Lynx, Bunnies, and Beetles: A Tale from Colorado’s Rio Grande National Forest

What are Canada lynx to do when a massive tree-killing spruce beetle outbreak dramatically alters nearly all their habitat? Keep having babies, it seems! When we recently visited the Rio Grande National Forest in southern Colorado, researchers from the U.S. Forest Service shared that they had just discovered a den of lynx kittens. This excellent news is evidence that the secretive forest cats are continuing to make a living on this national forest, even though their habitat is radically changing in the Southern Rockies.

The Return of the Lynx, and the Rise of the Spruce Beetle

The Canada lynx is listed as threatened under the Endangered Species Act in the lower 48 states. A few weeks ago, three of us Defenders made the trek to southern Colorado to learn about ongoing research on this imperiled cat and to get a better grasp of some complex dynamics in the Rio Grande National Forest.

Lynx live in this region’s high-elevation spruce- and subalpine fir-dominated forests. But a massive spruce beetle outbreak is killing mature trees throughout the area. In fact, the infestation is affecting a whopping 95 percent of the forest. We wanted to better understand what this could mean for lynx and their primary prey, the snowshoe hare.

Between 1999 and 2006, Colorado Parks and Wildlife reintroduced 218 lynx to the San Juan Mountains, the majority of them in the Rio Grande National Forest. Decades of hunting, trapping and habitat loss from human development had driven lynx to near extinction in the Southern Rockies. Fortunately, enough transplanted lynx remained within the San Juans to find mates, reproduce, and reestablish a population in the Southern Rockies. It was a huge step for lynx conservation in the U.S.

The beetle outbreak began in the late 2000s, and over the last five years, this national forest’s trees have been dying in droves. Spruce beetles are native to the region, and cycles of outbreaks and recovery have always been part of its natural history. However, climate change can tip the scales in the beetles’ favor, making outbreaks larger or recovery more difficult. Warmer temperatures enable the bugs to live year-round, for example, giving the forest little relief from the onslaught. Climate change combined with drought and other factors can lower a forest’s natural defenses and increase the potential for epidemic-level outbreaks.

Do Fewer Trees Mean Fewer Lynx? Not Necessarily

Some forest experts speculated that fewer live, mature trees meant the forest had become less valuable habitat for lynx, and that the animals must be leaving for other areas. However, preliminary results from a cooperative study by the Forest Service’s Rocky Mountain Research Station, Colorado Parks and Wildlife, the Rio Grande National Forest, and Montana State University indicate that lynx are still using beetle-impacted forests throughout the year, and females living there continue to reproduce. The cats may be able to persist in beetle-impacted spruce-fir forests until the trees have regrown and matured, and provide greater shelter and concealment preferred by snowshoe hares.

The key may be the forest understory: the small trees that were living under the large trees now have space and sunlight to grow. The national forest’s rapidly regenerating understory is likely creating suitable lynx habitat. Given that lynx have evolved with forest disturbances like the beetle outbreak, the animals may be adapted to these temporal recovery conditions.

New Science? Time for a New Plan

Our understanding of how lynx use forests following a beetle epidemic is evolving. When the science evolves, policies need to evolve with it – and that can be complicated.

The Forest Service has a number of policies that determine how it manages forestlands to support lynx recovery. But those policies were written when our understanding of healthy lynx habitat didn’t consider forests recovering from beetle epidemics. If you go by the current policy definition of lynx habitat, huge swaths of the Rio Grande National Forest have changed so much that they can’t be considered lynx habitat anymore. This discrepancy between older policy and newer science could have serious consequences on the ground.

For example, areas that no longer qualify as lynx habitat under current policy could instead be managed primarily for timber, even though we now know that lynx still use those areas to hunt for food or establish dens for their young. Without careful consideration, logging projects could disturb den sites, establish roads that fragment habitat, remove important foliage for snowshoe hares, and create clearings with too few trees (dead or alive), which lynx avoid.

Thankfully, we have a chance to correct this disconnect. The Rio Grande National Forest is revising its management plan, which governs activities like timber harvest. The planning process is an opportunity to update lynx conservation and habitat management based on the new research. Our team is working with lynx researchers, the Rio Grande National Forest, and other stakeholders to determine what the new lynx science means for the new Rio Grande forest plan. If emerging science shows that our understanding of lynx habitat is outdated, we need to modify the forest’s plan accordingly. Using this best available science will help ensure that the forest will provide the right kind of habitat and protections to help lynx continue to recover.