The Eucalyptus—How Useful Is It?

BY AWAKE! WRITER IN AUSTRALIA

SOME are giants—over 300 feet [90 m] in height—ranked among the tallest in the world. Others are short and twisted, crouching low against the parched earth. Their leaves are a marvel of design, and their blossoms, a delight to the eye. In one way or another, you have likely used part of this tree yourself.

A few have aristocratic names such as alpine ash and Tasmanian oak, but most are just known as the common gum tree. Technically speaking, though, true gum is a water-soluble substance made of carbohydrates, and no eucalypti produce this. So the name gum tree is actually a misnomer. The trees are more correctly identified as the genus Eucalyptus, and there are over 600 members in this family of Australian natives.

Eucalypti thrive in the tropical heat of Australia’s Northern Territory as well as in the arid plains of the outback. But they also flourish in the Antarctic winds of southern Tasmania and the misty conditions of the coastal mountain ranges. So pervasive are they that one 19th-century explorer and zoologist complained: “We can never get beyond the sight of the eternal gum trees: there is not the slightest variation whatever in the foliage for mile after mile.”

Since the influx of European settlers to Australia in the 19th century, the eucalyptus has suffered heavy casualties. An estimated 100,000 square miles [300,000 sq km] of these trees have been torn out by the roots because the trees were considered a hindrance to progress. However, not everyone showed such scant regard for this valuable resource. During the 19th century, the eucalyptus family began their conquest of the world.

An Emperor, and a Doctor

In the 1880’s, Emperor Menelik II of Abyssinia, now called Ethiopia, needed shade trees and a ready source of firewood for his arid new capital city, Addis Ababa. No native tree of Africa was found suitable for this deforested area. The emperor’s experts therefore looked elsewhere to find a tree that was thriving under a scorching sun at least as harsh as their own. “Addis Ababa” means “New Flower,” and the name may have been given in honor of the eucalyptus, a useful import that came to play a vital role in Ethiopia’s economy.

Another man who contributed to the modern migration of the eucalyptus is Dr. Edmundo Navarro de Andrade. Determined to rebuild Brazil’s rapidly dwindling forests, in 1910 he started importing eucalypti from Australia. He was responsible for planting 38 million of them. Today there are more than two billion eucalypti under cultivation in Brazil.

Thus, in addition to its native rain forests, Brazil lays claim to the largest population of  eucalypti outside Australia. The benefits to Brazil’s economy have been such that for introducing this valuable asset to his country, Dr. Navarro was awarded a special medal for distinguished service.

A Tree of Life

Some eucalypti, such as the mallees, make the most of the drought-cracked earth by storing large quantities of water in their roots. Australian Aborigines and early explorers survived in the arid outback by exploiting these underground water bottles. Lengths of the surface roots were dug up and broken into short sections. When air is blown into one end of a section, pale-brown sap can be forced from it. While not the most palatable of beverages, it is estimated that 1.5 quarts of this lifesaving liquid can be extracted from a 30-foot [9-meter] root.

Other members of the family flourish in marshy conditions, greedily soaking up water from sodden soils. This talent was utilized by the Italians, who used swamp-loving eucalypti to help drain the once mosquito-infested Pontine marshlands. This area has now been transformed into valuable farmland.

More than 50 countries across Africa, the Americas, Asia, and Europe have adopted eucalypti for their commercial and aesthetic value. Furniture makers prize their rich-red and honey-gold timbers. One authority states: “The eucalypts produce some of the heaviest, hardest and most durable woods known. The quality of the timber, coupled with the rapid growth-rate . . . , makes this genus the most valuable source of hardwood in the world.”

Water-resistant varieties of the tree are used in the construction of ships, marine piers, telephone poles, fences, and paving blocks. In addition, beautiful gum-nut blossoms on varieties known as yellow box and ironbark produce sweet nectar, which bees convert into a particularly delicious honey. In recent years, 4.5 million tons of eucalyptus  wood chips have been exported from Australia, resulting in an income of $250 million annually.

Kino, Oil, and Tannin

A blood-red, gumlike substance called kino oozes from the bark and timber of the eucalyptus. Some types of kino are used to protect wood from shipworms. Kino is also employed in producing a drug that helps stop bleeding. The bark of other species yields tannin, used for the tanning of leather and the dyeing of fabrics.

The leaves are a marvel of design and a reservoir of valuable oil. They droop like listless fingers on a limp hand, their tips pointing to the base of the tree. This design helps the foliage act like a large funnel. Precious moisture is captured on the surface of the leaves, and then it drips from their leathery tips to the waiting root system.

Eucalyptus oil, which has a strong, invigorating aroma, is extracted from the leaf by a steaming and distilling process. It is used widely, for example, in perfumes, soaps, medicines, confectionery, and cleaning products. In its natural setting, the oil transpires from the leaf and fills the air with tiny droplets that refract the sunlight, giving the eucalyptus forest a characteristic blue hue. The Blue Mountains, which define the western extremity of the city of Sydney, were given their unusual name because of this phenomenon.

Home to Some Fussy Eaters

The most famous inhabitant of the eucalyptus forest is the adorable ball of fur known as the koala. This fastidious herbivore prefers to dine on the tips of 12 or so varieties of eucalyptus leaves. Such an exclusive diet would prove lethal to most animals but not the koala. Why not?

This is because of the koala’s specially designed digestive system, which includes an appendix that is six to eight feet [1 to 2 m] in length. By comparison, a human appendix is only three to six inches [8 to 15 cm] in length. The koala’s unique appendix allows the little animal to extract from this menu all the proteins, carbohydrates, and fats that it needs.

A less-known Australian native that shares the koala’s strict diet of eucalyptus leaves is the largest of the gliding opossums. This furry marsupial is about the size of a domestic cat. It has a shaggy tail about a foot and a half [40 cm] long and flaps of skin stretched between its front and rear paws. Utilizing these fleshy wings, an opossum will leap from a limb, glide for up to 100 yards [100 m], make 90-degree turns as it flies, and then safely grasp the next branch.

Bushfires and Regrowth

Bushfires, as they are known in Australia, are a threat to the eucalyptus forest. Yet, the trees are designed so that they survive them. How so?

Well, buried just below a tree’s bark, along its trunk and branches, are dormant leaf buds. When a tree is stripped of its bark and leaves by a fire, these buds spring to life. They clothe the blackened trunk of the tree with an overcoat of fresh green leaves. As a result, the parent tree is able to survive. Moreover, seeds of the tree lying dormant on the ground often seize the opportunity to germinate, resulting in new growth.

A Tree to Be Appreciated

Have you soothed your throat with a medicine extracted from the eucalyptus or savored a sweet made with eucalyptus honey? Have you been transported by a boat constructed with the tree’s timbers, or have you been housed or warmed by the wood of a eucalyptus? Chances are that in some way you have been benefited by this remarkable tree. So the next time you see a furry koala—or admire the photo of one—may it call to your mind the marvelous design of the tree that the koala calls home.

Indeed, the versatile, tenacious eucalyptus is a tree with many uses.

[Picture on page 16, 17]

 Eucalypti are ranked among the tallest trees in the world

[Picture on page 17]

Bees use eucalyptus nectar to produce exquisite honey

[Picture on page 18]

Eucalypti “produce some of the heaviest, hardest and most durable woods known”

[Pictures on page 18]

Koalas (left) and the gliding opossum (above) feed on eucalyptus leaves

[Credit Line]

© Alan Root/Okapia/PR

[Picture Credit Line on page 16]

Geoff Law/The Wilderness Society

[Picture Credit Line on page 17]

Courtesy of the Mount Annan Botanic Gardens