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Designer trees

The potential for altering trees by genetic engineering is far greater than for crops. And the potential for damage to the environment is also far greater. In their latest report, GeneWatch UK look at the future of our forests.  

Genetic modification has not only been applied to food crops - trees are also being genetically engineered. The intention is to improve  productivity by making trees grow faster, have straighter trunks and less branches, be tolerant to herbicides and resistant to insect attack as well as being easier to turn into paper. For forest trees used in timber and paper production, issues about environmental safety have been raised. For fruit trees, the issues also include food safety. This briefing considers the genetic modification of trees, the risks and benefits and how these can be evaluated.


Trees are long-lived, large and have lengthy reproductive cycles. These characteristics have contributed to their relative lack of domestication (adapting them to particular human needs) through conventional breeding techniques. In contrast to, for instance, maize or rice - where one, two  or more generations can be obtained in a single year (with judicious use of both hemispheres) - even the most rapidly growing trees take at least 4 or 5 years, and often much longer, to produce the next generation.  

However, genetic engineering brings the prospect of speeding up the domestication of trees to meet 21st Century demands for more efficient  pulp and paper production. Speed and uniformity of growth and ease of  processing and management are the driving forces behind tree breeding for this  sector. In fruit and nut production, earlier maturity and increased yields are the main goals. GM trees are being developed across the globe and there is considerable interest in promoting their use. Whilst the USA has conducted most tests, other countries which have conducted outdoor trials with GM trees include the UK, Finland, Germany, France, Spain, Portugal, China, Australia, New Zealand, Canada and South America. However, controversy has already surrounded such experiments with GM trees and trials have been destroyed in both the USA and Europe.

Investment in long-term research in forestry is small compared to crop production and trees have proved more technologically demanding to manipulate than other plants. The only GM trees in commercial use is a papaya, genetically modified to be resistant to a viral disease and licensed for growing in the USA.

The main species involved are the poplar (including aspen and cottonwood), eucalyptus, spruce and pine. GM spruce and pine are much less advanced  than poplar and eucalyptus as they are technically more difficult to  genetically engineer.

In parallel with developments in crop genetic modification, the two most common ways in which trees are being modified are to be tolerant to herbicides and resistant to insect attack. These utilise the same genes that have been used in crops and mirror their pattern of use. Tolerance to glyphosate (Monsanto’s Roundup) is the most common type of genetic modification although trees tolerant to glufosinate, 2,4-D and sulphonyl urea have also been developed. Herbicide tolerance is considered useful in forestry because weeds can interfere with establishment of new tree plantations. The use of insecticidal toxin genes from Bacillus  thuringensis (Bt) dominates the approach to insect resistance and is intended to target pests such as spruce budworms and gypsy moths.

Applications that are more specific to forest trees include reducing the lignin composition of wood. In the production of pulp and paper, much of the cost involves the energy demands of removing lignin and even small reductions could save many millions of pounds because of the scale of the process. Much of the early work in this field involved genetic modifications that altered the activity of enzymes that are important in the synthesis of lignin by the tree. This led to alterations in lignin structure but no overall reduction in content. However, by targeting different enzymes, scientists in the USA have succeeded in reducing the levels of lignin in aspen trees that also had the unexpected and unexplained effect of increasing growth rate. An accompanying increase in cellulose was thought to account for the lack of cell wall collapse, a side-effect of many earlier efforts to reduce lignin content.  Whilst not yet at the stage of being field trialled, laboratory and greenhouse work with GM forest trees includes attempting to alter tree  form (e.g. to have less branches) and performance by, for instance, modifying the production of the plant growth hormones auxin and giberellin to increase growth rate. Enhancing growth rate by increasing giberellin synthesis also increased fibre length (which improves the strength of  paper produced) but reduced early root formation. In addition, genomics research to determine the function of genes is being used to identify targets for improving salt and drought tolerance and disease resistance.

Very recently, scientists at Dundee University reported that they have genetically modified elm trees which they hope will be resistant to Dutch elm disease, a fungal disease brought into the UK which has destroyed most of the species. However, they have not yet demonstrated that the  resistance will work. Scientists are also attempting to genetically modify the American chestnut - an important source of timber and nuts - to counteract another imported fungal disease, chestnut blight, which has devastated the species in the USA.

The use of trees for bioremediation - where living organisms are used to clean up toxic chemical waste - is also being investigated. Using a gene from a bacteria which is resistant to high levels of toxic organic mercury by converting it to less toxic elemental mercury, yellow poplar have been genetically modified so they can grow in high concentrations of mercury  and convert it to the less toxic form. However, the mercury is then released from the tree in vapour form and will eventually be recycled into the more toxic organic form.  

Because forestry is an industry that is increasingly global in nature, corporations are heavily involved in research on GM trees both directly  and by sponsoring research in the public sector. For example, corporate  members of Oregon State University’s Tree Genetic Engineering Research Cooperative (TGERC) include many multi-national timber companies such as International Paper, Westvaco and Weyerhauser. MacMillan Blodel, Monsanto and Union Camp are also reported to be funding research at TGERC along with public input from the US Department of Energy and Environmental Protection Agency. A similar consortium at Washington State University - the Plant Molecular Genetics Cooperative - receives financial support from Westvaco, Weyerhauser and Champion International.  Another joint venture, ArborGen, has been formed by Fletcher Challenge Forests (a New Zealand company), International Paper (the world’s largest producer of paper and packaging), Westvaco (a US company owning 1.5  million acres of forest in the USA and Brazil) and Genesis (a New Zealand tree genomics company). ArborGen has been established to facilitate research on GM trees and to try and overcome some of the obstacles restricting access to intellectual property - many genes and techniques have been patented by others making it more efficient to join forces and license the technology from them.

As with GM crops, therefore, GM tree research, its control and direction (both through funding and patenting) is dominated by the interests of the multinational forestry companies.

Do We Need GM Trees?

The reasons that GM trees are claimed to be needed in forestry have been given in the position statement of the International Union of Forestry Research Organisations (IUFRO) Working Party on Molecular Biology of  Forest Trees: “Tree plantations are expected to continue to expand as a result of increasing demand for their many renewable products, their importance to mitigation of greenhouse gases, and the environmental protection afforded to large areas of native forest. It is therefore important that rates of plantation productivity be made as high as possible within the context of good environmental stewardship. Transgenic technology, wisely used, promises significant economic and environmental benefits.”  How real are these benefits and do they justify the development of GM  trees despite the ecological and social harm that may arise?

l      Increased demand?

Like the justification for GM crops, increasing populations and the demand for more wood products for paper and construction are given as the main reasons for developing GM trees because of their predicted productivity increases. However, little attention has been paid to the option of reducing demand through decreasing usage and recycling. Enormous amounts  of unnecessary packaging are now used and much of the predicted increase in demand is predicated on consumption patterns following those in the USA.  

l      Mitigation of greenhouse gases?  In addition to GM low lignin trees reducing the amount of energy required for the intensive, polluting processes used in paper production, it is also claimed that growing more trees more quickly will help to absorb the carbon dioxide (CO2) produced  by burning fossil fuels. Trees, like other plants, absorb CO2 and use it to grow. With trees, the CO2 is ‘fixed’ in their wood and oxygen is released. However, the science is extremely uncertain and no-none knows exactly how much CO2 will be fixed by a tree under different conditions and, as  climate changes even more, a net increase in the production of CO2 from trees is considered possible as their metabolism may alter. If such a strategy were pursued, there could also be enormous social consequences for developing countries if they were ‘persuaded’ to set land aside to grow trees to compensate for the polluting activities of the developed world. As importantly, it diverts attention from strategies to reduce the production of CO2 in the first place, which is a much more straightforward way of tackling climate change but not in the economic interests of the developed world and its industries.

l      Protecting native forests?

If trees can be grown more productively in plantations, the argument is that there will be less demand placed on native forests. However, this avoids looking at alternative options for how native forests can be best preserved and how the reduction in use and recycling of tree products  could be improved. Instead, commercial interests are keen to promote an  increased use of paper and packaging.


When establishing agreement about the environmental safety of releasing GM trees the environment will pose more challenges than for GM crops. The  data considered necessary to determine genetic stability, the extent and rate  of gene flow and the persistence and invasiveness of a GM food crop typically involves experiments lasting over several generations of the plant conducted under different environmental conditions. The characteristics which make trees so attractive to genetic engineers - namely their long generation times and slow growth - means that collecting similar data  about their environmental performance will require much longer periods if it is to match that considered acceptable for GM crops. However, having to conduct ecological research over many years would compromise the economic viability of GM trees and conflict with the claimed benefits of speeding  up tree domestication and improvement.

Reconciling these issues in a manner that commands public confidence will be a particular challenge for the regulation of GM trees. Judgements will have to be made much more explicitly given the lack of data, revealing the inevitably subjective nature of risk assessment. Even more demandingly,  the approach that is taken will either have to satisfy, or be sensitive to, different social, economic and regulatory regimes in different countries  to avoid acrimonious trade disputes. A rigorous assessment of the claimed justifications for GM trees and a detailed evaluation of the alternatives are essential.

This is an extract of the latest briefing from GeneWatch UK: ‘Designer Forests - The development of GM Trees’  The full text can be found on their website: