Nevada ? A butterfly found only at a popular Nevada recreation area is thriving and new efforts to protect its habitat are enough to keep it off the threatened or endangered species list, the U.S. Fish and Wildlife Service said.

“Our finding, after looking at all the available information and the conservation strategy being implemented, is that the threat of the species becoming extinct is no longer there,” Bob Williams, field supervisor of the agency’s Nevada office, said Wednesday.

Conservationists who sued in efforts to get protections for the Sand Mountain blue butterfly, said they would review the decision to determine their next move.

“We have a finding based on a conservation plan that is politically, rather than science-based,” said Karen Schambach of Public Employees for Environmental Responsibility.

In March, federal land managers closed dozens of off-road vehicle trails at the Sand Mountain Recreation Area, one of the largest sand dunes in the West, to protect the dune’s shrubs and the butterfly’s only known home.