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Strange as it may seem, history and biology are linked! There are two views regarding history and exotic species introductions and the resulting effects. Throughout the history of Earth, species have crossed barriers like oceans and mountains many times. Nothing really new is happening now, and exotic species introductions are nothing to worry about. It is true that plants, animals, and even microbes are able to cross vast geographic barriers and survive despite incredible odds against them. Hawaii, the most remote island on earth, receives new species each year. However, most of these species are being helped by human activities. Before human settlement, it is estimated that Hawaii received a new species about once every 5,000 years and now a new species arrives and establishes about every 8 months. Hawaii is not alone because humans either purposefully or accidentally transport species across mountains, rivers, glaciers, and deserts on boats, cars, planes, or even on the dirt stuck to the soles of our shoes. As people travel and species are distributed, our planet is in the process of becoming homogenized. This homogenization occurs both by natural means and by humans. The native plants and animals adjust to these incursions, and other human activities such as urbanization and agriculture are greater threats. Today's species introductions are very different from the natural introductions or migration of species into new areas during the Earth's past and we need to be very careful in assisting such introductions. At least two differences are apparent. First, species that are transported across geographic barriers by humans will naturally tend to be species that are beneficial to humans or are adapted to human activity. Thus, domesticated animals and plants like pigs, cats, wheat, rice, and other species that provide food or have ornamental value will tend to arrive in new areas first. Soon after, species that are adapted to human activity like rats, cockroaches, agricultural weeds, and diseases arrive. Thus, humans bring their own mini-ecosystems with them. In the past, whenever new species invaded an area naturally, their greater ecosystem accompanied them. In the case of human transportation of species, however, the diseases or predators of an introduced species are often be left behind. This is especially the case with plants that are brought over as seeds. Because introduction of single species has a higher probability of leaving behind natural enemies and disease, the species also has a higher probability of becoming invasive. We must make an extra effort to prevent this migration or at least limit its impact. See also the Role of Economics Back to the ethics page The 3rd letter of the password - T |
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