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Endangered Species: The butternut tree

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Cheryl Santa Maria
Digital Reporter

Thursday, October 17, 2013, 1:30 PM -

The butternut tree can be found throughout central and eastern North America. In normal conditions, this species has a typical lifespan of 100-150 years, but today, many North American butternut trees only live for a decade or so, due to an imported fungal disease called the butternut canker.

Experts estimate that it has reduced this species' population by nearly 80 percent.

There is no cure, and every tree that is infected will eventually die.

Cankers enter the tree through openings in the bark, cutting off the flow of nutrients. Spores are carried down the tree through rain, resulting in several infection sites.

The disease is believed to have started in Wisconsin in the mid-1960s and spread outward slowly. The butternut tree "has become endangered because of a virus that was imported from the other side of the ocean," explains Tys Theysmeyer, Head of Natural Lands at the Royal Botanical Gardens in Burlington, Ontario.

"This isn't unusual: When something is imported across the ocean and it affects species on the other side, [but] it’s never intentional."

A relative of the walnut tree, butternuts are medium-sized trees that can reach a top height of 30 metres. Younger trees have smooth, grey bark that ridges with age. Different versions of the butternut tree can be found in other parts of the world, but the North American variety is best recognized by its almost tropical-looking leaves, which are almost 2 feet in length and arranged in a feather-like pattern.

You're likely to find butternut trees around a forest's edge, or in a well-lit space. Its fruit contains a single seed surrounded by an olive green, fuzzy husk, and it produces a nut early in the fall season.

"It's considered a cash crop tree because the nuts are edible and they ripen a bit earlier in the season than a lot of the other nut trees. For wildlife, the butternut provides one of the first good treats of the season," Theysmeyer says.

"Just like other nut trees and berry trees very valuable in the environment."


RELATED: Learn about the American chestnut, another endangered tree species in Canada


SAVING THE BUTTERNUT TREE

While most butternut trees have fallen victim to the canker disease, a small number have resisted infection. 

Experts hope that canker-resistant tree will be used to propagate the future of this species. Right now, wildlife experts are in the process of identifying butternut trees, in search of healthy ones.

It's a painstaking process: south of Ontario, about 95% of this species has been wiped out.

And there are other snags along the way. For one, butternut trees from other parts of the world are immune to the disease, and they bear a close resemblance to their North American relative.

"People will often have butternut trees in their yard because they were once extremely common, and if you have a healthy one the bark will look smooth and grey and won't have any blisters or cankers on it -- But there is a challenge associated with this," Theysmeyer says.

"Just like every species, there are versions of this tree on the other side of the ocean. If a number of those have been introduced into North America, you’ll run into situations where think you have a healthy North American butternut tree, but it’s actually a version from elsewhere in the world." 

WHAT YOU CAN DO TO HELP

  • Ontario residents can report butternut tree sightings to the National Heritage Information Centre
  • If you have a healthy butternut tree on your property, you may be eligible to apply for a stewardship program that supports the recovery of this species.  
  • Report any unauthorized logging, defacement or other illegal activities surrounding butternut trees to 1-877-TIPS-MNR (847-7667)

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