The Michigan Daily identified the issue of a monorail being located in the Arb. See: Proposed transit route through Nichols Arboretum met with pushback from UMich and Ann Arbor community The information in the linked article confirms that the UM plans to move forward with the project.

The city-owned Arboretum Nature Area and Nichols Arboretum combine to make up the Arb. Boundaries of the two areas are visible on maps, but invisible when walking through the Arb. We ask the UM to identify a monorail route that is entirely outside the boundaries of the Arb, to retain the nature area that supports varied wildlife, plants, and people.