The eucalyptus tree is native to the Australian continent and has been introduced to the other five continents due to its ability to grow quickly. In Pakistan it was introduced during the time of the British but concentrated research on its species performance was carried out at the Pakistan Forest Institute (PFI) since its establishment at Peshawar by eminent forest officers and research scientists.
In Australia there are about 700 species of eucalyptus but in Pakistan only five species were introduced, either for their fast growth or for their aesthetic value. Eucalyptus camaldulensis, its scientific name, is the species that has been planted extensively as roadside and canal-side plantations, as well as compact irrigated plantations in all the four provinces. It was also planted on farm lands in all the four provinces through USAID-sponsored Social Forestry Project in the mid-1980s and 90s.
The large-scale planting under the Social Forestry Project was for feeding a proposed paper pulp industry in Pakistan. Unfortunately the industry could not be established and therefore there was no market for its pole crop. The farmers were disappointed, as they were expecting financial returns similar to poplar as the agroforestry tree.
Both poplar and eucalyptus compete with crops for nutrients and reduce crop yields. High returns from poplar plantations on farmlands compensate the reduction in crop production; in fact, they give more profit. The low wood rates of eucalyptus in the 1990s made it unpopular as a farm forestry tree and a negative propaganda was started against it.
Environmental scientists also wrote and talked against eucalyptus plantations in Pakistan. Due to the controversy, provincial governments banned its plantations. However, the bans were lifted after some years due to pressure by farmers when its demand was created in coal mines in Balochistan for pit props.
Regarding the environmental implications of eucalyptus plantations, it has allelopathy on ground vegetation, has a negative impact on biodiversity, exhausts soil from nutrients, has oil in its leaves and accumulated litter leads to forest fire hazards. It also exhausts groundwater and lowers the water table. The abovementioned environmental impacts have been proved true in certain conditions only, though.
It is important to note that the allelopathic effect is because of chemicals released from eucalyptus leaves after disintegration. The chemical inhibits the growth of ground vegetation. Its compact plantations do have allelopathic effect in areas with less than 400 mm annual precipitation. However, linear and mixed plantations have little allelopathic effect on ground vegetation.
Secondly, compact and pure plantations do affect biodiversity. Therefore, the eucalyptus shouldn’t be planted in natural forests – and if planted its composition should not exceed five percent.
It does exhaust soil nutrients; one must note that all fast growing tree species use nutrients and water for their fast growth. Eucalyptus foliage and bark contains large amount of nutrients, and the retention of foliage and debarking of logs at the felling site is a good management practice to keep the site fertile.
Eucalyptus should not be planted on the farmlands if its returns are less than the reduction in the crop yield but if the return from its wood compensates the reduction in crop yield and gives extra profit then it can be planted on farm lands. It is true that eucalyptus has oil in its leaves and too much litter found under compact plantations can create forest fires. However, this has been reported from other countries but not Pakistan.
It is also true that eucalyptus takes shallow groundwater, but does not affect deep groundwater that has more than 25 ft depth. Since it has a spreading root system and tape root is not deeper than 20 ft it does not affect the deep water table. Studies have shown that the eucalyptus’s annual water consumption is about 1000 mm and if the rainfall is more than 1000 mm it will not affect the water table. If the precipitation is less than 1000 mm, it will tape groundwater where the water table is shallow.
Another benefit of eucalyptus is wood production for timber, firewood and pulpwood. Its fast growth also makes it suitable as windbreaks. Plus, the eucalyptus plays an important role in reclaiming water-logged and saline areas and also used in reducing malaria by draining swamps, which provide a habitat for mosquito larvae.
Furthermore, eucalyptus oil is used for cleaning, deodorising and in food supplements, especially sweets, cough drops, decongestants and insect repellent. The nectar of some eucalyptus produces high-quality honey. Being an evergreen forest tree it consumes carbon dioxide and releases oxygen. Therefore banning eucalyptus plantation was not a wise decision.
But eucalyptus should only be planted where it is required. On barren lands it should be planted to increase the forest cover. It can be planted as roadside and canal-side plantations. However, it should not be planted in the watershed areas and also not in the natural forests because it may affect biodiversity. It should not be planted near buildings as its surface roots penetrate the foundations and damage them.
For agro-forestry farmers who need fast growing tree species with a short felling cycle, poplar presents a good case. The species widely grows in the Peshawar valley but it can only be planted in higher elevations and up to foothill areas – the scrub zone.
Nothing competes with the eucalyptus as it easily grows in the plains of Punjab, Sindh, Khyber Pakhtunkhwa and Balochistan. It can also be planted in the scrub zone under rain-fed conditions. For pit props and the chipboard industry, eucalyptus can be managed on a 5-6 years rotation, which can give high profits to the farmers. It is now being planted on sand dunes in districts Mianwali and Khushab by farmers at a large scale to make sand dunes productive.
In the irrigated areas of the country, the eucalyptus will prove to be a good agro-forestry tree and increase the income of the farmers – since it now has a good market.
The writer is ex-director PFI.