GROOVY GROVES NOT SO

UC San Diego is situated in a biodiversity hotspot; however, the eucalyptus trees towering over you come from the other side of the world. While native to Australia, today they can be found worldwide. In their nonnative habitats, eucalyptus trees are often used for windbreaks, ornamentally, and for economic proft. However, as with any invasive species, eucalyptus trees afect native animal and plant life in ecosystems globally, including here in La Jolla.

Why Are They Here?

Eucalyptus plantations are found in over 100 countries around the world. They were frst brought to the United States for timber during the Gold Rush when wood was scarce, according to Daniel Potter in a KQED article. These trees were used to manufacture wagons, carriages, railroad ties, and furniture, according to research by R. C. Kellison. However, Californians soon found that eucalyptus wood split and cracked easily, making it a poor choice for timber. The trees also had extensive roots that drained nearby wells. Even after discovering the shortcomings of eucalyptus wood, tree plantings increased in the early 1900s due to concerns of a timber famine. When the timber famine never came, farmers left eucalyptus as they were because they were not worth harvesting.

Eucalyptus populations increased due to government eforts as well. In 1870, the California State Board of Agriculture decided that human-planted eucalyptus forests for shade trees, timber, ointments, scented products, and bee pollination would be benefcial. By 1887, the State Board of Forestry became involved in the eucalyptus introduction program by establishing experiment stations to observe how eucalyptus trees would grow in California. This was in hopes to urge landowners to establish plantations; however, the board was disbanded in 1893 due to a hostile political climate of national debates over the merits of having a Federal forest reserve system, according to Mark V. Thornton, a consulting historian working for CAL FIRE. The introduction program was then left to the UC Berkeley College of Agriculture. Nearly a decade later, the many potential uses of eucalyptus trees for railroad spikes, furniture, and frewood led to a major expansion of the program to plant eucalyptus from 1905 to 1912. This expansion gave California the large forests of eucalyptus trees that are scattered around the state now, such as in La Jolla and San Francisco.

In La Jolla, eucalyptus trees were planted in 1911 by Torrey Pines forester Max Watson, who said that the eucalyptus “ofered [the land] the possibility of producing something,” according to Roger Anderson in the San Diego Reader in 1989. However, the poor quality of the wood ultimately made this venture unproftable too.

Ecological Impacts

Eucalyptus trees are very adaptable to new habitats, as they lack natural pests and are able to outcompete native plants. Existing animal and plant species are impacted by the introduction of eucalyptus trees in their habitats.

In addition to far-reaching root networks, the trees litter the ground with a detritus layer from shedding bark and leaves. This shedding prevents growth of native plants because the detritus “sufocates” new plant growth, according to the San Marcos Growers, a commercial wholesale nursery. In nonnative habitats, eucalyptus groves provide shelter to native animals. In Morro Bay, California there is a stand of eucalyptus trees that nest herons, cormorants,

WRITTEN BY: IAN HICKE

PHOTO BY: TOMMY MURPHY

A History Of Invasive Eucalyptus

and egrets as seen in a San Francisco Forest Alliance article. However, the bird biodiversity decreases in the presence of eucalyptus trees. A study done by Lucilene Jacobski compared bird populations in native habitats and plantations in Southern Brazil. The study showed that bird abundance was consistently more than double in native forests than in eucalyptus groves.

Eucalyptus also afects abiotic factors in the ecosystem. The high oil concentration in eucalyptus trees and its detritus can add fuel to dangerous fre conditions.

According to the National Park Service in 2006, the total fuel from eucalyptus calculated within Point Reyes National Seashore and Golden Gate National Recreation

Area is 30.84 tons per acre, compared to California Bay communities with 18.93 tons per acre and Coast Live Oak communities with 11.82 tons per acre. In the Oakland “Tunnel” Fire on October 20, 1991, known as the worst wildfre in California’s history, it was estimated that over 70 percent of the energy released through the combustion of vegetation was due to eucalyptus.

The Future of Eucalyptus

Some areas in San Diego have removed eucalyptus groves. At the San Diego Zoo, according to Roger Anderson, eucalyptus trees were initially used to immerse guests into a new environment; however, in 1989 more than 100 of those trees were removed to combat their competitiveness and invasive growth against other exotic species. Despite the negative impacts of eucalyptus trees, they are still planted and used worldwide. UC San Diego’s landscape sustainability worker, Chris Johnson, said that the university has a mandate to preserve the eucalyptus grove on campus because of its historical importance. This means that for every eucalyptus tree that is removed, a new one is planted somewhere else on campus.