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Flashcards in exam II: supplement 9 Deck (22)
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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

---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


habitat fragments different from the original habitat in three important ways

-fragments have a greater amount of edge per area of habitat (thus greater exposure to the edge effect)
-the center of each habitat fragment is closer to an edge
-a formerly continuous habitat hosting large populations is divided into pieces, with smaller populations


solutions to habitat fragmentation

-corridors: anything from a hedgerow to a restored riparian (river edge) zone, to the huge landscape-scale links being developed in north america and elsewhere, creating a direct link between separate patches

-stepping stones: patches of habitat which ease movement through the landscape without necessarily creating direct links

-buffer zones: help to reduce the edge effect, and protect the interior of the woods from disturbance caused by activities such as agrochemical used on adjacent land

-other solutions
---highway officials are building animal underpasses, overpasses, and other improvements to minimize animal mortality
---fishways and ladders
---in response to microclimate conditions, a dense tangle of vines and fast-growing pioneer species may grow up to the forest edge and may create a barrier that reduces the effects of environmental disturbance on the interior of the fragment


habitat degradation

ecosystems can be damaged and species driven to extinction by external factors that do not obviously change the structure of dominant plants or other features in the community


pesticide pollution

-biomagnification is the concentration of toxins in an organism are a result of its ingesting other plants or animals in which the toxins are more widely dispersed: these chemicals are sequestered in the body, not eliminated-thus they can transcend through trophic levels


water pollution

-has negative consequences for all species: destroys important food sources and contaminates drinking water with chemicals that can cause immediate and long-term harm to health of people and other species that come into contact with it
-90% of the endangered fish and freshwater mussels in the US are affected



or hypertrophication, is when a body of water becomes overly enriched with minerals (nitrates) and nutrients--as a result of human sewage, fertilizers, detergents and industrial processes, which induce excessive growth of plants and algae


air pollution

-acid rain: produced when industries such as smelting operations and coal and oil-fired power plants release huge quantities of nitrogen and sulfur oxides into the air, where those chemicals combine with moisture in the atmosphere to produce nitric and sulfuric acids

-Ozone production and nitrogen deposition
---photochemical smog: waste products of automobiles, power plants and industrial activities, such as hydrocarbons and nitrogen oxides. when in the presence of light, react with the atmosphere to produce ozone and other chemicals
---high concentrations of ozone at ground level damage plant tissues and make them brittle, harming biological communities and reducing ag. productivity

-toxic metals
---leaded gasoline, mining and smelting operations, coal burned for heat and power, and other industrial activities release large quantities of lead, zinc, mercury and other toxic metals into the atmosphere
----directly poisonous to plant and animal life, and can cause permanent injury to children