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]