Invasive species are of increasing concern now, as global trade, global human migration and a taste for both exotic foods and pets has gotten out of control. The term "Invasive or alien species" covers all life forms, including animals, plants, zoonotic or other pathogens and insects.
Invasive species are defined in Executive Order 13112 as "alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health." 1 Billions in human and environmental damage and harm can be the result of more species invasions.
There are geographical barriers to the spread of plants and animal species. When the species has crossed a geographical barrier, such as mountains and oceans, it is considered to be an alien species. Humans are considered to be the primary source of alien species, but winds, birds and animals may transport them across geographical boundaries, too.
There are also germination barriers for plants. If the plant cannot survive to gestate seeds, then these barriers are effective in preventing the species from invading. But humans are interested in making survival assured for exotic plant species by providing far more than the moisture and other needs of the plantings.
There are political barriers to the spread. But quarantines, bans and customs and port inspections have proved to be ineffective in preventing much of the smuggling that goes on. Trade treaties that require allowing goods to cross borders can also be a source of the problems in not strengthing national boundaries against species invasions.
Currently, an alarming example lies throughout the US where wild or feral swine populations have gotten out of control due to a lack of natural predators. The feral swine population has spread as far West as California and Oregon and as far North as the Great Lakes Region. These are not our friendly little swine, either. They are far larger and far more aggressive. They are voracious and will eat almost anything in their path.
The United States Department of Agriculture (USDA) has a list of the invasive species for which there are extensive profiles, but the list does not cover the magnitude of spread throughout the world of insects, mammals, their related diseases and other pathogens, and their ability to decimate native species.
The aquatic invasive specieslist is another area of concern. Mussels and clams and aquatic plants and fish are a huge problem when boaters and fishermen travel the country and accidentally or deliberately introduce the invasive species. Intensive programs of boat inspections, laws requiring ships to kill all life in their ballast water, and rapid response programs are implemented.
Animal and plant pathogens are the final area of invasive species management. These include viruses, fungi, protists and bacteria. Protists are free living colonial organisms that have a diversity of feeding and survival modes.
Education, regulation, eradication, introduction of natural predators and rapid response are the main tools of local and regional officials. Requiring an inspection of the ballast water of boats that are entering an area from another state or locale, prohibiting and quarantining the import of certain plants and animals at border crossings, and extensive investigation and capture of smugglers are tools of invasive species managers.
Border and port inspections and quarantine periods are used to determine if unauthorized or smuggled plants and animals, or their associated pathogens are present.
Even cautioning campers to not bring firewood from other places helps to prevent the spread of insects and other pathogens to a region that has no natural protections.
But little can be done to stop determined smugglers and those who wish to introduce alien species to the environment.
As an example, the Lake Davis, California Pike infestation was caused by one person who moved to California and who wanted to fish for pike, which is a voracious fish that is decimating the trout population and is threatening to spread throughout the waterways of Northern California.
Management actions for the pike infestation alone have included investigation, attempted eradication through Rotenone treatments, public awareness campaigns that warn people not to introduce such species to the water, and legal sanctions that include a $50,000 fine and up to a year in jail.
A major problem with invasive species management as a whole lies in the complexities that each and every species presents. There must be investigation and analysis, determination of the correct management method, and the ability to execute the management method. As in the case of the rotenone eradication, there may be strong public resistance and legal entanglements that cost additional funds and cause delays when rapid action is called for.
With smuggling, there is no way to ensure that alien species will not cross geographical and national boundaries and be husbanded illegally and in secret, creating whole uncontrolled populations that are let go into the environment.
With legal alien landscaping and exotic food plants and pets, there is much work needed to educate the public and to introduce stronger social agreement that the populations are gettting out of control. Education and more "Alien Species Management" programs will help to prevent the problems from getting even more out of control.