3.3: threats to biodiversity

Question 1

estimates of the total amt of species on earth -

Answer 1

• vary considerably.
• are based on mathematical models, which are influenced by classification issues and a lack of finance for scientific research, resulting in many habitats and groups being significantly under-recorded.
• can’t get an accurate count since bulk of the things that have yet to be discovered and described are in the realm of the very small: insects, bacteria and other microbes.
• the tradition of taxonomy has been confined to the developed world for the bulk of its existence, leaving out the enormous diversity of much of the southern hemisphere, which is less developed on average. species aren’t equally distributed across the Earth; they have hotspots.

Question 2

rate of loss of biodiversity may vary from country to country depending on -

Answer 2

• the ecosystems present
• protection policies and monitoring
• environmental viewpoints
• stage of economic development

Question 3

factors that help maintain biodiversity -

Answer 3

• complexity of the ecosystem (more complex a food chain, more resilient it is to the loss of one species or a reduction in its population size. if one type of prey or predator is lost, the others fill the gap)
• stages of succession (species diversity increases with time until a climax community is reached when species composition is stable. communities in young ecosystems are more vulnerable)
• limiting factors (difficult for organisms in an organism to get enough raw materials for growth. if abiotic factors required for life are in abundance, system is more likely to manage if one is reduced)
• inertia (property of an ecosystem to resist change when subjected to a disruptive force - allows planers to know which sites will either resist change or recover most quickly)

Question 4

human activity that cause species extinctions include -

Answer 4

• natural hazard events (for example, volcanoes, drought, ice age, meteor impact)
• habitat degradation, fragmentation and loss
• agricultural practices (for example, monoculture, use of pesticides, use of genetically modified species);
• introduction and/or escape of non-native species;
• pollution
• hunting, collecting and overharvesting.
• spread of diseases

Question 5

natural hazards -

Answer 5

include volcanic eruptions, earthquakes, landslides, natural fires, avalanches, tsunami, and drought. these events are out of our control, but we could be the indirect cause of them.

environmental disasters are caused by human activity, e.g. loss of tropical rainforest, oil spills, etc…

Question 6

habitat degradation, fragmentation & loss -

Answer 6

habitat loss is the major cause of loss of biodiversity, which is caused by human activities either destroying or changing natural habitats.

overpopulation has led to more and more habitats being degrade in order to accommodate human activities like agriculture, which is needed to support the human population.

habitat fragmentation is the process whereby large natural areas are separated by roads, towns, fences, fields, etc…this leads to a decrease in ecological interactions between species and the isolation of populations. also leads to the interaction of wild and domestic species which could spread diseases between the populations.

Question 7

overexploitation -

Answer 7

hunting and harvesting of food resources has led to overexploitation of the environment. if we exceed the maximum sustainable yield of any species then the population is no longer sustainable.

Question 8

agriculture -

Answer 8

has caused many environmental problems. the introduction of monoculture (growth of one species), fertilisers and pesticides, as well as the introduction of genetically modified species has caused instability in the environment.

Question 9

pollution -

Answer 9

destroys and degrades habitats. pesticides, fertilisers, factory emissions, and oil spills, have caused tremendous amounts of damage to the environment and climate change, which has altered weather patterns and shifted biomes away from the equator.

this has disrupted the suitability of ecosystems to support the range of species naturally supported there. introduction of non-native species: has caused instability in many habitats. it disrupts natural ecological interactions and niches, which causes great problems for the ecosystem.

Question 10

IUCN - international union for the conservation of Nature (pt.1)

Answer 10

EXTINCT (EX)-when there is no reasonable doubt that the last individual has died. presumed Extinct when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. surveys should be over a time frame appropriate to the taxon’s life cycle and life form.

EXTINCT IN THE WILD (EW)- when it is known only to survive in cultivation, in captivity or as a naturalised population (or populations) well outside the past range. presumed Extinct in the Wild when exhaustive surveys in known and/or expected habitat, at appropriate times (diurnal, seasonal, annual), throughout its historic range have failed to record an individual. surveys should be over a time frame appropriate to the taxon’s life cycle and life form.

Question 11

IUCN - international union for the conservation of Nature (pt.2)

Answer 11

CRITICALLY ENDANGERED (CR)- when it is facing an extremely high risk of extinction in the wild.

ENDANGERED (EN)- when it is facing a very high risk of extinction in the wild.

VULNERABLE (VU)- when it is facing a high risk of extinction in the wild.

NEAR THREATENED (NT)- when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future.

Question 12

IUCN - international union for the conservation of Nature (pt.3)

Answer 12

LEAST CONCERN (LC) - when it is widespread and abundant taxa are included in this category.

DATA DEFICIENT (DD)- when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status.

NOT EVALUATED (NE) - when it is has not yet been evaluated against the criteria.

Question 13

range of factors used to determine conservation status -

Answer 13

population size;
reduction in population size;
numbers of mature individuals;
geographic range and degree of fragmentation;
quality of habitat;
area of occupancy and probability of extinction.

Question 14

factors making species prone to extinction (pt.1) -

Answer 14

narrow geographical range: species lives only in one place, if it is degraded or destroyed their habitat will be affected or gone.

small population size or declining numbers: smaller populations have smaller genetic diversity and are less resilient (large predators and extreme specialists e.g. snow leopard and tiger).

low population densities and large territories: if species requires large area to hunt and only meets others to breed then habitat fragmentation and degradation will greatly affect it.

few populations of the species: more populations of a species (in different locations) the better the chances of survival.

large bodied species: as energy decreases up the food chain, the higher the tropic level the rarer the species (e.g. top predators). the large bodied top predators require larger ranges, have lower population densities, need a lot of food, and are often hunted for sport or because of the threat to humans (lion, tiger, etc…)

Question 15

factors making species prone to extinction (pt.2) -

Answer 15

low reproductive potential: species which reproduce slowly and infrequently (e.g. whales, and larger seabirds e.g. albatrosses which only produce one egg per pair per year).

seasonal migrants: long migration routes (e.g. swallows, southern Africa to Europe), hazardous journeys, and they need both habitats. if one habitat is destroyed or degraded and then there is no food for them. barriers on their journeys (e.g. salmon trying swim upstream).

poor dispersers: species that can not move easily to new habitats are vulnerable. for example plants rely on seed dispersal to move which can take a long time and climate change can cause the plant to die before it can move. flightless birds of New Zealand are almost extinct because they can not escape hunters or fly to new islands.

specialised feeders or niche requirements: for example giant pandas, which eat mostly bamboo and koalas, which eat only eucalyptus leaves, can only survive on one food resource.

hunted for food or sport: over-hunting or over-harvesting can eradicate species quickly, especially if that species lives in large groups (e.g. herds of bison in North America)

Question 16

eg. of species extinction -

Answer 16

most palm oil is produced in Malaysia and Indonesia on land that was once thriving rainforest.
as global demand grows, more and more forests are being cleared. in areas such as Borneo and Sumatra, rich in biodiversity, deforestation can be catastrophic.
endangered species including orang-utans, tigers, elephants and rhinos are losing critical habitats, pushing them toward extinction.

Question 17

why & where is there conflict between exploitation, sustainable development and conservation?

Answer 17

most tropical biomes occur in less economically developed countries (LEDCs) and therefore there is conflict between exploitation, sustainable development and conservation -

MEDCs are able to preserve their remaining natural ecosystems as they do not rely on the ecosystems to provide income

MEDCs cleared the majority of the natural ecosystems in the past for agriculture and timber

LEDCs need to balance between conservation of tropical biomes and using the land to provide income

Question 18

eg. of an extinct species

Answer 18

extinct species: Dodo Raphus cucullatus
description: Large flightless bird endemic to the island of Mauritius.
ecological Role: No major predators on Mauritius so dodo had no need to develop flight. dodo was a ground-nesting bird.

pressures:
- in 1505, portuguese sailors discovered Mauritius and used it as a restocking point, ate dodos as a source of red meat.
- later the island was used a penal colony (jail/prison) and rats, pigs and monkeys were introduced. these ate the dodo eggs and humans killed the dodo for sport and food.
- crab-eating macaque monkeys introduced by sailors also seemed to have an impact as they stole the dodo eggs.
- the later conversion of forest to plantation also destroyed their habitat.
was known to be extinct by 1681.

consequences of disappearance: island fauna impoverished by its loss.

Question 19

eg. of a critically endangered species

Answer 19

critically endangered species: Rafflesia
description: A tropical parasitic plant in the forests of South-East Asia, parasitic on a vine.
ecological Role: single sexed (male or female) and pollination must be carried out when the plants are flowering. therefore a male and female plant in the same area must be ready for pollination at the same time. the seeds are then dispersed by small squirrels and other rodents and must then reach a host vine.

pressures:
- vulnerable because they need very specific conditions to survive and carry out their lifecycle.
- they are also vulnerable to deforestation and logging which destroys their habitat. humans damage them and fewer plants means less chance of breeding.

methods of restoring populations: in Malaysia & Indonesia, sanctuaries have been established. there are also many environmental and educational programs being set up to educate the public on this endangered species.

Question 20

eg. of a recovered species

Answer 20

recovered species: Australian saltwater crocodile
description: listed as a protected species in Australia in 1971, and is protected under CITES(the Convention on International Trade in Endangered Species of Wild Fauna and Flora), which ban trade in endangered animals.
ecological role: habitat is estuaries, swamps and rivers. it is a top predator.

pressures:
- exploited for its skin (leather), meat, and body parts through illegal hunting and smuggling.
- it was hunted for sport and was often deliberately killed for attacks on humans.

method of restoring populations:
- sustainable use policy, with limited culling of wild populations, ranching (collecting eggs and hatchlings and raising them in captivity) and closed-cycle farming (maintaining breeding adults in captivity and harvesting offspring at four years of age).
- the exploitation of farmed animals reduces the hunting of wild crocodiles. visitors tour areas to see wild crocodiles (ecotourism) so they are now a valued species. this policy was supported by the Species Survival Commission (SSC) of IUCN but was viewed by other as treating crocodiles inhumanely.