Exotic and invasive species

How long does a plant or animal species have to live in a region before it is considered native? And are all non-native species considered invasive?

Katherine Sabia, Monroe, Connecticut

The distinction between native and nonnative species does not disappear over time; if a plant or animal was introduced with human help, according to the Department of Agriculture, it is nonnative. There’s also a crucial distinction between nonnative species and invasive ones, notes Vicki Funk, senior research botanist and curator at the Museum of Natural History. To be considered invasive, a nonnative animal or plant species has to displace one or more natives. Chicory, introduced from Europe as a flavoring agent in the 19th century, grows wild in the United States but does not displace native plants; but kudzu, introduced from Asia for erosion control in the mid-20th-century South, does, and is considered therefore invasive.

After researchers tag or collar an animal, does the device ever lead to the animal being ostracized from its group?

John Fleming, Rockport, Massachusetts

Studies have found that African zebras wearing heavy collars may change their travel routes, and that collared water voles in the United Kingdom bear fewer female offspring, but the social implications of collaring have not been extensively researched. Peter Leimgruber, head of the Conservation Ecology Center at the Smithsonian Conservation Biology Institute, who studies Przewalski’s horses, says he has observed no negative effects on the social ranking, behavior or fitness of those horses, or on that of other collared equines. In fact, one of the goals of collaring animals is to record their behavior in order to better understand their social structure.

How did the word “volume” become associated with sound?

Raymond Stubblefield, Harrisonburg, Virginia

The word has several threads in modern English, says Mary S. Linn, curator of cultural and linguistic revitalization at the Center for Folklife and Cultural Heritage. When it entered English, in the late 14th century, it referred to a roll of papyrus and to a bound book. As books grew larger, “volume” referred to bulk more generally. By the late 18th century, according to the Oxford English Dictionary, scientists extended the meaning to refer to bodies of matter occupying space, and musicians used it to refer to the power of voices to project in a space.

How long would it have taken the United States to build a third atomic bomb after it dropped the second (and last) one on Nagasaki on August 9, 1945?

Gary Miller, Davenport, Florida

Less than two weeks. Michael Neufeld, senior curator at the National Air and Space Museum, says that on August 10, 1945, Maj. Gen. Leslie Groves, director of the Manhattan Project, notified the War Department that another plutonium bomb could be “ready for delivery on the first suitable weather after 17 or 18 August.” Documents from the era reveal that the United States was prepared to build at least 12 more bombs before Japan surrendered, on August 15.

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Invasive Species

“Invasive species”—they may not sound very threatening, but these invaders, large and small, have devastating effects on wildlife.

Invasive species are among the leading threats to native wildlife. Approximately 42 percent of threatened or endangered species are at risk due to invasive species.

Human health and economies are also at risk from invasive species. The impacts of invasive species on our natural ecosystems and economy cost billions of dollars each year. Many of our commercial, agricultural, and recreational activities depend on healthy native ecosystems.

What Makes a Species “Invasive”?

An invasive species can be any kind of living organism—an amphibian (like the cane toad), plant, insect, fish, fungus, bacteria, or even an organism’s seeds or eggs—that is not native to an ecosystem and causes harm. They can harm the environment, the economy, or even human health. Species that grow and reproduce quickly, and spread aggressively, with potential to cause harm, are given the label “invasive.”

An invasive species does not have to come from another country. For example, lake trout are native to the Great Lakes, but are considered to be an invasive species in Yellowstone Lake in Wyoming because they compete with native cutthroat trout for habitat.

How Invasive Species Spread

Invasive species are primarily spread by human activities, often unintentionally. People, and the goods we use, travel around the world very quickly, and they often carry uninvited species with them. Ships can carry aquatic organisms in their ballast water, while smaller boats may carry them on their propellers. Insects can get into wood, shipping palettes, and crates that are shipped around the world. Some ornamental plants can escape into the wild and become invasive. And some invasive species are intentionally or accidentally released pets. For example, Burmese pythons are becoming a big problem in the Everglades.

In addition, higher average temperatures and changes in rain and snow patterns caused by climate change will enable some invasive plant species—such as garlic mustard, kudzu, and purple loosestrife—to move into new areas. Insect pest infestations will be more severe as pests such as mountain pine beetle are able to take advantage of drought-weakened plants.

Threats to Native Wildlife

Invasive species cause harm to wildlife in many ways. When a new and aggressive species is introduced into an ecosystem, it may not have any natural predators or controls. It can breed and spread quickly, taking over an area. Native wildlife may not have evolved defenses against the invader, or they may not be able to compete with a species that has no predators.

The direct threats of invasive species include preying on native species, outcompeting native species for food or other resources, causing or carrying disease, and preventing native species from reproducing or killing a native species’ young.

There are indirect threats of invasive species as well. Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife. Aggressive plant species like kudzu can quickly replace a diverse ecosystem with a monoculture of just kudzu. Additionally, some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry or the intensity of wildfires.

Examples of Invasive Species

Asian carp are fast-growing, aggressive, and adaptable fish that are outcompeting native fish species for food and habitat in much of the mid-section of the United States. The huge, hard-headed silver carp also pose a threat to boaters, as the fish can leap out of the water when startled by boat engines, often colliding with people and causing injuries. “Asian carp” is a catchall name for species of silver, bighead, grass, and black carp from Southeast Asia. Voracious filter feeders, Asian carp consume up to 20 percent of their body weight each day in plankton and can grow to more than 100 pounds.

Asian carp were imported to the United States in the 1970s to filter pond water in fish farms in Arkansas and quickly spread across the country. Flooding allowed them to escape and establish reproducing populations in the wild by the early 1980s. Asian carp are swiftly spreading northward up the Illinois River, and are now on the verge of invading the Great Lakes. Once established in an ecosystem they are virtually impossible to eradicate. Adult Asian carp have no natural predators in North America and females lay approximately half a million eggs each time they spawn.

Temperatures in the Great Lakes are well within the fishes’ native climate range. Parts of the Great Lakes, including nutrient-rich bays, tributaries, and other near-shore areas, would offer Asian carp an abundant supply of their preferred food, plankton. Plankton is also favored by most young and many adult native fishes and the voracious carp would likely strip the food web of this fundamental resource. The U.S. Geological Survey has identified 22 rivers in the U.S. portion of the Great Lakes that would provide suitable spawning habitat for Asian carp.

The brown marmorated stink bug, Halyomorpha halys, is native to China, Japan, and surrounding countries. They were first discovered in the United States in Pennsylvania during the late 1990s, but no one knows for certain how they were introduced to North America. Brown marmorated stink bug (BMSB) populations are exploding in the absence of their natural predators, and they are quickly becoming a nuisance to people in their homes and to the agriculture industry.

A big problem with BMSBs so far is the infestation of people’s homes. The bugs begin to come indoors, searching for warm, protected areas when outside temperatures turn cooler in the fall. They don’t reproduce inside the home or cause structural damage, but their namesake odor, noisy flying, and teeming numbers can make the BMSB an extreme nuisance throughout the winter, especially on warmer days when they are more active.

BMSBs feed on host plants by piercing the skin and consuming the juices within; the signs of stink bug feeding appear as “necrotic” or dead spots on the surface. They’ve become a significant agricultural pest in the mid-Atlantic region, and other areas could see similar effects if the BMSB’s range continues to expand. A wide variety of plants are known food sources for BMSBs, including ornamental trees and shrubs; fruit crops like peaches, apples, grapes, and pears; vegetable crops like green beans and asparagus; and soybeans and corn.

Zebra mussels and quagga mussels are virtually identical, both physically and behaviorally. Originally from Eastern Europe, these tiny trespassers were picked up in the ballast water of ocean-going ships and brought to the Great Lakes in the 1980s. They spread dramatically, outcompeting native species for food and habitat, and by 1990, zebra mussels and quagga mussels had infested all of the Great Lakes. Now both quagga mussels and zebra mussels have spread to 29 states by hitching rides on boats moving between the Great Lakes and Mississippi River Basins. Artificial channels like the Chicago Area Waterways System facilitate their spread. These man-made channels act like super-highways and are also a pathway for Asian carp, which are currently spreading towards the Great Lakes.

The quagga and zebra mussels blanketing the bottom of the Great Lakes filter water as they eat plankton and have succeeded in doubling water clarity during the past decade. Clear water may look nice to us, but the lack of plankton floating in the water means less food for native fish. Clearer water also allows sunlight to penetrate to the lake bottom, creating ideal conditions for algae to grow. In this way, zebra and quagga mussels have promoted the growth and spread of deadly algae blooms.

Zebra and quagga mussels harm native fish populations, ruin beaches and attach to boats, water intake pipes, and other structures, causing the Great Lakes economy billions of dollars a year in damage. They devastate native species by stripping the food web of plankton, which has a cascading effect throughout the ecosystem. Lack of food has caused populations of alewives, salmon, whitefish, and native mussel species to plummet.

In her five-year lifetime, a single quagga or zebra mussel will produce about five million eggs, 100,000 of which reach adulthood. The offspring of a single mussel will in turn produce a total of half a billion adult offspring. There are an estimated 10 trillion quagga and zebra mussels in the Great Lakes today. Once zebra and quagga mussels become established in a water body, they are impossible to fully eradicate. Scientists have not yet found solutions that kills zebra and quagga mussels without also harming other wildlife.

Additional examples:

  • Cogongrass is an Asian plant that arrived in the United States as seeds in packing material. It is now spreading through the Southeast, displacing native plants. It provides no food value for native wildlife, and increases the threat of wildfire as it burns hotter and faster than native grasses.
  • Feral pigs will eat almost anything, including native birds. They compete with native wildlife for food sources such as acorns. Feral pigs spread diseases, such as brucellosis, to people and livestock. E. coli from their feces was implicated in the E. coli contamination of baby spinach in 2006.
  • European green crabs found their way into the San Francisco Bay area in 1989. They outcompete native species for food and habitat and eat huge quantities of native shellfish, threatening commercial fisheries.
  • Dutch elm disease (caused by the fungus Ophiostoma ulmi) is transmitted to trees by elm bark beetles. Since 1930, the disease has spread from Ohio through most of the country, killing over half of the elm trees in the northern United States.
  • Water hyacinth is a beautiful aquatic plant, introduced to the U.S. from South America as an ornamental. In the wild, it forms dense mats, reducing sunlight for submerged plants and aquatic organisms, crowding out native aquatic plants, and clogging waterways and intake pipes.

Curbing the Spread

One way to curb the spread of invasive species is to plant native plants and remove any invasive plants in your garden. There are many good native plant alternatives to common exotic ornamental plants. In addition, learn to identify invasive species in your area, and report any sightings to your county extension agent or local land manager.

Regularly clean your boots, gear, boat, tires, and any other equipment you use outdoors to remove insects and plant parts that may spread invasive species to new places. When camping, buy firewood near your campsite (within 30 miles) instead of bringing your own from home, and leave any extra for the next campers. Invertebrates and plants can easily hitch a ride on firewood you haul to or from a campsite—you could inadvertently introduce an invasive to a new area.

Invasive species

A global problem

invasive speciesSome plants, animals, and other forms of life can be described as invasive species when they are introduced to areas where they are not native, because they decimate native species and make other significant changes to native ecosystems. The most-effective solutions in dealing with an invasive species arise from a detailed understanding of that species’ natural history.© MinuteEarth (A Britannica Publishing Partner)See all videos for this article

Since the dawn of life on Earth, species have migrated and colonized new areas. In some cases, migrating species were unable to establish sustainable populations in new habitats and quickly died out. In other cases, they either were incorporated into the existing structure of the ecosystem or were responsible for modifying native food chains by outcompeting native competitors or decimating native prey. One of the most significant species invasions in Earth’s history took place during the Pliocene Epoch (5.3 million to 2.6 million years ago) after the formation of an isthmus connecting North and South America. Numerous predator species migrating from North America to South America are thought to have contributed to the extinction of many of South America’s mammalian species.

Norway rat (Rattus norvegicus).John H. Gerard

Since their emergence, modern humans (Homo sapiens) have played an ever-increasing role in species invasions. As a result of their colonization of all but the most extreme of Earth’s ecosystems and their tendency to transform natural environments into agricultural and urban landscapes, modern humans are among the most successful invasive species. However, humans also contribute substantially to the introduction of different species to new areas. Tens of thousands of years ago, migratory bands of humans were accompanied by parasites, pathogens, and domesticated animals. With the rise of civilization, many exotic plants and animals were brought from distant lands to broaden the palettes of consumers or serve as curiosities in gardens and circuses.

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Although the collection and transport of exotic species dates to ancient times, written records of their ecological effects extend back only a few centuries. One of the best-known historical examples of such species is the Norway, or brown, rat (Rattus norvegicus). This rodent, which is believed to have originated in northeastern China, spread throughout the islands of the Pacific Ocean. Since the rat’s accidental introduction during the voyages of exploration between the late 18th and 19th centuries, populations have established themselves on numerous Pacific islands, including Hawaii and New Zealand, where they prey on many native birds, small reptiles, and amphibians. Some other introductions during this time, however, were deliberate: dogs, cats, pigs, and other domesticated animals were taken to new lands, and there they caused the extinction of many other species, including the dodo (Raphus cucullatus) from Mauritius by 1681.

yellow-faced beeLearn about conservation efforts to help the endangered yellow-faced bee, whose populations are threatened by habitat loss and invasive plant and animal species.Encyclopædia Britannica, Inc.See all videos for this article

Although invasive species occur on all continents, Australia and Oceania have been particularly hard-hit. The first wave of invasive species arrived in Australia and the islands of the Pacific with European explorers in the form of feral cats and various rat species. European wild rabbits (Oryctolagus cuniculus), which originally inhabited southern Europe and North Africa, were deliberately introduced into Australia in 1827 to serve as a familiar elements for settlers in a new land, and the rabbits multiplied significantly. Over time, they degraded grazing lands by stripping the bark from native trees and shrubs and consuming their seeds and leaves. The red fox (Vulpes vulpes), a small predator found across much of the Northern Hemisphere, wreaked havoc on marsupials and native rodents since its introduction in the 1850s. Ironically, the red fox was brought to Australia to help control the aforementioned European wild rabbits. The voracious cane toad (Bufo marinus), whose native range spans from northern South America to southern Texas, is a poisonous species with few natural predators. It was introduced into Australia in the 1930s from Hawaii to reduce the effects of beetles on sugarcane plantations. Cane toads are responsible for a variety of ills, such as population declines in native prey species (bees and other small animals), population drops in amphibian species that compete with them, and the poisoning of species that consume them. A large number of invasive plants have also been introduced to Australia. Giant sensitive tree (Mimosa pigra) may have been introduced by the Darwin Botanic Garden sometime before the 1890s; upalatable to most wildlife, it forms vast thickets and disrupts native wetland ecosystems. Cherry guava (Psidium cattleianum), Surinam cherry (Eugenia uniflora), Arabian coffee (Coffea arabica), lantana (Lantana camara), and the ice cream bean (Inga edulis) are all invasive species that were brought as food or ornamental plants and escaped cultivation.

On Guam, Saipan, and several other Pacific islands, the brown tree snake (Boiga irregularis), a native of Australia and Indonesia, has caused the extinction of several birds, reptiles, and amphibians and two of Guam’s three native bat species since its accidental introduction to these islands in the 1950s. Although the snake may have been brought to the islands to control native rodent populations, it is more likely that the original invaders were stowaways aboard military aircraft and cargo ships.

brown tree snakeBrown tree snake (Boiga irregularis).Gordon H. Rodda/U.S. Fish and Wildlife Service

North American ecosystems have been greatly affected by invasive species over the last two centuries. During the 19th and 20th centuries the Great Lakes region was altered by the sea lamprey (Petromyzon marinus), a primitive fish indigenous to the coastal waters of the North Atlantic and western Mediterranean Sea. The sea lamprey uses a specially modified sucker to latch onto a game fish and drain its blood. It is thought that the development of the Erie, Welland, and St. Lawrence canal systems allowed the fish to migrate into the Great Lakes. In the 1980s the introduction of the zebra mussel (Dreissena polymorpha), a filter-feeding mollusk, created further ecological and economic disruption. This species is native to the watersheds supplying the Black, Aral, and Caspian seas. Many traveled in the ballast water in oceangoing ships, and they were subsequently released when this water was dumped into the Great Lakes. Large numbers of zebra mussels have been shown to clog water-intake pipes and remove much of the algae from the aquatic ecosystems they inhabit.

  • Sea lamprey (Petromyzon marinus) displaying its prominent mouthparts.Blickwinkel/Alamy
  • Zebra mussels (Dreissena polymorpha) attached to a pier that was pulled from Lake Erie in Monroe, Mich., U.S.Jim West/Alamy

Introduced into the United States from Eurasia in the 1970s to help control algae on catfish farms in the Deep South, Asian carp—most notably bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix)—escaped into the Mississippi River system during flooding episodes in the early 1990s. After establishing self-sustaining populations in the lower Mississippi River, they began to move northward. Although breeding populations have been restricted to the Mississippi River watershed, they could, if they enter the Great Lakes ecosystem, seriously disrupt the food chains of the major lakes and adjoining rivers. Compared with other species of Asian carp, these two pose the greatest danger. They consume large amounts of algae and zooplankton, eating as much as 40 percent of their body weight per day. They are fierce competitors that often push aside native fish to obtain food, and their populations grow rapidly, accounting for 90 percent of the biomass in some stretches of the Mississippi and Illinois rivers.

bighead carp; silver carpPoster depicting invasive bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix). UIUC/IL-IN Sea Grant/U.S. Fish and Wildlife Service

By 2010 the Burmese python (Python molurus bivittatus), a native of Southeast Asia, was challenging the American alligator (Alligator mississippiensis) for dominance in the wetlands of southern Florida. Released into the Florida landscape after Hurricane Andrew damaged pet stores in 1992, as well as by change-of-heart pet owners, Burmese pythons soon established breeding populations in the state. Growing to nearly 6 metres (20 feet) long, these giant constrictor snakes became significant predators in the area. The python’s penchant for consuming the Key Largo wood rat (Neotoma floridana) and the wood stork (Mycteria americana) have caused both species to decline locally.

kudzuLearn about the impact invasive kudzu vine (Pueraria montana) has had on the ecosystems of the southeastern United States.Encyclopædia Britannica, Inc.See all videos for this article

Parts of the United States are covered by kudzu (Pueraria montana, variety lobata), a fast-growing vine native to southern and eastern Asia. Kudzu was introduced into North America for erosion control and decorative purposes in the late 19th century; however, it deprives native plants of sunlight. In addition, a large section of the United States is plagued by the red imported fire ant (Solenopsis invicta), an aggressive swarming and biting species native to South America. The species may have arrived in the United States in shipments of soil and other landscaping materials.

Some introduced species have a global distribution. Most notable examples in this category are disease-causing microbes. Early European colonists of the New World and the Pacific introduced organisms that cause the common cold, smallpox, sexually transmitted diseases, and other illnesses to lands whose people had no resistance to them. Beginning in the late 1960s, a strain of human immunodeficiency virus (HIV), which causes AIDS, was first carried by infected humans from Africa to Haiti. Later AIDS would spread to populations across the globe. Global trade and pet trafficking are often blamed for accidental disease outbreaks among other species, such as the worldwide spread of amphibian chytridiomycosis in frogs and other amphibians and possibly even avian influenza (bird flu) and West Nile virus among various organisms.

Washington State

Why We Have Laws to Control Noxious Weeds

Weed laws establish all property owners’ responsibility for helping to prevent and control the spread of Noxious Weeds. Since plants grow without regard to property lines or political jurisdictions, everyone’s cooperation is needed – city gardeners, farmers, government land agencies, foresters, and ranchers all have a role to play.

Washington’s weed laws spell out these responsibilities and create the government infrastructure needed to educate citizens and ensure that the laws are respected.

Washington’s weed laws also direct the state Noxious Weed Control Board to create and maintain the state’s official list of noxious weeds that landowners may be required to control.

Washington is a National Leader in Establishing Weed Laws

Washington’s first weed law was passed in 1881 to fight the spread of Canada thistle, a weed that was accidentally brought by early settlers.

In the late 1960s, the state legislature established the state’s Noxious Weed Control Board, and authorized counties to establish County Weed Boards. Thirty-eight of Washington’s 39 counties have such boards. There are also a handful of Weed Districts that are contiguous with Irrigation Districts.

The Laws

RCW 17.10

RCW 17.10 (Revised Code of Washington) is the state’s basic weed law.
The Washington Administrative Code (WAC) contains the rules and regulations needed to carry out state law.

WAC Chapter 16-750

WAC Chapter 16-750 includes the state Noxious Weed List, definitions and descriptions of region boundaries for Class B weeds, and the schedule of monetary penalties.

WAC Chapter 16-752

WAC Chapter 16-752 describes the quarantine list maintained by the state Department of Agriculture. (The state law that calls for the creation and maintenance of the quarantine list is RCW 17.24.)

RCW 17.04, RCW 17.06

Weed Districts and Intercounty Weed Districts laws. There are nine Weed Districts in Washington: five in Kittitas County, two in Grant County, one in Adams County and one in Benton County. There are two Intercounty Weed Districts in Washington, both of which encompass parts of Grant and Adams counties.

The State’s Noxious Weed List is Organized into Three Classes of Weeds: Class A, B, and C.

  • Class A weeds are mostly newcomers to Washington, and are generally rare.
  • The goal is to completely eradicate them before they gain a foothold.
  • Landowners are required to completely eradicate Class A weeds. (Eradicating weeds means getting rid of the plants altogether, including plant roots.)

Class B Weeds

  • Class B weeds are those that are widespread in some parts of the state, but limited or absent in other parts of the state.
  • The goal with Class B weeds is to prevent them from spreading into new areas, and to contain or reduce their population in already infested areas.
  • The State Weed Board designates Class B noxious weeds for control in those parts of the state where they are limited or absent and threaten to invade. to view how Class B noxious weeds have been designated for control in Washington. Designations are based on this region map. Additionally, a County Weed Board may select a Class B non-designate for control if it is considered a local priority.
  • Landowners may be required to control Class B noxious weeds, depending on how widespread the species is and/or whether the species is a local priority. Check with your County Noxious Weed Control Board for more info on which Class B species you must control.

Class C Weeds

  • Class C weeds are often widespread, or are of special interest to the agricultural industry.
  • The State Weed Board does not require control of Class C noxious weeds.
  • The State and many County Weed Boards provide information on identification and best management practices for these species.
  • A County Weed Board may require landowners to control a Class C weed if it poses a threat to agriculture or natural resources. Check with your County Noxious Weed Control Board for more info on which Class C species you must control.

Quarantine Weed List

The Washington State Department of Agriculture (WSDA) maintains a plant quarantine list, called ‘Plants And Seeds Whose Sales are Prohibited in Washington State‘. This quarantine list consists of both terrestrial (land) and aquatic (water) plants known to be invasive and damaging. The quarantine list includes those plants whose sale or distribution is prohibited in Washington State.

All Class A weeds are on the quarantine list. Some plants are placed on the list to prevent them from ever being imported to our state.

It is illegal to transport, buy, sell, or trade any quarantined species. It is also illegal to distribute seed packets, flower seed blends, or ‘wildflower mixes’ that include these plants. Anyone who violates the quarantine restrictions is subject to a civil penalty of up to $5,000 per violation.

You can view a gallery of quarantined weeds with information on each weed on our quarantined noxious weed list page. For more information about the WSDA Quarantine Plant List, please visit their website.

What it Means to ‘Control’ Weeds

Controlling weeds means not letting weeds reproduce- usually, that simply means not letting them go to seed. Legally, control means to prevent the dispersal of all propagating parts capable of forming a new plant, including seeds.

Penalties for Landowners Who Fail to Control Noxious Weeds

If the landowner does not control noxious weeds after receiving several notifications, the County Weed Board or Weed District may come and control the weeds and bill the landowner or may issue a civil infraction.

Noxious weed is a legal definition associated with an invasive plant that has been introduced into an environment and causes or is likely to cause environmental or economic harm.

Many noxious weeds are pretty, but their effects are not. Pathogens, microbial activity in the soil, and absence of natural enemies in their new environment can allow noxious weeds to spread like a wildfire, transforming ecosystem function including biotic and abiotic processes.

In Wyoming, there are two “noxious weed lists” that a species can be placed on. One is the State Designated list where the species has been determined to be detrimental statewide. The other is the County Declared list where a local Weed and Pest District has determined the species to be a concern within that county. The legal definitions as per the Wyoming Weed & Pest Control Act are as follows:

“Designated noxious weeds” means plant species having seeds or other plant parts determined to be detrimental to the general health or welfare of the state based upon the following:

(A) Has demonstrated the ability to aggressively invade native plant communities and agricultural crops;

(B) Is injurious or poisonous to livestock;

(C) Is a carrier of disease or parasites;

(D) Can, by virtue of either direct or indirect effect, negatively impact management of agricultural or natural ecosystems.

State Designated Noxious Species List

“Declared weed” means any plant species which the district Weed & Pest board and the Wyoming weed and pest council have found, either by virtue of its direct or indirect effect to negatively impact management of agricultural or natural ecosystems, or as a carrier of disease or parasites, to be detrimental to the general welfare of persons residing within a district.

County Declared Noxious Species Lists

The Wyoming Weed & Pest Control Act can be found here under Title 11, Chapter 5

Noxious weed lists and laws

The King County Noxious Weed List includes all noxious weeds that property owners are required to control in King County according to the Washington State Noxious Weed Control Law. The list also includes weeds that are not regulated in King County but that also have negative impacts locally.

The King County weed list is set annually by the King County Noxious Weed Control Board, which administers the state noxious weed law in King County. The county weed list includes all Class A weeds on the state noxious weed list, all Class B weeds designated by the state for control in the county, and any additional Class B or C weeds that are designated by the county weed board for required control in the county. All Class A, B and C weeds on the county weed list need to be controlled by the property owner.

  • Class A Weeds: Non-native species whose distribution in Washington is still limited. Preventing new infestations and eradicating existing infestations are the highest priority. Eradication of all Class A plants is required by law throughout Washington.
  • Class B Weeds: Non-native species presently limited to portions of Washington. Species are designated for control in regions where they are not yet widespread. Preventing new infestations in these areas is a high priority. In regions where a Class B species is already abundant, control is decided at the local level, with containment as the primary goal.
  • Class C Weeds: Noxious weeds that are typically widespread in Washington or are of special interest to the state’s agricultural industry. The Class C status allows counties to require control if locally desired or to choose to provide education or technical consultation.

Controlling weeds means not letting weeds reproduce. Usually, that means not letting them go to seed. Legally, control means to prevent the dispersal of all propagating parts capable of forming a new plant.

In addition to the regulated weeds, the county weed list includes additional species that landowners are not required to control but for which the county provides technical assistance and information:

  • Non-Regulated Noxious Weeds: State-listed Class B and C noxious weeds not designated for mandatory control in King County but that have negative impacts for the people and the environment of the county. Often these species are already widespread in the county and requiring control countywide would not be feasible. The county weed board encourages landowners to control these species where possible and to avoid introducing them to the county.
  • King County Weeds of Concern: These are additional non-native, invasive plant species that are not classified as noxious weeds on the state list but are problematic in King County. These species often impact and degrade native plant and animal habitat. The County Weed Board recognizes these plants are invasive and is collecting information and providing education on control. The Board encourages and recommends control and containment of existing populations and discourages new plantings, but control is not required.

Understanding the Washington State Noxious Weed Law

Noxious weeds are non-native plants that, once established, are highly destructive, competitive and difficult to control. They have economic and ecological impacts and are very difficult to manage once they get established. Some are toxic or a public health threat to humans and animals, others destroy native and beneficial plant communities.

To help protect the state’s resources and environment, the Washington State Noxious Weed Board adopts a state weed list each year (Chapter 16-750 WAC), in accordance with the state noxious weed law (Chapter 17.10 RCW). Noxious weeds are separated into classes A, B, and C based on distribution, abundance, and level of threat (how dangerous the plants is to humans, animals, private and public lands, and native habitats).

The goal of the state weed law is to prevent the spread of new and recently introduced weeds while it is still feasible to do so. Class A weeds are the most limited in distribution and therefore the highest priority for control. Class B and C weeds vary in priority based on local distribution and impacts. Not all weeds are classified as noxious weeds in Washington State and only species that are not native to the state are considered for noxious weed listing. Between November and April, any person may request a change to the Washington State Noxious Weed List for the following year. For more information on the state’s weed listing process and how you can participate, please contact the Washington State Noxious Weed Board.

Noxious weeds are designated for control in all or parts of the state based on where it is still feasible to eradicate or contain the weeds. Property owners, both public and private, are required to control Class A weeds and any Class B or C weeds that are designated by the state or selected by the county weed board for control in their area. “Control” as defined in WAC 16-750 means to prevent the dispersal of all propagating parts capable of forming a new plant. Class A weeds need to be eradicated or removed entirely and Class B and C weeds designated or selected for an area need to be controlled to prevent their spread. For more information, see Washington’s Noxious Weed Laws.

For purposes of designating required control areas for Class B weeds, Washington is divided into six regions. King County is in Region 2.

The state noxious weed law also restricts the sale and transport of certain noxious weeds under its quarantine section. For more information on these quarantines, contact the WSDA Nursery Inspection Program or review the Quarantine List for the state of Washington.

(pictured Tegu Lizard Left, Azalea Right)

You may have heard the terms introduced and invasive species used in similar circumstance and may not necessarily know the difference between the two. This is understandable because the line is a little blurry between the two with the only real difference the end result of whether the species is impacting the environment in a negative or positive way.

An introduced species is a non native species that has one way or another been integrated into the native environment by human or other means. The key difference with introduced species are that they integrate into the native environment without negative effects to the surrounding ecosystem. Some examples of introduced species would be Bok Tower Garden’s Azaleas and Camellias that we have on the grounds. These have been adopted and are considered non threatening and have been a welcoming feature to many American gardens.

An invasive species on the other hand is an introduced organism that has become detrimental to the local environment. This is due to the fact that the species is either taking up resources used by native species, causing harm to local communities and people or directly attacking native species. These exotic species have been brought to Florida though the same means as the introduced species, however, they key difference is the impact they have. A common example an invasive species is the Tegu Lizard. The Tegu lizard is an invasive lizard from South America which was very popular as a pet, however are highly aggressive and most pet owners released them into the wild. Now thriving in many parts of Florida they are attacking native species and thriving in doing so.

At the end of the day the preservation of our native species in Florida should always be the primary concern of anyone buying or selling exotic species of plants or animals. It is apparent that even the smallest of changes such as buying a pet can have major implications in the local environment. Always be smart about pets!

Click here to view the FWC’s complete list of non native species in Florida:

FWC Non-Natives List

An invasive species is an organism that is not indigenous, or native, to a particular area. Invasive species can cause great economic and environmental harm to the new area.
Not all non-native species are invasive. For example, most of the food crops grown in the United States, including popular varieties of wheat, tomatoes, and rice, are not native to the region.
To be invasive, a species must adapt to the new area easily. It must reproduce quickly. It must harm property, the economy, or the native plants and animals of the region.
Many invasive species are introduced into a new region accidentally. Zebra mussels are native to the Black Sea and the Caspian Sea in Central Asia. Zebra mussels arrived in the Great Lakes of North America accidentally, stuck to large ships that traveled between the two regions. There are now so many zebra mussels in the Great Lakes that they have threatened native species.
Introduced Species
Some species are brought to a new area on purpose. Often, these species are introduced as a form of pest control. Other times, introduced species are brought in as pets or decorative displays. People and businesses that import these species do not anticipate the consequences. Even scientists are not always sure how a species will adapt to a new environment.
Introduced species multiply too quickly and become invasive. For example, in 1949, five cats were brought to Marion Island, a part of South Africa in the southern Indian Ocean. The cats were introduced as pest control for mice. By 1977, about 3,400 cats were living on the island, endangering the local bird population.
Other invasive species descended from pets that escaped or were released into the wild. Many people have released pet Burmese pythons into the Everglades, a swampy area of south Florida. The huge snakes can grow to 6 meters (20 feet) long. Pythons, native to the jungles of southeast Asia, have few natural predators in the Everglades. They feast on many local species, including white ibis and limpkin, two types of wading birds.
Invasive Species and the Local Environment
Many invasive species thrive because they outcompete native species for food. Bighead and silver carp are two large species of fish that escaped from fish farms in the 1990s and are now common in the Missouri River of North America. These fish feed on plankton, tiny organisms floating in the water. Many native fish species, such as paddlefish, also feed on plankton. The feeding cycle of the paddlefish is slower than that of the carp. There are now so many carp in the lower Missouri River that paddlefish do not have enough food.
Invasive species sometimes thrive because there are no predators that hunt them in the new location. Brown tree snakes were accidentally brought to Guam, an island in the South Pacific, in the late 1940s or early 1950s. No animals on Guam hunted the snakes, but the island was filled with birds, rodents, and other small animals that the snakes hunt. The snakes quickly multiplied, and they are responsible for the extinction of nine of the island’s 11 forest-dwelling bird species.
Many invasive species destroy habitat, the places where other plants and animals naturally live. Nutria are large rodents native to South America. Ranchers brought them to North America in the 1900s, hoping to raise them for their fur. Some nutria were released into the wild when the ranchers failed. Today, they are a major pest in the Gulf Coast and Chesapeake Bay regions of the United States. Nutria eat tall grasses and rushes. These plants are vital to the regions’ marshy wetlands. They provide food, nesting sites, and shelter for many organisms. They also help secure sediment and soil, preventing the erosion of land. Nutria destroy the area’s food web and habitat by consuming the wetland grasses.

Some invasive species do great harm to the economy. Water hyacinth is a plant native to South America that has become an invasive species in many parts of the world. People often introduce the plant, which grows in the water, because of its pretty flowers. But the plant spreads quickly, often choking out native wildlife. In Lake Victoria, Uganda, water hyacinth grew so thickly that boats could not get through it. Some ports were closed. Water hyacinth prevented sunlight from reaching underwater. Plants and algae could not grow, preventing fish from feeding and reproducing. Lake Victoria’s fishing industry declined.
Invasive species can also damage property. Small zebra mussels clog the cooling systems in boat engines, while larger ones have damaged water pipes at power plants throughout the Great Lakes region.
Eradicating Invasive Species
Officials have used a variety of methods to try to eradicate, or get rid of, invasive species. The cats on Marion Island were infected with a virus, for instance.
Sometimes other species are introduced to help control an invasive species. In Australia, prickly pear cactus, which is native to the Americas, was growing out of control. The cactus was destroying rangeland, where ranchers raised livestock. The government brought in cactus moth caterpillars to eat the cactuses. The caterpillars are natural predators of the cactus.
Introducing insects can be dangerous, however. Sometimes, the insects also damage other plant species—they can become invasive species themselves. Chemicals have also been used to control invasive species, but they can sometimes harm noninvasive plants and animals.
Governments are working to educate the public about invasive species. For example, in the United States, international fishing vessels are warned to wash their boats before returning home. This prevents them from accidentally transporting zebra mussels or other species from one body of water to another.
Sometimes, communities approach invasive species like an invading army. Nutria in Chesapeake Bay destroy the natural habitat, as well as cost local governments and businesses millions of dollars each year. Environmental groups, business leaders, and government officials are concerned about the harm done by this invasive species.
Officials at the Blackwater National Wildlife Refuge, in the U.S. state of Maryland, worked with hunters to eradicate the 8,500 nutria in the refuge. Hunters waded into specific areas of the marsh during specific times of the year. They tracked nutria using global positioning system (GPS) equipment and set traps that would kill the rodents. The hunters moved across the refuge in a massive, coordinated, west-to-east movement. In winter, the ice on Chesapeake Bay prevented the nutria from swimming away. Hunters could shoot them on sight.
The operation took two years, but nutria were eradicated from Blackwater National Wildlife Refuge. The wetland is slowly recovering.

What Is The Difference Between Introduced, Invasive, Noxious And Nuisance Plants?

If you’re an environmentally conscious gardener, you’ve no doubt come across confusing terms such as “invasive species,” “introduced species,” “exotic plants,” and “noxious weeds,” among others. Learning the meanings of these unfamiliar concepts will guide you in your planning and planting, and help you create an environment that is not only beautiful, but beneficial for the environment inside and outside your garden.

So what is the difference between introduced, invasive, noxious and nuisance plants? Keep reading to learn more.

What Does Invasive Species Mean?

So what does “invasive species” mean, and why are invasive plants bad? The United States Department of Agriculture (USDA) defines invasive species as “a species that is non-native or alien to the ecosystem – the introduction of the species causes or is likely to cause harm to human health, or to the economy or environment.” The term “invasive species” refers not only to plants, but to living beings such as animals, birds, insects, fungus or bacteria.

Invasive species are bad because they displace native species and alter entire ecosystems. The damage created by invasive species is mounting, and attempts of control have cost many millions of dollars. Kudzu, an invasive plant that has taken over the American South, is

a good example. Similarly, English ivy is an attractive, but invasive, plant that causes incredible environmental damage in the Pacific Northwest.

What are Introduced Species?

The term “introduced species” is similar to “invasive species,” although not all introduced species become invasive or harmful – some may even be beneficial. Confusing enough? The difference, however, is that introduced species occur as a result of human activity, which may be accidental or on purpose.

There are many ways species are introduced into the environment, but one of the most common is by ship. For example, insects or small animals are tucked into shipping pallets, rodents stow away in ship’s cellars and various forms of aquatic life are picked up in ballast water, which is then dumped in a new environment. Even cruise passengers or other unsuspecting world travelers can transport small organisms on their clothing or shoes.

Many species were innocently introduced to America by settlers who brought favorite plants from their homeland. Some species were introduced for monetary purposes, such as the nutria – a South American species valued for its fur, or various types of fish introduced into fisheries.

Exotic vs. Invasive Species

So now that you have a basic understanding of invasive and introduced species, the next thing to consider is exotic vs. invasive species. What is an exotic species, and what’s the difference?

“Exotic” is a tricky term because it is often used interchangeably with “invasive.” The USDA defines an exotic plant as “not native to the continent on which is now found.” For example, plants that are native to Europe are exotic in North America, and plants native to North America are exotic in Japan. Exotic plants may or may not be invasive, although some may become invasive in the future.

Of course, chickens, tomatoes, honeybees and wheat are all introduced, exotic species, but it’s difficult to imagine any of them as “invasive,” although they are technically “exotic”!

Nuisance Plant Info

The USDA defines noxious weed plants as “those that can directly or indirectly cause problems for agriculture, natural resources, wildlife, recreation, navigation, public health or the environment.”

Also known as nuisance plants, noxious weeds can be invasive or introduced, but they can also be native or non-invasive. Basically, noxious weeds are simply pesky plants that grow where they aren’t wanted.

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