Beetles and pines: slipping out of balance

Nature is all about balance. If a certain population disappears from an ecosystem, other populations in the ecosystem will either grow due to a missing predator, or shrink due to a missing food source. The reverse is true as well: if a certain population soars, other populations will shrink due to an increase in predator levels. This phenomenon is happening in the western United States and Canada, where the mountain pine beetle has gone from reproducing once a year to twice a year, destroying pine trees at an epidemic level. As reported by the Environmental News Network in March 2012, this epidemic is believed to be the largest of its kind in the history of North America.

How do the beetles kill the trees? They lay their eggs under the tree’s bark and secrete a fungus to protect the eggs. While the fungus works to hasten the tree’s death in its own way, the eggs soon become larvae and immediately begin to feast away. In the past, this type of competition was not a significant problem because the beetles would lay eggs only in old and weakened trees, whose deaths would allow new trees to grow. Unfortunately for the trees, the beetles’ increased populations have forced them to use healthy trees, too.

So why have the pine beetles started reproducing bi-anually? It’s the same reason Dickinson has been sitting outside in March: nature is moved by the warmer temperatures coming earlier and earlier in the spring. (Climate change works in far-reaching ways.) As research from the University of Colorado, Boulder has shown, the pine beetles have started to fly earlier and are remaining in flight longer than they have in the past. This has created an unprecedented generation of adult beetles in August. Thanks to this population increase, the pine beetles have traveled farther north than usual and higher in elevation as well. If their influence continues to spread, the pine trees and other vulnerable species will be very severely impacted.

 

From: Emily Fineberg ’15
Published: April 1, 2012