Environmental Impacts of Eucalyptus

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Last Updated on February 7, 2021 by Naeem Javid Muhammad Hassani

General Introduction

Eucalyptus spp belongs to family Myrtaceae which is a diverse genus of trees (rarely shrubs) are a member of which dominate the tree flora of Australia. It is an enormous and fascinating genus, comprises over 700-800 species. The Name Eucalyptus is derived from two Greek words “Eu” meaning “well” and “Kalypto” “I cover”, it is essentially Austro-Malayan trees mesh a natural latitudinal range extending from 7 to 43 N – 39 S.

They populate almost every habitat from high snowy mountains to arid deserts to tropical rainforests. Nearly all species of Eucalyptus go through a change (which may be abrupt or gradual) from juvenile foliage, which is often round and stem-clasping, to distinctly different mature foliage, which is usually long and willowy.

Not all eucalyptus species go through this foliage change in the same time frame or manner, and several different species planted together can make for quite a variety of foliage when the plants are young.

Many Eucalyptuses have showy flowers, but the majority of these are the more cold tender species from the desert or subtropical regions. Unless otherwise mentioned, most of them have white or cream flowers. Most species flower after about three to six years of growth. For example, E. gunnii can flower in three years and E. perriniana has been known to flower in as little as two years. Though some species flower unpredictably at various seasons, some will predictably flower at certain times of the year. This varies for each species, but quite a few of them bloom in the spring. Some of them even flower in the winter.

Much research has been conducted on the medicinal properties of Eucalyptus spp. Of the different species, E. globulus has been
the most widely studied. Eucalyptus is used to treat many human ailments and some livestock ailments. Eucalyptus extracts, oils, or fresh leaves are used in steam inhalation treatments, consumed in teas, or used in bathing.

Another application, that may be of interest to livestock producers, is as a treatment for ectoparasites and non-specific skin infections.

E. globules is one of the most important species of Eucalyptus. The quantity of essential oil ranges from less than 1.5 to over 3.5%. On average, between 70 and 95% of the oil is 1,8-cineole (eucalyptusol). The essential oil from the fruit, buds, and branches contain from 15-57% 1,8-cineole. Activities contributed to this compound include: anaesthetic, antibronchitic, antiseptic, choleretic, fungicide, hepatotonic, herbicide, hypotensive, pesticide, and sedative.

Common Names

• Blue Gum tree
• Eucalipto
• Eucalyptus
• Eucalyptus
• Fever tree
• Lemon Eucalyptus
• Okaliptus
• Silver-leaf Ironbark

E. camaldulensis essential oil (from the leaves) ranges from less than 1 to over 2%. The quantity of 1, 8-cineole in the oil ranges from 15-78%. Other compounds in the leaves include:

Betulinic acid
• Eucalyptusic and eucalyptusolic acid
• Oleanolic acid
• Ursolic acid Glycosides.

Eucalyptus spp. contain high levels of phenolics and terpenoids which can be toxic. As with toxicity, the efficacy of eucalyptus oils and extracts is most likely dependent on their chemical composition. In general, oils from Eucalyptus spp. have antimicrobial properties.

Several adverse reactions have been attributed to the use of or contact with Eucalyptus oils, extracts, and fresh and processed plant material. Some of the specific compounds that can be toxic or cause adverse reactions include: 1,8cineole, cyanogenic glycosides, rutin, and tannins.

Two studies which tested the oils from several species showed that E. citriodora had the most antimicrobial activity.

Other studies have demonstrated that the oil and leaf extracts of Eucalyptus spp. have antifungal and repellent activity.

Overdoses of the oil in humans cause gastro-intestinal burning, abdominal pain, vomiting, and convulsions, depress respiration and the central nervous system, and may lead to comas and death.

It is unfortunate that eucalyptus is commonly regarded as not being reliably hardy outside of the subtropics because it discourages people from planting them in cooler areas. There are many reasons to plant a euc – to begin with, they help to control aphids and other insects, most of them will grow rapidly even in poor soil (12′ per year is not out of the question), and most of them are very attractive–eucs have a unique beauty all their own. And eucalyptus foliage, which shows incredible variety, is excellent for cut foliage in floral arrangements.

Background and History of Eucalyptus

Although eucalyptus must have been seen by the very early European explorers and collectors, no botanical collections of them are known to have been made until 1770 when Joseph Banks and Daniel Solander arrived at Botany Bay with James Cook. There they collected specimens of E. gummifera and later, near the Endeavour River in northern Queen Island, they collected E. platyphylla; neither of these species was named as such at the time.

Between 1788 and the beginning of the nineteenth century several more species of Eucalyptus were named and published. They include the economically valuable E. pilularis, E. saligna and E. tereticornis.

The nineteenth century was a period of extensive land exploration. This resulted in the discovery of many new eucalyptus and their subsequent naming by several of the great botanists in Australian history, particularly Ferdinand von Mueller, whose work on eucalyptus contributed greatly.

In 2000, the senior author of EUCLID, published a formal classification of the genus, which is a synthesis in the form of an updated taxonomy to accommodate the numerous species of Eucalyptus.

History of Eucalyptus in Asia

Eucalyptus has long history in Asia. It was first planted around 1790 by Tipu Sultan, the ruler of Mysore, in his palace garden on Nandi hills near Bangalore. According to one version he received seed from Australia and introduced about 16 species.

It is reported that during 1954-55, herbarium specimens of eucalyptus tree grown at Nandi hills were sent to Australia and identified as E. camaldulensis,
E. citriodora, E.crebra, E.major, E.tereticornis
and hybrid E.robusta x E.tereticornis etc. Until the 19th century, small blocks of plantations were raised, often for experimental purposes.

Present Situation of Eucalyptus Plantation

The most important characteristics of E. hybrid contributing to its popularity under ASIAN conditions are: it is fast-growing, capable of overtopping weeds, coppices well, is fire hardy, browse resistant and it has the ability to adapt to a wide range of edaphoclimatic conditions. . There are several reasons for raising large scale eucalyptus plantations in the country; some are common and some are specific to each State. The most important common reason is to reclothe the denuded and barren hilly areas and replace low-value natural forests (FAO, 1979).

The policy of converting low-value natural forests into plantations was aimed at improving productivity and to generate government revenue. Some of the States took advantage of the centrally sponsored scheme of raising fast-growing species initiated during the 1960s and raised eucalyptus plantations by clear-felling even the Moist Deciduous forests.

Eucalyptus plantations were also raised to bridge the gap between the demand and supply of pulpwood created as a result of gregarious flowering of bamboo. The pulpwood shortage created the need for quick-growing species. The biggest single urge to plant eucalyptus in large scale plantations was provided by the demand for wood fibre for the industry.

Eucalyptus plantations were also raised under State and centrally sponsored schemes to meet the demands of local people in respect of the requirement of firewood, small timber, poles etc. Eucalyptus was also accepted as a good farm forestry species for planting on field bunds, canal sides and in marginal agricultural lands. In most states, the Forest Departments had schemes providing free supply of seedlings of various species, including eucalyptus. The success of eucalyptus both for regenerating degraded forest and wastelands made it more valuable.

Some States have encouraged pulp and paper industries to raise their own captive plantations by leasing degraded forests and Government wastelands, the industries should obtain their raw material from farm forest areas. The wood industries are encouraging farmers to raise trees in their lands by giving incentives.

Ecological Effects of Eucalyptus on Environment

Effect on Soil Fertility

The natural forest cover protects the soil from wind and water erosion. It also builds and maintains soil texture and nutrients. This is facilitated by the
decomposition of plant matter by microorganisms, which increase soil fertility. However, one of the allegations levelled against eucalyptus is that it depletes the soil rendering it unfit for any future productive use and depletion of nutrients and allelopathy caused by the litter, which is said to exert an antibiotic effect on soil microorganisms. This concern was verified by research that showed a very low concentration of nitrifying bacteria in eucalyptus plantations litter (Florenzano 1956).

However, many of the litter problems can be alleviated by alternating rotation or mixing species and clones to promote decomposition. An extensive literature review demonstrated that afforestation with eucalyptus improved soil fertility in the long term in several areas of the world. Eucalyptus plantations are also sometimes accused of not providing adequate soil protection. This lack of protection can lead to less water infiltration and greater runoff, resulting in soil erosion and watershed sedimentation.

A comprehensive study was undertaken to analyze the effects of the short rotation eucalyptus plantations on soil properties in 8- to 10-year-old Eucalyptus grandis stands established on lateritic and sandy soils. Samples of soils were collected at varying depths of up to 0.60 m on eucalyptus plantations as well as on a nearby savanna-like stand. Chemical, physical, and biological analysis of the soil samples showed no statistically significant differences between eucalyptus and savanna soils.

Another experiment was made to examine the impact of a 33-year plantation of Eucalyptus camaldulensis on an alluvial soil by comparing the soil under the plantation with similar soil under an adjoining native savanna woodland dominated by Acacia karoo. Soil clay content was significantly higher in the plantation soil in both the 0-10 cm and 10-20 cm layers. There were no significant differences between soil under the two ecosystems with respect to the levels of organic matter, exchangeable potassium and available phosphorus.

Despite the higher clay contents of the plantation soil, exchangeable calcium and magnesium and pH were higher in soil under the native woodland. This suggests that E. camaldulensis immobilizes soil nutrients faster and that plantation nutrient cycles are less efficient than in the native Acacia woodland. Consequently, soil nutrient deficiency will limit plantation productivity after the first few rotations. It is important to adopt tree harvesting techniques that reduce the drain on soil nutrients at the end of a plantation rotation.

Effect of Eucalyptus on Groundwater

The other primary concern about Eucalyptus plantation is that its large scale planting has caused concern to many people as they thought it would have adverse environmental impacts particularly in relation to nutrient depletion and high water use. Eucalyptus plantations lead to a diminished rainfall in their area of influence.

During the survey, the farmers claimed that Eucalyptus has badly affected the groundwater as it is water-intensive, and reduces water availability for other species, effectively out-competing them and they should be removed immediately. The impact of Eucalyptus is so severe on rivers, streams and catchments in some areas that rivers and other streams have witnessed a serious drop in their volume due to the rampant cultivation of Eucalyptus around their sources and at their course.

Some of these streams now dry up completely during the dry season. A high volume of water can only be registered in the rainy season especially in July. August and September, when the rainfall is at its peak.

Eucalyptus requires much water for its growth and the ability to get this water is facilitated by its taproot system. It is generally known that the planting and maintenance of trees on catchment areas reduce excessive evaporation and run-off.

This ensures a constant flow of water and prevents seasonal dry up. Eucalyptus cover equally favours infiltration of water down to the water table but its ability to suck up this water neutralizes everything. In order to avoid the problem of water shortages, researchers advise “Eucalyptus trees should be planted at least 500m away from watersheds, streams and rivers”.

In Tatum for example, during the dry season people encounter the problem of water shortage and travel far into valleys to carry unclean water. This shortage of water is because a lot of Eucalyptus has been planted around water catchments areas over the years. This same problem is experienced also in another part of NKUM.

These areas with pipe born water, suffer a lot during the dry season. In areas where there is no pipe born water, these problems are more serious. This shortage of water during the dry season negatively affects the socioeconomic activities such as brick moulding, house construction, public health and vegetable gardening and can you imagine, each eucalyptus tree consumes 300 litres of water, how can you allow such a waste of water. If this falling water table is not checked with the help of various measures, there will be a crisis in terms of drinking water 20-years later.

However, the population is already aware of the dangers of Eucalyptus and has started felling trees around catchments areas. Non Governmental Organisations (NGOs) like Strategic Humanitarian Services (SHUMAS), Citizen Development International (C.D.I.) respectively are educating the population on the harmful effects of Eucalyptus. A number of studies have been undertaken in various sites on the water use of eucalyptus but none of the findings is conclusive.

The recent findings of the collaborative research taken up between KFD, the Institute of Hydrology (UK) and the Mysore Paper Mills are interesting. The studies were carried out in areas receiving 800 mm average annual rainfall. The summary of the findings are:

• At the site, the water use by young eucalyptus plantation was no greater than that of the indigenous Dry Deciduous forest;
• At sites, annual water use of eucalyptus and the indigenous forest was equal to the annual rainfall (within the experimental measurement uncertainty of about 10%);
• At all sites, the water use of forests was higher than the agriculture crops.
• At the site, there are indications that water use over three dry years of measurement was greater than the rainfall. (Model estimates of evaporation
was 3,400 mm as compared 2,100 mm of rainfall.); and At none of the sites was there any indication of roots taking water directly from the water table.

From the literature review, it is clear that in natural environments the components of the hydrological system are rainfall, evapotranspiration, change in soil-water storage and drainage, are (on average) in balance.

The claim that plantations may lead to desertification is not substantiated, though ultimately such a process is more concerned with human agency, rather than an intrinsic feature of the genus.

Effect of Eucalyptus on Biodiversity

Fauna

There is an impression that eucalyptus and wildlife do not go together. While it is true that the natural forest is a better habitat for wildlife, eucalyptus plantations also support wildlife. Birds which are adaptable, still harbour in eucalyptus plantations. One example of Karnataka will indicate that eucalyptus plantations are not as sterile and unsuitable for wildlife as they have been considered to be.

The habitat of the Blackbuck in Ranebennur, Karnataka is eucalyptus plantation with sparse and bushy undergrowth. The habitat for Blackbuck requires open, Savanah areas. Since eucalyptus plantations were raised in Ranebennur during the ’60s, the Blackbuck population (which was scattered in small pockets due to loss of habitat) came to this newly created habitat of eucalyptus plantations.

The population has steadily increased, from nearly 900 around 1960 to over 3,000 during the mid ’80s, and it seems to have stabilized at that. The eucalyptus plantation in Ranebennur is also the habitat of the Great Indian Bustard which is an endangered species. There is a need to study the adaptability of animals and birds to the new habitats created by these plantations. One of the major problems related to short-rotation eucalyptus plantations and animal populations has to do with species that require habitat that consists of old trees or mature forests. Three actions have been suggested to help to alleviate this problem:

  1. leave some trees in the plantation at the time of harvesting,
  2. extend the rotation period, and
  3. leave natural vegetation intermixed with the short-rotation plantations (Loyin 1985).

One of the criticisms of eucalyptus in Pakistan is, being an exotic species, it does not provide shelter and food for the native fauna. This is probably true not only for eucalyptus plantations but any monoculture, be it an exotic or native. Compared with multispecies plantations, single-species forest plantations may reduce the availability of diverse food and shelter for the local wildlife.

Avoiding or diminishing silvicultural treatments after stand establishment allows birds and animals to occupy the area in search of food.

In general, (1) plantations have a less diverse fauna than indigenous forests, (2) plantations composed of exotic trees have a less-diverse fauna than plantations of indigenous species, (3) plantations can be made more favourable for animals and plants by appropriate management practices that provide the desired habitat, and (4) planting in treeless areas can provide shelter that would not otherwise be available to faunal populations (Poore and Fries 1985).

Flora

Planting eucalyptus and replacing natural vegetation has an effect on the flora of an area. This effect may result from shading, competition for nutrients and moisture, site disturbance, allelopathic effects, or the cumulative effects of changes in the soil. Eucalyptus has a negative impact on other plants and on annual crops. Nair P.K.R. (1990) stated that “Some Eucalyptus species produce toxins which can inhibit the germination or growth of some annual crops”. Eucalyptus has the tendency to highly compete for soil nutrients with other plants.

This competition is made possible by its lateral root system, which is capable of spreading to every direction in search of nutrients. This, therefore, renders the soil infertile and plants can hardly grow together with Eucalyptus trees. This is explained by the absence of thick undergrowth in a Eucalyptus plantation.

The extent of the impact will depend on the nature of the community the plantation replaces and the ecological characteristics of the region. For example, in an arid region eucalyptus may suppress ground vegetation by competing for water, but this is unlikely to occur in an area of high rainfall (Poore and Fries 1985).

Critics of short-rotation commercial eucalyptus plantations assume that eucalyptus has an allelopathic effect on the other plants, resulting in the
disappearance of the original native plants and local ecosystems (Poore and Fires 1985). For the same reason, there is a concern that agricultural crops cannot be cultivated on lands previously occupied by eucalyptus plantations or even on lands nearby (Lima 1993). It is believed that eucalyptus can affect other plants directly through the inhibitory influences of leaf litter and root exudates or through the effect of litter on nutrient mineralization and soil microflora (Florence 1986).

Some feel that management practices on plantations will enhance conditions for native flora. For example, an intense fire in the eucalyptus forest may provide, at least temporarily, a more biologically favourable soil environment for plant growth.

This more favourable environment is caused by many factors, including the removal of plant competition, an increase in soil pH and availability of ash nutrients, breakdown of inhibitory compounds, stimulated mineralization of nitrogen and phosphorus in the soil, and the effect of partial soil sterilization on soil microflora. Thus, it seems that many observed effects of fast-growing eucalyptus plantations might be attributed primarily to competition for soil nutrients and water during the rapid growth phase rather than any direct toxic influences the eucalyptus may have on soils and other plants (Florence 1986).

There is no doubt that management practices, the eucalyptus species used, length of the rotation, and the existence of nearby native vegetation will all influence understory composition in eucalyptus plantations.

Several studies have been conducted on the environmental aspects of the largescale eucalyptus plantations. Walter de Paula Lima of Piracicaba, São Paulo, observed recently that the existing scientific work indicates that:

  1. No evidence of any change in the precipitation regime in a region as a result of the establishment of eucalyptus or any other tree plantations;
  2. The losses of water through evaporation of the intercepted water from rainfall by the canopy is smaller for eucalyptus plantations than for another tree
    plantations or native forest;
  3. The eucalyptus plantation can contribute positively to control loss of the soil and nutrients by erosion;
  4. Water quality is not affected by eucalyptus plantations;
  5. The water balance of a eucalyptus plantation does not differ from other tree plantations or native forest;
  6. The main species that have been used in most of the short-rotation plantations have good control of stomatic transpiration;
  7. The eucalyptus is more efficient in the use of water than other tree species;
  8. The effects of the eucalyptus, other tree plantations, and native forests on the watersheds are the same;
  9. The demand for nutrients by eucalyptus is high but is comparable with that by other tree species and is much lower than that by agricultural crops;
  10. Here is no detrimental effect of the eucalyptus plantations on the native vegetation; and
  11. Eucalyptus plantations, like any other tree plantations, are not devoid of wildlife, and habitat can be improved by adequate management (Lima 1993).

Effect of Eucalyptus Plantation on Waterlogging and Salinity

Problem of waterlogging and salinity is a worldwide problem including humid as well as arid regions of the world. However, in arid and semi-arid regions, problems have shown very adverse effects on agriculture crops and tree growth. Therefore more interest has been centred around it and more effects have been directed to its solution.

According to a report, one-third of all the irrigated land, (approximately 7 million hectares), in the world has been estimated to be salt-affected. Generally, salinity and waterlogging go side by side in the arid and semiarid zones where adequate precipitation is not received to leach down the soluble salts. Of the total land area of 13.2 x10^9 hectares, about 7.58% is salt-affected more than one-third of which lies in Asia.

Pakistan is a land of many contrasts. High Hills in the north, arid plants in the middle and big deserts in the south, with exception of the Northern Himalayan Tract, a major part of country falls in an arid and semi-arid zone. Five major perennial rivers, traversing the country, made it possible to carry out forestry and crop husbandry with the help of the world’s largest and unique canal irrigation system.

So, irrigation is an agricultural practice designed to supplement a deficiency of climate and has helped the country to become self-sufficient in food. But has given rise to the twin menace of logging and salinity.

According to Dr Nawaz, irrigation, waterlogging and salinity are interrelated to each other. Irrigation causes waterlogging and waterlogging causes salinity.

The waterlogging and salinity have become an alarming problem in Pakistan adversely affecting the production of agriculture crops and tree growth. Millions of hectares of farmlands have been salinized due to faulty practices and lack of proper drainage over long periods of time and capillary nese of salts in soil profile due to high water table.

It has been reported that the table has risen from 0.15 to 0.61 meters per year. Waterlogging and salinity can be controlled in the irrigated areas by engineering means like pumping, flooding, leaching or by chemical amelioration which are not economically feasible.

However, new avenues to prevent further damage are being explored e.g. through biological amelioration which means the improvement of an area by planting tree species which can stand salinity and waterlogging condition to some extent. The perennial trees/ shrub species have a great potential to pump excess water and check excessive evaporation carrying the soluble salts to the soil surface.

So all over the world, foresters are trying to reclaim waterlogged and saline areas by planting trees because of transpiration and evaporation process, as trees act as large water pumps and help in lowering water table to reclaim the land.

There are many tree species suitable for water logged and saline soils out of which, Eucalyptus is one and has been proved to be the best one. Eucalyputs is considered as a living water pump.

Initially in Pakistan, the objective behind the planting of Eucalyputs was ornamental rather than getting any other tangible benefits in the form of wood. It was in fact the increase in demand of fuel wood, rather slow growth, long rotation of indigenous trees, and limitation of forests area, adverse climatic and edaphic conditions which became prelude to raising Eucalyputs for commercial purposes.

The observation revealed that Eucalyputs gives good results in arid low foot hills, semi arid areas as well as saline sites, while Eucalyputs proved to be a versatile species which could be raised form sea level upto 3000 feet. The planting of Eucalyputs gave satisfactory results on different soils, with variation in texture, fertility structure and moisture content.

Effect of Eucalyptus Shade on the Production of Grasses & Soil Moisture

Plants compete for sunlight, soil moisture and soil nutrients for development and succession. The trees, due to the long taproot system, are considered better competitors than herbaceous vegetation. The effects of trees on the production of herbaceous vegetation, soil moisture and soil nutrients have been studied by various researchers.

These effects are site-specific. The growth of under forest vegetation is dependent Chaturvedi (1981) studied that certain agriculture crops can be successfully grown in the first three years and other trees can be planted under Eucalyptus after the seventh year.

Impacts on Climate

Eucalyptus, like any other tree, is believed to have an impact on the climate since the cultivation is extensive; the influence is equally bound to be extensive in Nkum.

Effects on Rainfall

Areas with trees have high rainfall because as the wind blows over trees, it collects moisture from transpiration by leaves. The collected moisture when forced upward by a hill, cools, condenses and falls as local rain. This increased rainfall in this region recently is believed to have been influenced to an extent by Eucalyptus. This increased rainfall is therefore going to increase water erosion and further soil degradation.

Effects on Temperatures

Natural trees, as well as Eucalyptus, act as shade because in times of intensive sunshine the leaves and branches prevent solar rays from reaching the ground directly, thereby reducing excessive heat.

Effects on Wind

The forest naturally acts as windbreaks and shelterbelts. This is why the effects of the North-East Trade Winds (Harmattan) are not usually severe in savanna regions with forest. These Eucalyptus forest help to reduce water, which is lost through evapotranspiration. It reduces wind speed at ground level and thereby reducing the possibility of wind destroying houses and property. Wind erosion is also reduced.

Effects of Eucalyptus

Positive Effects of Eucalyptus

  • Eucalyptus is an evergreen tree.
  • A fast-growing tree so it is suitable for short-term purposes.
  • Eucalyptus has remarkably good coppicing power.
  • Eucalyptus has the capacity to produce a massive root system very rapidly. In its natural habitat, the taproot is well-formed and the lateral roots cover a very
  • large area, it is claimed that the lateral roots kill regeneration up to a distance of 2 ½ time the size of the crown.

Eucalyptus is a Hardy Species

One of the reasons for the success of plantation of Eucalyptus is its non-susceptibility to grazing/browsing and other environmental stresses. Thus the grower has to take very less risk and as such, less investment is required to establish a Eucalyptus plantation.

Resistant Species

Eucalyptus is a drought-resistant spp. and can be planted on the areas where scarcity of water is faced. Also heat and frost resistant.

Reclaiming Waterlogging and Salinity

Eucalyptus is the best suitable spp. for problematic areas like saline and waterlogged. Eucalyptus draw a tremendous amount of water from the soil through the process of transpiration. Therefore, planted to lower the water table and reduce soil salination.

Pollution Control

It grows easily, therefore, makes green belt and control pollution. Eucalyptus removes swamps which provide a habitat for mosquito larvae, therefore a way of reducing malaria by draining the soil.

Eucalyptus oil is readily steam distilled from the leaves and can be used for cleaning, deodorising and in very small quantities in food supplements; especially sweets, cough drops and decongestants.

Shelterbelts

It is also used as windbreaks for highways and other farms in mostly treeless part of the state. Also used in areas where the shifting of sand dunes occur due to strong prevailing winds, these winds are harmful to agricultural crops. For the protection of the crops from these winds, the planting of eucalyptus is recommended.

Mechanical Value

It is strongly resistant to disease. Oil and leaf extracts of the spp. have antifungal and repellent activity. The applications that are probably of most interests to livestock producers are as a mastitis preventative and treatment, as a treatment for endometritis and as an anthelmintic (dewormer). Animals, who used to eat eucalyptus (e.g. Koala) have developed methods for detoxifying the compounds in the liver. In addition, they have bacteria that degrade tannin-protein complexes. Most animals do not have this ability.

Source of Raw Material for Wood-based industries

Eucalyptus serve as a source of raw material for wood-based industries. It is fast-growing, its wood is useful, the trunk is straight and wood is relatively strong. So it is suitable to make lumber, processed as plywood, as pulp for paper, firewood, construction and charcoal. Increases employment under certain circumstances and creates additional employment for downstream industries.

Other Uses

  • The ghost gum’s leaves were used by Aborigines to catch fish. Soaking the leaves in water release a mild tranquillizer which stuns fast temporarily.
  • Provides packing material to hilly areas and thus save felling of trees in the watershed area.
  • Highly productive and may yield 20-25 m3/ha at 8-10 years rotation (short rotation) when grown in suitable conditions; can be coppiced readily. (Qadri, 1983).
  • A multipurpose tree providing wood, shade, shelter, honey, oils and from some species (e.g. Eucalyptus microtheca) seeds.
  • Litter can be collected and used as fuel.
  • Provides shade from the side and the shade is light so that there are good possibilities for intercropping.
  • The leaves are not palatable to animals, hence their protection requires minimum care and protection against the onslaught by man and animals is not needed at all.
  • Easy to raise in nurseries.
  • Fire-resistant and can grow in drought-prone areas.
  • Increases income considerably in shorter duration.
  • Eucalyptus can be grown profitably in combination with agricultural crops by adopting scientific techniques viz., genetically superior trees, spacing manipulations, using fertilizers, etc and maintain sustained supply of material to local people as also to wood-based industries, particularly pulp and paper industry.
  • Industrial plantations can easily be raised and managed within the economic zone of the industry.

Negative Effects

Allelopathic Effects

The tree has visible and scientifically established allelopathic effects on agricultural crops and other plants due to soil poisoning and toxicity. It is generally believed that oil-rich Eucalyptus leaf litter makes the soil toxic for seed germination and plant growth and thereby reduces the yield potential of most agricultural crops, certain grasses and even young Eucalyptus saplings (Salech, 2002).

Soil Erosion

The tree is found to contribute to soil erosion since the leaves do not decompose soon and are washed away by wind and rain from the hill slopes leaving the soil barren and exposed to erosion. In Malakand-Dir as well as in many other sites studied, Eucalyptus has been found to contribute to soil erosion due to poor or no ground vegetation.

Wastage of Nutrients

It was observed that the tree is a fast producer of biomass merely because of the large amount of water and nutrient intake as compared to all total plants and trees. There is also very little return of humus to the soil because of the slow decomposition of leaves. There is a rapid loss of nutrient reserves from the soil due to short interval cropping of Eucalyptus trees (Saleh, 2002).

Effect on Biodiversity

The numbers and diversity of animals, birds and insects are less in exotic eucalyptus than in natural forests. The tree does not support nesting and association of most birds because of its oily smell. Its’ leaves are not consumed by animals and it has therefore no fodder value. The eucalyptus grooves are inhospitable to the local wildlife which is not adapted to them, leading to silent forest and the decline of wildlife population.

Climate

Monoculture i.e. single tree plantations have definitely cast an adverse effect on the environment by creating an imbalance in the biodiversity cycle. The plantations have an effect on the micro-climate of the locality because of greater evapotranspiration change in soil moisture and air humidity. The tree is ultimately bringing about an imperceptible, yet definite change in the micro-climate.

Pests and Diseases

It has been known from many Eucalyptus growing countries and from experiments in research institutions in Pakistan that Eucalyptus has susceptibility of termite attacks. Other diseases might crop-up in the new ecological settings of Malakand-Dir region.

Fire

On warm days vaporized eucalyptus oil rises above the bush, this oil is highly flammable (trees have been known to explode) and bush fires can travel easily through the oil-rich air of the tree crowns.

Aesthetic Value

Because of its morphology crown form, smooth stem and being evergreen, the planting for aesthic purposes cannot be over looked.

Other Hazards

Eucalyptus has a habit of dropping entire branches off as they grow. Eucalyptus forests are littered with dead branches. The Australian Ghost Gum “Eucalyptus papuana” is also termed are “widow maker” due to high number of pioneer treefelling workers who were killed by falling branches. Many deaths are caused by simply camping under them as the shed whole and very large branches to conserve water during periods of drought. For this reason, one should never camp under an over hanging branch. This may be real reason behind the drop bear story told to children. The idea is to keep them away from under dangerous branches.

Utilization of Eucalyptus

Fuel

Eucalyptus was not considered a good firewood and timber species. This is being disproved. Due to the shortage of miscellaneous species, people have
found that eucalyptus is a very good substitute for firewood because of its calorific value and moderate burning qualities. In firewood depots in semi
urban and urban areas, it is gaining preference over other species.

In Mysore in Karnataka, two decades ago the only firewood was that of Anogeissus latifolia which is one of the important fuelwood species found in the natural forests. The Forest Department raised captive plantations of eucalyptus, catering to the needs of the city in view of the dwindling natural resources.

Today 90% of the firewood used in Mysore is from eucalyptus. In the rural area, the lops and tops (at times even leaves alone) are used by the people as
fuel.

Charcoal

Eucalyptus gives good charcoal. Wherever farm forestry has flourished, eucalyptus wood is used for charcoal manufacture to meet the semi urban and urban demand.

Poles

Eucalyptus poles are good for transmission purposes and are also used in construction of dwelling houses, work sheds and in mines. Eucalyptus poles
have good demand near cities for use as scaffolding material. Eucalyptus sold in the form of poles have price preference over firewood.

Timber

Earlier, eucalyptus wood was not considered a good timber. The quality of the timber depends upon the species and edapho-climatic factors. Considering the cost of eucalyptus timber, it is found to be quite economical to be used in low cost houses; as mine timber and in other construction purposes. It is also being used as furniture wood.

Rural small scale industries

Rural small scale industries are developing fast in the country-side, important ones among them being brick making, jaggery making, pottery, tile manufacturing, lime production, dyeing, smithy, etc. All these industries require firewood or charcoal, provided by eucalyptus plantations. They earlier depended on firewood from natural forests, which is no longer available. In a few locations, because of the plantations, industries have flourished eg the Kolar District of Karnataka.

Honey and Oil

Several eucalyptus species are rich in nectar and pollen. Bee keeping is profitable and this activity is improving. Leaves of Eucalyptus globulus and E. citriodora are used for extraction of oil. It is a cottage industry providing employment in some parts of India.

Paper and Pulp

One of the most important uses of eucalyptus wood so far has been in the paper and pulp industry. The demand for paper and pulp is going to increase many fold in India and eucalyptus, being one of the good pulpwood materials, will be in continuous demand.

Eucalyptus tereticornis and Eucalyptus hybrid are the two most widely planted eucalyptuss in India. The species have spread to most parts of the country, primarily because of their versatile nature and its amenability for harvesting in short rotations.

Despite the unclear situation regarding requirement of water, particularly in the semiarid areas, eucalyptus has commercial acceptability, and is being grown for various purposes.

Controversy

A study on the social, economic and ecological impact of social forestry is focused on the impact of large scale planting of Eucalyptus. This study raised the controversy regarding the effects of planting of Eucalyptus, without bringing out the good that plantings had done. The Forest Department did not accept the findings of the study and its conclusions.

This triggered off a controversy on Eucalyptus which spread to other parts of world and generated interest among environmentalists, scientists, sociologists, economists and others. The farmers, who were raising the species without hesitation in their marginal lands, took note of the controversy and wanted that the Government should clear doubts about the species. The issue was raised throughout the world on different occasions where ever Eucalyptus species were known and people took keen interest in the subject.

As part of propaganda against eucalyptus, it organised demonstrations against planting of eucalyptus. In few cases they even pulled out seedlings in the nurseries as a mark of protest against eucalyptuss. Workshops and seminars were conducted over the countries to discuss the merits and demerits of eucalyptus planting.

While the farmer took his own decision about planting of eucalyptus based on his own judgment about the species and its effect, the Central and State Governments took certain policy decisions regarding planting of the species in the country. The first was the decision of the Karnataka State Government in 1984 to ban planting of eucalyptus in areas receiving a rainfall of 750 mm and above. This was because of fungal disease affecting Eucalyptus hybrid in heavy rainfall areas.

The National Forest Policy 1988 of India provides that no plantations of exotic species can be taken up without the species being tested on an experimental basis. If no ill effects are noted, only then are large scale plantations permitted. They restrict the planting of eucalyptus in the State, permitting it to be raised only in areas receiving a rainfall of between 500 mm and 750 mm. Planting is further restricted to degraded Reserved Forest and waste lands, which are barren, and that along with eucalyptus a good proportion of indigenous species be mixed.

Numerous other issues sprang up around this central theme, as the momentum of the controversy increased and as the symbolism associated with eucalyptus grew and grew. It is instructive to attempt a more precise dis-aggregation and classification of the issues raised without taking sides and without recounting the actual arguments in detail. Table 5 presents a breakdown of the main issues identified in the literature review for this study, but even this extensive list cannot be regarded as a definitive catalogue of all the issues raised by the far-ranging eucalyptus debate.

The truth or falsity of any of the criticisms leveled against eucalyptus planting in India is not the question here. To qualify an issue as a legitimate concern, worthy of careful consideration by project planners seeking to anticipate and avoid potential problems, it is enough that the issue has been raised and debated.

The controversy which also seems to have occurred in other parts of the world led FAO to undertake a study on the subject to answer some of the doubts raised for the benefit of the countries which were involved in planting of eucalyptus. The eucalyptus controversy has died down considerably.

Whatever is said and done, the controversy has affected the planting programme both by the Government agencies and farmers. It has opened avenues for studies on ecological, economic, hydrological and sociological aspects. The controversy has also helped the State to have a fresh look at the species to make it more area specific, rather that plant it in all kind of lands irrespective of its suitability.

What this list of socioeconomic issues surrounding the eucalyptus controversy makes clear, is that the choice of an appropriate tree planting practice involves far more than just selecting trees with the right attributes. The attributes which determine the appropriateness of a particular tree are strongly conditioned by their interaction with a whole set of interrelated decisions about other aspects of the tree growing practice; namely, the management system under which the trees are grown (e.g. the pruning, lopping, coppicing, pollarding, thinning or harvesting regime), which is in turn determined by the spatial arrangement in which the trees are planted (i.e. the pattern and density of planting, either singly or in combination with other trees or
crops), which is strongly influenced by the location within the landscape at which the trees are planted–all of which will depend upon the specific function the tree is intended to perform for a particular user within a particular socioeconomic context and an overall economic development strategy.

If we want to avoid this kind of controversy in the future, it seems that we must tailor our tree planting programmes to meet the needs of all relevant user groups, base our planning on a careful assessment of the needs, constraints and tree planting opportunities of each group, and that we must make a deliberate and systematic effort to carry these findings forward as specifications for the design of appropriate tree planting interventions.

Conclusion and Suggestions

In summary then, the most important lessons we can draw from the eucalyptus controversy for a constructive change in the way we design tree growing interventions would appear to be:

  1. There is need for greater openness and imagination in the use of a systematic, client-oriented approach to the design of tree planting interventions based on a much expanded repertoire of tree growing practices and the recognition that what we are dealing with, are always the attributes of a particular species in the context of a particular technology intended for a particular user within a particular socioeconomic setting in support of a particular development strategy. There is no use in blaming a tree for human errors at other levels of the decision making process.A good number of problems have been identified as a result of eucalyptus cultivation. These problems arise because of their deteriorating effects on the physical environment and the rampant cultivation by everybody as well as their unwillingness to replace with other trees. This is all due to the economic advantages that these eucalyptuses provide to the people. In order to redress these problems, the following suggestions have been put forward for eventual amelioration.
  2. Eucalyptus should be planted far away from watersheds, rivers and streams to avoid water shortage since they are great consumers of water.
  3. Eucalyptus should not be planted near a natural forest, farmland or in association with other crops because of their ability to spread naturally.
  4. These trees should not be planted near residential areas since they will be too difficult to fell when they are mature as they threaten human life and property.
  5. The inhabitants should diversify their economic activities to other areas such as cattle rearing and market gardening so as to reduce their dependence on eucalyptus as a source of income.
  6. The N.G.Os as well as individuals should intensify their education to the eucalyptus cultivators on the dangers to the physical environment.
  7. A careful planning and study is required to determine the water requirements of other trees, plants, animals and human beings before undertaking Eucalyptus plantations and deciding on the number of Eucalyptus trees per unit area in consonance with water / nutrient resource constraints. This will be like appropriating the water / nutrient budget in the locality to each consumer to avoid imbalance or impoverishment of any of the other.
  8. In the monoculture plantations, adequate thinning should be done to reduce the number of trees and also to widen the gaps between trees. Indigenous tree species like phulai (Acacia modesta), Kau (Olea ferrugenia), Chir pine (Pinus roxburghii) and Oak (Quercus ilex) should be planted to end the monoculture and as a matter of policy, monoculture should be disallowed. Fruit orchards and economic olive need be proliferated in order to maximize profit to community individuals.
  9. Eucalyptus being a high consumer of water and soil nutrients may therefore be planted in rain fed areas with over 700 mm of annual rainfall after proper planning and assessment.
  10. Water logged and saline lands and other problematic lands rendered toxic due to industrial effluents, need be reclaimed by Eucalyptus plantation in a properly managed way.
  11. Rehabilitation of the damaged ecosystem be ensured through mitigative measures so as to arrest further decline of resources.
  12. Sustainability issues need to be linked with feasibility studies.
  13. Forest policy needs be strengthened to make environmental impact assessment studies mandatory for any project appraisal and approval.
  14. Soil nutrient balance should be critically examined and tree leaves and barks should not be removed from the forest floor so as to prevent further depletion. Periodic laboratory testing should be done to monitor the soil nutrient balance even in the converted mixed plantations. Leguminous plants may be intercropped to assist in maintaining the balance of soil organic matter and Nitrogen.

Eucalyptus in Pakistan

Pakistan is a developing country, which faces a lot of problems and difficulties in its way of progress due to certain problems, one of which is financial roblem. Majority of the population is living in rural areas which have no basic needs of life availability.

These poor people depend upon their livestock and burn fire wood. Livestock and wood are their main necessities. But our country is forest deficient country containing only 5.38% of the forest cover which must be 25%.

Government and the forest department tried their best to fulfill this deficiency, but due to illicit cutting and removal of forest, this percentage is not ncreased. And the demand of wood is increasing day by day. The gap between the demand and the supply has increased to a maximum point where now we are bound to import wood from the other countries on a huge amount.

To overcome this problem, foresters thought and came to the conclusion to grow such forest which has short rotation, greater adaptability and gives more income or return and is also fast growing.

All these demands were fulfilled by the specie “Eucalyptus”. They populated to arid deserts to tropical rain forests. Nearly all the Eucalyptus are ever green but some tropical species lose their leaves at the end of the dry season. The most readily recognizable characteristics flowers, fruits and else fragrance.

The introduction of Eucalyptus in Pakistan is not new, for over a century some very good specimens have been decorating the parks and gardens as well as arboreta’s, but the interest shown in the genus during the last two decades has been considerable and a good deal of effort towards its propagation has been made.

A large number of species have been tried over a long period and their performance assessed. The ones that really proved acceptable are Eucalyptus camaldulensis, E. microtheca and E. tereticornis.

Past Performance and Future Prospects for the Use of Eucalyptus in Pakistan

The introduction of species of the genus Eucalyptus extends back to before 1860. Precisely what was introduced before that date is not known but subsequently there has been good documentation of the history of introductions made. In 1925 considered the best Eucalyptus species in the area, E. citriodora, Crebra, Globulus, Melanophloia, Microtheca, Robusta, Rostrata, Rudis and Tereticornis.

There is no doubt that these species were so designated as the result of a review of the information on introduction for the previous 50 years or so. It is significant that on the present day evidence there is little modification of these conclusions warranted.

The Future Cultivation of Eucalyptus in Pakistan

Selection of Species

Throughout the country from about 4000’ elevation to the irrigated plantations the tallest good formed trees to be seen are E. tereticornis the largest tree at Changa Manga Rest House is about 156’ by 11’ – 9” girth, and in a Loquat garden at Chattar on the road to Ghora Gali from Rawalpindi, there is a specimen about 24’ in girth.

Good specimens were seen also in a garden at Muzzafargarh and in Sukkur. In this it is closely followed by E. camaldulensis but this latter species is of
inferior form and generally of a little slower growth, although it may be physiologically more adaptable than the former. E. citriodora, while slower growing, should not be left out of consideration particularly because of its good form and the suitability of young fast grown material for certain purposes. For particular purposes and harder sites, E. melanophloia is of value, and finally for “toughness” in surviving on hard sites E. microtheca is of outstanding value.

Amongst the species listed for general use, those which offer greatest flexibility in end use are the most important. This places E. tereticornis and E. camaldulensis in the fore-front. In fact in any tests, these two species should always be used as a yard stick against which to make growth and performance comparisons, for unless they are superseded, there is no point in turning to other species.

Plantation Methods

If it is accepted that the choice of species can be rather clearly defined, a reconsideration of the plantation methods to be used, especially in the irrigated areas, is of outstanding importance at present. From small trials seen in such places as Changa Manga, it is clear that Eucaluptus will give greater increments than the mixed Shisham-Mulberry plantations are giving at present and perhaps this will be much greater than the double increment forecast by Khan (1955).

Tests are needed in the following aspects:

  1. The establishment of pure Eucalyptus plantations and not in mixture with Shisham.
  2. Complete cultivation with initial deep ripping and subsequent surface clean cultivation with or without the use of temporary crops such as guar (Cyamopsis psoralioides).
  3. The use of fertilizer – particularly nitrogen and perhaps phosphorus.
  4. The finding of upper growth increments by heavier water use in relation to standard application and a re-examination of time and amount of water application.

Summary

Eucalyptus is the name of a genus that holds all those properties which make it universal, adaptable to every site. Eucalyptus has various benefits for the mankind including medicine, food, and beautification of his environment, oils, food bathing, and treatment of livestock. Various people worked on it and its name “Eu” meaning “well” and “calyptos” meaning “covered” shows that it was considered as much beautiful and denser one.

Eucalyptus plantations have diverse effects on different sites, their biodiversity both flora and fauna. It makes a site good for wildlife, by proper management. It makes a saline and water logged soil more fertile by lowering the water table. Firstly it was planted as ornamental but studies approved that it is diverse in its functions.

References

  • Ara, I. And N.S.M. Yahya. 1990. Profitability of Eucalyptus camaldulensis plantation in Bangladesh. Bangladesh Journal of Forest Science. Vol. 19. pp; 1-2, 45-55.
  • Ashraf, S. 1994. Perception of Tree Farmers about tree planting in Attock District. Thesis Report, Pak. Jour. of Forestry. p: 74.
  • Ferozuddin, 1992. Effect of Eucalyptus camaldulensis shade on the production of grass and soil moisture at Jamruad.
  • Tewari, D.N., 1992. Monograph on Eucalyptus, Surya Publications, Dehra Dun, India.

Courtesy:

Shawana Hamid

B.Sc Forestry (2016-18) Pakistan Forest Institute Peshawar

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Naeem Javid Muhammad Hassani

NJMH is working as Deputy Conservator of Forests in Balochistan Forest & Wildlife Department (BFWD). He is the CEO of Tech Urdu (techurdu.net) Forestrypedia (forestrypedia.com), Majestic Pakistan (majesticpakistan.pk), All Pak Notifications (allpaknotifications.com), Essayspedia, etc & their YouTube Channels). He is an Environmentalist, Blogger, YouTuber, Developer & Vlogger.

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