FAO has predicted that worldwide wood demand will have increased
by 25 percent between 1996 and 2010. This increase wont be
met from natural forests 35 percent of the worlds industrial
wood comes from plantations, although they made up only 5 percent
of total forest cover in 2000.
Plantation area will grow to meet demand. Globally, it increased
fourfold between 1990 and 2000, and that trend is expected to continue,
especially in developing countries. Where will the land come from?
It is impossible to ignore any sound strategy for making
plantations more productive, says FAO forest geneticist Pierre
Sigaud. Such strategies might include genetically modified
trees. But they also include better seed selection and management
And where genetic improvement is needed, he points out, there is
far more untapped potential in existing forest genetic resources
than in agriculture -- where the crops have largely been domesticated
and there are fewer wild relatives on which to draw for breeding
purposes. So GMOs could have a role but their use would be
limited to plantation forestry, while, globally, the majority of
forests will remain natural forests.
Longer life cycles may mean more instability
The longer an organism grows, the greater the opportunity for variations
in its environment. As a result, genetically modified trees present
unique challenges. The long life of a tree means that it is more
likely to encounter stresses such as weather and pests
that could trigger unpredictable genetic responses. The slower growth
of trees means that problems will take longer to show.
One risk is related to the spread of modified genes into natural
populations, as tree pollen disperses widely. On the other hand,
plantations often rely on introduced species that have no wild relatives
growing nearby limiting the opportunities for crossing with
But the differences between trees and crops cut both ways. With
crops, you can adapt the environment to the plant with agronomy
and agrochemicals, says Dr Sigaud. But forests take
years or decades to mature, and such practices are often uneconomic
and in any case are often regulated. So a tree has to be suitable
for its environment, whether its genetically modified or not.
There are few species for which genetic modification can bring significant
advantages compared to traditional selection and improvement programmes.
In any case, commercial constraints limit opportunities for genetic
modification of trees. Growing and harvesting a plantation takes
time and money, as do trials. Because of this and concerns over
public opinion, genetically modified trees so far have not been
planted commercially, although there has been plenty of research
especially in high-yield plantation species.
Opportunities and dangers
Besides faster growth, qualities anticipated from genetically modified
trees include: better tree form; more uniform wood quality; lower
or modified lignin content; pest resistance; herbicide tolerance;
sterility; and adaptation for harsh environments.
If genetically altered trees are released commercially, the first
modifications are likely to be for modified lignin content, pest
resistance and herbicide tolerance.
Lignin is a heavy tissue that gives strength to plant cell
walls and helps support the tree. Breaking it down during pulp
and paper production requires costly, environmentally hazardous
chemicals. Trees with reduced lignin could be processed more
cheaply and cleanly. But they may have less resistance to pests
and high winds.
Pest resistance has already been bred into commercially released
genetically modified food crops. It causes them to produce toxins
that kill pests and then degrade quickly in the environment,
thus causing limited direct harm to the environment. The same
technique could work for trees, although there are concerns
that their long life cycle could give pests more chance to develop
resistance to the toxins.
Herbicide tolerance could permit more targeted application
of herbicide, thus reducing the amounts used. But this application
is less important than with crops -- in forestry, herbicides
are generally used sparingly and only when a forest is being
Further ahead, there could be more environmentally friendly applications.
Trees can prevent or reverse land degradation, and tree improvement,
whether by genetic modification or not, could bring new opportunities
of this type. Trees bred for harsh environments could help protect
fragile land on desert margins, while those bred for salt tolerance
could help restore the productivity of land damaged by poor irrigation
practices. Also, faster-growing trees in addition to their
commercial possibilities could help fight global warming
by taking more carbon dioxide from the atmosphere and converting
it into plant matter a process called carbon sequestration.
A safe technology?
While wood is not consumed by humans, other parts of forest trees
do get into the food chain, through the consumption of pollen, honey,
wild fruit and game, for example. Long-term environmental risks
may be more easily overlooked, especially as forest plantations
may be remote and not closely supervised. In any case, all newly
introduced natural or improved tree species need careful
supervision, independently from genetic modification.
Making GMO trees sterile so they do not breed and release genetically
modified material into the environment is an important safeguard,
but it may not be completely reliable. Trees without reproductive
features might reduce the diversity of birds and insects that feed
on them. These questions call for caution, as should the cost and
effort of investing in such technology and the time needed to get
that investment back.
A further disincentive to genetic modification in forestry is the
wide, largely unexplored diversity of existing forest species. Much
of this can be used to make forests and forest plantations more
productive, using traditional tree improvement and breeding techniques
combined with sound silvicultural practices.
Commercialization of genetically modified trees could come and
may make trees even more useful in a number of ways. But the technology
is not likely to be adopted as quickly or as broadly as in other