MARBLEHEAD – The Marblehead Conservancy has permission to cut back some unwanted plants on two main walking trails next to Seaside Park.Those who have attended ball games and other events on the Atlantic Avenue athletic field next to the Star of the Sea Community Center may be unaware that the entire park area is about 34 acres, including 20 acres of forest behind the ballpark, all of it controlled by the Recreation and Parks Commission.Acting on a request from Donald Morgan of the Marblehead Conservancy Trails Committee, commission members voted unanimously Tuesday to allow committee volunteers to work on the Seaside Cliffs and Crow Fly trails in the forest area.The vote was 3-0, with the request favored by Derek Norcross, Linda Rice Collins and Charles "Chip" Osborne.Conservancy volunteers will clear invasive plants – Oriental bittersweet, multiflora rose and Norway maple, among others – from town-owned land along the two trails, starting in October. They will also trim other plants along the trails to make them more comfortable and tick-proof.Morgan said the invasive plants that will be removed have the potential ability to kill trees and other plants. The Conservancy has cared for five miles of Marblehead trails so far, at no cost to the town.Once the major projects are completed, Morgan said the Conservancy also wants to repair erosion damage to the trails, regrade them and reroute them if needed, cut fallen limbs if they represent a danger, remove off-trail invasive plants, improve harbor views and trail signs, restore a small pond and maintain plant screening to improve privacy for homes and walkers."We want people to know that the trail does not run though someone’s back yard," Morgan said.