20 Jan Where did all this eucalyptus come from?

Deep in the hills of Tennessee Valley, a camphorous scent fills the air near a small pond: a beautiful site to view but underneath the beauty lies several ecological problems. This small pond is a hopeful habitat spot for California Red-Legged Frogs (CRLF). In past years Red-legged frogs have not been found breeding in this area due to unknown reasons. In order to make this area a more suitable habitat for the frogs, an idea to remove several tall eucalyptus trees (Eucalyptus globulus) near the pond in order to illuminate the currently shady pond was put into place. Upon measuring the trees that needed to be removed, I began to wonder how these non-native trees got to California, how their allelopathic properties affect the land and water around them, and if these trees affect the pond in more ways than just the shade that they cast? 

Eucalyptus introduction to California

In the late 1840s and the early 1850s, the California Gold Rush was occurring, which meant high demand for wood to help with the construction of new buildings and for fuel. Concern of serious deforestation grew with the demand for wood and entrepreneurs rushed to find a new solution to help fuel the economic growth. By the 1870s several individuals advocated for the use of fast growing eucalyptus trees for its aesthetically pleasing appearance, and its useful properties. By the early 1900s, hundreds of acres of eucalyptus trees were planted in California by many companies in hopes of gaining a large profit from the trees’ potential uses. To the disappointment of many California-based eucalyptus businesses, it was found that young trees were unsuitable for timber. More disappointment occurred when it was discovered that the oils from Eucalyptus globulus were not as high quality as Australian-based eucalyptus trees. Their hope to sell the trees as fuel crashed when the primary source of fuel shifted from wood to electricity and gas and ultimately the trees became no longer profitable as fuel. Due to this aspiring business market these resilient fast growing trees can be found all over California today. 

Ecological effects

It’s unfortunate that eucalyptus trees were intentionally planted for their economic potential only to find out that their usefulness was not well thought out. While these trees were not economically prosperous, how does this non-native species ecologically affect the environment around it? It is widely considered that Eucalyptus trees are allelopathic, which means the trees carry chemicals in their roots, leaves, and stems that act as a natural herbicide. This can lead to a great decrease or complete lack of plant growth under the tree. Another ecological effect is that since California animals are not adapted to process the toxins contained in eucalyptus trees, very little birds, mammals, bugs, etc, choose to make eucalyptus groves their home. These two ecological effects combined can cause little diversity in eucalyptus populated areas. It is also found that the bark strips are extremely flammable and can lead to intense fires. 

While I didn’t find answers to all my questions, I learned a lot about this common California tree, that I knew nothing about prior to this internship. I’m excited to see how the removal of some of these trees affect the pond, and to find out if lack of sunlight is the only thing affecting CRLFs presence there. Could the allelopathic leaves that fall into the pond affect water quality or the pond’s productivity? Perhaps a study could be done to test this hypothesis if the frogs don’t return to the pond with the sun. 

As always, miigwech for reading, and see you next time!