Introduced and Invasive Species in the United States
Abstract
Throughout the past couple of centuries, humans have introduced species into new areas, both intentionally and unintentionally. This can be done in several different ways, all of which could affect the new environment the organism has been introduced to. These effects can be both positive and negative, but many turn out negatively. Introduced species cost the United States economy billions and billions of dollars every year. Educating the populous about this issue would help to resolve the problems facing many ecosystems in the United States today.
Throughout the past couple of centuries, humans have introduced species into new areas, both intentionally and unintentionally. They went through with these introductions without realizing that introducing one species to an area could completely change aspects of the ecosystem. If a species is introduced and works in harmony with the other organisms with no drastic effects, it is considered a successful introduction. Unfortunately, this occurrence is very rare, and almost never occurs. On the other hand, if an introduction results in a negative effect on an ecosystem, it can become an invasive species, a species that basically “takes over” all of the other organisms and jumps to the top of the food chain. This happens because these invasive species usually have no natural predators or consumers when they are introduced, so the population is not managed in a sustainable way, causing an overpopulation of the plant or animal. This species can then displace the native species and their habitat, either eradicating the native species or pushing it out of the area. If one of these oppressed native species is a keystone species, a species that is crucial to the success of the individual ecosystem, the removal of it can completely collapse the ecosystem, scrambling up the food chain and forcing different species to quickly adapt, which is very stressful on the organisms. This can cause extinctions of species in some cases.
Several introductions throughout history have been made for the sports of fishing and trophy hunting. Most people do not realize that species such as mountain goats, a species usually associated with Colorado, is not native to the Colorado landscape. Allen Best, a writer for Colorado Central Magazine explains, “In 1948, they [mountain goats] were introduced from Montana by the Colorado Division of Wildlife, or as it is known today, the Colorado Division of Parks and Wildlife” (Best). As their population increased, trophy hunters began to acquire tags to harvest them off the landscape, and they have become a prime hunting target ever since.
One more introduction people might find surprising is the introduction of brown trout. Many people believe that this species of trout are native to the United States and the Rockies, but that assumption will put you about five thousand miles away from where they were originally from; Eastern Europe and Western Asia. They were introduced in 1883 as a sportfish and have remained extremely popular until this day (Brown).
A third example of an intentional introduction could be that of tamarisk. Tamarisk is a type of plant that is similar in size to the native willows the Western United States has growing all along its rivers. Tamarisks have very deep and complex root systems, meaning that they can hold soil together incredibly well. Ken Belson, a respected reporter for the New York Times states, “They were originally introduced to prevent erosion on the side of highways in the United States” (Belson). This was done using their root systems as described above. Unfortunately, the tamarisk did not remain on the side of highways for long. They moved to major waterways such as the Colorado and Green Rivers in Utah, because the tamarisks flourish near water sources since they need much of it to survive (Belson). After the tamarisks started spreading, the native willows were choked out. They now remain in small patches along several rivers in small numbers, as opposed to when they used to be everywhere in large quantity.
After the tamarisk started to “take over” the different water sources, some people started to look into how to get rid of them. Ken Belson states, “They tried burning, cutting, and removing the stumps, but to no avail. The root systems were too complex to remove, and burning was unsuccessful” (Belson). Then they started to brainstorm other ideas than the original. They discovered a beetle that feeds on tamarisk, and only tamarisk. So, they acquired hundreds of thousands of these beetles, hoping that they could release them on the tamarisk in the West. They had to run many tests to determine if it was safe for the beetle to be released into this new environment. One of the many tests they ran was putting the beetles into a container with tamarisk and some native species such as willows. The goal of the experiment was to see if the beetles would adapt and start eating the willows when the tamarisk was all eaten. If they did adapt, it was not safe to release them into the ecosystem, while if they didn’t, it was safe in that regard. It turned out to be safe, so they released the beetle, and the tamarisk populations have plummeted ever since, conserving the water supply, and making more room for the native species to grow (Belson).
Unfortunately, the tamarisk beetle, mountain goat, and brown trout are some of the very few examples we have of a successful intentional introduction of species into a new environment. Most have been unsuccessful and/or accidental in nature. There is an excellent example of accidental introduction within species of plants all around the world. Many species of plants, such as the burdock plant, which was used to model Velcro, have seeds with a Velcro-like coating that will stick to fur or, more detrimentally, human clothing. This was intended as a way for plants to create offspring that dispersed widely to another area. The seeds stick to a mammal’s fur, and after that animal carries the seeds to another place and grooms itself, the seeds drop onto new soil in the hope that they will sprout and grow. Since these seeds can stick to human clothing, it means that they can be spread around the world unintentionally and completely accidentally since humans can travel around the world in a relatively short amount of time, keeping the seeds alive and well until they reach a new environment.
A cause of widespread accidental introductions is the operation of thousands of cargo ships around the world. These ships will take in water and soil from their surroundings to fill the ballast tank, which helps with the stability of the vessel. In this water can be thousands of little aquatic plants and animals. These ships then travel around the world, and before they are about to hit shore, they empty the ballast tank, along with all of the organisms inside. This can introduce thousands of foreign species into a new marine environment, creating stress on the species that are already inhabiting that area (Ballast).
Some other types of ships use a ballast tank, but they fill it with dirt instead of water. The same dilemma occurs when these ships empty out the soil into a different ecosystem than where they took it from. The problem with this is that seeds of foreign species could be in this soil, or there could be microscopic organisms within the soil (Ballast). These can tear apart an ecosystem just as well as some foreign marine life, as will be explained in a moment.
There are billions upon billions of dollars being spent by the United States on the management and eradication of these different invasive species. The United States Fish and Wildlife Service states, “The most widely referenced paper (Pimental et al. 2005) on this issue reports that invasive species cost the United States more than $120 billion in damages every year” (The Cost). Eradication is carried out by several different methods such as burning, cutting down, hunting, and so on. If many more foreign species are introduced, the United States may be unable to afford the management, creating a large problem for the native landscape and ecosystems, and we may lose several of our native species such as Cutthroat Trout or Rocky Mountain Elk. Cutthroat trout are a huge attraction in Colorado for sport fishermen around the world, and if they become extinct, the money coming in from fishermen becomes “extinct” as well. This can have a huge impact on small communities that rely on yearly tourism to keep supporting their families.
More needs to be done about the several invasive species in the United States; those that are here and those still to come. We need to implement stricter laws that require things such as cargo ships to filter their ballast water before emptying it back into the oceans. There also needs to be more money put into the education of the populous about these issues. Hopefully, by doing this, it will create awareness about the threats introduced species can cause, and help to prevent more from being introduced.
An example of an invasive species coming about from a ship emptying its ballast water could be that of the zebra mussel. These small mussels have a microscopic larvae that can go almost anywhere where there is connecting water. After several cargo ships emptied their ballast water in the Atlantic Ocean, the species quickly spread to the great lakes, creating destruction in their path (Zebra).
These mussels can cling to anything, especially boat engines, dams, and water treatment facilities, where they are the most annoying and cost the most to get rid of. The Minnesota Department of Natural Resources states, “Zebra mussels can be a costly problem for cities and power plants when they clog water intakes” (Zebra). When they cling to boat engines and other important mechanical objects, they can cause a malfunction or even destroy the engines, causing a hassle for fishermen, but more importantly, dams that hold water in place. If too many of them pile up on a dam, the mechanisms can become unusable and may result in a flood, making it very dangerous. The same type of thing can happen in water treatment plants, causing the mechanisms to malfunction, creating unclean water. This is why several states have boat inspections; they are trying to prevent species like the zebra mussel from entering the ecosystem and causing economic losses (Zebra).
San Francisco Bay is probably the most notable of these different places where ships empty their ballast water, introducing an average of five foreign species to new areas a day. Each one of these species could create a chain reaction in the ecosystems around them, which could ultimately lead to a small collapse in large topics such as the United States economy. For example, if these species push out fish or shellfish that are important in the fishing industry, there becomes a shortage, and supply and demand become unbalanced, creating economic losses (Ballast).
One last example of an accidental or unintentional introduction due to ship ballast is that of the crow-of-thorns sea star. Haley Davis, a scientist who investigates the impacts of the sea star, states, “Crown-of-thorns live and prey on live corals, often killing them in the process. Through this destructive feeding, crown-of- thorns disrupt the entire reef ecosystem” (Davis). These starfish now primarily feed on the coral in the coral reefs in the Pacific Ocean. They were accidentally introduced to several new areas due to cargo ships, and became a nuisance to many different coral reefs including the Great Barrier Reef.
Many fishermen, being uninformed and uneducated on the anatomy of star fish thought that they would try to help, and whenever they netted one of these sea stars they would chop it up into little pieces and throw it back overboard. What they did not know is that starfish can grow back almost eighty percent of their body after they have been cut, so instead of decreasing their numbers, the fishermen increased them exponentially.
This example goes to show that more education needs to be put into learning about the environment and the organisms that inhabit it. If the fishermen had been informed and educated about the nature of starfish sometime in their life, they might have remembered that they would just make matters worse by chopping them up. If we were able to prevent enough of these introductions to the United States, we could put even more money into the education of the country and world, such as television ads or free informational courses.
It is definitely possible for an introduction to be a combination of both intentional and unintentional causes. An example of an introduction that could have been both intentional and unintentional could be that of the Burmese Python in Everglades National Park in Florida. Burmese pythons have completely taken over the park over the past couple of decades, consuming more birds and mammals than is healthy and sustainable for the ecosystem. The suggested and common-known theory of how the pythons got into the park is because of irresponsible pet owners, who owned the pythons, and let them go in the park, or they accidentally got out of their enclosure and into the forest. Michael Dorcas, a scientist that has been recording the impacts of the python states, “All it took was one male and one female to be released to create thousands of offspring. As a result of this, the pythons can gorge themselves on whatever they want to eat, and there have even been reports of them engulfing larger prey such as small alligators and crocodiles” (Dorcas).
This is where the adoption and purchase of exotic plants and animals can come into play and be quite dangerous in different environments. There are several other examples other than the Burmese python of this occurrence. If people are educated on how to properly care for foreign plants and animals in a closed environment away from the native ecosystem, situations like what happened with the Burmese pythons will be more preventable.
There needs to be a program put into place, something similar to CPR training, where people could become certified to own foreign and exotic plants and animals. There are some licenses in different states to own exotic pets, but it needs to become nationwide so we do not risk another accidental introduction. This certification would make the chances of accidental introductions plummet, thus making it so that the United States does not have to spend as much on it every year, and can put that money into other projects.
There is a plant called kudzu that has been taking over different landscapes in the southern United States for more than a century. Rebecca Pappert, a researcher with the University of Virginia states, “It [kudzu] was introduced at the Centennial Exposition in Philadelphia for purchase in 1876. Its main purpose was to be sold to shade porches from the intense sunlight, but matters soon got out of hand when hundreds of people bought the plants, and were unaware that it would prosper in the American south” (Pappert). The plants spread way further than they should have, and started taking over the other native plants. Now, there are whole square miles where there are no other plants to be seen except for the kudzu. The vine has taken over and choked out all signs of native species, which does not make for good biodiversity, thus creating an unhealthy ecosystem that will be near to impossible to return to its original state.
The whitefly is another stunning example of an unintentional invasive species. They originated in East Asia, and were brought over accidentally in shipping containers that contained different fruits to be sold in the United States. M.R.V. Oliveira, a well-known scientist known for his research with whiteflies states, “After being unintentionally transferred to the United States, they started to adapt to their new landscape causing their population to spike and grow like wildfire” (Oliveira). In biology, we typically learn that the smaller the organism is, the easier it is for it to adapt and evolve into separate new species. Now, the whiteflies have evolved into three different species, one that feeds on citrus fruits, and two that feed on agricultural and ornamental crops, which has caused losses of hundreds of millions of dollars in the American agriculture industry.
This is the reason several countries do not allow foreign fruits and vegetables to be transported or taken into their ecosystems. When people get onto a plane to fly out of the country, they are usually given a slip that is mandatory to fill out to obtain a stamp on your passport to allow you to stay in that country. These slips usually ask several different questions including one that asks if you are transporting any plants and/or fruits. It is an intelligent precaution to prevent the accidental introduction of a foreign organism to a new area. These plants can contain seeds, and if accidentally dispersed, could be disastrous to a different ecosystem. They could also contain bacteria or larvae that cannot be seen with the naked eye, which can also turn into a bad situation for foreign soil.
Another example of unintentional introduction due to transportation of cargo ships is that of spotted knapweed. Spotted knapweed has become an incredible problem in the western United States, especially for ranchers and farmers. The Minnesota Department of Natural Resources states, “Spotted knapweed is poisonous to other plants” (Spotted). This means that it can choke out the native plants relatively easily and very quickly, making them the top of the food chain in the plant kingdom in that area. The introduction of knapweed is theorized to have come from two different sources. For one theory, it is thought that knapweed seeds were unintentionally transported in hay from outside of the country. When people fed this hay to their animals, the seeds dispersed upon the ground and sprouted. The other theory is that of cargo ship ballast. They get into the supply of hay people buy for their different livestock, and thus make business worse for the ranchers, because no one wants to buy hay with knapweed in it when they are feeding it to their animals.
One more similar example to that of knapweed is that of the Russian thistle. Many people in the United States know this plant as a tumbleweed, but most do not realize that tumbleweeds are an invasive species. Mark Hoddle, a researcher with the Center for Invasive Species Research states, “They [thistle] were introduced accidentally by Ukrainian farmers who brought a mixture of flax and thistle seeds from Ukraine” (Hoddle). They were planted in 1877 in South Dakota, and by two decades later, had spread to twelve different states, making it one of the most rapid organism population growths in United States history. The industry of Wild West films did not do their due diligence on researching the tumbleweed before they created their films, because tumbleweeds are depicted in their films. Most of these take place in the early 1800’s, and when a tumbleweed crosses the path in movies, it depicts an impossibility since tumbleweeds were not in the United States back then.
Another example of an intentional introduction would be that of the Asian carp. Carp are known for being able to keep large bodies of water very clean, making them a helpful tool for fish hatcheries and such. Asian carp were imported from East Asia for this exact purpose. Cindy Kolar, a researcher for the University of Nebraska states, “Fish hatcheries used Asian carp in retention ponds and reclamation facilities to filter and clean the water” (Kolar). Unfortunately, when these ponds and facilities flooded, the carp were able to disperse into different lakes and rivers. Now, you can find carp in almost every waterway in the eastern United States. They have taken over the habitat from other native species, and state fish and game agencies are trying desperately to remove them from the waterways (Asian).
This goes to show that more precaution should have been taken with this foreign species. Before they were even imported, it should have been more thought out. Flooding is not an often occurrence, but it does still occur. They should have taken more precautions, and maybe the carp would not be in the wild. Something as simple as a net around the retention ponds would have prevented this widespread dispersion of Asian carp, but there was too much emphasis on the money aspect of the projects for people to think of preemptive measures to protect the environment around the hatchery facilities.
As a result, many examples have been laid out to illustrate the problem the United States faces today. Invasive Species have costed the United States over one-hundred-and-twenty billion dollars per year! Imagine what other programs that money could have been put into if people were more careful and cautious about introducing foreign species into a new area. Introduced species have costed the economy too much already, and after education systems are implemented to educate the populous on this issue, I am sure that the cost will go down significantly, creating more money for better government projects and services.
