News / USA

Alien Species Not Always Welcome Visitors

Some non-native species are harmless, but others wreak havoc on other species, human health and the economy

Sea lampreys attach to fish with a suction cup mouth ringed with sharp teeth.
Sea lampreys attach to fish with a suction cup mouth ringed with sharp teeth.


Rosanne Skirble

Not all non-native species are created equal, says ecologist Mark Davis. He wants to do away with the popular view that divides the natural world into two opposing camps - native species and non-native species.  

In an essay in the journal Nature, the Macalester College biology professor joins 18 other scientists to argue that action to protect ecosystems should be based on species impact and not species origin.  

He urges conservation managers to order their priorities around how non-native species impact other species, human health, waterways and the economy.  

“What we should focus on is what is the species doing?" he says. "What are its functions within the community and then (decide) to keep or not."  In some cases those would be non-native species and in other cases, not native.

Davis and his colleagues do not deny that real problem species exist.  “Some of them are native. Some are non-native.  The ones that are non-native we should try to keep them out from countries in which they are not currently inhabiting.  But once the species are in, you often have to learn to live with them.”  

But that’s not always an option. Jennifer Nalbone is director of Invasive Species Navigation with Great Lakes United. The U.S. Canada coalition is dedicated to keeping aggressive invaders out of the lakes, and controlling those already there.  

She points to the on-going struggle with zebra mussels. They arrived in the mid-1980’s in ship ballast water from the Black and Caspian Sea region, and have become a major threat to wildlife, navigation, and boating.  “You could look back in history to the (19)80s and (19)90s in Monroe, Michigan when a power plant and the city’s water supply were shut down because its intake pipes were clogged with zebra mussels. Mussels contributed to a valve problem in the 1990s at the Nine Mile Nuclear Power plant in Lake Ontario.”

Each year zebra mussels cost the region between $100 million to $200 million.

Sea Lamprey is an eel-like fish native to the U.S. Atlantic coast that is also now found in the Great Lakes. Twenty million dollars are spent each year to fight this parasitic pest. Nalbone says with that in mind, the focus is on stopping the next big invader - Asian Carp. “These are burdens that the Great Lakes are struggling under right now and we don’t want another one in the region.”

Yet, she says, the Asian Carp, which can grow up to a meter long and weigh as much as 45 kilograms, is making its way north.  The voracious eater, imported by Midwestern fish farmers in the 1970s, could end up devastating the region’s 7 billion dollar fishing industry.

All that is holding it back now is an electric fence. Nalbone says keeping carp from Chicago is high on her list.

However, not all non-native species pose such a threat.

The large, bell-shaped Devil's claw, which is native to Central and South America, was introduced into Australia in the 19th century.
The large, bell-shaped Devil's claw, which is native to Central and South America, was introduced into Australia in the 19th century.

Take the Devil’s Claw, a Mexican herb that today grows wild in Australia. The campaign to eradicate the weed has mobilized hundreds of volunteers. Despite those efforts, Devil’s Claw persists and Davis says there is little evidence that the ecosystem is at risk.

“This tendency to jump to conclusions, the assumption of negative impacts, that has cost us a lot of money and resources directed to areas where there really wasn’t a lot of harm which meant they were not available to be used on species which were really causing harm.”

Another example is tamarisk. The shrub was imported from Eurasia and Africa in the mid-1800s to control soil erosion in the American Southwest, but it spread to river systems across the West and up mountainsides, to elevations of 2,000 meters.

After tamarisk removal, some land managers are turning to an innovative grow-out method called long-stems.
After tamarisk removal, some land managers are turning to an innovative grow-out method called long-stems.

While millions of dollars have been spent to suppress tamarisk, Davis, says the shrubs are not all bad.

“In fact (they) are now providing important habitat for some of the wildlife there, and if we eradicate them, we are actually making things worse.”

Stacey Kolegas, director of the Tamarisk Coalition, says tamarisk control is part of a coordinated plan for river health. She agrees with Davis that conservation must be science-based and site specific.  

“A community that has monoculture of tamarisk running through their downtown right where their river runs is going to be managing tamarisk for fire mitigation, whereas a wildlife area is going to be managing tamarisk because they want to increase the berry producing shrubs on their land to enhance wildlife habitat.”

You May Like

Key Al-Shabab Commander Captured

Zakariye Ismail Hersi was captured in a raid Saturday morning in the town of El Wak near the border with Kenya More

Relations Between Pakistan, Afghanistan Key to Fighting Taliban

A Pakistani official tells VOA that anti-terrorism campaign has resulted in improved counter-terrorism cooperation with Afghanistan More

160,000 Displaced by Flooding in Malaysia

Prime Minister Najib Razak visits hard-hit Kelantan state, announces nearly $145M in additional relief for victims More

This forum has been closed.
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Estimates Rising of Foreign Fighters in Iraq, Syriai
Jeff Seldin
December 24, 2014 11:38 PM
Foreign fighters are making more of a mark on the battles raging across Syria and Iraq than initially thought. VOA's Jeff Seldin has more.

Video Estimates Rising of Foreign Fighters in Iraq, Syria

Foreign fighters are making more of a mark on the battles raging across Syria and Iraq than initially thought. VOA's Jeff Seldin has more.

Video Russians Head Into Holiday Facing Economic Malaise

Russian preparations for the New Year holiday are clouded by economic recession and a tumbling currency, the ruble. Nonetheless, people in the Russian capital appear to be in a festive mood. VOA's Daniel Schearf reports from Moscow.

Video Mombasa in Holiday Tourism Slump Due to Security Fears

Kenya's usually popular beachside tourist destination of Mombasa is seeing a much slower holiday season this year due to fears of insecurity as the country has suffered from a string of terror attacks linked to Somali militants. Mohammed Yusuf reports for VOA on how businessmen and tourists feel about the situation.

Video For Somalis, 2014 Marked by Political Instability Within Government

While Somalia has long been torn apart by warfare and violence, this year one of the country's biggest challenges has come from within the government, as political infighting curtails the country's progress, threatens security gains and disappoints the international community. VOA's Gabe Joselow report.

Video US Political Shift Could Affect Iran Nuclear Talks

Secretary of State John Kerry’s efforts to resolve Iran’s nuclear crisis are continuing into 2015 after Iran and six world powers failed to agree by a November deadline. U.S. domestic politics, however, could complicate efforts to reach a deal in the new year. VOA State Department correspondent Pam Dockins has the story.

Video NYSE: The Icon of Capitalism

From its humble beginnings in 1792 to its status as an economic bellweather for the world, the New York Stock Exchange is an integral part of the story of America. VOA’s Bernard Shusman reports from Wall Street.

Video Islamic State Emergence Transforms Syria and Iraq in 2014

The emergence of the Islamic State in Iraq and Syria as a potent force in early 2014 changed the dynamics of the region. Their brutal methods - including executions and forced slavery - horrified the international community, drawing Western forces into the conflict. It also splintered the war in Syria, where more than 200,000 Syrians have died in the conflict. VOA’s Henry Ridgwell looks back at a deadly year in the region -- and what 2015 may hold.

Video Massive Study Provides Best Look at Greenland Ice Loss Yet

The Greenland ice sheet is melting faster than predicted, according to a new study released in the Proceedings of the National Academic of Sciences that combines NASA satellite data and aerial missions. As VOA’s Rosanne Skirble reports, the finding means coastal communities worldwide could be at greater risk, sooner, from the impact of rising seas.

Video US Marines, Toys for Tots Bring Christmas Joy

Christmas is a time for giving in the United States, especially to young children who look forward to getting presents. But some families don't have money to buy gifts. For nearly 70 years, a U.S. Marines-sponsored program has donated toys and distributed them to underprivileged children during the holiday season. VOA's Deborah Block tells us about the annual Toys for Tots program.

Video France Rocked by Attacks as Fear of ISIS-Inspired Terror Grows

Eleven people were injured, two seriously, when a man drove his car into crowds of pedestrians Sunday night in the French city of Dijon, shouting ‘God is Great’ in Arabic. It’s the latest in a series of apparent ‘lone-wolf’ terror attacks in the West. Henry Ridgwell looks at the growing threat of attacks, which security experts say are likely inspired by the so-called "Islamic State" terror group.

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.

All About America