This third installment of a four-part series on the Hart Mountain National Antelope Refuge gives a big-picture look at the basic ecology of the region and identifies some of the management challenges the refuge faces today. Read on to learn what is limiting the health of big game populations within these unique public lands.

Thousands of petroglyphs scattered across the black basalt rim-rock convey the importance that the Hart Mountain region has long held as a place for wildlife and hunters. The drawings, some of them from more than 6,500 years ago, show how the Northern Paiute fished, hunted, and lived along the shore of the Warner Lakes, at the base of the mountain, and moved higher to hunt pronghorn and big game during the summer.

Later, in the 1920s, biologists recognized the region as the potential cornerstone of an ambitious plan to re-establish abundant herds of pronghorn antelope. This was reliant on the area’s unique ecology.

The Hart Mountain National Antelope Refuge lies in the heart of the Northern Basin and Range ecoregion and is part of the greater sagebrush steppe ecosystem, which occupies more than 165 million acres across 13 Western states. The Cascade Mountains create a rain shadow that anchors sagebrush, bunchgrass, and forbs as the dominant vegetation. Elevations are high, between 4,500 and 8,017 feet at the top of highest point on the refuge, Warner Mountain. This high-elevation, semi-arid climate creates a region known for extremes.

The refuge acts as an elevational island, which sets the vegetation apart from the lower and drier surrounding Bureau of Land Management lands. At its highest elevations, Hart Mountain accumulates considerably more winter snowpack and acts as a sponge that trickles out water throughout a lifeline of streams and wet meadows during the summer growing season. Snowmelt facilitates abundant growth of aspens, mountain mahogany, bitterbrush, chokecherry, and even ponderosa pine stands, which provide key summer range, forage, and cover for countless species.

Years ago, many groups—including the National Audubon Society and Boone and Crockett Club—worked together to advocate for hundreds of thousands of acres of this high-value habitat to be set aside for wildlife and managed as part of the National Wildlife Refuge System. Today, more than 800,000 acres on the Hart-Sheldon Refuge complex are managed by the U.S. Fish and Wildlife Service with a one-of-a-kind mission to manage for wildlife above all other uses.

But this land of extremes also presents significant challenges for wildlife managers. Over the past two decades, populations of mule deer, bighorn sheep, and sage grouse have been declining both on the refuge and across the region. There are many reasons for this, but a few causes stand out as particularly concerning to the health of big game in the sagebrush steppe ecosystem—here are four.

Climate Change

Climate change is taking a toll on wildlife habitat across the West, and the Northern Great Basin is seeing some of the most drastic impacts. The spread of invasive annual grasses, such as medusahead, ventenata, and cheatgrass, diminish native plant communities, reduce the forage available to wildlife and livestock and—perhaps most concerning—alter the historic fire regimes that once helped to maintain the sagebrush steppe. Invasive annuals dry out much quicker during the growing season and create finer fuels that ignite quickly, compared to native perennial bunch grasses. Once invasive annual grasses gain a toehold, they tend to increase the frequency, intensity, and spread of fires, which can damage or replace critical sagebrush and bunchgrass that is more adapted to infrequent, patchy fires.

Rangeland ecologists are also seeing increasingly prolonged and persistent drought cycles in the Intermountain West. These droughts are tough on mule deer, bighorn sheep, and all other wildlife, because they shorten the growing season and decrease the availability of key nutrients needed to sustain pregnant does and ewes through the long winters.

In much of its range, western juniper has increased tenfold in the past 130 years. And rapid expansion of encroaching juniper forests is exacerbated by all of the conditions mentioned above. Warming temperatures, increased CO2 in the atmosphere, changing fire regimes, and historic overgrazing have all helped junipers spread, and their long, deep taproots steal from the limited water available to native plants during a drought. Additionally, these juniper forests can create places where predators have a much better advantage over prey species like sage grouse, mule deer, and bighorn sheep, upending the balance in the food chain.

Wildlife managers need additional resources to fight these effects of climate change.

Recreational Changes and Increased Public Use

One lesson of the COVID-19 pandemic was that our public lands are a treasured resource, and people are enjoying them in ever-growing numbers and a myriad of ways. Trail runners, mountain bikers, OHV users, equestrians, wildlife watchers, and hunters increasingly compete for a limited amount of space that also serves as habitat for wildlife. The public use of the refuge—and all public lands in the West—has increased drastically since the turn of the 21st century. Hunting seasons and tag allotment on the refuge are tightly regulated to limit the level of habitat disturbance, but more people are using the refuge for hiking, biking, and wildlife watching than in recent history. Right now, these activities come with less regulation aimed at limiting impacts to big game.

Energy Development

Last year, Oregon signed into law House Bill 2021, which requires the state to transition to 100-percent clean energy by 2040. While this is needed to combat the effects of climate change, there are growing pressures to site renewable energy projects on landscapes within the Great Basin, where solar and wind energy potential is high. Future renewable energy projects will need to be carefully planned to ensure that they limit and/or mitigate for any impacts to important wildlife habitat, including winter range, stopover areas, and migration corridors. The lands within the refuge are off-limits to energy development, but adjacent habitat could be considered for development under existing BLM management plans, thus affecting the refuge’s big game.

Wild Horses and Burros

Despite the legal classification as “wild” on federal land, free-roaming horses and burros are non-native, feral livestock that do not have any natural predators and can create significant detrimental impacts to native ecosystems within sagebrush steppe habitat. Currently, there are an estimated 86,000 wild horses and burros on BLM and national forest lands, which exceeds the agencies’ Appropriate Management Levels by more than 300 percent. The quality of habitat for wildlife in many places within the West is declining as a result.

These impacts are elevated by a changing climate. Native species like bighorns, mule deer, and pronghorn antelope are being negatively affected as they compete for limited forage and water resources.

Similar to the threat from energy development, the Hart and Sheldon refuges themselves are protected—the U.S. Fish and Wildlife Service has utilized its wildlife-first mandate to remove all wild horses and burros from both refuges in recent years—but neighboring BLM lands continue to suffer. This affects the bigger picture for game species in the region and underscores the importance of preserving the wildlife-focused management of these important refuge lands.

All photos by Sage Brown. Find him on Instagram @sagebrown.

Stay tuned for the final blog in this series, where I’ll outline some ways the U.S. Fish and Wildlife Service can improve wildlife habitat on the refuge by revising its Comprehensive Conservation Plan, which was created in 1994 and is long obsolete.