Climate change has been the focus of much of the opposition to TransCanada’s Keystone XL pipeline. But many conservationists are also concerned about more immediate environmental consequences.

They’re worried about the pipeline construction’s impact on wildlife and ecosystems, and of possible spills of the heavy crude oil that will flow through the pipeline at the rate of 830,000 barrels a day.

Some people, seeing a map of the pipeline’s proposed 875-mile route through the Great Plains, may picture the region in the terms of 19th-century explorers who called it the “great American desert”: a barren land lacking in natural-history interest. In fact, though the vast herds of grazing animals that Lewis and Clark saw are greatly diminished, rich ecosystems endure. And while the pipeline route crosses some agricultural land, much of it would traverse natural habitats in Montana, South Dakota, and Nebraska where harmful effects on native animals and plants could—some say would, inevitably—occur.

Missouri and Yellowstone Rivers

The Keystone XL route crosses the Missouri and Yellowstone rivers, two of more than 50 crossings of perennial streams. Both rivers are home to the federally endangered pallid sturgeon, a bizarre-looking fish up to six feet long adapted to life in large rivers with silty bottoms. A serious oil spill has the potential to damage or even destroy habitat for this species. Such a spill could also harm habitat for least terns and piping plovers, two birds that nest along rivers and that have suffered serious declines in recent decades.

And pipelines do fail, conservationists note. The failure in 2010 of an Enbridge pipeline carrying Canadian crude oil triggered the costliest onshore oil spill in U.S. history, contaminating 40 miles of Michigan’s Kalamazoo River and surrounding wetlands. Last year, another pipeline carrying Canadian oil, Exxon-Mobil’s Pegasus line, ruptured in a the small Arkansas town of Mayflower, affecting wetlands connected to the largest man-made game and fish commission reservoir in the United States. Officials are still reckoning the lingering environmental damage after massive and expensive cleanup efforts.

In its recent Final Supplemental Environmental Impact Statement, the State Department admits that oil spills will occur and are a danger, but asserts that current technology and rigorous inspections make the odds of a serious spill remote.

Davis Sheremata, a spokesperson for TransCanada, said Keystone will incorporate construction and maintenance techniques more advanced than those of earlier pipelines. Safety measures “are the culmination of six years of consultation between TransCanada, the United States Fish and Wildlife Service, and many other federal and state environmental agencies,” he said. “The required environmental protection and pipeline safety measures set a new, and very high, standard unequaled by any other pipeline project.”

Whooping Crane

One of the greatest conservation concerns about the immediate effect of the pipeline centers on the critically endangered whooping crane. Most of these tall white birds nest in Canada and migrate through the central United States to and from their wintering grounds on the Texas Gulf Coast. The cranes’ flight route passes directly along the pipeline route for hundreds of miles.

It’s not the pipeline itself that’s of greatest potential danger to the cranes, though. Pumps needed to keep the thick Canadian oil flowing through the pipeline require power lines to supply them with electricity, and conservationists wonder what will happen when more than 300 miles of new power lines appear in formerly wide-open spaces in the birds’ flight path.

“The whooping crane is a species that we’ve really homed in on,” said Jim Murphy, senior counsel for the National Wildlife Federation. “Power lines account for about 40 percent of juvenile whooping crane mortality, which is a big deal when you’re talking about a bird that has a population of about four hundred in the wild. Those concerns have never really been taken seriously.”

TransCanada’s Sheremata said his company and pipeline contractors “have committed to incorporate a number of conservation measures to prevent potential direct or indirect impacting to the whooping crane.” Measures include installing and maintaining avian markers (conspicuous objects designed to make lines more visible to flying birds) at pump stations “to reduce impacts to whooping cranes from power lines.”

Greater Sage-Grouse

Although the greater sage-grouse isn’t officially an endangered species, many bird experts believe it should be. They claim it has been kept off the list for fear of political backlash in conservative western states, where farming and ranching might face restrictions.

There’s no question that the grouse has suffered from loss of habitat: 20 of 27 known population groups have declined since 1995. The pipeline route passes within a few miles of dozens of grouse leks (sites where males “dance” to attract mates); ornithologists fear that noise from construction, roads, and pumping stations could affect breeding success of these notoriously shy and easily disturbed birds.

In addition, power-line towers serve as hunting perches for eagles and hawks, which prey on grouse. In treeless areas where grouse live, towers will bring new threats and greater potential mortality by providing raptor lookouts where formerly there were none.

Swift Fox

The swift fox, a small canine of grassland regions, is another controversial species that the Arizona-based Center for Biological Diversity believes belongs on the endangered-species list. The CBD finds it “dumbfounding” that Keystone XL environmental-impact statements fail to address the pipeline’s effects on the fox.

“It’s like they took a map and drew a pipeline along the remaining locations of known bands of the swift fox,” said Amy Atwood, senior attorney for the CBD. “That’s where the fox lives, because those are the areas that are not being used for agriculture and are on public land. That’s where pipeline companies like to site things these days to minimize landowner conflict or having to deal with eminent domain. And that’s where the wildlife is. They’ve been pushed out of other areas.”

American Burying Beetle

The only endangered species that the U.S. State Department’s Environmental Impact Statement concluded would be harmed by the pipeline is the American burying beetle. The odd splotchy orange 1.5- to 2-inch (4- to 5-centimeter) insect once roamed 35 states, but has been disappearing since the early 1900s and is now is found mainly in areas undisturbed by human influence, with populations in South Dakota, Nebraska, Oklahoma, and Kansas. (The beetle is named for its habit of burying corpses of small animals, which are used as food by larvae hatched from eggs laid nearby.) The department’s report admits that some beetles will be killed and their habitat destroyed by pipeline construction, but says that a monitoring and habitat-restoration program will mitigate the losses and the species will not be seriously threatened.

Although no one knows the precise reason for the American burying beetle’s demise, one theory is that light pollution has disturbed the feeding and breeding habits of the only purely nocturnal species in the genus of burying beetles.

In 2011, biologists hired by TransCanada actually collected and moved more than 2,000 American burying beetles in anticipation of pipeline construction, a move that drew a legal challenge from environmentalists.

Important Bird Areas

TransCanada rerouted the proposed Keystone XL to avoid most of Nebraska’s Sandhills, a native grasslands that contains one of the largest aquifers in North America, the Ogallala, drinking water source for two million people in eight states. But other ecosystems remain in the pipeline path.

In Montana, Keystone XL would cross the North Valley Grasslands, an officially designated Important Bird Area. (This is a designation used globally under an initiative of the nonprofit BirdLife International, and implemented in the United States by the Audubon Society and its partners.) In recent breeding bird surveys, grassland species showed the greatest decline of any group of birds in the United States. Two declining species, Sprague’s pipit and chestnut-collared longspur, nest in the North Valley Grasslands.

In south-central Nebraska the proposed pipeline route passes through the Rainwater Basin Important Bird Area, a 6,000-square-mile wetlands region that provides migratory habitat for literally millions of geese, ducks, and other waterbirds, including whooping cranes. The prospect of a significant oil spill in this vital habitat ranks among the greatest fears of wildlife experts opposed to the pipeline. Ninety percent of the greater white-fronted geese in central North America migrate through the Rainwater Basin, as do nearly 100 percent of the buff-breasted sandpipers.

Niobrara River

Farther north in Nebraska, the pipeline would cross the Niobrara River, a popular regional recreational resource. Though the proposed pipeline crossing has been relocated and would be sited 11 miles downstream from the official boundary of the part of the waterway that is designated the Niobrara National Scenic River, an oil spill would affect valuable wildlife habitat, a possibility that worries Marian Langan, executive director of Audubon Nebraska.

“We have a photo of a whooping crane that was taken on the Niobrara within a quarter-mile of where that pipeline is going to cross,” Langan said. “When the State Department had hearings here, I submitted the photo, and they’re ignoring it.”

Apart from major river crossings such as the Missouri, Yellowstone, Niobrara, and Platte, the fate of small streams and wetland areas concerns the National Wildlife Federation’s Murphy.

“The State Department relies on the Clean Water Act to make sure that these impacts are accounted for,” Murphy said. “But a lot of these places are pothole-type wetlands that may not be protected under the act. What happens if there’s no real obligation on the part of the company to clean them up? They’re not year-round wetlands, but they’re still used for stopover on bird migration paths and for things like amphibian breeding. So they’re still important.”

This type of habitat loss also worries Amy Atwood. “Lots of little wetlands are going to be destroyed,” she said. “It’s going to have an impact.”

Whether on a river, small stream, or native prairie habitat, it’s the possibility of a major pipeline leak that’s the nightmare outcome for environmentalists.

“One of the scary things about the spill that happened in Michigan was that the reaction time there was about sixteen or seventeen hours,” Murphy said. “They misread their alert systems, and they actually ended up pumping more oil after the breach had taken place. It’s easy to imagine if a breach happened in the right place in the line that a tremendous amount of habitat damage could occur very, very quickly.”

Marian Langan agrees. “TransCanada will say, ‘All these communities have emergency plans,’ ” she said. “‘If something happens they can take care of it.’ But if you talk to the people in those rural communities, they don’t know what do. There’s no capacity to clean up that kind of stuff in those remote locations. Maybe they have a cleanup contract with a company that’s two or three hours away, but they don’t deal with this kind of thing. They’re not going to know what to do. It’s just going to be a disaster.”

If President Obama approves the Keystone XL pipeline later this year, many conservationists and landowners along the route are prepared to continue their opposition. A well-organized group of farmers and ranchers in Nebraska continues to gather momentum in their anti-pipeline fight, and several Native American nations oppose the pipeline. The Center for Biological Diversity is among several environmental groups that have vowed to file lawsuits to block the pipeline project.

“We’re going to be preparing a legal challenge between now and whenever approval comes down,” Amy Atwood said. “These animals connect us to the past, to the people who used to live here. They’re part of our nation’s heritage.”