Alien Invasion? An Ecologist Doubts the Impact of Exotic Species

Many conservationists have dedicated their lives to eradicating invasive plant and animal species, but Mark Davis wants them to reassess their missions
1 of 8

Kudzu Killer

For ecologist Dan Simberloff of the University of Tennessee Knoxville, understanding and fighting invasive species has been a lifelong project, and he doesn’t buy Mark Davis's arguments. "He's contrarian," Simberloff says.....[ More ]

Water Sucker

The tamarisk tree has been called the "second-worst invasive species in the United States," and millions of dollars have been spent on its eradication. Early studies had reported that tamarisks used more water than native vegetation, and one author wrote that they sucked up "almost twice as much water per year as the major cities in southern California." Forgotten in the hubbub were later measurements that failed to replicate those studies, and no one has established whether the tamarisk causes soils to go salty or if it simply has a higher tolerance for salty soils.....[ More ]

I Heart Tamarisk

Matthew Chew of Arizona State University stands in front of the tamarisk tree, or salt cedar, a nonnative species vilified for displacing native vegetation and sucking up scarce water resources. "I'm skeptical of some of the basic assumptions of invasion biology," Chew says.....[ More ]

Fast and Loosestrife

Davis's doubts date back to early attempts to eradicate purple loosestrife from around Minnesota lakes and waterways.  Eradication proponents argued that the imported plant, which has spread across North America, was seriously displacing the native plant species that muskrats and ducks eat, thereby displacing the animals.....[ More ]


Mark Davis of Macalester College has been one of the most vocal critics of invasion biology alarmism, but his perspective is still controversial in a field that considers all-native ecosystems to be the pinnacle of restoration.....[ More ]

Toad Busting

Australia is one big island—a continent, actually—and ever since Europeans arrived there in the 18th century, it has been wracked by outbreaks of nonnative rabbits, mice and even camels .....[ More ]

Snakes Alive!

After World War II, the brown tree snake arrived on the U.S. Pacific island of Guam, 6,100 kilometers west of Hawaii. It has since extirpated 10 of the island's 12 native forest bird species, and ecologists are now studying the wider impacts of these bird extinctions on the forest.....[ More ]

Mussel Madness

For ecologists Mark Davis of Macalester College in St. Paul, Minnesota and Matthew Chew of Arizona State University, rhetoric over invasive species has crossed the line from science to propaganda.....[ More ]

risk free title graphic

YES! Send me a free issue of Scientific American with no obligation to continue the subscription. If I like it, I will be billed for the one-year subscription.

cover image Subscribe Now
Share this Article:

Starting Thanksgiving

Enter code: HOLIDAY 2015
at checkout

Get 20% off now! >


Email this Article