Disrupted Ecosystems
LT: I can read an
example of a disrupted ecosystem and model the reasons and effects on
the changes in that ecosystem.
What kinds of
factors can disrupt an ecosystem?
1 ) Changes to the biotic factors
- Invasive species
- Big growth in a native species population
- Big drop in native species population
- Top predator is gone
- Disease enters an ecosystem
2) Changes in the abiotic factors
- Change in amount of sunlight (ex: volcano erupts, particles block sunlight for years).
- Changes in water quality
- Changes in water amounts
- Change to the size of the habitats (ex: Humans build roads that divide habitats)
- Change in the amount of nutrients available
- Fire, severe storms, flooding, climate change
Wolves were
killed by humans in western USA. In Yellowstone national park, the
loss of wolves meant that the elk had no more predators. The elk eat
aspen and willow trees. With so many elk, the tree populations were
overeaten. Wolves have been reintroduced to Yellowstone National Park
in order to let the plants grow again.
Sea otters on
the west coast of America almost went extinct. They eat a certain
kind of sea urchin, an organism that loves to eat large kelp. The
kelp forests died, until people started making efforts to being back
the sea otter population.
In the
1950's-1960's, a pesticide called DDT was heavily used across
America. Populations of bald eagles and other birds crashed when DDT
thinned their eggs, killing their embryos. The pesticide, known for
accumulating in food webs and persisting in soil and river sediment,
was banned in the United States in 1972.
Illustration 1: http://www.fws.gov/contaminants/images/DDT.jpg
Zebra
mussels can cause important damage to both the ecosystem and
man-made structures. They are extremely detrimental to native
mussel species, frequently out-competing them for the same
resources. In some cases Zebra mussels attach themselves to
native mussels, eventually killing them.
Volcanic
eruptions can quickly change an ecosystem with lingering effects.
Deforestation
Give
an example of your own example of ecosystem disruption.
