In comparison, the problem of determining the ecological threat posed by northern snakehead can look quite simple! Luckily, researchers in other disciplines have also become interested in nonnative species. Historians study the motivations for human transport of species, and how new species in turn affect human societies e. Legal scholars examine how regulations to control the spread of species can be enacted, and how and why they succeed or fail e.
Economists look at how trade and other human activities lead to species movement, and the economic consequences of those species e. Examples of other disciplines could be given, but the point here is that many people from many disciplines are trying to understand nonnative species. Although experts from many disciplines are now studying invasive species, interaction across these disciplines has so far been minimal. For example, many ecologists are interested in how new species arrive but are unfamiliar with the work of economists and legal scholars that describe how patterns in trade, and its regulation, affect the transport of cargo that may contain invasive species.
The lack of interaction may reflect the relative infancy of nonnative species as a topic of study; the field of "invasion biology" is generally considered to have been established during the s and it wasn't until decades later that it began to grow. Other disciplines have come to invasive species more recently.
Additionally, intellectual cross-pollination has certainly been hindered by different paradigms and languages specific to each discipline. Regardless of the cause, the lack of interaction has hampered a deeper understanding of invasion processes and how they can be managed. Full understanding of the issues will require a synthetic approach, with contributions from a range of viewpoints and disciplines. The necessity for interactions among disciplines is illustrated by the continuing spread of northern snakehead and other fishes across the United States.
In an ideal world, policy for these invasions would begin with a clear picture of the ecological risks posed by each species, and whether there are methods available to reduce population sizes and spread rates.
Lawyers and legal scholars would contribute an understanding of how currently available legislation should be applied, and whether the creation of new legislation is warranted. Economists could calculate the effects of different management approaches on trade, and on local economies. The work of social scientists would also be necessary to determine society's level of desire to control the species, and society's tolerance for different management approaches, which may involve harmful chemicals. With all of this information, policy makers would be in a strong position to make wise decisions.
Although there will never be enough nonnative species experts to manage all species in the integrated way just described, continuing work from the disciplines described, and especially interaction among disciplines, has shown great promise for the creation of better management approaches. As the number of studies grows, it is inevitable that general rules will emerge to guide future policy.throptiothajemer.ml
Large Mouth Bass
Interactions among economists and ecologists, for example, have begun to show when it is and is not economically rational to control a nonnative species, and how this depends on the basic biology of the species e. Likewise, legal scholars have worked with biologists and economists to recommend new legislative approaches and institutions for managing nonnative species Shine et al. Although these interactions are positive, they are too rare to have produced the integrated knowledge required to effectively respond to most nonnative species.
The following two examples illustrate the complexities involved in managing nonnative species transport and impacts, and the difficulties in developing and implementing policy. In particular, these examples demonstrate the range of disciplines required to address invasive species threats, and the pressures put upon managers and policy makers who are responsible for mitigating those threats. Most cargo moved around the world travels on ships, and the world merchant shipping fleet now includes more than 50, vessels, with these being registered in over nations International Chamber of Shipping Movement of these ships through the global shipping network now connects every port on earth by a small number of voyages Keller et al.
These close linkages are ecologically important because the safe operation of ships requires them to regularly take on and discharge ballast water. This water can contain organisms representing many species, and the movement of ballast water across the global shipping network means that all ports are effectively ecologically connected. Not surprisingly, ballast water has been the source of many of the world's most damaging marine and freshwater invasions Ricciardi ; Molnar et al.
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The movement of nonnative aquatic species in ballast water has long been acknowledged, as has the damage from those species that become established beyond their native range Carlton and Geller In the international community, through the International Maritime Organization IMO , agreed on ballast water discharge standards that are designed to reduce invasions.
These have not yet come into force, however, because not enough countries have ratified them. At the national level there are few policies in place, although the United States is moving toward adopting ballast water standards that are likely to mirror those in the IMO regulations. Because of this lack of implemented international and national policy the problems of ballast water invasions remain unsolved and invasions continue.
The lack of regulations that address this well-known vector of invasive species illustrates several general problems for the creation of invasive species policy. First, effective regulations need to be based on scientific evidence that they will reduce the harm from invasive species to an acceptable level.
This is difficult to calculate in any system, and in the case of ballast it requires reducing the number of organisms transported in ballast tanks to a level that gives an acceptably low risk of new invasions. Although this sounds simple, the relationship between the number of individual organisms released by ships and the likelihood of new invasions is unknown Gollasch et al.
In the case of ballast water, and for many other vectors that move nonnative species, it is difficult for scientists to make clear recommendations for what appropriate standards would be. Second, treating ballast water will likely require most large ships to install expensive on-board water treatment plants. Ship owners are reluctant to invest in this technology, especially when there is doubt about what standards will be implemented and whether current technologies can achieve those standards.
Reducing the risks from other vectors can also require potentially expensive changes to trade and other practices. Balancing these against the expected benefits from fewer invaders is rarely straightforward, especially because the costs often fall on specific industries while the benefits of fewer invaders are more widely dispersed. Third, it is almost always impossible to accurately determine the ship s that delivered a new invasive species.
For ballast water releases, invasions are detected some unknown amount of time after the individuals were released. This is in contrast to, for example, most chemical pollution, where blame can often be assigned and compensation sought. David Professor of Art History Cottington. Michael Clark. Edward White. Jane EDT Turner. John Rutter. Paul EDT Dimaggio. EDT Downie. Linda Carol Edwards. James Smith Pierce. Got it! Change Country. Shipping country you have chosen is currently only available through Egypt store.
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