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Boiga irregularis /Brown tree snake [Gordon Rodda]
Rhinella marina/cane toad [Craig Morley]
Mus musculus [Giorgio Muscetta]
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Invasive Species

 

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What are they?

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How do they spread?

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What are their impacts?

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Managing their spread
   
   
   

 

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About Invasive Species

How do they spread?

Humans have always transported species as they traversed the world, bringing with them pieces of their culture and homeland. Today, with modern transport systems and global economic trade, people are moving species at unprecedented rates across ecological barriers and political borders. Invasive species are spread through a variety of accidental and purposeful methods. Some organisms may be introduced inadvertently in the course of lawful activities, such as shipping and tourist travel, or species may be purposefully imported, for example, by the horticultural trade or the pet and exotic animal industry. Risk assessments of the negative impacts of purposeful introductions of species while rarely done, provide the research to take a preventative approach to the economic benefit and ecological impacts of a species introduction. Preventative measures are the most economical and ecologically sound method to prevent an invasive species to establish. Legislative and regulatory efforts exist at national and international levels to “stem the tide of invasion.”

Understanding the accidental introductions of invasive species to a new region requires us to understand the complexity of global trade and travel. In the global market the basic shipping materials may come from wide geographical sources. Shipping containers and packaging material are potential sources of accidental introductions of seeds, insects, diseases and other organisms. First recognized in North America in 1889, cheat grass (Bromus_tectorum), a native of Eurasia arrived on the continent as a contaminant in shipments of grain seeds from Europe. Wooden packing material used to protect shipping goods also provides habitat which can harbor damaging plant pathogens and insects. Native to China and Korea, the Asian long horn beetle (Anoplophora_glabripennis) has been intercepted in solid wood packaging material in the USA and the UK. Education and collaboration enable us to prevent accidental introductions.

Pets and plants are a part of human nature. We humans take our loved flora and fauna with us wherever we go. Some ornamental plants adapt to many environments and may escape from gardens and landscaping areas into native habitat, where they disrupt species diversity and abundance, community composition and ecosystem processes. Hiptage_benghalensis, a native plant of Asia is a cultivated tropical ornamental. A pest of Australian rainforests and a disrupter of native plant regeneration on Mauritius and Réunion it could be considered no longer as a just an ornamental, but also as an ecosystem disrupter. Unwanted pets are released into wild ecosystems worldwide by owners that do not realize the ecological consequences of their actions. The Mississippian red-eared slider (Trachemys_scripta_elegans) has invaded wetlands and lakes and competes with local turtle species in the Caribbean and Europe. The Burmese python (Python_molurus_bivittatus) is breeding in the Florida Everglades National Park, where over 15,000 snakes have been removed in an effort to control this species’ impacts.

Over two thirds of the Earth’s surface is covered by water. These aquatic ecosystems are rich in biodiversity, many of the species unique to the region in which they live. Current and expanding global trade threatens to erode the ecological barriers that have maintained these diverse ecosystems by introducing exotic species. The two main vectors for the introduction of invasive marine species are hull-fouling and ballast water. With approximately 90% of global trade transported on the oceans, the possibility of introducing an invasive marine species is not only increasing, but difficult to prevent. It is estimated that biofouling is responsible for the introductions of over two-thirds of all non-native algal species globally, and about three quarters of all non-native marine invertebrates in Hawaii. Approximately 3–5 billion tonnes of ballast water are transferred throughout the world each year. This transfer of ballast water associated with large ships is believed to be the main vector for the spread of invasive aquatic species today, with an estimated 7,000 species transported each day. The concern about the spread of invasive species has led to the development of regional and international collaborative efforts to address the gaps in prevention, early detection and control of invasive species.


 

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Related links:

The list of '100 of the World's Worst Invasive Alien Species' illustrates the incredible variety of species that have the ability, not just to travel in ingenious ways, but also to establish, thrive and dominate in new places. Today, alien invasion is second only to habitat loss as a cause of species endangerment and extinction.

View 100 of the  World's Worst Invasive Alien Species

Click here to view images and follow links to species profiles of '100 of the World's Worst Invasive Alien Species' on the Global Invasive Species Database.


 

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