Background for Teachers

Cover-Alien Invaders

TPW Magazine, January 2010
If you don't have a copy of the TPW magazine, you may print a copy of Alien Invaders!.

An Introduction to Invasive Species by the Lady Bird Johnson Wildflower Center at The University of Texas at Austin

Many thanks to the Lady Bird Johnson Wildlflower Center for providing the introduction to Alien Invaders! To learn more about their great work, see their website. To learn more visit Texas Invasives.

What is an invasive species?

A host of plants and animals from exotic places with exotic names (Emerald ash borer, Formosan termite, Asian long-horned beetle, Japanese climbing fern, and Asian dodder) threaten the health of Texas’ native ecosystems, yet few people know that these pests and pathogens are already present or standing at our door step.

An "invasive species" is defined as a species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. (Executive Order 13112).

Sometimes you will see invasive species referred to as exotic, alien, or non-indigenous species. The problem with these names is that they only refer to the non-native part of the definition above. Many exotic or alien species do not cause harm to our economy, our environment, or our health. In fact, the vast majority of "introduced" species do not survive and only about 15% of those that do go on to become "invasive" or harmful.

An invasive species grows/reproduces and spreads rapidly, establishes over large areas, and persists. Species that become invasive succeed due to favorable environmental conditions and lack of natural predators, competitors and diseases that normally regulate their populations.

Invasive species are a form of biological pollution. Invasive species decrease biodiversity by threatening the survival of native plants and animals. They interfere with ecosystem function by changing important processes like fire, nutrient flow, and flooding. Invasive species hybridize with native species resulting in negative genetic impacts.

Invasive species spread easily in today's modern global network of commerce and are difficult and costly to control. Invasives impede industries and threaten agriculture and can endanger human health. Invasive species are a significant threat to almost half of the native US species currently listed as federally endangered.

The costs to prevent, monitor and control invasive species are enormous not to mention the costs to crop damage, fisheries, forests, and other resources. Invasives cost the US $137 billion annually. Some of the most invasive and harmful species cost in excess of $100 million each annually.

What is an introduction?

When a species ends up in a new ecosystem, it is considered "introduced." Species do naturally change their ranges slowly over time, but it is not these "natural" events that we are concerned with. Most of the introductions that result in invasive species are human caused.

In some cases, we deliberately introduce species. Examples of this include garden ornamentals, range forage plants for cattle, animals and insects used to control other organisms (particularly in agriculture), and plants used for erosion control and habitat enhancement for wildlife.

Other species are introduced accidentally on imported nursery stock, fruits, and vegetables, in ship ballast waters, on vehicles, in packing materials and shipping containers, through human-built canals, and from human travel.

How does this issue affect you?

* After habitat destruction, invasive species are the second greatest threat to biodiversity. Invasives threaten the survival of native plants and animals, interfere with ecosystem functions, and hybridize with native species resulting in negative genetic impacts.
* Invasive species impede industry, threaten agriculture, endanger human health, and are becoming increasingly harder to control as a result of rapid global commercialization and human travel.
* Invasive species are a significant threat to almost half of the native species currently listed as federally endangered.
* The costs to prevent, monitor and control invasive species combined with the costs to crop damage, fisheries, forests, and other resources cost the U.S. $137 billion annually.

Go Native!  Learn How You Can Help

To learn more, see:

Invasive species maps: http://www.eddmaps.org/texas/

http://texasinvasives.org/training/index.php

http://www.nature.org/wherewework/northamerica/states/texas/files/invasive_species_in_texas_fact_sheet_1008_lowres.pdf

Marine Invasive Species http://www.tpwd.state.tx.us/fishboat/fish/didyouknow/invasivegalveston.phtml


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