Are Eucalyptus a desirable species in the California landscape?
According to one researcher: “Eucalyptus … creates the threat of desertification.”
[Nyerges is the author of “Guide to Wild Foods,” “Foraging California,” “How to Survive Anywhere,” and other books. He can be reached at Box 41834, Eagle Rock, CA 90041, or www.SchoolofSelf-Reliance.com.]
Eucalyptus has been in the news the last few weeks because naked protesters are unhappy with U.C. Berkeley’s plan to remove thousands of these Australian natives.
When I was growing up, we had a neighbor with a few eucalyptus trees in their backyard. I remember that nothing else grew in the back, around and under the eucalyptus tree. We boys liked to climb that tree, but the owners glumly told us that the huge tree was there when they moved to that house, and they could not afford to remove it.
Later, in high school, a schoolmate took me to see his many worm farms that he’d constructed in his large back yard. He showed me the tiny earthworms that grew in the worm farm under the eucalyptus trees. The worms that were raised on the other side of the yard had large normal-looking earthworms. This friend, Scott, also showed me carrots he’d grow on each side of his yard. The carrots under the eucalyptus trees had lots of ferny tops, but very tiny carrots. The carrots on the far side of the yard, away from the eucalyptus, were large normal-looking carrots. “Don’t grow things around eucalyptus,” Scott told me.
On a property governed by a local non-profit, I was once asked to plant bamboo on the property line. The property line was also planted in eucalyptus trees. Nothing grew well under those trees in some 40 years. I planted the bamboo, and watered it. It died, whereas other bamboo beyond the influence of the eucalyptus thrived like weeds.
These are just personal observations, though I have heard dozens of stories like this. What is the “bottom line” about eucalyptus?
Eucalyptus is a tree with a mixed reputation. This stately tree is renown for the “forest effect” due to the high transpiration rate of its leaves. According to one report, “In Sydney, a large gum tree [eucalyptus] transpires up to 200 litres of water a day. A well-maintained garden in Sydney will transpire nearly twice the volume of water as the total rainfall.”
The tree was included in my Guide to Wild Foods book since it was so useful in its native Australia by the Aboriginees: the leaves for various medicines (mostly upper bronchial issues), the bark for infections and many other uses, and even the little psyllid bugs can be harvested and eaten like a backwoods sugar. And the honey produced from eucalyptus flowers is a dark almost-medicinal honey.
But is it good for the California environment to remove the eucalyptus trees and replace them with natives? In fact, is being non-native the only reason that UC Berkeley wants to remove the trees?
In order to fully grasp the effects of eucalypti on the environment, let’s look at its effect in other parts of the world and the problems experienced there.
Eucalyptus is a fast-growing tree. When you cut them down, they will sprout right back up again. Because of this, there have been major plantations in various countries throughout the world from Europe to China to Africa in order to supply the wood for lumber, paper products, and firewood. If the eucalyptus trees are planted in non-agricultural areas where nothing else will grow, they survive quite well. A eucalyptus tree in a plantation can be cut as little as every four years.
Around the time that the U.S. was experiences long gas lines during the 1970s ”energy crisis,” many countries around the world discovered that the eucalyptus tree seemed like a miracle tree. It grew easily anywhere, and could be regularly harvested for fuel wood, building materials, and pulp for paper. It was also a financial boom to the public and private businesses in various countries who grew these plantations. Today, eucalyptus is one of the top trees planted in plantations around the world (pine is apparently the top tree). With so many undeniable benefits, what could go wrong?
Over the last 30 to 40 years, countless business, governmental, and academic studies have been done to weight the pros and cons of the largescale plantings of the eucalyptus tree. I’ve spent time over the last year reading these studies, and compiling hard data on the eucalyptus tree.
There were very real worries about deforestation and desertification that intensified in the 1980s. Eucalyptus, with its obvious economic benefits, were planted in ever-greater numbers. Today we can analyze the ecological effects of over 30 years of eucalyptus plantations.
For starters, there have actually been riots in protest of new eucalyptus plantings. Really, riots? In Northeast Thailand, most of the native forests had been completely logged by private companies, which affected the water, and forced local people to relocate. The Thai government, along with the World Bank, planted eucalyptus trees both as a cash crop, and so that local villagers would have fuel wood for their daily needs. However, it was noted that some results of the thousands of eucalyptus trees planted included lowering the water table for villages, drying up local wells, and making the farmable land less valuable due to the allelopathic effects of the eucalyptus leaves. When the Thai government began to grow even more eucalyptus plantations, villagers in the Tung Kula Ronghai section of Thailand, held meetings, marches, rallies, and they also blocked roads, burned eucalyptus nurseries, ripped out eucalyptus seedlings, and chopped down eucalyptus trees, and planted fruit trees.
Because the eucalyptus tree is such a great transpirer, it follows that it generally consumes far more water than other native or non-native trees. In fact, one of the stated reasons that eucalyptus is planted in certain countries is to dry up swamps and wet areas, either for development or because the wet area was believed to be a source of malaria. The deep roots of eucalyptus, and their extensive network of small surface roots, has been noted to extend deep to the water table.
Although a eucalyptus plantation does very well in dry areas where nothing else is growing, in areas as diverse as China, Ethiopia, Vietnam, etc, local villagers of these diverse places have noted that their water wells run dry. In fact, this seems to be one of the main objections to eucalyptus plantations: it dries up the local sources since it generally consumes more water than is received by rain in any given area, which then means there is far less water for agricultural crops and orchards. In the various studies about eucalyptus, it is always pointed out that the effects of eucalyptus on the water table can be minimized by carefully choosing the locations of the eucalyptus plantations, and by interspersing other forest trees with the eucalyptus. However, in practice, this has not been the case because it is also widely acknowledged that to get the greatest economic advantage from the eucalyptus trees, the eucalyptus are grown tightly in huge acreages, like a crop of corn.
In studies done to determine if the leaf drop from eucalyptus is "allelopathic" (exuding soil toxins), various plants grown in a mixture of eucalyptus mulch and soil have exhibited a germination rate as low as 3%, compared to normal rates of germination with an oak mulch. This means there is typically little or no undergrowth in the eucalyptus groves, and therefore there is a lack of food for grazing animals in the eucalyptus groves. Formerly, villages would be able to graze their animals in the forest and let them feed on the undergrowth, and even the leaves of the forest trees. But the eucalyptus leaves themselves are not eaten by grazing animals, which is good if you are growing the trees, but not good if you raise animals.
Another argument against the eucalyptus plantations is that there is a great depletion of soil nutrients. In general, eucapytus take up more nutrients (and water) from the soil than other native or non-native trees because they are fast-growing. And, in theory, if all the leafy matter was left on the ground (as opposed to cleaning it up), those nutrients would degrade and enrich the soil. But unfortunately, eucalyptus mulch takes a very long time to be degraded by bacteria and fungus due to its oils, and so in actual practice, the soils around eucalyptus tend to be very desert-like due to the unavailability of nutrients. [Source: The Effect of Eucalyptus and Oak Leaf Extract on California Native Plants, Kam Watson, UC Berkley]
This effect results in the lack of biodiversity and understory that is commonly observed under and around eucalyptus trees, in stark contrast to native forests.
One study was also done with soil under the eucalyptus trees, along with a soil sample not influenced by eucalyptus. Soil samples from under eucalyptus trees proved to be less able to absorb water. This meant that though eucalyptus trees have been planted in areas to reduce runoff and flooding, this result is not usually successful because of the effect of the tree’s oil on the soil.
These same results have been documented in eucalyptus plantations in China, Kenya, Ethiopia, Vietnam, and other sites.
Kenya Forest Service has published guidelines, basically aimed at promoting eucalyptus plantations in the country, called “A Guide to On-Farm Eucalyptus Growing in Kenya”, December 2009.
They advise not growing eucalyptus in wetlands and marshy areas, and riparian areas. They advise not growing eucalyptus closer than 30 meters from rivers, and ideally 50 meters, so that the trees do not adversely interfere with the water source.
They add that other areas where eucalyptus should not be planted include around lakes, ponds, swamps, estuary and any other body of standing water. They advice that eucalyptus not be plants closer than 50 meters to (about 55 feet) farm lands, and other measures. In other words, even those who are pro-eucalyptus recognize the adverse effects of eucalyptus on the environment, and offer ways to minimize those effects.
The study done of the eucalyptus effect in the Tung Kula Ronghai project in Thailand is somewhat typical of the relationship between local villagers and the various entities who run the eucalyptus “farms” (though, admittedly, every situation is unique). For example, in theory, the eucalyptus plantings are ideally done “where nothing else will grow,” though this is simply not always the case. In this project in Thailand, many of the “public lands” were occupied by poor people, who were evicted from the lands so that eucalyptus could be planted.
Remember, World Bank and other funds were provided with the stated intent of providing a cash crop, as well as providing daily fuel for the poorest of the poor. Though the former has materialized, the latter has not. Protests occurred when it became clear that eucalyptus forests did not solve villagers problems, and created new ones. It turned out that firewood from eucalyptus was not “free,” and it burned too fast compared to former forest woods. There was no benefit from the forest for grazing animals, areas for growing rice disappeared, and the benefits that were supposedly going to assist villagers went to the Thai government and to multi-national wood pulp industries.
By the way, according to Midgley and Pinyopu, “The Role of Eucalyptus in Local Development in the Emerging Economies of China, Vietnam, and Thailand,” there are nearly 10 million acres of eucalyptus under cultivation in the Asia region, which includes Bangladesh, China, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Pakistan, Phillipines, Sri Lanka, Thailand, and Vietnam.
Because of the kneejerk reaction to “plant trees” to help offset drought and desertification, some believe that any tree is acceptable to plant. Yet according to Shiva and Bandyopadhyay, “Ecological Audit of Eucalyptus Cultivation” (1987), the “complex multi-dimensional impacts on soil moisture and ground water, on the soil fertility; on other plant life and on soil fauna undermine potential of land for biological productivity. Eucalyptus cultivation therefore creates the threat of desertification.”
Obviously, the disputed eucalyptus trees in the Bay area were not planted to provide firewood for local San Francisco “villagers.” And they serve no purpose for a third world’s needed cash economy. They, in fact, serve no purpose at all, except their ease of care and growth, and their very subjective value of beauty . With so many negatives, and so few positives, why does anyone insist on keeping those trees?
U.C. Berkeley should proceed with the removal of eucalyptus trees on the lands under their control, and begin the long process of re-introducing natives, and the many benefits that will come therefrom.
If you have a single eucalyptus in your backyard, you will not likely experience any of the negative effects mentioned here. However, if you have 3 or more, close together, it is likely that you have noted that not much grows under these trees, and other plants struggle. What should you do?
You could remove the tree, use the wood for firewood, and plant something more suitable. Yes, large tree removal is expensive, and some local communities make funds available to help homeowners pay the cost. You could also try drying and selling the eucalyptus leaves to people who do not have them growing nearby. And you could make and sell walking sticks, and other carvings from this hard wood.
[The facts stated in this article come from over a dozen research papers; sources provided upon request]