17 - Invasive Species (w/ Kyla Garten!)
17. Invasive Species (w/ Kyla Garten!)
Invasive species challenge the natural environment of many places they once did not call home. Why are invasive species dangerous? What are invasive species contributions to ecology, geomorphology, the economy, human health, or biodiversity? Let’s learn to be scientifically conversational.
General Learning Concepts
1) What does invasive mean?
a. Endemic: Native and restricted to a certain place in terms of life. This term is very different for micro-organisms; this time meaning there is a disease or condition found among people regularly in a certain area (eg. chickenpox vs. malaria).
i. Example: Endemic snakes of the Galapagos, “Galápagos Racer” (Pseudalsophis biserialis biserialis).
b. Invasive: Species from another region of the world that were not originally from that place; they tend to cause harm to natural resources or compete with humans for those resources.
c. Competition: Section 2 discusses common effects of invasive species, but it remains pertinent to remember that the issue with invasive species tends to be outcompeting the endemic ones. This could be because of a life cycle difference (rapid reproduction / growth), lacking predators / pests, or other similar reasons.
i. Example: Acoustic Space! The environment that allows for a sound to be sent and received. Established ecosystems may have organized times for acoustic space, like birds using dusk / dawn and frogs at night.
d. Anthropogenic vs. natural invasion: At a very small scale, endemic species may evolve over millions of years from stratified, isolated areas (eg. islands, lakes, etc.). Over geologic timescales, those areas may become capable of mixing and species “invade” from one place to another. Spiders may balloon from one place to another; lizards may ride rafts to reach new locations. Humans, however, have complicated this “natural” mixing of species by introducing rapid global travel and agricultural lifestyles. Even in the history of the human mind, explorers have brought back novel specimens to their home countries for zoological examination or to gauge further interest in expeditions.
2) What are common effects of invasive species?
a. Ecological: Invasive species may impact their local environment in order to make it more fruitful for their own species. For example: Yellow starthistle has also been introduced to the West Coast and secretes the chemical compound 8-hydroxyquinoline from the root. This chemical harms native plants, which allows starthistle to increase its range as its chemicals wipe out native competitors.
b. Geomorphological: Plants can alter sedimentation rates or change how streams are channeled, while insects affect landscapes by burrowing or even killing endemic trees that provide stabilization. This can be especially challenging in spaces that are subject to two different environments (like coastal areas).
c. Economic: A 2005 study estimated that the economic damages associated with invasive species in the United States reached approximately $120 billion/year (FWS 2012).
i. Example: Insects like the pink bollworm; recently eradicated from the US and caused economic losses to cotton farmers in Arizona / California (reduced yields and decreased quality).
d. Health: Parasite ranges change and lead to impacts to human health. The Asian tiger mosquito has been linked to more than 20 diseases, including yellow fever and chikungunya fever. It has come to Europe mainly through the intercontinental trade in used tires, and is now prevalent in several southern European countries, especially Italy. Allergens can also travel and affect human health.
e. Biodiversity: There are massive losses of biodiversity associated with invasive species; some by direct competition and some by indirect competition. Next to habitat loss, over 50% of the loss of native biodiversity globally has been attributed to introduced species, and nearly half of the species listed as threatened or endangered under the Endangered Species Act in the U.S. are at risk due to competition with alien or introduced rivals. 
3) Famous examples of invasive species
a. Lionfish: Originally from coral reefs in the South Pacific and Indian oceans that was first detected off of Florida coasts in the mid-1980s before blooming at astonishing speeds. These beautiful creatures are often appreciated in aquariums and may have been released in the ocean, causing this invasion. Adult lionfish eat other fish (decrease biodiversity) and have few predators outside of their home range. A method to reduce lionfish numbers has been the increased presence of the lionfish food market: if you can’t beat them, eat them.
b. Tangentially related Smallpox: Smallpox, caused by the variola virus, was highly infectious and caused fever, rash, and 30% of those to be infected to die. The last time the virus naturally infected an individual was in 1977; but a famous example of using the arrival of the Europeans into the Western Hemisphere meant that Native American peoples were exposed to new infectious diseases that they had no immunity to. 
4) Fun Tidbits
a. Where are these invasive species seen and where are endemic species lost? A majority of recorded extinctions happen on islands; island biogeography tends to be very different from continental size geography. Often, predation can be much more severe with newly introduced species.
b. Invasive species eradication: Potentially possible if done with newly introduced invasive species. Beyond this, it is very difficult to completely eliminate invasive species and is often more relevant to control the populations.
5) Solicited Naïve Questions
a. Why are native species so susceptible to extinction from invasive species? Sometimes, native species thrive only in a very specific habitat. Sometimes, those native species may not be aware of what a “more competitive” environment is like (eg. predation or even out-competition of resources). Finally, species that rely on one another to survive may be wiped out by accident on the side (bees and flowering plants).
b. Is humankind an invasive species? This is an ambiguous question from a moral standpoint, but it is clear that humankind fits the definition of an invasive species. Ask the dodo.