A Story by Melissa Farlow

Attack of the Alien Invaders, National Geographic Magazine

In our increasingly connected world, global trade and travel are accelerating the movement of organisms to places that they couldn’t have reached without our help. It is a thoughtless rearrangement of misplaced creatures, or as one biologist put it, “evolution on steroids.”

Biological invasions rank second to habitat loss as a threat to native biodiversity. Most people are unaware of the enormous problem, partly because the invaders are so common, and partly because few understand that our pests, weeds, and diseases are related.

The extinction rate is accelerating rapidly. Over the next 100 years, it is estimated that roughly half of the species on Earth will completely or functionally disappear. Forty percent of those extinctions are caused by invasions. And we are …

Attack of the Alien Invaders, National Geographic Magazine

By Melissa Farlow

In our increasingly connected world, global trade and travel are accelerating the movement of organisms to places that they couldn’t have reached without our help. It is a thoughtless rearrangement of misplaced creatures, or as one biologist put it, “evolution on steroids.”

Biological invasions rank second to habitat loss as a threat to native biodiversity. Most people are unaware of the enormous problem, partly because the invaders are so common, and partly because few understand that our pests, weeds, and diseases are related.

The extinction rate is accelerating rapidly. Over the next 100 years, it is estimated that roughly half of the species on Earth will completely or functionally disappear. Forty percent of those extinctions are caused by invasions. And we are making the planet increasingly hospitable for the weedy species—things that thrive in disturbed, human-dominated environments.

One example in the plant world is Kudzu, which drapes over tree canopies in the South. First introduced from Asia in the 1800s as a crop, it was heavily planted in the ‘50s along roadsides for erosion control. Anything that doesn’t move may be covered since it grows a foot a day.

Other invasives are so commonplace that they are not recognized as a problem species—like a litter of unwanted kittens. The kind-hearted may volunteer to feed homeless cats that roam a neighborhood, but there are an estimated 60 million feral cats in the U.S., and they are responsible for the deaths of over a billion small mammals and hundreds of millions of songbirds.

There are 10,000 feral cats in the Florida Keys alone. Once a month volunteers in Islamorada trap feral cats, and a vet comes to spay and neuter them to try to reduce the forever-growing cat population.

Some very unlikely exotic species have become invasives, and the pet industry is largely responsible. There are few controls on imports — 22 of 24 species of pythons are available at pet stores, along with boas, crocodiles, iguanas, and bird-eating spiders.

And although many appropriate pets are available that capture the attention and curiosity of a young child, there are no warning labels on reptiles and other species that can quickly grow into unmanageable or dangerous animals.

A young, one-foot-long Burmese python will grow to six feet in length the first year and ten the following year. It can grow to a total of 20 feet and 200 pounds and can live more than 25 years. It’s no wonder they are dropped off in the wilds of Florida swamps.

An eight-foot-long Burmese python is one of the smaller snakes caught along the main road into Everglades National Park. Wildlife biologists there say a breeding population from released snake that is established, and they fear their numbers will explode.

An island Ecosystem such as Hawaii is especially fragile and over the years is highly impacted by invasive plants and animals. A family that farmed taro for seven generations now watches as the golden apple snail decimates their crop.

The story of the apple snail’s origin seems as innocent as that of many introduced species. To supplement a family’s meager farming income, the apple snail was introduced, hoping it could be cultivated as escargot.

Not only was it a bust as a cash crop, it became an invasive species by growing in numbers beyond control and ruining taro and rice crops.

The newest arrival to Hawaii is the Coqui, a frog that has moved from island to island with its chirpy little call that has the decibel level of a lawn mower. War is waged on this frog because its numbers are exploding and it has no predators. Lawsuits now force homeowners to disclose the fact that they have these frogs because Hawaiians are so upset by the noise. It was first imported on plant material and even carefully quarantining goods have only slowed its spread.

Another invasive in Hawaii is the Axis deer, originally a royal gift to the islands in 1868 from Hong Kong. Five were brought to Maui in 1959 for hunting and now there are 10,000 deer eating their way through Hawaii’s native plants. Opinions are sharply divided on managing axis deer.

A fence was built around endangered plants on Haleakala National Park to protect them from the deer, and the deer are hunted, in an effort to eradicate them within the fenced area.

But people also come to Hawaii to hunt Axis deer. It is a good source of income for people on the island of Lanai who are guides for those who enjoy the sport of hunting the small, elusive deer that never loses its spots.

Besides the disturbing environmental imbalance that invasive species bring, there is a huge economic cost. Biological invasions in the U.S. alone cost $137 billion annually, which translates to about $2,500 a year for every American family.

The crackdown on invasive species is not a war to win. Invasions are chronic, and require expensive, unglamorous, sustained solutions.

Read The Full Story
A Nile Monitor lizard awaits its fate after capture. Nile Monitors were originally brought to this country from their native habitats in southern and central Africa as part of the exotic pet trade. They have long been available in Florida pet stores, thanks to liberal State laws concerning the importation of exotic species. Their introduction into the wild is most likely due to escapes or intentional releases by owners who could no longer handle them. Known for their sharp teeth and bad tempers, Nile Monitors may grow to over seven feet long and are excellent swimmers. In the early 1990s, reports started surfacing concerning the sightings of gigantic, monster-sized lizards in the Cape Coral area, a burgeoning development community of 400 square miles of waterways, home sites, and undeveloped land. Monitors eat birds, turtles, and reptiles but analysis of the stomach contents of trapped lizards showed that they also feed on dogs and cats. New regulations were passed in Florida in June 2010 that ban some species from ownership including the Nile monitor lizard as well as the Burmese/Indian python, reticulated python, green anaconda, and African rock python.  
Coral Gables residents gaze in wonder at a four-and-a-half-foot Nile monitor lizard captured near their home in Florida. Imported from Africa as pets, the reptile can grow to more than seven feet long, way too big and feisty for the average owner to handle. “They are horrible pets,” says Todd Campbell, the University of Tampa ecology professor who trapped this lizard. “They have a high propensity toward being aggressive and untameable.” They have razor-sharp claws and teeth, and a nasty temperment. As a result, many are “released into the wild” and end up in the canals behind suburban homes where they breed and prey on native birds, small terrestrial manmmals, and other reptiles. Approximately 100 lizards were trapped and the contents of their stomachs were analyzed, revealing that they also feed on dogs and cats. New regulations were passed in Florida in June 2010 that ban some species from ownership including the Burmese/Indian python, reticulated python, green anaconda, Nile monitor lizard, and African rock python.
A woman at the National Reptile Expo in Dayton Beach, Florida, holds an endangered Chinese crocodile that is protected by Chinese and International law. Related to the American alligator, the Chinese reptile is smaller, usually only attaining a length of five feet. While it originally ranged through much of China, this species’ wild habitat has been reduced to little more than a few ponds containing a small number of animals (fewer than 200 individuals, only approximately 50 of which are mature) along the lower Yangtze River. Its population reduction has been mostly due to conversion of its habitat to agricultural use. The building of dams in the wetlands is also destroying its home.
A woman holds two Ciman rhinocerous iguanas outside the Save the Carribean Iguana booth at the National Reptile Expo in Dayton Beach, Florida. Reptile shows are held by the pet industry to sell to collectors and to inform the public about unusual animals. Cyclura cornuta is a threatened species of lizard found on the Caribbean island of Hispaniola, Haiti, and Dominican Republic. It grows up to 4 ½ feet long and is characterized by the growth of prominent, bony tubercles on the snouts, which resemble horns. The most common species of Cyclura kept in captivity, only 10,– to 15,000 survive in the wild. Captive breeding programs work to continue the species. Convention on International Trade in Endangered Species (CITES) considers the reptile a protected animal.
Containers separate snakes in a booth at National Reptile Expo in Daytona Beach, Florda, where they are displayed and sold to the public to buy as pets. A few of the exotic pets for purchase include species of pythons, boas and poisonous snakes, crocodiles, iguanas, and bird eating spiders. The U.S. dominates both import and export in the booming reptile trade with more than 2.5 million reptiles brought in annually. New regulations were passed in Florida in June 2010 that ban some species from ownership including the Burmese/Indian python, reticulated python, green anaconda, Nile monitor lizard, and African rock python. Problems have occurred when exotic pets become costly or too time consuming for owners. They are often “released into the wild,” resulting in 32 non-native species such as cane toads, feral colonies of green lizards, cobras and boa constrictors setting up housekeeping and making Florida their home.
Felines flock to a golf course feeding at Ocean Reef, a private community that provides veterinary care to help curb the number of feral cats in the Florida Keys. ORCAT is Ocean Reef’s Trap-Neurter-Release program that began in the 1980s when the area had a serious cat overpopulation problem and 2,000 cats lived on the island’s four square miles. Today it is recognized as a successful model with the number of feral cats down to around 350, 100 of which reside at the Grayvik Animal Care Center. Elsewhere, the feral cat has not been tamed and was named one of the 100 of the world’s worst invasive species.
After surgery, cats are lined up in beds until they wake up from anesthesia under the watchful eye of workers.  Homeless felines find compassion at Caring for Cats, an all volunteer, no-kill shelter and foster network for cats and kittens in Florida. Feral cats are trapped, spayed or neutered, vaccinated, tested for feline AIDS and leukemia. Their left ear is clipped to show they’ve been processed. They are adopted or released back into the wild and fed by volunteers. Feral cats can have a devastating effect on the songbird population. It is estimated that there are tens of millions of feral cats in the U.S. that have been abadoned or lost in the wild, which is why they top the world’s 100 worst invasive alien.
Volunteers open up the clinic to care for homeless felines at Caring for Cats, an all volunteer, no-kill shelter and foster network for cats and kittens in Islamorada, Florida. Domestic cats that are abandoned or lost adapt and live in the wild in the regions warm climate. Feral cats are trapped, spayed or neutered, vaccinated, tested for feline AIDS and leukemia, and their left ear is clipped to show they’ve been caught. Then they are released (or adopted if possible) and fed by volunteers. A veterinarian travels to eight clinics in South Florida and the Keys trying to help curb the escalating numbers of cats. He estimates there are 10,000 feral cats in the Keys. It is estimated that there are tens of millions of feral cats in the U.S. that have been abadoned or lost in the wild.
A woman puts out food for feral cats in her neighborhood. Soft-hearted volunteers care for homeless felines in the Florida Keys, where one veterinarian estimates their population at more than 10,000. It is estimated that there are tens of millions of feral cats in the U.S. making them one of the top 100 of the world’s most invasive aliens. The impact of domestic cats on wildlife is a centruy-old debate, but they are predators to a winnowing songbird population. The American Society for the Prevention of Cruelty to Animals endorses a Trap-Neuter-Return program to manage feral cat colonies.
Sheep chomp through a field of yellow-flowered leafy spurge in North Dakota, where ranchers attempt to control the plants’ spread by moving a flock into a field to mow it to the ground. Leafy spurge made the listing of the world’s top 100 worst invasive aliens as a noxious weed that infests more than five million acres in the U.S and Canada. It drastically reduces rangeland productivity, native plant diversity, wildlife habitat, and land values. Native to Europe and western Asia, leafy spurge (Euphorbia esula), was introduced into the western U.S as a seed contaminate in the late 1800s. The Eurasian weed contains latex, is poisonous to some animals, and causes burning sensations in the mouth for cattle and cows. Sheep, however, flock to eat leafy spurge like it’s a salad bar. It is a woody plant and it’s bright yellow flower brackets appear in the spring. Its roots can reach depths up to 15 feet with a lateral spread of up to 35 feet. Seed capsules open explosively, dispersing seeds up to 15 feet which can then live in the soil at least seven years. Even if the foliage is destroyed, the roots will regenerate new shoots. Herbicide and biological controls show some results at curbing the plant.
Neighbors clear weeds from the Guggenheim School Preserve in Port Wasington, New York, joining an effort to preserve wild and natural places to use them for environmental education. Non-native  plants are opportunistic when competing with native fauna and flora. Ecosystems go out of control when the balance is upset by plants with fast growth becoming established in disturbed areas. It takes continued restoration efforts to reverse the ecological impacts.
The Melaleuca tree is considered the most prominent of 60 non-native plant species invading south Florida. Each seedpod contains up to 200 seeds, which are released into the environment when the tree is subjected to stress factors such as fire, herbicides, or manual cutting. A mature tree can produce up to 20 million seeds per year, making this tree a land manager’s nightmare. The invasive Melaleuca tree (Melaleuca quinquenervia) took over 500,000 acres of wetlands before restoration efforts were initiated near Lake Okeechobee in Florida. Everglades National Park and the South Florida Water Management District have spent 25 million dollars  a ten-year effort to eradicate the plant. An exotic import from Australia, the tree was originally brought to Florida in the early 1900s as a landscaping ornamental and to help dry out wetlands. A mature Melaleuca forms a dense monoculture, choking out other plants in the Everglades. It uses up to seven times as much water as a native tree.
The community of Pahoa, south of Hilo in Hawaii, bought a 10,000 gallon sprayer to coat the jungle in their backyards with hydrated lime which they hope will curb the number of Coqui frogs. The Coqui—much revered in its native Puerto Rico—was first imported on plant material. It is the size of a quarter and has a chirpy call with a decibel level equal to a lawnmower. It is listed on the top 100 of the world’s worst invasive aliens. Eleutherdactylus coqui was able to quickly adapt to Hawaii from its native Puerto Rico and reach unprecedented numbers because of the absence of predators. Its noisy mating behavior has made the Coqui frog the target of government and community eradication and control efforts.
War is waged on the Coqui frog (Eleutherdactylus coqui) because its numbers are exploding and it has no predators. Much revered in its native Puerto Rico, the coqui was at first unnoticed when it was imported on plants. It was soon discovered because although it is the size of a quarter, it has a chirpy call with a decibel level equal to a lawnmower. It made the list of one of the world’s worst 100 invasive alien species. Lawsuits now force homeowners to disclose if they have the frogs because Hawaiians are so upset by the noise. The community of Pahoa, south of Hilo and near Lava Tree State Park, bought a 10,000-gallon sprayer and is coating the jungle and backyards with hydrated lime, which they hope will curb the number of Coqui. Dr. Arnold Hara, of the University of Hawaii, helped the community apply for funding. The Coqui frog was able to quickly adapt to Hawaii from its native Puerto Rico and reach unprecedented numbers because of the absence of predators. Its noisy mating behavior has made the Coqui frog the target of government and community eradication and control efforts.
The golden apple snail is devastating taro crops in Hawaii. A native of South America, the Channeled Apple Snail (Pomacea canaliculata) was introduced to Taiwan, the Philippines, and other countries in Southeast Asia in the late 1970s and early 1980s as a food item. The culinary demand for the species did not materialize and it was not long before the apple snail escaped captivity and spread, decimating rice fields of Southeast Asia, particularly the Philippines. The alien species was introduced in Hawaii in 1989 where it damages taro (elephant ear) and rice crops. It is listed on the world’s top 100 worst invasive aliens.
A family works in their taro patch on the island of Maui. Their crop is being devastated by the impact of the invasive apple snail eating the tender stems of the plant which is a staple among native Hawaiians. A native of South America, the Channeled Apple Snail (Pomacea canaliculata) was introduced to Taiwan, the Philippines, and other countries in Southeast Asia in the late 1970s and early 1980s as a food item. The culinary demand for the species did not materialize and it was not long before the apple snail escaped captivity and spread, decimating rice fields of Southeast Asia, particularly the Philippines. The species was introduced in Hawaii in 1989 where it damages taro (elephant ear) and rice crops. The apple snail is listed on the world’s top 100 worst invasive aliens.
Colorful aquatic worms swim across the computer screen as scientists and researchers study samples in a lab after collecting water in San Francisco Bay. According to Dr. Andrew Cohen, hundreds of nonnative species have had a profound impact on the ecology of the Bay making it the world’s most invasive species-impacted ecosystem. Ballast water dumped by ships moving from port to port spreads bacterial pathogens as evidenced by a cholera outbreak in Peru, which was the first outbreak of the disease in the Western Hemisphere in a century. One serious invading problem introduced into the Bay waters are Chinese Mitten Crabs, medium-sized burrowing crabs named for their dark furry claws. They cause severe damage to embankments, erosion and clogged drainage systems.
An oil tanker glides under San Francisco’s Golden Gate Bridge, one of the many ships arriving daily in this busy port. Large ships can carry 20 million gallons of ballast for stability in open waters. Traveling globally from port to port they fill and dump their water, spreading microscopic organisms as they go. Biologists have found hundreds of invasive species in San Francisco Bay, which Biologist Andrew Cohen of the Center for Research on Aquatic Bioinvasions, says makes it one of the most invaded estuaries in the world. The Bay averages one invasive species introduced every 24 weeks since 1970, says Cohen. Overall, 84 percent of the world’s coasts are being affected by foreign aquatic species, according to a Nature Conservancy report. California is cracking down on invasive species, and that could have a big impact on national regulations. The state has passed the strictest rules in the country to prevent cargo ships from bringing foreign plants and animals to San Francisco Bay. But the standards are so firm that California may not be able to enforce them.
Skilled hunters bagged several elusive Axis deer on opening day of hunting season on Lanai, the sixth largest of the Hawaiian Islands. Axis deer were a royal gift to the islands in 1868 from Hong Kong. Five were brought to Maui in 1959 for hunting and now there are 10,000 eating their way through Hawaii’s native plants. They can be found on several islands and are proliferating without the pressure of predators. Opinions are sharply divided on managing axis deer. A fence was built around endangered plants on Haleakala National Park to protect them from the deer, and the deer are hunted in an effort to eradicate them within the fenced area. And guiding hunters is a good source of income for locals.
A litter of feral kittens are dropped at the doorstep of a clinic run by Caring for Cats in Islamorada, Florida. The Keys have an enormous feral cat problem—an estimated 10,000 feral cats live on the chain of islands. Though cute when they are little, the kittens grow up learning to survive in the wild by hunting and are partly responsible for the decline in the songbird population. Caring for Cats is an all volunteer, no-kill shelter and foster network for cats and kittens in Florida. Feral cats are trapped, spayed or neutered, vaccinated, tested for feline AIDS and leukemia, and their left ear is clipped to show they’ve been caught. Then they are released (or adopted if possible) and fed by volunteers. Programs like this are controversial because they release feral cats back into the wild. Feral cats are listed on the world’s top 100 worst invasive aliens.
Cat under anesthesia A cat is given anesthesia before being neutered. Volunteers spend time caring for homeless kitties at Caring for Cats, a no-kill shelter and foster network for cats and kittens in Florida. Feral cats are trapped, spayed or neutered, vaccinated, tested for feline AIDS and leukemia, and their left ear is clipped to show they’ve been caught. Then they are released (or adopted if possible) and fed by volunteers. Veterinarian Elton J. Gissendanner travels to eight clinics in South Florida and the Keys trying to help curb the escalating numbers of cats. He estimates there are 10,000 feral cats in the Keys. Feral cats are listed on the world’s top 100 worst invasive aliens.
A Burmese Python slithers across a road before it is caught in Everglades National Park. One-time pets get too big and hungry for owners to handle and are “released into the wild.” Fanciful legends of exotic snakes in the Everglades jungle have persisted since the late 1800s. South Florida officials were surprised when a 16-and-a-half-foot python was killed and cut open and inside was an intact, 76-pound deer. In the 70s, a few Burmese python sightings were documented in the park. In the mid-90s, there were more reports. Nonnative Burmese pythons are a widespread problem and over 600 individual snakes have been captured since 2000. Everglades Park staff removed nearly 250 snakes in 2007 alone. Although native to Southeast Asia, the snake is established and breeding in the park. It can grow up to 20 feet and weigh 200 pounds. Hungry pythons prey on native wildlife including raccoons, rabbits, bobcats, and many birds, causing a disruption of the natural food chain and potentially serious impacts to the ecosystem. New regulations were passed in Florida in June 2010 banning owership of some species that includes the Burmese python, Nile monitor lizard, reticulated python, green anaconda, and African rock python.  
A young boy pleads with his father for a leopard gecko at a reptile breeder show in Florida. This lizard is not considered an environmental threat, unlike many snakes and lizards for sale at exotic shows put on by the pet industry. Some two million reptiles are imported to the U.S. every year. Many are released into the wild where they breed and overtake native species. Florida passed new regulations in June 2010 that ban some exotic species from ownership. These include the Nile monitor lizard as well as the Burmese/Indian python, reticulated python, green anaconda, and African rock python.
Jason Millsaps rips into a shroud of kudzu covering a car in his Georgia yard. Kudzu (Pueraria montana), a native of Japan, China, Taiwan, Korea, Vietnam, Thailand, the Philippines, and Pacific islands, was introduced into the U.S. from Japan in 1876 at the Philadelphia Centennial Exposition. It was promoted as ornamental and for animal feed, and first planted in Florida in the 1920s. It is now listed as one of the word’s top 100 invasive species. From 1935 to the mid-1950s, farmers in the South were encouraged to plant kudzu to reduce soil erosion, and the Civilian Conservation Corps planted it widely for many years. Kudzu is tenacious, growing 60 feet annually. It infests 7 million acres throughout the southeastern United States. Kudzu forms a dense thicket of little use to wildlife and it crowds out other plants, disrupting the ecosystem. Its tuberous root habit makes eradication difficult. “I’ve measured a foot a day,” says Daisy Millsaps, Jason’s mother. “It’s a never ending battle to keep it back.” Nicknamed “the vine that ate the South,” in 1953 it was removed from the USDA’s list of permissible cover plants. But it was too late, and kudzu has become something of a southern icon. Its ubiquity has had a profound effect on people who live near it, says James Miller, a weed scientist with the U.S. Forest Service in Alabama. “The story of kudzu is a story of resignation,” he says. “Some folks of the Southeast say, “We can’t do anything about invasives. After all, we haven’t been able to do anything about kudzu.’ But they are wrong. Many people are doing something to stop kudzu, and they are winning.” The plant may have met its match with another invasive. An insect from Asia is spreading through the South devouring kudzu. But it doesn’t stop there. Biologists and plant geneticists say the resilient insect is feasting on soybeans, which will likely cause problems down the road in the agriculture industry.

Find a Photograph

TIP: Use this to find a stock photo in the OlsonFarlow stock archives. Enter a name, region, country, activity or keyword phrase, For example: “Alligator, Okefenokee Swamp”

Subscribe To Newsletter

"*" indicates required fields

Hidden
Name
Hidden
This field is for validation purposes and should be left unchanged.

© 2024 olsonfarlow.com. All rights reserved. Images are protected under the U.S. DMCA.

To Top ▲