Presence of Invasive Species Complicates Efforts to Protect Dwindling Native Species

Turn to the nation's most objective and informative daily environmental news resource to learn how the United States and key players around the world are responding to the environmental...

By Alan Kovski  

Aug. 7— For industries struggling to comply with protections for endangered species—or declining species that may soon be listed as endangered—one of the most difficult complicating factors is the presence of invasive species.

Invasive species, often uncontrolled and possibly uncontrollable, can substantially threaten or even wipe out other species. Failure to limit one threat forces regulators to rely more heavily on control of other threats, such as oil and gas development, electricity generation and transmission, logging, mining, ranching, farming and residential development. One widely cited reference estimated that invasive species cause more than $120 billion a year in damages in the U.S.

For the greater sage grouse, a candidate for listing as threatened under the Endangered Species Act, wildfires are a primary threat in the western portion of the bird's range. An invasive plant called cheatgrass is a primary contributor to those fires.

In the Pacific Northwest, the spread of the barred owl is a primary threat to the northern spotted owl, listed as threatened.

In the Southeast, wood storks are listed as threatened, and they also are becoming part of the diet of Burmese pythons, spreading through southern Florida.

In the Southwest, the spread saltcedar shrub is intensifying the competition for scarce water and growth habitat along river systems and adding to the pressures on rare birds.

In many parts of the U.S., hungry nonnative fish pose basic threats to the survival of native fish and amphibians. In some areas, trees are being devastated by nonnative insects, fungi and molds, such as the sudden oak disease killing California coastal oaks or the emerald ash borer killing ash trees in the East and Midwest.

Congress Shows Its Interest

Control of invasive species may rarely serve as a simple solution even where it is found to be possible. But it is a tool, and its potential significance has not gone unnoticed in Congress.

Rep. Rob Bishop (R-Utah), with Rep. Steven Horsford (D-Nev.) as a co-sponsor, introduced in February the Federal Lands Invasive Species Control, Prevention and Management Act (H.R. 3994) to require the Interior Department and the Agriculture Department to reduce invasive species populations by 5 percent annually.

During a July 9 House Natural Resources subcommittee hearing on the bill, George Beck, a Colorado State University weed science professor, testified that he believed invasive species are manageable. However, he also offered statistics on acres of federal lands that are infested with invasive weeds to show that the Bureau of Land Management and other federal agencies are rapidly falling behind in those management efforts.

The sheer scale of the problem leads many experts to question how manageable some invasives really are.

Sen. Kirsten Gillibrand (D-N.Y.) introduced in June the Invasive Fish and Wildlife Prevention Act (S. 1153), which would establish a screening program to reduce the risk that imported species will turn out to be harmful to native wildlife or people. It was one of the bills discussed at a July 16 hearing of a Senate Environment and Public Works subcommittee.

Sage Grouse Stirs Worries

The prospect of the greater sage grouse being listed as threatened has raised fears of economic disruptions and costs across 11 Western states. Members of Congress have discussed the subject repeatedly and have questioned whether the U.S. Fish and Wildlife Service—which will make the listing decision—is researching its subject adequately.

An indication of the trouble brewing came in June when the BLM issued a memorandum on protections for a related species, the Gunnison sage grouse, proposed for listing as endangered. The agency said it was imposing seasonal moratoriums on oil and gas development (excepting valid existing rights) throughout BLM-managed land in the bird's Colorado and Utah territory.

Oil and gas development also poses threats to the habitat of greater sage grouse, found in 11 Western states. On BLM and U.S. Forest Service land, the oil and gas companies already help protect the species with a variety of measures, notably the seasonal timing of work and reduced footprints for projects.

Other causes of habitat loss for the species include mining, wind farms, power transmission lines, ranching, farming, housing—and invasive species.

BLM, manager of 245 million surface acres, could have an enormous impact by itself on economic activity through measures to protect the greater sage grouse. The agency is preparing 15 regional resource management plans involving greater sage grouse protection. At the same time, the Fish and Wildlife Service is facing a September 2015 deadline on deciding whether to list the bird. If the bird is listed, the protections would go well beyond federal lands.

Control of invasive species is one of the tools that might either help prevent a listing or at least help reduce the severity of industrial and residential restrictions and the local economic impacts that would come with such restrictions.

Killing Cheatgrass for Grouse

Cheatgrass, an invasive species originally from Europe, now covers hundreds of thousands of square miles of U.S. land, public and private, and is spreading rapidly through the Great Basin region between the Rockies and the Sierra Nevadas.

Cheatgrass colonizes areas disturbed by fires or human activities. In drier and lower-elevation areas, its growth is faster than the native sagebrush and bunchgrass that would provide the preferred habitat for sage grouse. Cheatgrass dries out in summer and burns easily, feeding fires that help eliminate sagebrush and bunchgrass.

Mike Pellant, a BLM rangeland ecologist based in Idaho who coordinates the Great Basin Restoration Initiative, told Bloomberg BNA that federal agencies are working on a variety of strategies to reduce the spread of cheatgrass and fires together.

“We can do something about both,” Pellant said. “The issue is the scale of the problem.”

Current strategy involves not only the obvious step of trying to prevent fires but also, when fires do occur, seeding ground with native species within a year after the event. “If we wait two years, it's too late. The cheatgrass will be reestablished almost to pre-fire levels,” he said.

‘Sins of the Past' Linger

Past grazing practices were damaging, allowing livestock to overgraze native plants and opening the way for cheatgrass to spread. “We're basically living with the sins of the past to a large degree,” Pellant said.

Now ranchers say grazing of cattle on cheatgrass in the spring before the grass dries out can reduce fire risk. Rep. Mike Simpson (R-Idaho) alluded to that during a July meeting of the House Appropriations Committee as the subjects of sage grouse and fire came up. Republicans on the House Appropriations Committee added a one-year delay on the sage grouse decision to a spending bill for Interior and related agencies, but that bill and others from the committee are not expected to see action in the Senate.

Other strategies include spraying herbicides such as Roundup and planting strips of fire-resistant plants that serve as living fuel breaks. Land managers also hope to obtain approval from the Environmental Protection Agency to use a native bacterium, dubbed ACK55, as an herbicide, because it does not harm native vegetation but it does inhibit cheatgrass and another invasive species, medusahead grass.

Mike Gregg, an Oregon-based Fish and Wildlife Service biologist who helps with land management research and demonstration work, said ACK55 would not be a magic bullet but a valuable additional tool that has performed well in tests on a small scale. The idea would be to spray it on the invasive grasses in the fall, after which it would colonize the roots of the grasses, stunting their growth.

If EPA approval is granted, a scaling up of production of the bacterial pesticide would not be that difficult, Gregg said, adding that he has heard it might cost $10 an acre. But it could take five years to get EPA approval for such a new herbicide, and the decision deadline for the sage grouse is only 13 months away.

Killing Owls for Other Owls

In the Pacific Northwest, restrictions have been placed on logging to protect the northern spotted owl. At the same time, the Fish and Wildlife Service has established a four-year test program to kill a competing invasive species, the barred owl.

Barred owls, larger and more adaptable than northern spotted owls, are native to forests in the eastern U.S. and Canada and the boreal forests north of the Great Plains in Canada. In the 20th century, barred owls spread through British Columbia and then Washington, Oregon and northern California. Some environmental activists insist that humans are to blame for the spread of the barred owl, although there is no solid evidence for that theory. The Fish and Wildlife Service leaves the question open, saying it may be the result of human activity or a natural range expansion.

The idea of large-scale and routine shooting of barred owls, a beautiful raptor, is offensive to many people, though predator control is a strategy occasionally used with other species. It remains to be seen whether it will work. The timber industry has argued that what will not work is overreliance on logging restrictions to save the northern spotted owl.

“Habitat is no longer the limiting factor in the owl's survival,” Tom Partin, president of the American Forest Resource Council, said in 2013 when his timber industry group joined in a lawsuit challenging the critical habitat designation for the northern spotted owl. “The real threats are barred owls and wildfire,” he said.

A group called Friends of Animals, insisting that habitat destruction connected to logging is the primary threat, sued in 2013 to block the plan to kill barred owls. The group said the plan was “immoral, unethical and cruel,” in addition to being a violation of the Migratory Bird Treaty Act.

Neither lawsuit has been settled.

Pythons Spread Through Florida

Unlike the barred owl, the Burmese python might not be beautiful in the eyes of most people. What is indisputable is that the python, spreading across the Everglades region of southern Florida, is a top predator.

Populations of mammals have plummeted in areas occupied by Burmese pythons. A study in Everglades National Park in 2011 found that, compared with 2003, wildlife observations were down 99 percent for raccoons and opossums, 94 percent for white-tailed deer and 87.5 percent for bobcats. No rabbits or foxes were observed at all.

Michael Dorcas, a Davidson College biology professor who led the study and co-authored a book on invasive pythons, told Bloomberg BNA the pythons have spread east and west as far as they can in southern Florida, and there is no way to know how far north they will spread.

“We don't have any technique right now that's been developed that can suppress their population,” Dorcas said.

Endangered and threatened species are on the menu.

“They've already been documented eating endangered wood storks,” Dorcas said.

The Fish and Wildlife Service reclassified wood storks June 30 from endangered to the lesser category of threatened, a decision based on the species' increasing territory outside Florida and its increasing numbers. That reclassification came as a result of a petition from the Florida Homebuilders Association.

If the pythons eat more storks, homebuilders may find themselves facing stricter restrictions or mitigation costs than they would otherwise, simply because homebuilders are controllable while pythons, so far, are not.

Shrub Intensifies Water Competition

The Office of Management and Budget completed interagency review July 30 of a proposed designation of critical habitat for the western distinct population segment of the yellow-billed cuckoo. In the arid Southwest, where competition for water and riverside habitat is especially strong, the proposal is one more worry for many people and companies.

The Arizona Mining Association submitted comments in February taking issue with the quality of the science listed in support of the proposal by the Fish and Wildlife Service. Mining operations can be water intensive. Ranchers have to worry about being fenced off from stream segments to protect vegetation from being eaten and trampled.

One of the many factors threatening birds and vegetation alike in the Southwest is an invasive species, the saltcedar shrub, also called tamarisk. Well established in much of the region, it crowds out preferred native species such as cottonwood and willows near river banks, and its fallen leaves add salt to the soil, making the soil too saline for many other species. It is such a water hog that it is cited as a substantial factor in reduced water levels in rivers.

The Fish and Wildlife Service has described saltcedar as one of the threats to yellow-billed cuckoos. Where saltcedar totally dominate a riparian area, no yellow-billed cuckoos are found, the service said.

The Agriculture Department lists herbicides and mechanical removal as two primary methods of saltcedar control. Burning also can be used, and there have been numerous test releases of the saltcedar leaf beetle as a biological control. For now, however, the shrub continues to spread.

Fish Eat Fish and Frogs

In April, the Fish and Wildlife Service said it would list the Sierra Nevada yellow-legged frog and the northern distinct population segment of the mountain yellow-legged frog as endangered, both of them found in the Sierra Nevada Mountains of California.

The final rule indicated the primary threat to the frog populations comes from trout stocking of streams for recreational fishing. Bullfrogs, native to the Eastern U.S. but invasive in the Western U.S., also eat the frogs and their tadpoles.

Rep. Tom McClintock (R-Calif.) has warned that the frog listings and critical habitat designations could have a severe impact on the local economy through restrictions on grazing, logging, mining and recreation.

Many fish species have been listed as threatened or endangered in the Southwest, where water withdrawals strain the water resources of streams and where dams, sedimentation and livestock have harmed stream habitat. One of the latest additions to the list of endangered species is the Zuni bluehead sucker, a fish in Arizona and New Mexico, listed July 24.

A nonnative predator, the green sunfish, is a primary threat to Zuni bluehead suckers and other native species in the area. Efforts to eradicate green sunfish have helped populations of Zuni bluehead suckers rebound, at least partially, in some New Mexico streams.

Attack of the Asian Carp

Asian carp are mentioned more often than any other invasive fish because of their spread northward through the Mississippi River watershed and the fears that they will find their way into the Great Lakes. Most often mentioned is their potential to devastate fisheries, but they also can threaten the existence of some species.

Numerous factors may bring species close to the edge of endangerment, and competition for food and space from an invasive fish “definitely can be something that can push them over the edge,” said Kelly Baerwaldt, a Fish and Wildlife Service biologist who coordinates work on trying to detect the presence of Asian carp by testing waters for traces of DNA.

Populations of Asian bighead carp and silver carp have been exploding, and although they eat algae and not other fish, they can outcompete many species, and there is evidence that they have begun to do that. Gizzard shad and buffalo fish have been declining in some parts of the Illinois River where the Asian carp are especially numerous.

“Now we have empirical data to say, yeah, they do eat a lot of food, and yeah, they do push other species out,” Baerwaldt told Bloomberg BNA.

Gizzard shad are an important forage fish for predatory fish, and buffalo fish are commercially important, a food fish for people in the Illinois region. Neither species is close to being endangered, but the fact that their condition would decline in parts of their native habitat invaded by carp is a warning bell for other species and for whoever might have to cope with species and habitat protections.

To contact the reporter on this story: Alan Kovski in Washington at

To contact the editor responsible for this story: Larry Pearl at

The Fish and Wildlife Service website for greater sage grouse, with a variety of documents on species status and conservation objectives, is available at

A study released July 23 on conservation measures by oil and gas companies for greater sage grouse is available at

A Fish and Wildlife Service website for the northern spotted owl is available at

Invasive Pythons of the United States, a book co-authored by Michael Dorcas, is available through or at

Reference materials on saltcedars (tamarisk) are available at an Agriculture Department website,

A Fish and Wildlife Service website on invasive species is available at

Request Environment & Energy Report