The first assumption one must make to agree with the assertion that "genetic modification is useful and necessary for improving trees," is that the consumption of trees can and should continue to increase infinitely, because we can modify trees to grow "more wood on less land" (which is ArborGen's motto).
The second assumption one must make is that scientists can create trees that can ignore ecological limits--such as water availability, soil nutrients, etc--and grow faster and faster on smaller and smaller areas of land.
The third assumption one must make is that scientists can understand and address the full range of potential impacts from these trees by testing them in field trials for 5 or so years, even though the traits they are engineering into these trees have never before existed, and the trees can potentially survive in the environment for many decades. One must also believe that genetic engineering itself is inherently safe, and that the scrambling and mixing of tree genomes with genes from unrelated organisms will have no unintended, unpredictable or negative consequences.
The final assumption one must make is that scientists can manufacture trees that will never escape into native forests--either through pollen contamination of related wild species or through the escape of non-native invasives like eucalyptus. One must believe this, even though trees can spread their pollen and seeds for hundreds of kilometers, and GE tree scientists themselves report major concerns about unintended contamination of non-target species.
So if one is able to turn off the rational side of their brain, and only believe in a fantasy world then, and only then, will they be able to believe that "genetic modification is useful and necessary for improving trees." Fortunately, most of us still have a rational brain turned on and expose this as a lie.
Anne Petermann, Global Justice Ecology Project, USA