Glossy buckthorn leaves are shown in an undated, handout photo. Teams of volunteers with the Nature Conservancy of Canada will fan out in a Nova Scotia forest on Sunday armed with saws and clippers to hack down thousands of glossy buckthorn trees, an invasive species that is crowding out native trees in protected lands along the Northumberland Strait. THE CANADIAN PRESS/ho-Nature Conservancy of Canada

PUGWASH, N.S. - They usually busy themselves planting trees, doing bird surveys or building hiking trails.

But on Sunday, a small army of volunteers with the Nature Conservancy of Canada will fan out through a Nova Scotia forest to take down 5,000 pesky trees.

Bearing handsaws and clippers, the group is going after the glossy buckthorn, a pretty but pernicious shrub that threatens to crowd out native species in the Pugwash estuary.

"It sounds really unusual for a nature group to be ripping trees out of the forest, but that's exactly what we're going to be doing," Andrew Holland, a spokesman for the group, said with a laugh.

"We call it the glossy buckthorn beatdown!"

The group is trying to remove as many of the trees as possible to protect native species in a large tract of land along the Pugwash River that the conservancy owns.

Holland said the invasive species arrived more than a century ago from Europe and can grow up to seven metres tall and change the natural native habitat. The shrub is spread by birds, who pick up and distribute its seeds, so Holland said trying to contain the aggressive growth is an ongoing battle.

"The real issue is that it outcompetes native plants and trees in the area and it can crowd them out for water and for sunlight," he said.

"It's just not healthy for that natural landscape."

The group will tackle two parcels of land in the Pugwash estuary, where it owns and manages 405 hectares of land. Holland said it is a key area for migratory birds and ducks, and is one of the largest protected areas on the Nova Scotia side of the estuary.

They will cut down the trees or rip them out, and spray the stumps with a herbicide.

When glossy buckthorn is young, it often has multiple stems that merge into a tree trunk that can be up to 20 centimetres across. Its leaves are oval and slightly wavy, shiny on top and hairy underneath. The bark on older branches is grey-brown, speckled with white dot and it produces greenish white flowers.

Glossy buckthorn's range extends from western Manitoba to eastern Nova Scotia, and as far south as Minnesota, Illinois, New Jersey and Tennessee.

This is the fifth year the group has held the event, which has already attracted more than a dozen volunteers. It removed about 5,000 stems of glossy buckthorn in June 2014.

"We're going to try to take back the forest," Holland said.

— By Alison Auld in Halifax.

News from © The Canadian Press, 2015