Globalization and Human Interferences on Animal Distribution

The presence of adventive (= nonindigenous) species in new areas and regions can be due not only to natural shift but also increased by human accidental or conscious transport. In these regions, the allochtonous species can proliferate, spread, and persist to the detriment of the environment and human safety. The invasive species threaten native biodiversity, disrupt ecological processes, and cause significant economic loss. In a world without borders, few if any zones remain sheltered from these immigrations. In fact, in every area reached by humans, new species have been imported from other regions - even in the polar Antarctica continent. In this continent and in the Sub-Antarctic islands a large number of alien microbes, fungi, plants, and animals arrived over approximately the last two centuries, coincident with human activity in the region. Most of the alien species are European in origin. Introduction routes have varied but are largely associated with movement of people and cargo in connection with industrial, national scientific program, and tourism operations (Frenot et al. 2005). Many detrimental nonindigenous organisms have been accidentally introduced through commercial foreign trade, as for example the Western Conifer Seed Bug Leptoglossus occidentalis recently introduced in Europe, probably with trees imported from North America (Vanin et al. 2005) and the Red Palm Weevil (Rhynchophorus ferrugineus) with palms imported from Asia. The frequency of the introductions through commercial pathways and the subsequent potential for establishment and spread has increased with expanding international trade and globalization. Methods of packing and shipping may play an important role in determining arrival and survival rates of nonindigenous species. For example, 19% of insects intercepted on maritime cargo entering New Zealand were alive upon reaching port destinations, whereas estimates of insect survivorship in air cargo entering Hawaii were much lower. Moreover, insects and other organisms introduced in refrigerated containers may survive at relatively high rates, increasing the risk associated with this pathway, because containers are kept at constant, nonlethal temperatures throughout transport (Work et al. 2005).

Not only expanding global trade is responsible of human alien organism introduction but also the use of nonindigenous parasites and predators for biological control of pests, the introduction of livestock and domestic animals (e.g., Australia), and the trade and abandonment of nonindigenous pets. For example, in southern Florida the proportions of adventive species of fishes, amphibians, reptiles, birds, and mammals range from 16% to more than 42%; the proportion of adventive plants is about 26%, and the proportion of insects is 8%. Almost all the vertebrates were introduced as captive pets but escaped or were released into the wild and established breeding populations; few arrived as immigrants. Almost all the plants were introduced as well, with a few arriving as contaminants of shipments of seeds or other cargo. In contrast, only 42 insect species (0.3%) were introduced for biological control of pests. The remaining 946 species arrived as undocumented immigrants, some of them as fly-ins but many as contaminants of cargo. Most of the major insect pests of agriculture, horticulture, manmade structures, and the environment arrived as contaminants of, and stowaways in, cargo, especially plants (Frank and McCoy 1994). Few species survive in the new climatic and ecological condition, and only a small fraction becomes naturalized, although some naturalized species become invasive. There are several potential reasons why some immigrant species prosper: some escape the constraints of their native predator or parasite; other are aided by human-caused disturbances that disrupt a native community as, for example, landscape fragmentation, cultivation, and husbandry. Moreover, the new climatic conditions allow the survival of several species introduced in northern regions.

0 0

Post a comment