DISCOVER INVASIVE SPECIES
Welcome to Discover Invasive Species, a blog dedicated to inform and spread awareness on the devastating impacts invasive species are having on our ecosystems and way of life. To understand their we have to know what invasive species are:
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What You Need to Know
An invasive species can be any kind of living organism—an amphibian, 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.”
WORST INVASIVE SPECIES
10) Kudzu
Also known as the "mile-a-minute vine" and "the vine that ate the South," the Kudzu vine is native to Japan, but was first brought to the United States in 1876 when it was featured at the Philadelphia Centennial Exposition as a hardy, fast-growing vine that could help inhibit soil erosion. What they failed to mention at the Exposition was just how fast they meant when they said Kudzu was "fast growing." Since its introduction, Kudzu has been spreading across the U.S. at a rate as fast as 150,000 acres annually, due primarily to the fact that its individual vines can grow upwards of a foot per day in the right conditions.
9) The Black Rat
The black rat is most likely one of the first invasive species to ever be inadvertently distributed by humans. The species originated in tropical Asia, but is believed to have reached Europe by the first century A.D. before spreading across the world, hitching rides en masse on European ships. Since then, the black rat has thrived in just about every region of the world, and has adapted exceptionally well to rural, urban, and suburban environments alike. Unfortunately, its success as a species, in combination with the success of numerous other species of rats, is believed to have come at the expense of dramatic population declines and even extinction of countless bird, reptile, and other small vertebrate species the world over.
8) The Asian Tiger Mosquito
This Asian tiger mosquito is characterized by its distinctive black and white stripe pattern, and while it's native to tropical and subtropical areas of Southeast Asia, scientists believe it has quickly become one of the planet's most widely-distributed animal species, spreading to at least 28 countries outside its native range in the last two decades alone. The tiger mosquito is believed to be spread through — of all things — the international tire trade, as tires stored outside tend to retain rainwater, and provide the ideal breeding and living conditions for the mosquito. It poses a distinct threat to populations worldwide, not only because it carries viruses like Dengue and West Nile, but because it tends to associate closely with humans, and is known to feed 24 hours a day (many species of mosquito only feed at dusk and dawn).
7) The Cotton Whitefly
The cotton whitefly is living proof that some of the most hard-hitting invasive species come in tiny packages. Adult whiteflies measure just a millimeter long by the time they reach adulthood, but are known to feast (in staggering numbers) on 900 different kinds of plants worldwide, and are capable of transmitting upwards of 100 different plant viruses. While whiteflies are believed to have originated in India, you'll find them thriving on every single continent but Antarctica.
6) The Snakehead Fish
The snakehead is an absolutely nightmarish animal. In fact, National Geographic went so far as to nickname the Northern Snakehead "Fishzilla,"and with good reason. Snakehead fish are a veritable force of nature — they have sharp, shark-like teeth; an appetite for for blood; can grow to over three feet in length; can lay up to 75,000 eggs a year; and can even breathe and migrate on land, searching for other bodies of water for up to four days at a time through the use of a primitive breathing organ.
While they were originally native to East Asian waters, various species of snakehead have decimated native food chains in the US ranging from Maine to California.
5) The Asian Longhorned Beetle
The Asian longhorned beetle actually spends the most destructive period of its life in a larval stage, during which time it tunnels and feeds on the layer of trees found between their bark and their wood. In large enough numbers, these larvae can eventually kill the tree. To prevent new infestations, officials often must resort to cutting down and burning infested trees.
Originally native to countries in Asia like Japan, infestations of Asian longhorned beetles were first detected in New York around 1996, but quickly spread to the majority of the East coast, where they are estimated to threaten 30-35% of trees on the Atlantic coast's urban areas. They're also found in California, Ontario, and parts of Europe. The economic toll of the Asian longhorned beetle is estimated to number in the tens to hundreds of billions of dollars.
4) The Burmese Python
The Burmese Python provides the perfect example of what can happen when a large, predatory species is introduced into an environment where the native wildlife offers little-to-no competition for resources. The huge snakes — which can grow to upwards of 20 feet in length — are native to the tropic and subtropic areas of Southern Asia, where they are just as at home hanging out in and around water as they are slithering around in the treetops. Their accidental introduction to the wild in Florida, however, has shown that the species also does particularly well in the semi-aquatic environment of Everglades National Park, where an estimated 30,000 Burmese Pythons have made a habit of feasting on a variety of endangered birds and alligators (yes, alligators).
3) The Cane Toad
Sometimes invasive species are introduced into regions as a form of biological pest control. Sometimes these non-native species actually do a pretty good job of handling the initial pest problem. And sometimes they do such a good job that they become an enormous pest problem themselves. The cane toad is often cited as the perfect example of an introduced species gone horribly wrong. The cane toad is native to South and Central America, but when its introduction to regions of Hawaii, the Caribbean, and the Philippines to fight pests in sugarcane fields yielded impressive results, it was quickly imported to various other regions worldwide.
Unfortunately, cane toads have a nasty habit of not just eating crop pests and insects, but also just about any terrestrial animal that they can fit their grotesquely huge mouths around — which is saying something, given that they can grow to over 30 cm in length. They also secrete toxins capable of killing just about any animal they come in contact with (humans have died after ingesting their eggs), meaning that they tend to be seriously lacking in the natural predator department.
2) The European/Common Rabbit
The common rabbit is native to southern Europe and north Africa, but the tendency for rabbits to... overproduce... has led to their introduction and unchecked expansion on just about every continent but Antarctica and Asia. The most famous case of population explosion probably occurred in Australia, where, in 1859, an English farmer by the name of Thomas Austin introduced just 24 grey rabbits to his plot of land to remind him of home; Austin surmised that "the introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting."
1) The Nile Perch
The Nile Perch is native to a number of freshwater African lake and river systems. When it was introduced to Lake Victoria in the 1950's however, the lake's ecosystem was not prepared for it. While populations of the fish were kept in check through commercial fishing for several decades, the population exploded in the late 1980's, leading to the extinction or near extinction of several hundred native species. The devastating impact of the gigantic fish — which can grow up to 2 meters in length and weigh in at over 200 kg — is believed to be the result of its voracious appetite for key ecosystem-supporting members like fish, crustaceans, insects, and zooplankton.
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IMPACTS OF INVASIVE SPECIES
Invasive species can have a number of negative impacts on the areas that they invade. Perhaps the most significant of these is the widespread loss of habitat. The hemlock woolly adelgid is an invasive insect from Asia that rapidly kills infested hemlock trees. In some parts of the Eastern United States, it is estimated that up to 80% of hemlock trees have been killed. These forests represent important habitat for many animals and with crucial habitat gone, species that rely on them may face extinction. Similarly, the health of many forests is threatened by kudzu vines, introduced from Japan in the 19th century as an ornamental plant. This plant was widely distributed across the Southeastern United States as a means of erosion control and as a food source for grazing animals. The vine soon became invasive, however, and can completely overgrow entire forests. In the process, it prevents sunlight from reaching the trees, effectively killing the forest. Additionally, the weight of the thick mats of vines on trees can cause trees to break and fall over. Its ability to quickly overgrow and destroy forests has earned it the nickname “the vine that ate the South.”
Some invaders can physically alter the habitat in addition to destruction. 50 beavers from Canada were relocated to Tierra del Fuego, an archipelago at the southern tip of South America, in 1946 to be hunted for their pelts. Since then, they have multiplied and now number in the hundreds of thousands. The trees in the region are not adapted to beaver activity as they are in North America, and most do not grow back after being gnawed by beavers. Portions of the formerly pristine forests now look like a bulldozer has plowed through them. Additionally, beaver activity creates ponds that flood portions of the forest. These bodies of stagnant water alter the nutrient cycle in forests and invasive plants thrive in them. Beavers also build dams in drainage ditches of grasslands and livestock commonly fall into them, where they become stuck and die.
Other invasive species may not destroy habitat but can have an impact by killing large numbers of endemic species. Burmese pythons, for example, are top predators in the Everglades. As such, they have decimated local mammal and bird populations. Capable of consuming deer and even alligators, these creatures eat virtually any animal they encounter in the Everglades. A number of threatened and endangered bird species have also been found in the digestive tracts of pythons, prompting concern that they could drive some species toward extinction. Lampreys in the Great Lake parasitize native fish. Because the native species have not evolved defenses to lampreys, they often die outright from wounds, or wounds become infected and eventually cause mortality. Invasives can also threaten native species by outcompeting them for resources. Asian carp introduced into the United States outcompete native fish for both food and space, leading to large declines in native fish populations. Invasive species are the second largest cause of species extinctions in the United States.
Invasive species can also impact human health. Invasive zebra mussels accumulate toxins in their tissues like PCB's and PAH's. When other organisms prey on these mussels, the toxins are passed up the food chain and can also enter animals consumed by humans. Ballast water from ships also sometimes contains harmful bacteria like cholera. Invasive animals can also be vectors for disease.
In addition to these impacts, invasive species can also have enormous economic costs. Zebra mussels in the Great Lakes can rapidly cover submerged surfaces, clogging up water intakes at water treatment facilities and power plants. Removing this invasive species costs an estimated $500 million annually in the Great Lakes alone. Power companies spend an estimated $1.5 million each year to control kudzu vines growing on power lines. Lampreys in the Great Lakes have decimated many fishery stocks to the point that they are no longer profitable. In the United States, invasive species cost an estimated $120 billion annually in control methods and in loss of environmental resources.
WHAT CAN BE DONE?
https://www.environmentalscience.org/invasive-species
Many strategies have been developed to stop the damage caused by invasive species and to prevention future invasions. An important component is educating people about the dangers of transporting wildlife to new areas. Many laws and regulations have also been passed to combat the future spread of invasives. Ballast water in tankers is required to be decontaminated before it can be released from the boat.10 Laws have also been passed to restrict the exotic pet trade, such as banning the import of Burmese pythons in the United States.25
Promoting the harvest of invasive species is another widely used technique, although it has been employed with limited success. A python hunt in Florida in 2013 provided cash awards to people for killing pythons.9 In Argentina, officials have tried to promote a market for beaver pelts and hunters were encouraged to hunt them.17 People have also used the woody vines of kudzu to craft baskets and other items. A problem encountered with this strategy is that often the demand is not nearly high enough to make a discernible impact on invasive populations. In the case of pythons, they are extremely secretive and elusive, which makes them difficult to find them for eradication.
As with many environmental problems, continued research will yield insight into effective control measures. For example, research studies have been conducted to determine how effective traps are in catching pythons.26 Genetic studies can also yield important information about how invasives have spread in an area and their potential to hybridize with native species.27 Predicting how the geographic range of an invasive species will increase is important for preparing new areas that may be invaded. Much research has also been devoted to determining the most effective ways of removing invasive plants, whether through herbicides or through mechanical destruction of the plants. Using chemicals to kill sea lampreys in the Great Lakes during their vulnerable larval stages has been shown to effectively kill them without harming other wildlife.20 While many invasive species may not ever by fully eradicated, increased awareness and research offer methods of preventing their spread and controlling the economic and environmental damage they can incur.