Researchers: Focus policy to better control redcedar invasion

Eastern redcedars | Courtesy Christine Bielski
Eastern redcedars | Courtesy Christine Bielski

The invasive spread of eastern redcedar across Nebraska will continue as long as policy is mismatched with known science, University of Nebraska-Lincoln researchers have found. Without resolving the disconnect, grasslands will keep transitioning into cedar woodlands, a detriment to the state’s ecosystem services.

“We know redcedar causes a lot of problems,” said Caleb Roberts, lead author on the study recently published in PLoS ONE and applied ecology graduate student at Nebraska. “But our management hasn’t caught up with it.”

Eastern redcedar has been identified as one of the major threats to Nebraska’s natural resources by the state-mandated Nebraska Invasive Species Advisory Council. Yet the researchers found state and federal agencies promoted eastern redcedar — planting 850,000 per year in Nebraska between 1925 and 2001, and 310,000 annually thereafter — while, at the same time, providing financial incentives to remove it.

This “doublethink” often is driven by opposing user needs, Roberts said, but also because science and policy have not yet identified how to handle native species valuable in some uses but invasive in others. Eastern redcedar, for example, serves well as a windbreak, but when unmanaged, overtakes and wipes out entire grassland areas, removes wildlife habitat, increases wildfire risk, and collapses profitability of grass-fed beef enterprises.

“Prevention is the key to effectively deal with invasive species,” said Dirac Twidwell, assistant professor at the Department of Agronomy and Horticulture, who has studied juniper invasions across states in the Great Plains for more than a decade. “Policy for eastern redcedar has never addressed this issue, causing agencies to underinvest when the problem was preventable and overinvest later on to attempt to restore what was lost. There are no examples where this mentality has worked long term for eastern redcedar.”

In their study, the researchers examined three regions listed as priority for grassland conservation in Nebraska, which included the Sandhills, and analyzed eastern redcedar groundcover as well as the land management policies in place. They found eastern redcedar was planted and spread to regions where it used to be absent or rare, and that control measures were not put into place until the tree was rapidly expanding into grassland environments.

Prevention was not included in any of the policies.

“This is an example of how the actions of managers with seemingly similar goals, can contradict each other and lead to perverse outcomes,” said Craig Allen, director of the Nebraska Cooperative Fish and Wildlife Research Unit at the School of Natural Resources. “This policy assessment demon-strates how and why this can happen, and the consequences at risk for natural resources.”

To address the issue, the researchers made two recommendations:

  • Look to the Sage Grouse Initiative, a federally backed multi-state partnership, as an example. The group recently adopted new guidelines that incentivized control of eastern redcedar at earlier stages of invasion. Science has proven this approach is more cost effective and better at preventing adverse consequences of invasive species.
  • Follow the federal guidelines set for non-native invasive species. The policy requires agen-cies to minimize risks posed by invaders and only facilitate their use when they have de-termined that the benefits clearly outweigh potential damages.

“Nebraska’s grasslands are on the front lines of shifts from grasslands to juniper woodlands,” Roberts said. “We can possibly avert it if we match the policy with the science. We have a chance if we act quickly to make a difference.”

Roberts is a graduate student with the Department of Agronomy and Horticulture and the School of Natural Resources at Nebraska. Co-authors include Dan Uden, researcher with the Nebraska Fish and Wildlife Cooperative Unit at SNR; Craig Allen, director of the COOP unit; and Dirac Twidwell, assistant professor within the Department of Agronomy and Horticulture.

Writer: Shawna Richter-Ryerson, Natural Resources