A2 Edexcel geography, unit 3- biodiversity under threat revision notes

Overview and notes for biodiversity under threat.

Edexcel, A2, contested planet.

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Biodiversity under threat
Defining biodiversity
Key definitions
BIODIVERSITY-this is the variety of genes, species and ecosystems in an area.
BIOSPHERE-this is the thin veneer of living material on the planet's surface.
BIOME-this is a global scale ecosystem, e.g. tropical forest.
BIOMASS-this is the total weight of living matter.
ECOSYSTEM DIVERSITY-this is the range of different ecosystems, habitats and niches in an area.
SPECIES DIVERSITY-this is the number of different species within in an area.
GENETIC DIVERSITY-this is the genetic variability within all species.
Examiner's tip: remember that the more isolated a location (e.g. an island) the more evolution is likely to take a distinctive
course. The evolutionary divergence produces unique endemic species.
What is the importance of biodiversity?
30 million species approximately on the Earth but only 1.4 million have been identified.
Biodiversity hotspots
Typical mistake: many candidates think that a hotspot is an area of
high biodiversity. However, it is an area of high biodiversity that is
under threat.
Species richness is 0.5% of the world's recorded plant species.
High level of endemism usually above 50%.
Severe levels of threat from human actions.
Hotspots hold a high number of endemic species yet their combined remaining habitat on the Earth is 2.3%.

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Hotspots have lost 70% of their natural vegetation.
Types of hotspots
Examiner's tip: learn the names and locations of at least one of each of the three types of land-based biodiversity hotspots.
1. Continental hotspots, e.g. Brazil's Cerrado.
2. Large island hotspots, e.g. Madagascar.
3. Small island hotspots, e.g. Sri Lanka.
In addition, 11 marine hotspots are also recognised and all of them contain coral reliefs which are threatened by human activities.
They only account for 0.025 of the oceans.…read more

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Light intensity
There is a range of ecological zones as a result of altitude and each with its own endemic species. Commonly, biodiversity is high on
large, high tropical (low latitude) islands, e.g. Madagascar.
Large areas
This is because of the complex food chains.
Decay and nutrient cycling are rapid in tropical soils.
Lack of limiting factors
This increases the rate of evapotranspiration and wind-chill factor.
This is found in one place/region and not found naturally anywhere else.
1.…read more

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Energy flows
Primary producers convert sunlight into chemical energy and as energy is lost, the volume of biomass decreases.
Goods and services of an ecosystem
Goods Services
Medicine Habitats
Timber Carbon sink
Water cycle
PROVISIONING SERVICES-they are products, e.g. food.
REGULATING SERVICES-they are benefits, e.g. climate.
CULTURAL SERVICES-they are non-material benefits, e.g. recreation.
SUPPORTING SERVICES-they are essential, e.g. forming soil.
Tropical rainforests
Gersmehl's nutrient cycle.
Biodiversity threats
Examiner's tip: it is not just terrestrial (land) biomes and ecosystems that are under threat.…read more

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EXTINCTION-this is a natural event of death of all members of a species but humans are accelerating the rate of extinctions.
Examiner's tip: candidates often confuse the destruction of an ecosystem (e.g. shrimp farming) with the more gradual
degradation of an ecosystem (e.g. by over-exploitation or tourism).
Human threats
Daintree rainforest
Covers 0.2% of Australia.
It is designated a World Heritage Site, parallel to the Great Barrier Reef.
70% of tourists are independent travellers.
Largest range of ferns in Australia.…read more

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Cycle of decline
Players and stakeholders
Key player Opinion expressed
The Wet Tropics Management Authority It is responsible for managing the World Heritage Site. It wishes
to research and monitor the state of the World Heritage Site. Its
aim is to develop management agreements with landholders
and Aborigines.
Cairns council It maintains economic growth and biodiversity by determining
issues such as planning permission to maintain the tourist
numbers.…read more

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World Biodiversity Reserve
Physical geography
18 main islands, 3 smaller islands and 107 rocks.
Upwelling of nutrients as a result of the cold currents.
El Nino and La Nina: El Nino causes temperature rise and La Nina vice versa.
Threats to the Galapagos Islands
1. Invasive species (e.g. goats) are brought accidentally/by humans and the native species don't have natural predators so
the alien species dominate the habitat.
2. Fishing (e.g.…read more

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It is a fragile and vulnerable ecosystem. The tundra has very low organic productivity (primary productivity) is a measure of how
quickly vegetation grows. The ANWR lies in the Arctic tundra and has a polar climate. The winters are long, dark and cold with short
summers. Precipitation is low (known as a cold desert) and winds are strong.…read more

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When was the ANWR created?
The region first became of federal protection in 1960
Western Arctic Reserve
They are known as the National Petroleum Reserve because it was designated by the US Congress as an area of strategic oil and gas
reserves which the nation could draw on. It is a region of pristine wetlands which in the summer, they are habitats to millions of
Environmental factors from oil and gas exploration
1. Land and oil production.
2.…read more

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Regional organisations, e.g. TVE Asia Pacific
Advantages Disadvantages
Raised awareness of the importance of mangroves. Doesn't provide enforcement, it is only advice.
Use of the media and so equal access.
Allows local communities to reach the initiative and do it
NGOs, e.g. Wetland International
Advantages Disadvantages
Provides further support through grants and equipment to Advice does not enforce activities.
resolve the environment.
Includes private companies which influences their actions and
prevents them damaging the environment.
Not focused on making a profit.…read more


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