examples of local pollution

A

Spraying of pesticides may drift into wild areas

Oil spills may kill many sea birds and others

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17
Q

What can environmental pollution lead to?

A

Environmental pollution by emissions from factories and transport can lead to acid deposition or photochemical smog

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18
Q

2 examples of when introducing non-native species has worked

A
  • potatoes from the Americas to Europe

- rubber trees from the Amazon to SE Asia

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19
Q

3 examples of when introducing non-native species has been a disaster

A
  • Dutch Elm disease came from imported American logs to Europe + decimated elm populations
  • Sudden oak death also imported same way
  • Flora+fauna in Australia well adapted to environment but has been unable to compete with aggressive invasive species e.g rabbits, red foxes, camels, blackberry
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20
Q

Name a population that was wiped out in the wild by the spread of disease

A

The last population of black-footed ferrets in the wild was wipe out by canine distemper in 1987

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21
Q

How do modern agricultural practices reduce biodiversity?

A
  • monocultures
  • genetic engineering
  • pesticides

Fewer species + varieties of species are grown commercially and more + more pest species removed

22
Q

What is the importance of tropical rainforests?

A
  • contain over 50% of all species of plants + animals on Earth in just 6% of the land area
  • produce 40% of oxygen that animals use
  • high species diversity
  • high habitat diversity
23
Q

How much of the land area on Earth did tropical rainforests cover in 1950?

A

14% of the Earth’s land surface

24
Q

How much of the Earth’s timber is in tropical rainforests?

A

50% of the Earth’s timber is in tropical rainforests

Timber is the next biggest resource after oil in the world today

25
Q

How many people live in the wet tropics?

A

At least 2 billion people live in the wet tropics + many of these rely on rainforests for subsistence agriculture

26
Q

Why is a low density human population sustainable in the tropical rainforest?

A
  • A low density of human population is sustainable as they clear a small area of forest, grow crops for two or three years then move on to the next as the soil is exhausted
  • This is called shifting cultivation
  • Works as long as there is enough time for forest to regenerate before the same area is cleared again (up to 100 years)
27
Q

What happens if the forest does not fully regrow before it is cleared again?

A

There is a gradual degradation of nutrients + biodiversity

28
Q

Once plants are cleared or burned, why does fertility reduce rapidly?

A
  • Fast rate of respiration + decomposition means forests are v fertile w high levels of biomass in trees + plants
  • Most nutrients held in plants, not the soil
  • Once plants cleared // burned, fertility reduces rapidly because heavy rainfall washes the nutrients + soil away
  • Vegetation is not there to lock up the nutrients nor to protect the soil
  • So more forest is cleared to get the short-term fertility for crop growth
29
Q

How does a narrow geographical range increase the risk of extinction?

A

If a species only lives in 1 place + that place is damaged or destroyed, the habitat is gone

e.g. the Golden Lion Tamarin

30
Q

How does a low genetic diversity (small pop. numbers) increase the risk of extinction?

A
  • A small pop. has a smaller genetic diversity + is less resilient to change
  • As individual numbers fall, there is more interbreeding until pops. are so small they are the ‘living dead’ or become extinct

e.g. Snow leopard, tiger, Lonesome George

31
Q

How do low population densities + large territories increase the risk of extinction?

A
  • If an individual of a species requires a large range over which to hunt + only meets others for breeding, then habitat fragmentation can restrict it territory
  • If there’s not a large enough area left, or they’re unable to find each other (due to city/road/farm splitting up territory) they are less likely to survive

e.g. giant panda

32
Q

How do large bodies increase the risk of extinction?

A
  • the 10% rule means that large top predators are rare
  • they tend to have large ranges, low pop. densities + need a lot of food
  • they also compete w humans for food, may be a danger to humans + are hunted for sport
33
Q

How does a low reproductive potential increase the risk of extinction?

A

Reproducing slowly + infrequently means the population takes a long time to recover

e.g. whales

34
Q

How does migrating seasonally increase the risk of extinction?

A
  • Migrating animals need the habitats at both ends of the migration route. If one is destroyed, they get there to find no food or habitat
  • Barriers on their journey can precent them from completing it e.g. salmon trying to swim upriver to spawn
35
Q

How does having niche requirements increase the risk of extinction?

A

e.g. the giant panda (only 2000 left) mostly eats bamboo shoots in forests in central China

36
Q

How does being edible to humans and herding together increase the risk of extinction?

A

Overhunting or over harvesting can eradicate a species quickly, esp. if species lives in large groups e.g. shoals of fish

Also under threat from humans are tigers // whilst not eaten, their body parts are used in traditional Chinese medicine so demand for them is v high

37
Q

How doe being an island organism increase the risk of extinction?

A

Dependent of the size of the island:

  • populations tend to be small
  • islands have high degree of endemic species
  • genetic diversity tends to be low
  • vulnerable to introduction of non-native species to which they have no defence mechanism

e.g. the dodo

38
Q

What is the minimum viable population size for large carnivores?

A

Thought to be 500 individuals

  • There may be 400 Sumatran tigers left
39
Q

What is the ICUN?

A
  • World Conservation Union
  • Aim is to encourage + assist societies to conserve the diversity of nature
  • To ensure use of natural resources is ecologically sustainable
40
Q

What is the ICUN Red List?

A

Determines conservation status of a species based on several criteria including:

  • population size
  • degree of fragmentation
  • trophic level
  • probability of extinction
41
Q

How many species on the ICUN Red List are listed as threatened?

A

40%

42
Q

Recovered species - Golden lion tamarin // description

A
  • Small monkey
  • Endemic to Atlantic coastal rainforests of Brazil
  • Amongst rarest animals in world
  • 1000 in wild and 500 in captivity
43
Q

Recovered species - Golden lion tamarin // ecological role

A
  • omnivores
  • prey to large cats, birds of prey
  • live in family groups in tropical rainforest in the canopy
44
Q

Recovered species - Golden lion tamarin // pressures

A
  • only 2% of native habitat is left
  • poaching can get US$20,000 per skin
  • predation is great in the wild + their food source is not dependable
45
Q

Recovered species - Golden lion tamarin // methods of restoring populations

A
  • Captive breeding programme for last 40yrs
  • Over 150 institutions involved + exchange individuals to increase genetic diversity
  • Some reintroduced into wild but only 30% success rate as habitat is threatened + many predators (inc. humans)
46
Q

Extinct species - Dodo // description

A

Large flightless bird endemic to island of Mauritius

47
Q

Extinct species - Dodo // ecological role

A
  • No major predators on Mauritius so dodo had no need of flight
  • Dodo was a ground-nesting bird
48
Q

Extinct species - Dodo // pressures

A
  • In 1505 Portuguese sailors discovered Mauritius + ate dodo as source of fresh meat
  • Later, island used as penal colony + rats and monkeys introduced
  • These at dodo eggs + humans killed them for sport and food
  • Conversion of forest to plantations destroyed their habitat
  • Known to be extinct by 1681
49
Q

Extinct species - Dodo // Consequence of disappearance

A
  • island fauna impoverished by loss of dodo

- became an icon due to its apparent stupidity (it had no fear of humans, never having had need to fear predators)

50
Q

Mountain gorilla, Rwanda (critically endangered, umbrella species) // why endangered?

A
  • For years has been victim of deforestation, poaching + accidental victim of civil wars + unrest
  • Destruction of its habitat has left it without a home or food source
  • Population been reduced to 800 members
50
Q

Mountain gorilla, Rwanda (critically endangered, umbrella species) // why is it critically important they should be conserved

A
  • Ecocentrics argue gorillas have intrinsic value + human impact on environment should be reduced
  • Conservation of gorillas requires preservation of forest, land + food sources
  • Not only conserve gorilla but also retain ecosystem they’re part of + species within it
  • Anthropocentrics argue gorillas have aesthetic value (ecotourism)
  • Many people visit countries like Rwanda with sole intention of seeing gorillas + this has given struggling economy boost + positive international attention

Environmental Systems (30 decks)

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