BIOD54H3 Lecture Notes - Lecture 8: Wader, Haida Gwaii, Environmental Health
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Lecture #8 – Invasion
Invasion
Invasive species are plants, animals, or pathogens that are non-native (or alien)
to the ecosystem under consideration and whose introduction causes or is likely
to cause harm.
o The negative impact of invasive species is one of the strongest on
conservation science.
o Thinking about the conservation of certain species, when the habitats that
are critical examples of where those species exist are invaded, which can
cause significant negative impacts on the species.
o Their presence in a new environment is a result of human intervention.
Naturalization is any process by which a non-native organism spreads into the
wild and its reproduction is sufficient to maintain its population.
o A nonnative, nonindigenous species of plant survives in a new
environment in which it is introduced. Through the process of invasion,
establishment occurs. Establishment results in the growing of that
population. In the end, the plant has an impact on the recipient
community.
o e.g., Dandelions and European Starlings arrived and self-spread. They
don’t need to be re-entered into the environment via human intervention.
Harm?
1) Displace native species. (Reduce resources available to them.)
o Sun, nutrients in the ground, prey items, etc.
2) Reduce environmental health and productivity.
o The balance that many natural ecosystems have maintained
through evolutionary time is altered when one species capable of
reshaping these ecosystems enters.
3) Compete with and replace rare and endangered species.
o Rare and endangered species are the first to disappear in these
environments.
4) Hybridize with native species, altering their genetics and reducing the
gene pool.
o e.g., Arctic White Fox.
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Extinction is the end result of invasion.
o How invasive or how negative an impact a species might have can be
measured to the extent of how many species have become extinct as a
result of the species’ introduction.
o When a species arrives in a new environment, it’s important to identify
invasive traits or the likelihood of invasion as early on as possible so that
the eradication of that species can be dealt with.
o With invasion, at one point there’ll be an exponential increase, after
which the species becomes almost impossible to control completely.
o Nonindigenous species that enter a new environment can often just be
that in the sense that they don’t have a great negative impact. They
simply exist there. e.g., An abound ash tree that provides food for Robins
and other birds. It’s not native, but it’s also not spreading to some extent.
Biodiversity in a Globalized World
o Wherever we go is often the entry point or pathway where species are
able to spread around the world.
o i.e., Roads and shipping lanes.
o Cities are hotspots for invasion because it’s where invasive pathways exist.
Spread of Invasive Species
Globalized Trade
Pet Trade (e.g., Pythons in Florida)
o Pythons are large snakes obtained from South America and other
countries. They’re cute pets when they’re younger, but of course, they
become humungous after a period of time. As a result, people release
them into their backyards, unknowingly contributing to the invasion of this
species into different environments.
o Due to the popularity of pythons, many of them are released, building on
the population to the point that they can reproduce without the human
hand continually adding more.
Everglades
❖ Raccoon and Possums decline by 98%.
❖ Bobcat sightings down 87%.
❖ Rabbits and Foxes have not been seen at all in years.
o In Everglades, Florida, there are several mammals that feed
alligators and other predators in these environments. These
mammals have disappeared entirely because of the
preponderance for these pythons.
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Document Summary
Naturalization is any process by which a non-native organism spreads into the wild and its reproduction is sufficient to maintain its population: a nonnative, nonindigenous species of plant survives in a new environment in which it is introduced. Establishment results in the growing of that population. In the end, the plant has an impact on the recipient community: e. g. , dandelions and european starlings arrived and self-spread. They don"t need to be re-entered into the environment via human intervention. They simply exist there. e. g. , an abound ash tree that provides food for robins and other birds. It"s not native, but it"s also not spreading to some extent. Pet trade (e. g. , pythons in florida: pythons are large snakes obtained from south america and other countries. They"re cute pets when they"re younger, but of course, they become humungous after a period of time. Rabbits and foxes have not been seen at all in years.