The truth is that you are not alone. A lot of misconceptions surround the environmental impacts of eucalyptus spp (blue gum or the gum tree). It is often claimed that large-scale eucalyptus farming causes environmental impacts.
Interestingly, however, a growing number of scientific studies on how eucalyptus species affect the environment present contradicting findings. In this blog post, I will summarize what studies say about the effects of large-scale eucalyptus farming on the environment.
Reference article: A Guide to On-Farm Eucalyptus Growing in Kenya
Eucalyptus and water use
It has been claimed that large-scale eucalyptus farming leads to the drying up of rivers, springs, and other water sources. However, studies (such as Munishi 2007), reported that eucalyptus requires less amount of water, compared to most tree species, to yield one kilogram of biomass. For example, while a typical eucalyptus tree will consume about 785L of water to produce 1kg of biomass, coffee, cotton, and bananas each require 3,200L whereas sorghum, potatoes, and maize require 1,000L for the same. Table 2 on page 11 demonstrates that eucalypts do not consume more water than other native forest tree species.
The Kenya Forest Service (KFS) has indicated that the effects of eucalyptus spp on the water budget are largely dependent on several factors such as soil and climate conditions, the nature of rock substratum, tree density, vegetative cover, amount of rainfall, tree growth stage, slope, and the type of eucalyptus species in question. Nevertheless, it is generally agreed that the growing of eucalyptus in dry areas may lead to adverse environmental effects because of eucalyptus’ high competition for water.
Eucalyptus and soil fertility
It is also argued that eucalyptus spp adversely affects soil fertility, especially in monoculture. Consistent with this claim, research shows that eucalypts can deplete soil nutrients rapidly when grown as a short rotation crop for high biomass production and removal.
Does that mean large-scale eucalyptus farming affects the environment more compared to other commercial crops? No.
Researchers have indicated that eucalyptus farmlands tend to exhibit a higher level of micronutrients than areas under some types of commercial crops like tea. In fact, it is reported that the long-term growth of eucalyptus enhances soil fertility and even restores the fertility of degraded soils in arid and semi-arid areas. The litterfall of eucalyptus also has net positive contributions to the fertility of degraded wastelands and hillsides where the tree exhibits good potential for topsoil retention.
The allelopathic effects of Eucalyptus spp
Large-scale eucalyptus tree farming has a positive effect on the environment in terms of what is called allelopathy. In fact, one of the most important findings on eucalyptus spp is that it exudates allelopathic chemicals.
These chemicals are known to hinder the regeneration of undergrowth. Because of this, eucalyptus can influence agricultural production. However, the allelopathic effects of eucalyptus on other crops are reversed by high rainfall.
Eucalyptus and bio-diversity conservation
Another claim regarding the environmental effects of large-scale eucalyptus farming is that eucalyptus plantations have limited biodiversity. While native plant advocates, however, are yet to provide scientific evidence to support this view, eucalyptus cultivation saves biodiversity in many ways. For instance, eucalyptus replaces indigenous species for fuel woods, timber, and numerous other uses.
Consequently, the growing of eucalyptus trees helps to prevent desertification and lower the destruction and degradation of natural forests. Furthermore, “Contrary to popular belief, many animals, both vertebrates and invertebrates, have adapted to life in the Eucalyptus groves,” Million Trees.