Download Natural Ecosystem Change Loss of Biodiversity

Natural Ecosystem Change
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Climate shifts – organisms that cannot adjust to changes in climate are more likely to become extinct
species movement – Wings, Waves & Wind carry seeds, eggs, organisms from one place to another.
ecological succession - natural changes & species replacement in an ecosystem over time
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A Primary (1 ) Succession (100s-1000s of years) - succession that describes the order of plant & animal species “take-over” on new
land that starts as rock (slowly weathered into soil) due to volcanic eruption, landslides, earthquakes, severe erosion
1 Bare rock is exposed.
2 Since there is no soil, LICHENS are first to appear since they can live on rocks
3 Lichens SLOWLY dissolve rock into sand
4 Plants die & become humus & allow rooted plants to grow
5 Small plants first, then big ones take over
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B Secondary (2 ) Succession (decades) – succession that describes the order of plant &
animal species “take-over” on existing land (Ex: abandoned farms, parking lots, land
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after a natural disaster) MUCH faster than 1 b/c soil is already present
1 Flowers take over firest
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Shrubs & bushes second
3. Pine saplings return
4. park returns to climax community of tall trees & hardwoods
Pioneer
Species
Loss of Biodiversity
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 According to IUCN, 21% of mammals, 12% of birds & 30% of amphibian species are threatened with extinction
 In the past 500 years (in the US) 237 animal species & 30 plant species have become extinct
Habitat loss
A Disturbed or degraded 40-50% of earth’s land surface
B 95-98% of all virgin forests in US have been destroyed since 1620
Overuse - poaching
pollution; introduced species;
A Nonnative (exotic) species (Biological Pollution)
(i) 49% of all US endangered species are caused by nonnative species
(ii) many introduced species have no natural predators, competitors, or pathogens to control numbers
(iii) ex. Kudzu vine(SE US for erosion control), Brown Tree Snake (kills birds in Guam)
 Zebra mussels (from E. Europe threaten native mussels in Great Lakes)
 Gypsy moth (eat American forests), Brazilian pepper (in Everglades)
 Rosy tree snail (introduced in Hawaii to kill the giant African tree snail)
 Feral & outdoor pet cats—kill 568 million birds annually
 Fire ants (accidentally introduced into Alabama, spread into south US)
IV endangered and extinct species
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A Endangered Species: any organism (plant or animal) whose population has dropped drastically
1 Major causes (anthropogenic): poaching, habitat destruction
2 Non-anthropogenic causes: (see below… characteristics that make a species vulnerable)
B Extinction
1 Background Extinction (Natural rate of extinction)
a natural, low level of species extinction each year, 3-14/ yr. based on fossil record
b estimate = 99.9% of all species that have ever existed are now extinct
2 Mass extinction
a catastrophic, widespread event kills many existing species
b Earth has experienced five mass extinctions (20-60 million years apart)
c Adaptive radiations follow mass extinctions when the diversity of life increases and spreads into empty niches
d some biologists believe we are experiencing the sixth mass extinction
e rise today in extinction rates above background level = 3-200 species/day
3 Characteristics that make a species more vulnerable to biological extinction
a Low reproductive rate (K-strategists) ex. blue whales, giant pandas
b Specialized niche (not adaptive to environmental changes) ex. giant pandas, Everglades kite
c Narrow distribution (not many mates) ex. many island species
d Feeds at high trophic level (less diversity of food) ex. Bengal tiger, bald eagle, grizzly bear
e Fixed migratory patterns (development interferes – dams, windmills, powerlines) ex. whooping crane, sea turtles
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Rare (not many to begin with) ex. many island species, some orchids
g Commercially valuable (poachers more likely to kill them) ex. tiger, elephants, rhinoceros
h Large territories (hard to find a mate, habitat fragmentation) ex. California condor, Florida panther
4 Causes of Species Extinction
a Habitat Loss (#1 cause)
(i) tropical deforestation is greatest eliminator of species followed by:
(ii) destruction of coral reefs & wetlands c. plowing of grasslands
(iii) d. pollution of freshwater & marine habitats
(iv) Greatest threats in US are:
(v) Agriculture, Commercial development, hydroelectric development,
Outdoor recreation (off-road vehicles), Livestock grazing, Pollution
b Commercial hunting & poaching
(i) trade in wild plants & animals generates $10-20 billion annually
(ii) Gorilla ($150,000), elephant & rhino ivory ($?), Amazon macaw
($20,000)
(iii) for every live animal sold as a pet in US, 50 other animals were killed
(iv) sale of bushmeat (gorilla meat) by local people
(v) Over-harvesting of commercial fisheries
c Predators & Pest Control
(i) extinction of Carolina parakeet by US fruit farmers, prairie dog holes
break cattle’s legs
(ii) African farmers kill elephants that trample their food crops
d Loss of Genetic Diversity
(i) limits ability to survive by limiting phenotype outcome possibilities,
less chance of having right combination if environment changes
(ii) Inbreeding allows recessive genes to accumulate
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Maintenance through conservation
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A Species Approach
1 involves identifying which species are at greatest risk of becoming extinct, gaining understanding of the species, &
legally protect them & their habitats (problem = we protect only “cute”)
2 propagate endangered species in captivity
3 reintroduce species into sustainable habitats
4 Endangered species
5 has so few individual survivors that the species could soon be extinct
6 Threatened species
7 still abundant, but declining in #’s & is likely to become endangered
B Ecosystem Approach (National Parks, etc.) more effective than species approach
1 focuses on ensuring that enough land and aquatic areas are protected to provide habitat for the majority of terrestrial
and aquatic wild species
2 eliminate or reduce populations of alien species from protected areas
3 restore degraded ecosystems
4 saves multiple species
5 Problems: mostly scenic areas protected, poor countries don’t enforce
C Reasons for preservation
1 Intrinsic value & preserving genetic diversity
2 Economic goods (species provide food, fuel, lumber, medicines, etc.)
3 Ecosystem services (photosynthesis, pollination of crops, soil formation, nutrient cycling, pest control, climate
regulation, flood control, waste decomposition, etc.)
4 Recreation—ecotourism (generates $500 billion worldwide)
5 Ex. Male lion in Kenya generates $515,000 in tourist dollars but only $1000 if killed for its skin.
6 Solutions to Protecting Wild Species
VI Relevant laws and treaties
1. International treaties
a. International Union for Conservation of Nature (IUNC) Red List
i. list of species at high risk of extinction
b. Convention on International Trade in Endangered Species (CITES)-1975
i. lists more than 800 species that cannot be traded
ii. lists 29,000 species whose international trade is monitored & regulated
iii. limited effectiveness (difficult to enforce, convicted violators pay small fines, member countries can
exempt themselves, much illegal trade occurs in countries that have not signed the treaty-152 have
signed)
2. National Laws
a. Lacey Act (1900)-prohibits transport of live or dead wild animals across state lines without federal permit
b. Endangered Species Act (1973)-makes it illegal for Americans to import or trade any product made from an
endangered species
i. forbids federal agencies & private land owners to carry out, fund, or authorize development that would
jeopardize endangered species
ii. Fish & Wildlife service must design a recovery plan for all endangered
3. Zoos & Game parks
a. Egg pulling-collect wild eggs of endangered species & hatch them in zoos or research centers
b. Captive breeding-wild animals are captured and bred in captivity, or artificially inseminated, then reintroduce the
offspring into the wild (ex. Peregrine falcon & black-footed ferret)
c. Seed Banks
4. Wildlife Management
a. manipulating wildlife populations and their habitats for their welfare & for human benefit
b. uses laws to regulate hunting & fishing
c. plant vegetation that is preferred food for wild species
d. sport hunting is allowed only during certain seasons and is limited to size, number, and sex of animals killed
e. major flyways for migratory waterfowl are managed by international treaties