NON-NATIVE INVASION

What's in a name? Invasion species, non-native species, non-indigenous species, introduced species, exotic species, and lots of other names are used to describe parasites, plant and animal species that are not native to a particular area. Today many of these non-native species are thriving in North American competing against native species for food or space and damaging environments. Three often asked questions about non-native species are:

1. How do non-native species get brought, imported, or migrate into North America?
   
   
2. What are the impacts of non-native species on the environments, animals, and plants of North America?
   
   
3. What is our responsibility to the environment and species native to North America

The number of non-native plants and animals has risen dramatically during the 1900s as travel and trade increased worldwide. Currently non-native species come to North America in a number of different ways. Listed below is a way of classifying how or why some non-native species come to North America.

1. Exotics (people like rare and different animals and plants) - piranha, European starlings
   
   
2. Usefulness/Research (animals and plants are brought to North America to control a current problem, aid the local environment, or for profit) - kudzu, nutria, Chinese tallow trees
   
   
3. Migration (animals or plants find their way to North American through their own persistence or because someone imports them intentionally or accidentally)
   
   a. Natural Migration - armadillos, Argentine fire ants, African honey bees
   
   b. Man's Actions Cause for Migration - rats, horses, milk and beef cows, zebra mussels, kudzu, Formosan termites, sea lamprey

Non-native plants and animals that get into the natural environment and begin to reproduce in large numbers can be a threat to native animals and plants in the environment. The most common reasons non-native species thrive in a new environment is because abundant food sources are available and they have few, if any, natural predators or parasites to moderate their growth.

Non-native species can cause consequences that are often unseen when they begin to inhabit an area or while their numbers are low. In the western United States non-native horses and burros have thrived over the past 200 years. Their numbers have grown, subsequently decreasing the food supply available to the native deer and antelopes. They also impact the land by making trails that increase the potential for erosion. There are almost no native predators for the burros and horses. As long as they can find food, their numbers grow as does their impact on the environment.

Economic Impact of Non-native Species
Each year non-native species cause millions of dollars of damage and problems for individuals, governments, businesses and industries. Consider the economic impact caused by non-native species listed below:

• Florida spends more than $14 million per year to control the growth of hydrilla in its fresh water lakes and rivers.
• Business, industries, and municipalities around the Great Lakes and on the Mississippi River spend as much as $360,000 each per year to control zebra mussels from restricting their intake of water from lakes and rivers. It was estimated that during a five year period, from 1989-1994, $120 million was spent to control zebra mussel infestations.
• The Great Lakes sport and commercial fishing industries, which account for more that $4 billion annually in revenue and more than 7500 jobs, are at risk due to growing numbers of non-native species fish (ruffe and round goby), sea lamprey, and mussels that are decreasing the commercial and sport fish caught by these industries.
  
  Our National Parks Are Under Attack
  Alien or non-native species are considered to be one of the greatest threats to the animal and plant life in our national parks. A tourist who caught a mature lake trout in Yellowstone Lake, Yellowstone National Park on July 30, 1994, was not big news. But scientists in the park considered the event a biological catastrophe because the trout was a non-native species and could signal the end of the native cutthroat trout. The Hawaii Volcanoes National Park has more than 1000 plant species, of which more than 600 are non-native species.

Control of Non-native Species
With more that 4500 non-native species in North America and many who are pests to agriculture, businesses, industries, and humans, people have developed methods to get rid of non-native species. A few of the methods used to control non-native species are:

• Physical control for plants - Cutting or harvesting plants, crop rotation, and burning to keep their numbers from growing, spreading and reduce their reproductive rates.
• Chemical control for plants - Chemicals can be sprayed directly on plants to kill them or introduced in the soil to inhibit plants from germinating.
• Physical control for animals - Hunting to extinction, trapping, and fencing to control their movement into uninfested areas. In the case of zebra mussels, washing boats in infested waters with soap and hot water will control growth and further infestations. Alternation of planting dates for crops are used to control insects.
• Chemical control for animals - Field sanitation with chemicals are used to control insects. Poisons can be used to kill animals that are hard to catch. Chemicals can often be added to water to kill or retard the growth of animals. Water can be chlorinated to kill zebra mussels or other aquatic plants and organisms.
• Biological control for plants and animals - This method generally consists of identifying a natural enemy or predator for the known pest and introducing it into an area to control the population of the pest. In some instances animals can be given birth control chemicals to decrease the birth rate. A birth control program has worked well with wild horses in the western United States.
  
  

Many of these control methods can significantly decrease non-native populations and their effect on the environment.

Legislation
The United States government, as well as many states, local governments, and private initiatives, have sought to pass ordinances and laws to control the importation of non-native species. The United States government passed the U.S. Non-indigenous Aquatic Nuisance Prevention and Control Act of 1990 which established the Great Lakes Panel on Aquatic Nuisance Species (ANS). The panel coordinates research and information/education efforts and advises the U.S government on ANS prevention and control. The U.S. government also passed the National Invasion Species Act of 1996 to help control the growing number of non-native/invasion species being found more and more in the U.S.

A Short List of Non-native, Non-indigenous, Invasion, Exotic Species That May Be In Your Backyard

Plants - kudzu, purple loosestrife, tallow trees

Animals - African honey bee, Asian clam, fire ants, European gypsy moth, Russian wheat aphid, salt cedar, zebra mussels

Maps of the Distribution of Some Non-native Species - Below are some maps showing current infestations of Flathead Catfish, Chinese Tallow, and Zebra Mussels.

Map Source: The Nature Conservancy