Class Notes (806,973)
Canada (492,546)
Biology (6,676)
Hugh Henry (242)

Lecture 22 - Conservation Biology

4 Pages
Unlock Document

Western University
Biology 2483A
Hugh Henry

LECTURE 22: CONSERVATION BIOLOGY Introduction  As the human population has grown, and our use of resources has increased, we have destroyed the habitat of many species  A biodiversity crisis has developed. The World Conservation Union lists 16,913 species as threatened with extinction  Conservation biology – the scientific study of phenomena that affect the maintenance, loss and restoration of biodiversity  Conservation biology is an integrative discipline that applies the principles of ecology to the protection of biodiversity  Stabilization of populations requires expertise from several biological disciplines, as well as law, political science, and sociology  Conservation biology is a value-based discipline  The scientific method calls for objectivity—collection and interpretation of data without bias  But it is not free of human values, and takes place within a larger social context  Biodiversity is declining globally  Rates of extinction are difficult to measure because the number of species on Earth is currently unknown  Extinction rates determined from the fossil record are used as background rates o For mammals and birds, the background rate is one species every 200 years o This is equivalent to an average species life span of 1 million to 10 million years  The current extinction rate for mammals and birds is one per year, equivalent to an average species life span of 10,000 years  Overall, extinction rate in the twentieth century was 100 to 1,000 times higher than the background rate  Estimates of current extinction rates rely on: o The species–area relationship o Changes in the threat status of species (e.g., shift from endangered to critically endangered) o Rates of population decline or range contraction of common species  It is sometimes difficult to know when a species is definitely extinct  Many species are known from a single specimen or location; the logistics of relocating them may be insurmountable  Declaring a species extinct can stimulate biologists’ search efforts  A flora of Hawaiian plants (1990) listed many extinct species. 35 have since been relocated, though only a few individuals  These extremely small populations cannot serve the same ecological functions as larger populations  Humans have always had a large impact on other species  Bones found on Pacific islands reveal the prehistoric extinction of up to 8,000 species of birds following colonization by Polynesians  Most of the species were endemic. Some entire guilds went extinct, which must have caused large community changes  Much research on extinction has focused on problems of small populations, which are vulnerable to genetic, demographic, and environmental events  Extinction vortex – a small population declines even further and becomes ever more vulnerable to processes that lead to extinction. There is a need to determine the causes of population declines, to identify actions that could counteract problems before the extinction vortex takes hold  A spatial approach tracks changes in species’ ranges  A study of 173 declining mammal species worldwide showed that, collectively, these species had lost half of their range area  Example: the cheetah occupies only 56% of the land it once did  When populations are lost from a community, there are consequences for that species’ predators, prey, or mutualistic partners  The resulting changes may bring about secondary extinctions and ultimately affect ecosystem function  Generally, the stronger a species’ interactions in the food web, the greater the impact of its removal  In a study of plant–pollinator interaction webs, the effect of removing pollinators depended on whether they were specialists or generalists o Tend to suffer less in the community when specialists are removed relative to generalists – general species, thus have a more critical role in pollinating various species  The movement and introduction of species to all parts of the globe has increased greatly over the last century  The range expansion of some species has coincided with range contraction of many native species  The greatest “losers” among native species tend to be specialists with adaptations that resulted from evolution in a particular place  The “winners” tend to be generalists with less stringent habitat requirements  The spread of introduced species and native generalists, and the decline of native specialists, is leading to taxonomic homogenization of Earth’s biota  Introduction of game fishes in the U.S.A has resulted in homogenization of freshwater fishes  On average, pairs of states share 15 more species than they did at the time of European colonization  Genetic homogenization is also occurring through hybridization between native and non-native species  Example: The California tiger salamander, a threatened endemic, has hybridized with another species of tiger salamander introduced from the Midwest 50 years ago as fish bait Threats to Biodiversity  Primary threats to biodiversity include habitat loss, invasive species, overexploitation, pollution, disease and climate change  Understanding the causes of biodiversity loss is the first step toward reversing them  Aside from the differences of what factors affect various biomes, there area also differences in the severity as well as trends  Multiple factors are likely to contribute to decline and extinction of a species  The Pyrenean ibex was endemic to the Pyrenees. Its decline was due to hunting, climate change, disease, and competition with domestic livestock and non-native ungulates such as chamois  The last one was killed in 2000 by a falling tree  Over 1,100 mammal species are currently threatened with extinction  Primary threats facing mammals are loss of habitat, hunting, accidental mortality, and pollution  The relative importance of these factors differs between terrestrial and marine mammals  Addressing the degradation, fragmentation, and loss of habitat is central to conservation work  Habitat loss – greatest effects on terrestrial organisms  Habitat loss—conversion of an ecosystem to another use  Habitat fragmentation—breaking up continuous habitat into patches amid a human-dominated landscape o Edge effects, reduction in species population  Habitat degradation—changes that reduce quality of the habitat for many, but not all, species  As human population increases and natural habitat shrinks, the harvesting of many species from the wild has become unsustainable  Globally, overexploitation is contributing to the decline of many species  Overhunting in tropical forests, facilitated by road building and availability of guns, has removed large vertebrate faunas  Millions of animals are taken from
More Less

Related notes for Biology 2483A

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.