Chapter 43 Bio
– – When no alternative habitat is available or a species is unable to move habitat loss may mean extinction.
– – The IUCN implicates destruction of physical habitat for 73% of the species that have become extinct, endangered, vulnerable, or rare in the last few hundred years.
– – Habitat fragmentation leads to species loss because the smaller population in habitat fragments have a higher probability of local extinction.
– These introduced species are now free from predators, parasites, and pathogens that limit their population in their native habitats. So such transplanted species may spread rapidly through a new region.
– Some introduced species disrupt their new community often by preying on native organisms or outcompeting them for resources.
– Overall: introduced species are a worldwide problem contributing to 40% of the extinctions recorded since 1750 and costing billions of dollars each year in damage and control efforts (There are more than 50,000 introduced species in the US alone).
(Genetic variation is a key issue with the small-population approach because it enables evolutionary responses to environmental change, such as the appearance of new strains of pathogens)
small pop approach focuses on smallness itself and loss of genetic variation/ diversity as the cause of extinction
Negative: Corridors can be harmful, for example by allowing the spread of disease (ex: Habitat corridors can facilitate the movement of disease carrying ticks)
Nutrient enrichment becomes a problem when the nutrient level in an ecosystem exceeds the critical load which is the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity. When nitrogenous minerals in the soil exceed the critical load eventually the nitrogen leaches into groundwater or run off into freshwater and marine ecosystems. It sometimes can contaminating water supplies, kill fish, and make the water unsafe to drink. Another big consequence that happens is that the nitrogen from agricultural runoff and sewage drain into the Atlantic Ocean and Mississippi River. The Mississippi River carries the nitrogen pollution to the gulf of Mexico which flues a phytoplankton bloom each summer.. When the phytoplankton die their decomposition by oxygen using organism creates an extensive dead zone of low oxygen concentration along the Gulf Coast. Fish and marine animals disappear from the dead zone and some of the most economically important waters in the United States is damaged.
The effects of this increase is that the average global temperature will increase with increasing CO2. This warming would also then alter the geographic distribution of precipitation which likely making agricultural areas of the central United States much drier. Also it will cause the snow to melt and decreasing habitats for polar bears, seals, and seabirds. Higher temperatures also increase the likelihood of fires.