Abstract

Non-indigenous, invasive species (NIS) are a significant and increasingly prevalent stressor in both freshwater and marine environments. Approximately 300 NIS are established in marine and estuarine habitats of the continental U.S., and that rate of invasion is rapidly increasing. Aquatic NIS are taxonomically diverse and include: plants, fish, crabs, snails, clams, mussels, bryozoans, and nudibranchs. Invasive alien species are defined by the International Union for the Conservation of Nature (IUCN) as all organisms, animals, or plants that have a negative effect on “the local ecosystem and species” because humans have introduced them to an area that is outside of “their natural range,” and they then establish themselves and become broadly distributed in these areas. It is usually because of their impacts that invasive species are of concern—and sometimes generate controversy.



Table of Contents

Abstracti

Introduction1

Discussion1

Invasion of species2

Global Environmental Change3

Freshwater Invasive Species4

Effects of Invasive Species on Ecosystems6

Economic Effects of Invasive Species7

Impact on Biodiversity10

Impact on Trade10

Risk Management11

Conclusion12

Works Cited13

Economic Effect of Invasive Species in the Great Lakes

Introduction

An invasion of a species is defined as the introduction, establishment, and subsequent spread of that species in a geographic area different from its original or native geographical range (Kenis, Auger-Rozenberg, Roques, Timms, Pere and Cock, 21). Once a species has been introduced into a new habitat, it can be naturalized; that is, it can adapt to the new environment and expand its population, usually producing negative effects on native species and on the whole ecosystem structure. Not all human-induced introductions of species are successful, and invasive populations can become extinct shortly or even after a long time. There are two aspects to consider in the ecological study of invasions: (1) the susceptibility of a territory to an alien invasion (i.e., the suitability of a territory to the ecological requirements of an invasive species and its proclivity to be invaded) and (2) the invasiveness of the species (i.e., its capacity to become an invader), which depends on its ethological, physiological, and morphological characteristics, as well as on the number and frequency of invasions on the same habitat over time (Kenis, Auger-Rozenberg, Roques, Timms, Pere and Cock, 21).

Discussion

Historically, species have often shifted their ranges naturally in response to changed environmental conditions (Nairn, Inglis, Tanner and Allen, 235). However, documented species invasions have overwhelmingly originated from purposeful or accidental introductions by humans. Growth in international trade and travel is increasing the opportunities for species to invade new areas, both through their accidental transportation and because people deliberately transport exotic species that they value for their use as food, fiber, or medicine; for their beauty; as exotica or as pets; for sport; and for their usefulness in the biological control of other organisms (Nairn, Inglis, Tanner and Allen, 235). In Australia, a review led by Malcolm Nairn found that more than 70% of the 290 plant species naturalized during 1971 to 1995 were introduced through human activities. However, not all species that are introduced become pests. One rule of thumb suggests that 10% of species imported are introduced to ecosystems in the ...