The Joshua tree is cherished for its distinctive silhouette and singular role as a linchpin of the Mojave Desert ecosystem. Yet the iconic succulent is losing suitable habitat at a brisk clip due to climate change, worsening wildfires and development, scientists and environmental advocates say. A new plan by the California Department of Fish and Wildlife to ensure the Joshua tree’s survival calls for limiting development in certain areas, including those where the plant may be able to thrive in a future anticipated to be warmer and drier, even as other portions of its range become uninhabitable. The draft plan also calls on government agencies to develop strategies to mitigate and fight wildfires that threaten Joshua trees.