Global Change and a Sustainable
Future
Chapter 18
Mass Extinction
• Biodiversity
a. instrumental and intrinsic value
• Extinctions
a. “last member of the species dies”
b. 5 major
- 50,000 species extinctions/yr (0.5%)
c. now experiencing the 6th
- human cause
Global Declines in Genetic Diversity
• Wild Organisms
a. prone to inbreeding depression
- produces impaired offspring
b. natural causes v. human causes
• Crops and Livestock
a. producers have started concentrating on
breeds that are most productive resulting
in lower genetic variation
b. forces breeds to become endangered
Global Decline in Species Diversity
• Status of species
a. Data deficient – no reliable data to assess
b. extinct – no longer exist since 1500
c. threatened – high risk of extinction
d. near-threatened – very likely to become
threatened
e. least concern – very widespread species
• Since 1500
a. birds
- 10,000 existed, 133 extinct, 21% threatened
b. mammals
- 5,500 existed, 79 extinct, 25% threatened
c. amphibians
- 6,200 existed, 39 extinct, 49% threatened
Causes of Declining Biodiversity
• Habitat Loss
a. greatest cause of decline
ex) northern spotted owl
- old growth forests
• Alien Species
a. native species – native to the land
b. alien/exotic species
- species living outside of their normal range
- introduced accidentally or intentionally
c. invasive species
- no natural enemies
- 2 most common in North America
* Kudzu vine
* Zebra Mussel
- act as predators,
pathogens, competitors
to native species
• Overharvesting
a. removed faster than population can replace
themselves – can cause extinction
b. Dodo bird, sloths, mammoths
c. poaching
d. regulations
- state and federal restrict hunting/fishing of
game animals to particular times of the year
and limit the number that can be harvested
• Pollution
a. pesticides, heavy metals, oil spills,
endocrine disruptors (reproduction),
release of nutrients (N and P), thermal
pollution (cooling of power plants)
• Climate Change
a. changes in patterns of temperature and
precipitation in different regions of the
world and how it will affect the organisms
Conserving Biodiversity
• Two general approaches
a. single species approach
b. ecosystem approach
• Single Species Approach
a. focuses on one species at a time
b. approach
1. encourage population rebound
- improving living conditions
- providing additional habitat
- reducing contaminants
- captive breeding (California Condor)
c. legislation
1. Marine Mammal Protection Act
- prohibits killing of all marine mammals
in the US and prohibits the import/export
of an marine mammal body parts
- exceptions can only be made through:
* US Fish and Wildlife Service
* National Marine Fisheries
2. Endangered Species Act (1973)
- authorizes US Fish and Wildlife service to
determine which species can be listed as
threatened/endangered
- prohibits the harming of the listed species as
well as trade of species
- authorizes govnt to purchase habitat for
species
- listed species
* 201 invertebrate
* 795 plants
* 381 vertebrate
3. Convention of Biological Diversity
- international treaty
- 3 objectives
* conserve biodiversity
* sustainably use biodiversity
* equitably share the benefits that arise
from commercial use of genetic resources
• Ecosystem Approach
a. preserves particular regions (biodiversity
hotspots) – national parks, marine reserves
b. Factors to consider
1. size and shape of protected area
2. connectedness to other protected areas
3. recognize how to incorporate
conservation while seeing the need for
sustainable habitat use for human needs
c. Island Biogeography applied to protected areas
1. distance between areas
- further apart, harder for species to travel
among them
2. metapopulations
3. edge habitat
- where two different communities come
together