You have probably encountered eucalyptus trees during a walk or drive and admired their distinctive scent and towering presence. In Lebanon, these trees have become a common sight, known for their impressive height and resilience. However, their presence here is largely due to historical interventions rather than natural occurrence, which in many cases is doing more harm than good.

Eucalyptus trees were introduced to Lebanon during the French Mandate period in the early 20th century. The French authorities planted these trees to control the malaria outbreak they inadvertently introduced. Malaria became a significant problem in Lebanon during the French Mandate. The French military and civilian presence, along with increased mobility and changes in land use, contributed to the spread of the disease. Malaria caused considerable health issues, prompting the French to seek effective measures to combat it, and planting eucalyptus trees was one of these strategies.

It might be surprising to some to learn that large areas in Beirut, such as Bourj Hammoud and surrounding areas, Ain el Remmene, and others, were once swamps prone to flooding. These conditions made them ideal breeding grounds for mosquitoes responsible for spreading malaria. The rationale was straightforward: eucalyptus trees, with their ability to tap into the nearest water source and transform it into bark, were ideal for draining marshy areas, thereby reducing mosquito breeding grounds.

Today, you can find extremely large and old eucalyptus trees across Lebanon, serving as living testaments to this historical intervention. These trees have become an integral part of the landscape in many parts of the country. In urban areas like Bourj Hammoud, their towering canopies provide much-needed shade, enhancing public spaces such as parks, sidewalks, and gardens.

While eucalyptus trees played a crucial role in combating malaria in early 20th century Lebanon and are famous for their medicinal purposes, they now contribute to the depletion of Lebanon's water resources and the decline of its native flora. Eucalyptus is a heavy water-consuming tree with extensive root systems that tap into deep groundwater, hoarding it for growth. This depletes soil moisture for other plants and severely affects groundwater supplies in both farms and urban areas.

The trees also produce a thick leaf litter that is slow to decompose, altering soil chemistry and inhibiting the growth of native plants. This can lead to a decline in local biodiversity, as eucalyptus groves create an environment that is less hospitable to other plant species. The chemical compounds in eucalyptus leaves can also have allelopathic effects, further suppressing the growth of surrounding vegetation.

Another concern is the fire hazard posed by eucalyptus trees. Their leaves and bark contain oils that are highly flammable, which can increase the risk and intensity of wildfires. In Lebanon’s dry seasons, this can be particularly dangerous, as fires can spread more rapidly and be more difficult to control.

It is also important to note that many farmers are fencing their lands with eucalyptus or using it for planting on borders without knowing the effects of their actions. Municipalities have a crucial role in managing the use of eucalyptus trees to mitigate potential downsides. This includes regulating where and how these trees are planted to prevent overuse of local water resources and ensuring biodiversity is maintained. By providing clear guidelines and educational materials, municipalities can help residents understand both the benefits and risks of eucalyptus trees, fostering a safer and more sustainable environment for all.