9.8 Invasive Species

Species Introduction 

An invasive species is a non-native species that has been introduced to a new area and has the ability to establish a population and spread, often causing harm to the native biodiversity, economy, or human health. Invasive species can be plants, animals, fungi, or microorganisms. 

Human activities such as transportation, trade, and the introduction of exotic species have led to the spread of invasive species around the world. When introduced to a new environment, invasive species can have severe impacts on native plants and animals, and can also cause changes to the ecosystem, such as changes in nutrient cycling, water flow, and fire regimes.

Invasive species can also have negative impacts on human activities, such as agriculture, forestry, and recreation, and can also increase the risk of new diseases. For example, the fungus that causes chestnut blight and the fungus that causes Dutch elm disease were both accidentally introduced from Europe and have caused widespread mortality of American chestnut and American elm, respectively. Invasive species can also have economic impacts, for example, zebra mussels, a species of freshwater mollusk native to Eurasia, were accidentally introduced to the Great Lakes in the 1980s and have caused millions of dollars in damage to water intake systems and other infrastructure.

To prevent these impacts, it is important to prevent the introduction and spread of invasive species. This can be done through measures such as quarantine and inspection of imported goods, controlling the spread of invasive species, and through public education and campaigns to raise awareness of the issue.

Strategies for Control

There are several strategies that can be used to control invasive species populations, including:

1. Physical removal: This involves manually removing individuals or entire populations of invasive species. Methods include hand-pulling, cutting, digging, and trapping.
2. Chemical control: This involves using pesticides or other chemicals to kill or inhibit the growth of invasive species.
3. Biological control: This involves introducing natural predators, pathogens, or competitors of the invasive species to reduce its population.
4. Habitat modification: This involves altering the environment to make it less suitable for the invasive species and more suitable for native species.
5. Monitoring and early detection: This involves regularly monitoring for new invasive species and taking action as soon as they are detected.
6. Public education and outreach: This involves educating the public about the negative impacts of invasive species and encouraging them to take action to prevent the spread of these species.

Prevention is considered the most effective and cost-efficient strategy for controlling invasive species. This includes measures such as strict quarantine regulations, inspections of cargo and vehicles, and regulations on the import and trade of live organisms.

In cases where invasive species have already been introduced, early detection and rapid response (EDRR) is an important strategy. EDRR involves monitoring for new invasive species, identifying their early signs and symptoms, and taking action to prevent or minimize their spread. This can include physical removal, chemical control, or biological control methods.

Physical removal methods can include hand-pulling, cutting, digging, or trapping. Chemical control can include the use of pesticides, herbicides, or other chemicals to kill or inhibit the growth of invasive species. Biological control can include the introduction of natural predators, pathogens, or competitors of the invasive species to reduce its population.

It's important to note that control methods should be chosen based on the specific characteristics of the invasive species, the ecosystem it is in, and the goals of the management plan. An integrated approach, using a combination of different control methods, is often the most effective way to control invasive species populations.

Zebra Mussels

Image Courtesy of Wikimedia

Zebra mussels (Dreissena polymorpha) are small freshwater mussels that are native to the Black and Caspian Sea regions of Europe. They were first discovered in North America in 1988 in the Great Lakes and have since spread to rivers and lakes in over 20 states. They are considered an invasive species because they reproduce quickly and can outcompete native species for food and habitat.

Zebra mussels are known to clog water intake pipes, damage boat motors, and alter the food web by outcompeting native species for plankton. They also have a negative impact on native mussel populations by attaching themselves to native mussels and suffocating them.

Control methods for zebra mussels include physical removal, chemical control, and biological control. Physical removal can include manually removing individuals or entire populations of zebra mussels from boats, water intake pipes, and other structures. Chemical control can include the use of pesticides, herbicides, or other chemicals to kill zebra mussels. Biological control methods include the introduction of natural predators such as native fish species that feed on zebra mussels.

Preventative measures are also implemented to stop the spread of zebra mussels, such as inspecting boats and other watercraft before they enter a new body of water to make sure they are free of the invasive mussels and implementing decontamination procedures for boats and other equipment that have been in infested waters.

Cane Toads

Image courtesy of Wikimedia

Cane toads (Rhinella marina) are native to Central and South America, specifically in countries such as Mexico, Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Panama, Colombia, Ecuador, Peru, Bolivia, Brazil, French Guiana, Guyana, Suriname, and Venezuela. They were introduced to other countries, including Australia, as a biological control method for sugarcane pests, but have since become an invasive species.

Since they were introduced in 1935, they have outcompeted native species for food and habitat, and have also been known to prey on native animals such as small mammals, reptiles, and frogs. They also have a detrimental effect on native predators, such as snakes and marsupials, as many are not adapted to hunting the toxic toads.

Furthermore, their presence also causes changes in the ecosystem such as altering the behavior of native animals and insects, and also changing the structure of the ecosystem. They also have economic impacts, as they damage crops, gardens, and lawns, which causes financial losses for farmers and homeowners.

Efforts are being made to control the population of cane toads through methods such as fencing, trapping, and biological control. Some researchers are also exploring genetic control methods to stop the spread of the toads.

Other Examples

Here are a few more examples of invasive species:

European starling

The European starling, also known as the common starling, is a species of bird that is considered to be invasive in many parts of the world, including North America. This is because it was introduced to the United States in the late 19th century by a man named Eugene Schieffelin, who wanted to introduce all the birds mentioned in Shakespeare's plays to the country. The starlings quickly spread and now have a population of around 200 million birds in the US, out-competing native species for food and nesting sites. They are also considered a problem in other parts of the world, such as Australia and New Zealand, where they were introduced for similar reasons.

Argentine ant

The Argentine ant (Linepithema humile) is an invasive species that is native to Argentina, Uruguay, and southern Brazil. It was first accidentally introduced to the United States in the late 19th century and has since spread to many parts of the world, including Europe, Asia, and Australia.

This ant is considered an invasive species because it forms large, dense colonies that can outcompete native ant species for food and nesting sites. It also has a tendency to displace native species and disrupt natural ecosystems. In addition, they can be a problem in human environments, such as homes and gardens, where they can be difficult to control.

Argentine ants have also been known to invade beehives and steal honey, and also feed on the eggs and young of native birds, lizards, and other small animals. Control measures include baiting, using pesticides, and physical removal.

Giant hogweed

Giant hogweed (Heracleum mantegazzianum) is considered an invasive species in many parts of the world, including North America and Europe. It was originally brought to these regions as an ornamental plant but has since spread rapidly and has established itself in many natural habitats such as riverbanks, forests, and roadsides. Its rapid growth and large size allow it to outcompete native plants for resources, leading to the displacement of native plant species and the alteration of natural ecosystems.

Cane beetle

Cane Beetle, also known as the sugarcane beetle or the sugarcane grub, is a species of scarab beetle that is native to tropical regions of Africa and Asia. It is considered an invasive species in many parts of the world, particularly in sugarcane-growing regions.

Asian carp 

Asian carp is a term used for several species of fish native to Asia that have been introduced to North America, including the bighead carp, silver carp, and grass carp. These species are considered invasive because they reproduce rapidly, consume large amounts of plankton, and compete with native fish for food and habitat.

Burmese python 

The Burmese python is a large non-venomous snake native to Southeast Asia, which has become an invasive species in the Florida Everglades in the United States. It was most likely introduced to the Everglades as a result of pet owners releasing their snakes into the wild.

Kudzu

Kudzu is a perennial vine native to Japan, China, and southeast Asia. It was introduced to the United States in 1876 as an ornamental plant and for soil erosion control, but has since spread rapidly and is considered an invasive species.

Japanese knotweed

Japanese knotweed is a perennial plant native to East Asia. It was brought to Europe and North America as an ornamental plant in the 19th century and has since spread rapidly, becoming an invasive species in many parts of the world. It is considered invasive because it can outcompete native plants for resources and can cause structural damage to buildings, roads, and other infrastructure.

Impact of All Examples

All these invasive species can have a significant impact on native ecosystems and economies. Control measures include physical removal, herbicides, biological control, and public awareness campaigns.

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