ESS Topic 4.2 - Evaluating Biodiversity and Vulnerability
Topic 4.2 - Evaluating Biodiversity and Vulnerability
4.2.1 Identify factors that lead to loss of diversity
• natural hazards (volcanic eruption, fire, ice age, drought, meteor impact)
• habitat degradation, fragmentation, and loss
• degradation: reducing the quality of available habitat
• fragmentation: splitting a single large, contiguous system into numerous smaller,
disconnected areas (putting a road through a wilderness area, logging parts of a forest,
constructing a dam across a river)
• loss: paving natural areas, filling in wetlands for building sites, converting prairies to
farmland or residential subdivisions
• agricultural practices
• monoculture: one type of crop grown on a large scale (compare to intercropping)
• pesticides: often lethal to species other than the targeted agricultural pest
• herbicides: like pesticides, may affect species other than the targeted weeds
• GM crops: ‘heirloom’ varieties evolved and selectively bred over 1000’s of years; GM
standardizes crops and diminishes genetic diversity within the species
• introduction of alien invasive species
• often resistant to local predators or pathogens, so they are able to out-compete natives for
resources
• examples:
• Nile perch
• water hyacinth
• kudzu
• Indian crows in Tanzania
• scotch broom
• Eucalyptus trees in Africa and western US
pollution:
degrades the environment, may interfere with reproductive or other metabolic
•
functions of organisms living in the affected area
• hunting, collecting, and harvesting wild populations: unregulated, it can diminish local
populations or even drive some to extinction
• Tasmanian tiger
• dodo
• North American sea mink
• prairie buffalo
• blue whale
4.2.2 Discuss the perceived vulnerability of tropical rainforests and their relative value in
contributing to global biodiversity.
• vulnerability of other systems
• deciduous forests: similar biodiversity, but faster regeneration time because of slower
nutrient cycling
• prairies: native prairies have vanished almost entirely already and are sometimes cited as an
example of humans’ willingness to let a biome degrade/disappear
• deserts: expanding globally due to population pressure and climate change; this expansion
directly threatens existence of rainforests
• regeneration rate of rainforests
• very slow due to poor soil quality (low nutrient content because of rapid, year-round
nutrient cycling)
Brad Kremer 2010 - 2011
bkremer@istafrica.com
ESS Topic 4.2 - Evaluating Biodiversity and Vulnerability
• most nutrients in rainforests are found in the biomass; when forests are cut or burned, those
nutrients are removed from the system, setting the ecosystem back to an earlier
successional stage
• total area and species diversity
• primarily found in 3 areas: Amazon basin (S. America), Congo basin (Africa), Indonesia
• RF are the most diverse biome on Earth, accounting for more than 50% of all known species,
even though they only cover about 6% of Earth’s land area (source:
http://www.srl.caltech.edu)
• global area covered by RF has decreased by _____ % in past 20 years
rainforests
and “green politics”
•
• green politics advocates economic policies which safeguard the environment, local political
activism, and greater individual freedom; it opposes the influence of large corporations in
national and international policies; often strong government regulation of perceived
polluting industries also advocated (i.e. taxes and duties on fossil fuels, nuclear power, and
other non-renewable energy sources)
• rainforests are viewed as a source of many economically and ecologically valuable resources
(timber
4.2.3 Discuss current estimates of numbers of species and past and present rates of species
extinction.
• there is an unknown number of species on Earth - we have yet to identify/classify them all, and
new ones are discovered all the time
• most sources claim between 1 million and 1.5 million identified/classified species, with a
possibility of 4-40 million total
• in the geological past, an average of one mammal species became extinct every 1,000 years.
• in the recent past (or the current time, depending on how you classify “current”), that rate has
changed to roughly 100 mammal species extinct every 1,000 years (100x faster)
• future predictions claim significantly higher rates of extinction based on continuing human
population pressure, climate change, and habitat loss
• there have been 5 major waves of extinction in Earth’s history; many scientists claim that we are
currently undergoing a 6th extinction wave larger than any of the previous 5
4.2.4 Describe and explain the factors that may make species more or less prone to extinction.
• numbers: species with small populations are more susceptible to extinction
• specialization: highly specialized species are more prone to extinction
• distribution: species occupying a wide variety of habitats and/or found in a variety of places are
less susceptible to extinction
• reproductive potential and behavior: short, fast life spans provide many generations’
opportunities to exchange genetic material (recombination through meiosis and crossing over)
• trophic level: organisms occupying higher trophic levels of an ecosystem tend to have lower
populations, longer life spans, and a lower reproductive potential, making them more prone to
extinction
4.2.5 Outline the factors used to determine a species’ Red List conservation status.
• population size: how many organisms of the species still exist?
• reduction in population size: are the numbers falling rapidly or slowly?
• numbers of mature individuals: if many of the remaining individuals are already at or past their
reproductive peak, the species is likely to decline even further
• geographic range and fragmentation:
Brad Kremer 2010 - 2011
bkremer@istafrica.com
ESS Topic 4.2 - Evaluating Biodiversity and Vulnerability
• wide geographic range makes the species less prone to extinction
• fragmented habitat makes it more difficult for populations to interbreed
• quality of habitat: degraded habitat supports fewer individuals
4.2.6 Describe the case histories of three different species: one that has become extinct, another
that is critically endangered, and a third species whose conservation status has been improved
by intervention.
• Please consult the case histories discussed in the IB ESS Course Companion, beginning on p.130
• visit the IUCN Red List website (http://www.iucnredlist.org/) and read about species in the
‘extinct’, and ‘endangered’ categories
• research some examples of species whose conservation status has improved:
• northern flying squirrel
• gray wolf
• Eggert's sunflower (Helianthus eggertii)
• Robbins' cinquefoil (Potentilla robbinsiana)
4.2.7 Describe the case history of a natural area of biological significance that is threatened by
human activities.
Brad Kremer 2010 - 2011
bkremer@istafrica.com