A Tale of Trouble -- Two Trees and Two Insects

Dead and dying Fraser Fir in Great Smoky Mountain National Park

One day as we were hiking in the Linville Falls area, we saw a team of National Park Service workers applying pesticide to the roots of many of the hemlock trees along the trail.  While we were in Great Smoky Mountain National Park we learned about the plight of both the hemlock tree and the Fraser fir all along the eastern mountain ranges.  Both trees are being attacked by different aphid-like insects that were accidentally brought in on imported plants from Asia.  So we thought this might be a great opportunity to learn more about what was being done to save the trees straight from those who are doing it.  Excited to learn more, we “treed” the park service guy nearest us.
 
Poor guy, he never had a chance.  But he was so nice and glad, I think, that we were interested in his work.  We talked a lot about what David and I had already learned from interpretive trails that we had walked and pamphlets we had read in the Smoky Mountains.  

Firs in trouble in a fragile environment

 The hemlock woolly adelgid is specific to the hemlock tree and the balsam woolly adelgid is attacking the Fraser firs.  Since these insects came from another continent and ecosystem, they have no enemies here in North America and are destroying both trees.  It is predicted that if no ‘control’ is found that the devastation will be worse than when we lost our eastern Chestnut forests to an imported fungal disease from Europe in the early 1900s. 
 
Terrible as it was losing the Chestnut tree, there were other hardwoods in the forest to help fill the niche and the forest as a whole still lived on.  That doesn’t mean the ecosystem didn’t suffer.  It is believed that black bears used to grow bigger and have more cubs in the days when there were chestnuts to fatten up on for the winter.  The squirrel population was larger and this supported more foxes, coyotes and other predators.  Countless other plants and animals were affected by the demise of the Chestnut trees.  Humans lost a beautiful and valuable wood and we have to roast European 'chestnuts over an open fire' these days.

Blow-down in a spruce-fir forest along the BRP

 
Hemlocks and firs are evergreens that provide shade and protect the delicate riparian areas and alpine plants that grow around them.  There are few other trees that can fill their place.  The Fraser fir habitat is especially precarious because it is an 'island' type ecosystem.  When the glaciers retreated thousands of years ago, the spruce-fir forests retreated back to Canada except for the little islands of forests left at the higher elevations.  Once the Fraser firs die they are easily blown down by high winds and very often spruce trees no longer protected by the fir are blown down with them.  Then large areas are open to harsh sunlight killing the shade loving plants, lichens and mosses that had thrived in the shade of the firs and spruce.  Consequently the animals that depend on these plants are now in peril. When a system that has evolved over time is disrupted, the consequences can be very far reaching.
 
Our national park service guy let us know that both the park service and the forest service were working hard to try to save as many trees as possible. The park service has been treating the hemlock with pesticide about every three years and this was keeping them alive.  Those hemlocks that hadn’t been treated were dead or dying.  The pesticide treatment being used is expensive and time consuming because the pesticide has to be injected into the ground around the tree roots (which is what the park service workers were doing when we saw them). Only the trees nearest trails or roads can be treated and the majority of the hemlocks are unreachable.  So they are fighting a losing battle.
 

Most of the spruce-fir forest on this ridge is gone

 

 

But there is a new plan underway to release another insect, a beetle from China that preys only on the hemlock woolly adelgid.  Extensive tests are being conducted to make sure this beetle will be safe to release here and won’t cause even more problems.  Our park service guy was somewhat skeptical and said that in the past most biological controls have been failures. But still there is great hope that this beetle will save the hemlocks.
 
As for the Fraser firs, many of them are becoming somewhat resistant to the balsam woolly adelgid and the forest service is working to breed resistant firs.  Over time it is hoped that these resistant trees will become dominant but by then the spruce-fir ecosystem may be too invaded with other kinds of plants to fully recover. 

Maybe some of the spruce-fir forests will become new balds?

 
It was fascinating to find out what is being done to save these two trees, how hard and complicated the fight is and just how much trouble and devastation two small insects could cause.  It also reinforced for us how complicated our life system is and how hard it is to know just what the consequences of any action will be.  And how familiar this story is becoming as insects, diseases, etc. travel the globe so  much more freely these days.

Change is inevitable...

Who knows what tomorrow's eastern spruce-fir forest will become?