exam II: supplement 9 Flashcards
seven major threats to biodiversity
- habitat destruction
- habitat fragmentation
- habitat degradation (including pollution)
- global climate change
- the overexploitation of species for human
- invasion of exotic species
- increased spread of disease
fundamental explanation
- the seven major threats to biodiversity are all caused by an ever-increasing use of the world’s natural resources by an expanding human population
- the primary cause of the loss of biodiversity, including species ecosystems, and genetic variation, is the {habitat destruction} that inevitably results from the expansion of the human populations and human activities
three ways humans dominate the global ecosystem
- land surface: human resources need land use, mainly ag. and forestry, transformed as much half of the earth’s ice-free land surface
- nitrogen cycle: each year human activities, such as cultivating nitrogen into terrestrial systems than is added by natural biological and physical processes
- human use of fossil fuels and deforestation: by middle of this century, human use of fossil fuels and cutting down forests will have resulted in doubling the CO2 level in the atmosphere
vegetarian argument
- globalization: or the increasing interconnectedness of resource and labor markets–has captured the idea of the ecological footprint
- –eliminates meat via natural resource of animals would reduce the habitat destruction/fragmentation caused by human harvesting of said resource
9.4 pattern
- many of the major biomes have already had a large proportion of their area converted to human use
- in particular, islands where human population density is high, most original habitat has been destroyed
- predicted rise of destruction based on human population growth and transformation of ag. lands for human sustainability
prediction regarding 9.4
- temperate forests are predicted to increase in area over the coming decades because of the abandonment of ag. in many areas of North America and Europe
- most potential loss will happen in tropical forests due to being converted to ag. land
threatened tropical rainforest
- statistics
- –tropical rain forests occupy 7% of the earth’s land surface, but they are estimated to contain over 50% of its species
- –supposedly 17 million km2 of land, but only 11 million km2 remain
- –more than 60% of the recent loss has occurred in the neotropics, with brazil alone accounting for almost half
- –55% of all recent forest losses occurred within only a 6% total area
- –current rate of deforestation represents approximately 1% of the original forest area lost per year
tropical rainforest
overall pattern
- at the current rate of loss, there will be little tropical forest left after the year 2050, except in the relatively small national parks and remote, rugged, or infertile areas of the Amazon Basin, Congo River Basin, and New Guinea
- much of the destruction may still result from small-scale cultivation of crops by poor farmers
shifting cultivation
-a kind of subsistence farming, sometimes referred to as slash-and-burn, or swidden, agriculture, in which trees are cut down and then burned away
island biogeography model
the number of species on any island reflects a balance between the rate at which new species colonize it and the rate at which populations of established species become extinct
tragedy of the commons
a term used in environmental science to describe a situation in a shared-resource system where individual users acting independently according to their own self-interest behave contrary to the common good of all users by depleting or spoiling that resource through their collective action
- deforestation can be related to loss of O2 produced by tree’s in the tropical rainforest, since air and air quality is an open air resource
- is common that is affected and affects many countries around the world
habitat fragmentation
- serious threat to biodiversity, as species are often unable to survive under the altered set of conditions
- reduces the ability of plants and animals to move across the landscape and can cause the decline of populations and the loss of species from fragments
habitat fragmentation (population effects)
limited to dispersal and colonization
—fragmentation may limit a species potential for dispersal and colonization by creating barriers to normal movements
restricted access to food and mates
—many animals species, as either individuals or social groups, need to move freely across the landscape to feed on widely scattered resources
division of population
—smaller populations are more vulnerable to inbreeding depression, genetic drift, and other problems associated with small population size
habitat fragmentation (edge effects)
microclimate changes
- –habitat fragmentation increases edge effects, changes in light, humidity, temperature, and wind that may be less favorable for many of the original species
- –because plan and animal species are often precisely adapted to temperature, humidity, and light levels, changes in these factors eliminates many species from forest fragments
increased incidence of fire
-when a forest is fragmented, increased wind, lower humidity, and higher temperatures makes fire more likely
interspecies interaction
-habitat fragmentation increases the vulnerability of the fragment to invasion by exotic and native pest species
potential for disease
- –habitat fragmentation puts wild populations of animals in closer proximity to domestic animals
- –diseases of domestic animals can then spread more readily to wild species, which often have no immunity to them
habitat fragmentation part II
the process whereby a large, continuous area of habitat is both reduced in area and divided into two or more fragments
—edge effect: these fragments are often isolated from one another by a highly modified or degraded landscape, and their edges experience an altered set of conditions
