3.4.1 -
Biodiversity Enquiry question: What is the nature and value of biodiversity?
patterns
The different ways of defining biodiversity in terms of genetic, species and ecosystem diversity
and the merits of each.
Defining Biodiversity
Biodiversity: the flora and fauna species found in an ecosystem.
Ecosystem: communities of plants and animals (biotic) interacting with non-living (abiotic)
components of their environment working together as a natural system.
o Biotic and abiotic factors are linked through nutrient cycles and energy flows.
Biodiversity is often used as a measure of the health of biological systems.
Definition Advantages Disadvantages
Genetic Genetic variation within Accurate picture of diversity – Hard to determine as would
Diversity one species. shows the gene pool within a need to analyse the DNA of
species, which can indicate the many individuals of a species,
health of a species. Small gene which requires a lot of skill,
pool may lead to extinction as time and money.
individuals unable to
successfully breed.
Explains how isolated groups
have adapted.
Species The number of different Good general measure as it Areas need to be of similar size
Diversity species in an area uses a range of indicator to compare.
(species richness). species.
Hard to ensure all species
Can indicate the health of an within an ecosystem are
ecosystem – a large number of represented, e.g.,
different species in an undiscovered microscopic
Biodiversity ecosystem indicates high species – may skew
can be biodiversity, so the ecosystem biodiversity index.
defined in is stable.
different Species richness does not
cover the distribution or
ways
interaction between different
species.
Ecosystem Range of different Useful when assessing areas to Difficult to determine the
Diversity ecosystems, habitats and protect as has a wider focus. boundary of an ecosystem.
niches in an area. Need consistent set of criteria
Shows biodiversity on a global to demarcate an ecosystem.
scale.
Complex – need to measure
interaction of species in their
environment and with each
other.
The processes and factors that influence biodiversity (climate limiting factors, isolation and the
role of endemism, age and area, human activity and actions).
Factors Influencing Biodiversity
Process/
Influence on Biodiversity
Factor
Climate Climate limiting factors (temperature, humidity, precipitation) determine the limits within
Limiting which species exist.
Factors Biomes and biodiversity found in an area is closely correlated to the type of climate
experienced.
o Equatorial areas (tropical rainforest): high levels of sunlight, warmth and
precipitation means year-round productivity, high levels of biodiversity and
biomass, and rapid plant and animal reproduction. E.g., Indonesian islands
and central Africa, which have warm temperatures and high levels of
precipitation, resulting in lush, green forests and a wide range of
biodiversity. Tropical rainforests have the highest biodiversity in the world,
, with over half of the world’s species, but only cover 7% of the Earth’s
surface.
o Sub-tropical areas (desert): high temperatures and little rainfall, e.g.,
northern Africa and west-central Australia contain sparse vegetation. Lack of
rainfall is a limiting factor in plant and animal growth, so restricts biomass
and biodiversity.
o Polar areas (tundra): lack of light and warmth are limiting factors, so
biodiversity is low.
The climate experienced in an area is directly influenced by the latitude.
o Temperature decreases with increasing latitude.
Climate affects GPP and NPP.
o GPP: the rate at which plants photosynthesise.
o NPP: the amount of CO2 vegetation takes in during photosynthesis minus
how much CO2 the plants release during respiration (the proportion of GPP
available to consumers).
o GPP = NPP – energy lost from respiration
o Plants form the base of all terrestrial food chains and grow best in warm,
moist conditions.
o Biomes with highest biodiversity also have highest NPP, e.g., rainforests:
lack of climate limiting factors = high NPP = high biodiversity (species
richness) as more life can be supported.
o Animal diversity is greatest with great plant diversity.
Isolation Endemism: the ecological state of being unique to a particular location.
and High biodiversity in highlands and on islands.
Endemism o Islands: physical isolation, so evolution leads to new species, resulting in
high, endemic biodiversity.
o Mountainous isolated areas: same process with island; additionally,
altitudinal zonation – temperatures, season length and precipitation levels
change up a mountain side, resulting in different environments at different
altitudes, each with their own species types.
Age and Large areas, e.g., Australia, have higher biodiversity than small ones as they can
Area support more species in complex food chains.
Places that have remained relatively unchanged for millions of years, especially
when physically isolated, have experienced unique evolutionary processes and often
have high biodiversity levels.
Human Urbanisation, human population growth, expansion of farming, deforestation,
Activity pollution, tourism, mining and climate change can destroy ecosystems and reduce
biodiversity as there is greater competition for space and resources.
Threats vary spatially.
Humans can protect biodiversity by conservation and preservation, but very rarely
can they restore lost biodiversity.
Case Studies
Costa Rica’s Rainforest
Holds 4% of world’s species (over 500,000 species) in 0.33% of the world’s area.
Many endemic species – 10% of species are endemic.
High ecosystem diversity: cloud forest, mangroves, coral reefs.
Natural Factors
Climate Lies 9-11° N of the equator, within the tropical climate zone.
Tropical rainforest biome: average annual temperature is 21-27°C, rain occurs year-
round, but the wet season between May-November brings intense, consistent rainfall.
Age and Richness of biodiversity is due to Costa Rica’s central location in the Americas,
Area allowing it to accumulate species from the combining of the northern and southern
continents 4 million years ago.
Isolation Rainforests lie on the eastern and western margins of Costa Rica, so different species
and are found in both areas.
Endemism The Pacific coast is more indented and more mountainous and has a number of
discontinuous sections of rainforest extending ¾ of the country, allowing for
endemism to develop.
Human Factors
Eco- Canopy tours – hanging bridges and ziplines through the rainforest.
tourism $2bn/year from eco-tourism.
Conservati Over ¼ of land is protected as national park, wildlife refuge and forest reserves. There
on and are three UNESCO World Heritage Sites in Costa Rica.
, Preservati Compensation paid to landowners to dissuade them from clearing their land.
on Costa Rica has 4th highest deforestation rate in the world, losing 4% of forested areas
to agriculture (primarily cattle ranching).
Australia’s Savanna Grasslands
Natural Factors
Climate Distinctive two-season savanna climate – long, hot dry season and short, hot wet
season.
Short wet season from December-March as the ITCZ shifts southward.
o 200 mm of rain in February, 7 mm in May, no rain between June-early
September.
High temperatures year-round.
o Average monthly temperatures over 30°C every month. Almost 39°C in
November.
Age and Tropical savanna extends across the northern third of Australia from the west to east
Area coast and accounts for 23% of Australia’s surface.
Isolation Vegetation has adapted to extended hot, dry season, with grasses dominating the
and area.
Endemism Trees, e.g., eucalyptus, stay green throughout the year and have small, tough rubbery
leaves which reduce transpiration when there is a shortage of water.
Vegetation adapted to cope with frequent fires. Lightning strikes in the hot, dry
season can ignite fires which spread through grasses. Grass root systems can survive
fires and tree seeds are adapted to resist fire.
Human Factors
Human Mineral mining
Developm o Australia produces bauxite, alumina
ent Cattle grazing
o Invasive animal species, e.g., buffalo, pigs, cane toads, can damage
ecosystem by removing natural vegetation and leading to increased soil
erosion.
o Invasive weeds eradicate native plant species.
Climate Forecast of average annual temperature increase of 1-6°C by 2070.
Change Decrease in average rainfall in Queensland and overall drying tendency.
Desertification – central deserts of continent expand and convert savanna into desert,
making the remaining savanna more vulnerable to further environmental change.
The global distribution of terrestrial biomes is related to climate, but local factors (altitude,
The
soils, drainage) also play a role. (6)
distribution
of Terrestrial Biomes
biodiversity
Biome: ecosystem on a global scale; a large area of land characterised by the same ecosystem (same
depends on
a range of biotic and abiotic factors).
factors Latitude: the distance of a place north or south of the equator.
o Latitude influences the amount of insolation received, and so affects temperature, leading to
different biomes being formed.
