When you think of a quiet, sandy island, your mind probably drifts to a warm, tropical paradise. But forget your snorkel and flip-flops for a minute. Grab your binoculars and trail boots as we pay a visit to the islands of central Nebraska.
That’s right. Over the eons and through the endless, flat landscape, the meandering Platte River has carved out acre upon acre of landmasses surrounded by the river’s north and south channels. These are not just large sandbars that wash away as quickly as they form. They are long, narrow swaths of sand and loam that support riparian forests, prairie grasses, and wetland ecosystems.
The quiet islands are popular neighborhoods for local fauna, but for well over a century now one old friend of the prairie has been noticeably absent: the American bison.
During the settlement of the Great Plains by European immigrants in the 1800s, the massive wild herds of bison were reduced to a few hundred animals in the Yellowstone area of the Rocky Mountains. But this year, thanks to the work of a nonprofit organization called the Crane Trust, a small group of the giant herbivores have made their triumphant return to Shoemaker Island, an 11-mile-long, 1.25-mile-wide plot of grassy habitat surrounded by river.
Mark Morten, the Crane Trust’s land manager, said there are currently six bison on the island. They make up an “exhibition” herd, a herd that the public can easily access and view, but eventually a “wild” herd of 40 animals will arrive and wander 1,000 acres of the island at their own pace, eating what they want to eat, and behaving the way they want to behave in a natural grassland environment.
Why bison? Why on an island? And why is an organization called the Crane Trust initiating an effort to manage a herd of big mammals?
“We're a nonprofit organization dedicated to protecting habitat for whooping cranes, sandhill cranes, and other migratory birds, and we do that through land management, science, and outreach and education efforts,” said Mary Harner, the director of science for the Crane Trust. The group of scientists and conservationists manages approximately 10,000 acres of land around and on the Platte River in central Nebraska so that the annual arrival of approximately 550,000 birds goes off without a hitch.
To date, the Crane Trust has accomplished this through a variety of actions that mimic the natural events that would have occurred on a pre-settled prairie landscape. For instance, controlled burns are utilized where there once would have been naturally occurring wildfires fostering the growth and diversity of prairie vegetation. Trees and overgrowth are removed with tractors and chainsaws to replicate the effects of the natural but catastrophic floods of the past, floods that are now stymied by river basin management and widespread irrigation.
It’s all done in an effort to keep the river exactly how the cranes have known it for centuries, and it turns out that bison have a big hand (or hoof) in maintaining a healthy, crane-friendly habitat. The Crane Trust has typically used cattle to mimic the presence of the enormous, thundering migratory bison herds of the past, but cows enjoy a different diet and don’t weigh as much as bison. They’re not a perfect replacement.
Greg Wright, the Crane Trust’s wildlife biologist, said, “We expect to see [the bison] graze differently and wallow and use the land differently than would a cattle substitute.” Little behaviors like these have been shown to have big impacts on prairie landscapes, and the Crane Trust team will be taking notes on how Shoemaker Island changes with the addition of the bison.
“Some of the more rare, hard to find plants may respond differently to bison than they would another set-back process,” Wright said. “So the vegetation is probably our number one indicator, but we expect things like our grassland birds or small mammals or, further along, the snakes and lizards and those types of things to respond in some way.”
As the bison settle in, scientists at the Crane Trust will be measuring variables like species richness and species diversity in the island’s vegetation. The new herd will also help biologists learn more about the difference in the ways that cattle and bison affect grassland ecosystems.
“We’ll continue cattle grazing on other properties we have,” Harner said. “Some of those sites will provide the opportunity for comparative research.”
“We want to learn about the bison and their direct impact on grasslands compared to cattle,” Morton explained. “We also want to show that these were the original grazers out here on the Great Plains. There were millions and millions of bison and we want people to be able to see that, to be able to see the animals themselves.”
And while 40 head of bison is a far cry from the millions that once roamed the prairie, Wright said there is still a buzz in the air as locals prepare to see the majestic crane and the mighty bison reunited on this beloved river.
“Along the Platte River, this is probably the first time in over 100 years that bison and cranes have coexisted in these kinds of numbers,” Wright said, “The neat thing about it is that because it is a natural grassland, it will give people a glimpse…back in time to what things once looked like. So if you can…block out the fast food signs in the distance and the hum of the interstate and things like that, it'll give you an idea of what would have occurred.”