Yellowstone National Park has released a draft EIS on how to manage bison in the park/NPS file

Yellowstone National Park's Plains bison numbers could rise to 7,000 under one of three alternatives being considered for managing the iconic animals.

Spurred by new information on how brucellosis, a bacteria that can cause spontaneous abortions in livestock, is spread in the Greater Yellowstone Area, the draft management plan released Thursday for a 45-day public review contains no National Park Service-preferred alternative, but looks at three options ranging from keep managing the bison herds as they have been to a plan that could allow the herds to grow to 7,000 individuals with more allowed to migrate out of Yellowstone in winter.

The issue of bison migrating out of Yellowstone and possibly spreading brucellosis to cattle herds in Montana long has been controversial and led to adoption of the Interagency Bison Management Plan in 2000 after that state in 1995 sued the federal goverment over fears bison were spreading brucellosis to cattle. However the Bison Management Plan Draft Environmental Impact Statement points out that genetic research conducted in 2016 concluded that elk, not bison, infected cattle herds in Montana and, overall, posed a greater threat than bison to spreading the disease in the region.

"Elk exposed to brucellosis inhabitated an area encompassing about 17 million acres, whereas bison inhabitated 1.5 million acres near the (Greater Yellowstone Area) core," the draft EIS noted. "In 2020, the National Academies of Sciences, Engineering, and Medicine concluded infected elk had transmitted brucellosis to livestock in the GYA at least 27 times since 1998 with no transmissions attributed to bison." 

Trying to eradicate brucellosis in the region would be impossible, the draft said.

"The eradication of brucellosis would require eliminating the disease in elk, which would involve attempting to capture, test, and vaccinate or slaughter tens of thousands of elk across the entire GYA, which most people consider unacceptable and impossible at this time," the document stated.

Against that background, the draft EIS offers three management alternatives: 

• Alternative 1: The NPS would continue management of bison pursuant to the existing Interagency Bison Management Plan (IBMP), approved in 2000. This would maintain a population range of bison similar to the last two decades (3,500 to 5,000 bison after calving), continue hunt-trap coordination to balance population regulation in the park by using culling and hunting opportunities outside the park, increase the number of brucellosis-free bison relocated to Tribal lands via the Bison Conservation Transfer Program (BCTP), and work with the State of Montana to manage the already low risk of brucellosis spreading from bison to cattle.
• Alternative 2: Bison would be managed within a population range of about 3,500 to 6,000 animals after calving with an emphasis on using the BCTP to restore bison to tribal lands and tribal treaty hunting outside the park to regulate numbers.
• Alternative 3: The NPS would rely on natural selection, bison dispersal, and public and tribal harvests in Montana as the primary tools to regulate numbers, which would likely range from 3,500 to 7,000 or more animals after calving.

The 149-page document outlines the cross-governmental intricacies of managing Yellowstone bison. Once the animals leave the park, they no longer are under National Park Service jurisdiction but fall either under state control or the U.S. Forest Service if on national forest lands.

Additionally, several tribes have treaty rights to hunt bison that leave Yellowstone and head onto the Custer Gallatin National Forest. Private landowners also come into play when bison move onto their properties, while non-governmental organizations that want to preserve Yellowstone bison also voice their concerns.

On the Yellowstone landscape, the draft EIS looks at how climate change might impact the park and so bison, how greater numbers of bison in Yellowstone would impact grazing on the grasslands, as well as the amount of winter-killed bison that would be available for scavengers and predators.

Not overlooked is how greater numbers of bison could serve as a draw of more tourists, who in turn might encounter conflicts with the big animals. While a greater number of Yellowstone bison could be an economic boost, through wildlife viewing and hunting outside the park, "[T]his benefit would be counteracted somewhat because a higher density of bison is more likely to result in conflicts, injuries, and property damage," the EIS said. "Exact causal relationships are difficult to quantify because most injuries are a result of visitors approaching bison too closely rather than the total number of bison in the park."

"The purpose of the EIS is to preserve an ecologically sustainable population of wild, wide-ranging bison while continuing to work with other agencies to address issues related to brucellosis transmission, human safety, property damage and to support tribal hunting outside the park," a release from Yellowstone said.

At the National Parks Conservation Association, wildlife director Stephanie Adams encouraged the Park Service and stakeholders to ensure the species' long-term survival.

"More than a century ago, Yellowstone National Park saved bison from the brink of extinction. Today, because of decades of science and work by thousands of land managers, landowners and volunteers, the herd is flourishing within and outside of park boundaries. But NPS cannot accept the status quo. They must continue to further expand this successful restoration,” she said.

The draft EIS does not differentiate the park's central and northern bison herds for management, nor does it mention the pending legal question of whether the bison should be declared a threatened or endangered species.

In January 2022, the Buffalo Field Campaign and Western Watersheds Project renewed their legal battle with the U.S. Fish and Wildlife Service over that question. That prompted a federal judge to order FWS to re-examine, for a third time, the groups' petition. While U.S. District Judge Randolph D. Moss at the time did not rule one way or another on whether Yellowstone's bison merit ESA protection, he did say the Fish and Wildlife Service needs to do a better job of explaining why it doesn't think they do. He also expressed some consternation that a case brought in 2014 has not been satisfactorily handled by the agency.

In June 2022 the Fish and Wildlife Service announced it would take another look at the question.

And earlier this year, the Buffalo Field Campaign, which long has questioned how the National Park Service manages bison at Yellowstone, said it wants to see tribal entities given co-stewardship of the iconic animals, along with seeing their numbers rise roughly 10-fold to 50,000 in the Greater Yellowstone Ecosystem. That proposal by the organization, which has tenatively scheduled a Tribal Summit in November, seeks to replace “the existing failed bison management plan with a historic agreement that appropriately honors the fiduciary responsibility of the United States to Tribes.”

The park has scheduled two webinars to go through the draft EIS:

After the public comment period ends, on September 25, Yellowstone staff will review comments and prepare a final EIS, which is expected in 2024.