At a Club 20 natural resources committee meeting some years ago, members were discussing a resolution seeking to stop the spread of non-native invasive species, like tamarisk. One member, only half-joking, asked if we could add Californians to the list, arguing that they had just as much negative impact on the natural habitat as any other non-native plant or animal. Another member wanted to add New Yorkers, and the discussion deteriorated to the point that nothing was done, and the meeting adjourned.
Serious discussions about the impact of non-native invasive species often go the same way. Eradication efforts remain underfunded and mostly unsuccessful, though public awareness is higher than ever, thanks to widespread media coverage of high-profile species like Burmese pythons in Florida, zebra mussels in the Great Lakes, and starlings everywhere.
Six years ago several friends and colleagues founded a group called the Reduce Risks from Invasive Species Coalition (RRISC) to highlight the impacts of invasive species across the country, and to address the issue through education and advocacy. Its founder and first president, Scott Cameron, is now an Interior Department Official. The bi-partisan advisory board includes Harris Sherman, whose non-consecutive appointments by different Governors made him both my predecessor and successor at the Colorado Department of Natural Resources, and Former Interior Secretary Gale Norton, along with several other notable conservation leaders.
The group has called attention to the enormous destruction caused by non-native fish, insects, mammals, mollusks, and plants in nearly every state and every ecosystem. One of the primary arguments, which has attracted considerable attention, is that non-natives are actually a primary cause of “endangerment” for hundreds of native endangered species.
For example, the spread of cheat grass across the West has replaced native juniper and sagebrush plants, destroying vital habitat of the greater sage grouse. Similarly, the cane toad, native to Central and South America, was imported to Florida, the Caribbean, and Hawaii, where it now out-competes and gobbles up dozens of native species. Northern tamarisk beetles control tamarisk, but that destroys the prime habitat of the southwest willow flycatcher.
The National Wildlife Federation says 42 percent of endangered species (over 700 species) are threatened specifically because of non-native invasive species. That’s because when species are moved from their natural habitat, they often find a more hospitable environment, one that generally lacks their natural predators. Then, they either prey on the native species, outcompete the natives for food, carry diseases with them, or all of the above.
Some of these species were introduced to the U.S. on purpose, often with good intentions. Kudzu controlled erosion, Russian olives were pretty, Asian carp cleaned ponds, cane toads eliminated sugarcane pests, and brown tree snakes ate rodents. All seemed like goods idea at the time – all are devastating native species today.
Tamarisk seemed like a great idea, since it is both ornamental and erosion-controlling. But it is also among the most serious causes of Western water shortages. Today, government scientists dispute that latter point, disputing numbers they themselves used for 30 years. They now dispute the 1987 study, which claimed tamarisk trees drink 200 gallons of water daily. They now say tamarisk consumes no more water than the native trees. That might be right, for individual trees, but the native cottonwood and willow vegetation historically occupied less than a fourth as much land with considerably lower density. Still, several scientists took issue with a column in which I used the larger number, based on that study, which was cited by experts for three decades.
I am no scientist, so what do I know? I know we are supposed to listen to scientists when making natural resources policy. But sometimes they change their minds, and their advice. We understand knowledge is continually growing, but sometimes changes are also “convenient.” When they wanted $50 million in taxpayer funds, tamarisk was said to be the greatest threat to western water imaginable. Now, they want to blame water shortages on climate change, and suddenly tamarisk poses no such threat. By the way, no agency or university has yet offered to give back the money they were given to eradicate this dire threat.
Now, voters are being asked to import gray wolves into Colorado – not the original native wolves, which are extinct, but a species considerably larger and meaner. Proponents say it will help the environment, and they might be right. They mean well, as did those who imported tamarisk. But messing with nature causes unintended consequences, whether we’re introducing weeds, wolves, or Californians.
An edited version of this column originally appeared in the Grand Junction Daily Sentinel June 12, 2020.
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