Friday, May 6, 2016

The Beetles' Invasion: A Tiny Terror for Forests

            Winter of 2015 has been one of the hottest winters on record for a significant portion of northern United States (1).  The warmer winter is likely a result of the increase in climate change caused by the emission of carbon dioxide into the atmosphere.  As a result from the warm winter, beetles have not been killed from the cold and have traveled north into Canada (1, 2).  Similarly, beetles are attacking forests worldwide such as Poland, China, and Nepal (3, 4, 5).  Beetles pose a significant threat to forests due to several forests dying off causing a huge environmental impact.  Beetles are a serious threat to the forest ecology because some of them are highly invasive while others are overfeeding due to densely packed forests and warmer conditions.
            Beetles are a severe problem for forests worldwide.  Beetles feed on the resins beneath the tree’s bark, which is one of the tree’s first defenses against predators, and make distinct S-shaped patterns below (2).  If the tree senses there are invaders, the tree will activate cell death, where the beetle is burrowing, releasing a toxin (2, 5).  In the meantime, the female beetle is feasting and laying eggs beneath the bark (5).  Although the toxin is enough to kill the female beetle and her offspring, if there are large swarms of beetles, the tree is certain to die (2).  Once the tree experiences death, the eggs will hatch into the larvae and they will continue to burrow during the winter until they grow to adulthood (5).  The cycle can then begin anew and infect several other trees, effectively killing the forest.  An infestation can be called an epidemic when at least one percent of the total growing population is afflicted (5).  An epidemic can easily wipe out an entire forest destroying both homes for several animals and renewable resources for people.
            Scientists have several explanations are to what is fueling the beetle invasion. Firstly, warmer temperatures and humid conditions have contributed to the increase of beetles (1, 2, 3, 4, 5).  The forest density being overcrowded is also lending for more trees to be infected (1, 2, 3, 4, 5).  Overcrowding is when there are too many trees all in a small amount of space which can allow for the transmission of disease and especially beetles to ravage the forest.  Tree health and age are other factors that allows for trees to be more susceptible (3, 4, 5).  Aside from the common explanations as noted above, “arid climate, strong winds, low rainfall, sparse vegetation” and human interference have created favorable conditions for species to survive and carry disease (4).  In addition, little attention has allowed the species to boom and quickly extinguish forests (3, 4).  A lack of natural enemies for both native and invasive species has also contributed to the tree death (5).
Mountain Pine Beetle
            Invasive species have been a significant issue for several forests.  These species choke out native species due to competition and a lack of predators.  The southern pine beetle is an invasive species that originated in southern United States (1).  Typically, the northeastern winters have kept the beetles at bay due to them not being able to survive a temperature of negative eight
degrees Fahrenheit (1, 2).  The beetles are closely related to the mountain pine beetle, which is also destroying forests in northern United States and even extending into Canada and the boreal forest (1, 2).  The mountain pine beetle is native to the United States but an invasive species for British Columbia.  The beetle is slowing gnawing its way through the forests and causing a great deal of damage to the timber industry in Canada (2). Since the 1990s, approximately 60 million acres of British Columbian forest has been destroyed by the mountain pine beetle (2).
            Not all beetles have been invasive.  In fact, a number of native species have drastically
Bird's eye view of Bialowieza Forest. 
The browned trees are attacked by beetles
increased and have been the culprit of tree death.  A primeval forest, the Bialowieza Forest, located on the border of Poland and Belarus, has been ravaged by the bark beetle which has chewed through several spruce trees affecting over 4,000 hectares (3).  Currently, people are petitioning to cut down affected trees to stop the spread of beetles, which is the worst infestation on record (3).  However, the forest is a national park barring the cutting of trees and local environmentalists are fiercely fighting against the petition (3).  There is also a beetle epidemic in China.  The Asian longhorned beetle is one of the most destructive species of beetle has destroyed 80% of poplar stands planted in the Three North region of China (4). Sadly, the life of the poplar stand was slashed to a ten year average in areas infested with the Asian longhorned beetle (4).  Finally, in Nepal, the heartwood borer has been attacking Sal trees (5).  Despite being a native species, Nepal’s forests are on the decline (5).
 There are several proposed ideas in order to remedy the beetle epidemic. Firstly, cutting down infected trees would prevent the beetles from moving to another tree.  In addition, thinning the forest will reduce the amount of spaces the beetles can spread to and less competition increase the health of the forest (3, 5). China has suggested using biopesticides to control the beetles without harming the forest and pheromones to deter the beetles from finding potential trees (3). 
Beetles are pose a serious threat to the health of forests worldwide.  The increase in temperature, humidity, and overcrowded forests created conditions for beetles to thrive.  In doing so, forests around the world are declining.  However, there are conservation possibilities to control beetles from feasting on forests.  Although there is a looming invasion for the US, efforts are being made to save the forests.


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