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3.3. THREATS TO BIODIVERSITY (Factors that lead to loss of biodiversity…
3.3. THREATS TO BIODIVERSITY
Knowledge and Understanding
global biodiversity is decreasing rapidly due to human activity
classification of species conservation status can provide a useful tool in conservation of biodiversity
estimates of total number of species on earth varies - current rate of species loss are far greater than in the recent past due to increased human influence
human activities that cause species extinctions include habitat destruction, introduction of invasive species, pollution, overharvesting and hunting
International Union for Conservation of Nature
(IUCN)
publishes data in the red list of threatened species in several categories
Factors used to determine the conservation status of a species include
Population size
Degree of specialisation
Distribution
Reproductive potential and behaviour
Geographic range + degree of fragmentation
quality of habitat
trophic level
Probability of extinction
tropical biomes - some of the most biodiverse areas - their unsustainable exploitation results in massive losses in biodiversity and their ability to perform globally important ecological services
Most tropical biomes occur in LEDCs and therefore there is a conflict between exploitation, sustainable development and conservtion
Factors that help maintain biodiversity
Complexity of the ecosystem
the more complex, the more resilient to loss of species or reduction in population size - in one type of prey or food source or predator is lost, the others will fill the gaps left.
Stage of succession
Species diversity increases overtime until a climax community is reached
Communities in young ecosystems just undergoing succession may be more vulnerable than those in older ones which are more resilient and stable
Limiting factors
e.g. water is limiting in a desert
If the abiotic factors required for life are available in abundance then the system is more likely to manage if one is reduced
Inertia
property of an ecosystem to resist change when subjected to a disruptive force
Current extinction rates
100 species per million species per year
higher in hotspots
Factors that lead to loss of biodiversity
Natural hazards
- can destroy habitat e.g. oil spill or cause a loss of habitat e.g. tsunami or forest fire
Loss of habitat
e.g. from developing or building on land - estimated Madagascar by 2020 will have no moist rain forest left except for the area under protection
Fragmentation of habitat
- process where a large area is divided by roads, towns, factories, fences, powerlines etc.
fragments are isolated in a modified or degraded landscape - act as islands in a large sea of modified ecosystems
Pollution caused by human activity
local pollution e.g. pesticide or even oil spills
emissions from factories and transport - acid deposition or chemical smog
run off fertilisers causing eutrophication or causing toxic chemicals to accumulate in food chains
climate change - alters weather patterns and shifts biomes away from equator
Overexploitation
- exceeding the maximum sustainable yield of species
Introducing non-native (alien) species
- can upset a natural ecosystem and can be invasive e.g. rabbits in australia
Spread of diseases
- especially in areas with high population density - usually diseases are species specific but they can mutate
Modern agricultural practices
- monocultures, genetic engineering and pesticides
Vulnerability of tropical rainforests
contain over 50% of species of plants and animals on earth and only covers 6% of land on earth - produce 40% of the oxygen that animals use - one hectare of rainforest may have 300 species living within it
50% of earth's timber in natural rainforests - next biggest resource after oil in the world today
Cultivating on rainforest land does not allow the forest to regrow when done on a large scale as there is a gradual degradation of nutrients and biodiversity
What makes a species prone to extinction
Narrow geographical range
- if a species can only live in one place and that place is destroyed then the habitat has gone.
Small population size or declining numbers - low genetic diversity
- small population = small genetic diversity and less resilience to change
Low population densities and large territories
- esp if habitat fragmentation occurs - it is harder for them to find each other and mate
Few populations of the species
- if there are few populations left that is their only chance at survival
A large body
- 10% rule for each trophic level - large top predators are rare - need more food. they can also be hunted for sport
Low reproductive potential
- slow and infrequent reproducing means population takes longer to recover e.g. whales
Specialised feeders
e.g. Koalas only eat eucalyptus leaves
IUCN red list
different criteria for how endangered certain species are
EX, EW, CR, EN, VN, NT, LC