Invasive Species in the United States
By
Josh Young
Thesis
Invasive species are a growing problem in the United States and as Christian scientists we need to be more aware of how to handle this problem and realize the potential impact that invasive species pose.
Definition
Invasive species are generally defined as “a species that does not naturally occur in a specific area and whose introduction does or is likely to cause economic or environmental harm or harm to human health (Invasive Species, 2001, para. 4).” This topic was chosen because of the potential impact that invasive plants, animals, and insects can have on the environment. As an environmental science major, it’s important to tackle this subject as more and more alien species are introduced each year throughout the United States. The question of what to do and how to do it is always asked and usually not easily answered. Being a Christian I believe that we have the responsibility to be good stewards and should care for the earth. The moral question then is what to do with these invasive species. This paper will look at current and past ways that invasive species are being dealt with, along with future plans.
Invasive species are generally grouped as species which do harm to native species. So these introduced species are viewed as environmentally unfriendly by many scientists. These species present a difficult problem which environmentalists today are trying to solve, that is determine what to do with them.
Rising Problem:
Currently all fifty states suffer from invasive species and the resulting diversity that is lost to them. A good example of invasive species would be the European starlings (Sturnus vulgaris) (Sibley, 2000, pg. 416). This medium sized black bird was introduced to the United States and now is found in virtually every habitat. As a result of these birds being introduced, many native species have had to compete with the starling for food and shelter. Some bird species declined so much that active steps had to be taken to preserve the species. The Eastern Bluebird (Sialia sialis) is a good example of this (Sibley, 2000, pg. 401). If it weren’t for the numerous bird lovers who erected artificially created cavities, who knows if this lovely bird would still be around.
It is more than just birds which are affected by invasive species. In the north-eastern United States, including northern Indiana, there is a current war against Purple loose-strife (Lythrum salicaria ). This plant, found mainly in wetlands, is threatening to over take the habitats which many native wetland species of plants now reside (Thompson et al, 2006, para. 1).The situation is serious in that Purple loose-strife can over take a whole wetland area, rendering it a mono-culture. This loss of bio-diversity would be devastating to the wetland ecosystem.
It is important to realize why invasive species are harmful. The main reason why is because they lack the natural predators which would naturally keep the number of individuals in check. Without these they have the upper hand and can reproduce unchecked.
International Trade:
Mountains and oceans have acted as natural barriers which have isolated organism allowing them to then adapt to specific habitats. Unfortunately over the past few centuries the development of technology which allowed people to travel great distances has also allowed for the transport of different species, some of which become invasive. Today’s international trade has lead to the spread of many different species throughout the world. Everyday millions of packages are shipped all over the world. For instance, according to the UPS website, they have more than 2,000 daily flights to over 200 countries and territories. Anyone of these packages could have an unsuspecting travel buddy which could wind up being the next invasive specie.
Ballast Water:
Accidental transportation appears the most frequent way which species are spread. A classic example would be organisms catching a ride in the ballast water in ships. Ballast water is water which is taken in by a ship generally when loading or unloading its cargo to help counterbalance the weight change (EPA, 2006, para. 2). This is a huge problem today as hundreds of species catch a ride in the ballast water, that’s everything from fish to tiny microorganisms. Certain bodies of water tend to be more vulnerable than others. The Great Lakes are a good example of this. It’s estimated that thirty percent of the invasive species in the Great Lakes were transported there by ballast water. The U.S. Coast Guard which is in charge of this problem now requires that ships either exchange there ballast water or seal the ballast tanks while they remain in the lakes. Because of the success of this program a plan for the entire nation was formulated which should help to curve the number of species being introduced this way (EPA, 2006, para. 2).
Emerald Ash Borer:
A good example of a species which was accidentally introduced because of international trade is the Emerald ash borer (Agrilus planipennis Fairmaire). It is an exotic beetle which was discovered in southeastern Michigan in 2002. The mature adult beetles feed on leaves but do not do any real damage to the trees. The immature larvae however, feed on the inner bark of ash trees. There feeding habits “ring” the cambium of the tree and prevents the flow of nutrients in the tree essentially killing it. It’s speculated that Emerald ash borers arrived in pallets which must have originated from its native Asia. The pest is currently extending its rage and can be found in northern Ohio and Indiana. Drastic measures where taken when first discovered and thousands upon thousands of ash trees were removed from infected sites. It’s estimated that more than 20 million ash trees have been killed by the ash borer in the three infected states alone (Emerald Ash Borer, 2006).
International Travel:
Millions of people travel each year somewhere outside their home country. Any global traveler could bring back to there home a plant or fruit which may be infested with some foreign specie. Potentially this species could infest the local agriculture and if spread unchecked could do significant damage. It is more than just agricultural damage which could be done. There is always the possibility of spreading infectious diseases which could result in the loss of life. A good example would be the SARS outbreak which happened in 2003. This viral respiratory disease was spread primarily through person to person contact and before it was contained it had traveled to over twenty-four countries and killed over 700 people (CDC, 2005, para. 2).
Purposely Introduced Species:
Not all invasive species are a result of accidental introduction. Many species were imported because people simply wanted them around. Numerous plant species were brought to the U.S. just because they looked nice and people wanted them in their yard. Majority of these plants pose no threat to the native ecosystem but some grew out of control and have become major problems. For example, the hydrilla plant (Hydrilla verticillata)which populates numerous lakes and rivers in the south is a popular aquarium plant (Ramsey, 2001, para. 1). At some point some people dumped out their aquariums and the plant is now a major nuisance.
Some species are introduced just for sport. Rainbow trout (Oncorhynchus mykiss)are a great example of this. Originally found only in western North America it has been introduced across the country and can even now be found world wide. While valued as a sport fish this species can sometimes inter breed with other salmon. This has lead to the virtual extinction of the Alvord cutthroat (Oncorhynchus clarki). Numerous other salmon species are currently threatened because of the ongoing hybridization (Global Invasive Species, 2006).
Pets:
Perhaps the biggest impact from invasive species is pets. Feral cats pose an enormous problem to local wildlife. These cats escape from their owners and quickly revert to a wild state without the interaction of people. In Wisconsin a study was done which suggested that cats killed around 39 million birds annually. Compound that number by the fifty states and the song birds lost to these wild felines is staggering. It is estimated that there is around 70 million feral cats prowling the U.S. looking for handouts and unsuspecting birds (FWS, 2002). Cats are not the only pets which are causing problems. In Florida Burmese pythons (Python molurus bivittatus)have become established in the Everglades National Park where they reach a very large size and prey on many native species, even alligators (Lovgren, 2004). They were only able to gain a foothold because people released their pets when they felt they had grown too big and became an inconvenience.
These days the Internet is even a potential hazard. Anyone can order just about anything from over the web. That includes anything from microbes to seeds to even some large animals such as tigers and bears. Without any real way of controlling this there is always a hazard that someone would release an animal into the wild when it has outlived its cuteness.
Biodiversity:
Biodiversity is dynamic, and the movement of species around the world is a continuing process that is accelerating through expanding global trade. By trying to identify which species are especially likely to become invasive, and potentially harmful to people, ecologists are improving the quality of invasion biology as a predictive science so that people can continue to benefit from global biodiversity without paying the costs resulting from species that later become harmful.
This work helps resolve the controversy over the relationship between biodiversity and invasions, suggesting that the scale of investigation it is a critical factor. Common sense seems to be that non-native species should have a more difficult time invading an ecosystem which is diverse. This would be because the sheer number of species which interact with each other would be more efficient in using resources. These resources, sunlight, water, and nutrients would then not be as plentiful for any invading specie. However, research has shown that even in well-protected areas such as national parks, invasive species often seem to be more successful in diverse ecosystems (NPS, 2006, para. 6). So it appears that even though diversity does play a role in fending off invasive species, its effects are negated by other factors at larger scales. The most diverse ecosystems might be at the greatest risk of invasion, while losses of species, if they affect community-scale diversity, may erode invasion resistance.
Conclusion:
So as Christian’s then, what steps should be taken, if any. The concept of being a good steward is not a new concept. It was commanded to man. In Genesis 1:28 it states,
“God blessed them, and said to them, ‘Be fruitful and increase in numbers: fill the earth and subdue it. Rule over the fish of the sea and the birds of the air and over every living creature that moves on the ground.’ ” (NIV)
So what them does this entail? Does man have free reign over all living creatures and can do whatever we desires? I believe that it gives us a right to use responsibly the earth’s resources. With this then we should be able to hold ourselves responsible for our actions. If we unbalance an ecosystem, then we should try to right it. The question then would be when then should that happen. The effects of species long ago introduced still have ramifications for today. For instance, some still argue that the great lakes should be cleared of all king Salmon. These fish were introduced to help control the alewife fish population which was also introduced (Stump, 2006, para. 3). The population has grown so much that the kings are naturally reproducing and are themselves endangering the lake of overpopulation.
Careful consideration needs to be taken when introducing species into an ecosystem. Those species may be presented initially as beneficial but only time can really tell the real impact. Also we need to be more careful about accidental introduction of species which are a big factor these days. More special steps are needed to ensure that we are more careful about creatures crossing from region into another. This most certainly applies to the shipping industries. It only takes a few organisms to create a new more threatening outbreak.
Bibliography
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