Hybrid Poplar for BC 's Future Pulp

MillWatch Special Report July 1998

By Jay Cates

Call them hybrid poplars, genetically enhanced poplars, or super-trees, there are plantations of them springing up all over the world, many of them in Canada and the US.

The main feature of the trees is that they grow fast, as much as three metres in height per year, or an average Mean Annual Increment of between 20 and 50 cubic metres per hectare in fertile coastal soil. While still below the phenomenal growth rate of 55 cubic metres per hectare boasted by southern eucalyptus or pine plantations, which are rapidly forming the main competition in global pulp markets, this kind of fast-growing fibre source could be good news for northern bleached kraft pulp mills.

But is it good news for the environment?

When used for pulp, as they are in BC, they provide a bright, white wood that requires less hydrogen peroxide for bleaching, and they 've been touted as a way to take some of the pressure off those species that have been traditionally used for pulp, such as balsam and hemlock. In the time a hybrid poplar takes to grow to harvestable size, a pine or fir will still be the size of a Christmas tree.

All of which raises two questions: is there anything inherently wrong with such an altered tree? And even if there is not, are they the best possible crop for our lands?

Poplar is fast gaining favour in the US, where it is being considered for uses other than pulp. (A news release from Oregon State University says hybrid poplar plantations "are popping up around Oregon faster than espresso stands." The university is experimenting with the growing of other crops, such as squash, alfalfa, and wheat, between rows of poplar during the first two or three years of growth, before they grow tall enough to provide too much shade for other crops.)

Some of the hybrid poplar grown south of the border is destined for Canadian pulp mills. A spokesman for MacMillan Bloedel in BC says "a fair amount of our program is in northwest Washington." The location of Mac-Blo 's poplar plantations is based on proximity to pulp mills.

Poplar is a hardwood that includes species of aspen, cottonwood, and willow. The wood is straight and hard, and can take nails and screws without splitting. Although not as strong as pine or fir, it can be used in engineered wood products: that is, boards or beams made of veneer that 's been glued together. The trees have to grow for only about 10 years, until they reach 30 cm in circumference, to be peeled for veneer. It might also be possible to turn trees into ethanol. There are hybrid poplars in Europe; Italy is reported to have extensive plantations. And they are grown in India as a source of wood fuel.

But in Canada, hybrid poplar means pulp.

On south eastern Vancouver Island, logging companies own 650,000 hectares of private land, most of it frozen into forestry uses by the Forest Land Reserve. If this land, most of it in second growth Douglas Fir between 40 and 80 years old, were to be converted to poplar plantations, it would provide the mills with around 13 million cubic metres of fibre a year, almost one fifth of BC 's inflated annual cut. Invested in secondary industry, if British Columbians were to choose such an economic model, at the same rate as most industrialized countries, this wood could support 65,000 jobs.

In BC, pulp producers that already have plantations of hybrid poplar include MacMillan Bloedel and Scott Paper Ltd. The programs of both companies are still in the early stages, in relatively small areas. Scott Paper has made some harvests already, but Mac-Blo 's program, which started later, has not yet brought any trees to harvestable size.

Still, nothing succeeds like success, and if the early progress looks good, and profitable, we can count on seeing more plantations full of super-trees.

In some areas, poplar plantations are so new that a first harvest has not yet been made, but the concept of improved trees is not new. The International Poplar Commission (IPC) was created in 1947, and 34 countries, including Canada, attended its 1996 session. At that time the IPC reported that although poplar plantations had increased in number, they remained of "relatively low significance," except in China. China was said to have 1.34 million ha. of natural and planted poplar, 350,000 ha. of that established between 1991 and 1995. Canada, said the IPC, had the largest area of natural poplar/aspen stands of all reporting countries.

One of the observations made at that conference was that: "A decrease in the area of riparian forests, in which Salicaceae play an essential part, is noticed in most of the countries reporting. There are numerous reasons for this, including the draining and channelization of riverbeds, but also the competition with agriculture and other human activities for the use of soils in river valleys. Intensive poplar cultivation also contributes to the decrease in the natural riparian stands. Taking into account such issues, protection rules for the preservation of wetlands are in effect in most of the countries reporting."

The genus Populus is a member of the willow family, Saliceae; there are about 30 natural species in the northern hemisphere. The best soil type for growing hybrid poplars, according to a study made in the US, is loamy, with a pH of 5.5 to 7.8, a slope of less than eight percent, organic matter of three-to-eight percent, and a high holding capacity for water, or a shallow water table.

Mac-Blo says its trees are a cross between the Western and Eastern cottonwoods, while Scott Paper describes its trees as a cross between local black cottonwood and Eastern poplar.

Hybrid poplars are generally propagated from cuttings; they do not produce seed readily, and when they do, it is often dead or results in seedlings that are not very robust, and unlikely to survive away from the care of plantations. Hybrid poplars do not spread by root suckering.

In short, they need a lot of care. The MacMillan Bloedel program is called Short Rotation Intensive Culture (SRIC). The company began its hybrid poplar program in 1995, planning for the planting of about 300 ha. of the trees per year in plantations on Vancouver Island, the Sunshine Coast, and Washington State, on private or leased land.

Planted in rows three metres apart, the plantations can produce about 1200-1300 trees per hectare. Since the company 's rotation cycle will be about 12 years, Mac-Blo 's first harvest has not yet been made, and it will produce no operational paper until at least 2004. The program is long-term and ongoing; it will continue "into the foreseeable future," the company says, and is expected to represent about five to 10 percent of the company 's pulp needs.

New Westminster-based Scott Paper has a similar project, but with some differences. That company has planted only 50 ha. a year, but has been doing so since the late 1950s. Also, Scott requires larger blocks of wood, so uses longer rotation periods, of 15-35 years. Which means it is already on its second, and in some cases third, rotation, although the growth rate of its trees is comparable to those of MacMillan Bloedel.

(Some companies have an even smaller program: Timberwest Forest Ltd. manages a plantation for Fletcher Challenge Canada Ltd., but it is only about 16 ha.)

Scott Paper produces about 30-40% of its fibre from poplar, and wants to increase that amount. New trees are clones, produced from cuttings. The company 's current equipment is not suited for other possible pulp sources, such as hemp, but it believes poplars to be a good farm crop because trees also provide habitat for wildlife.

These hybrid trees have not been subjected to the kind of genetic manipulation that takes place under a microscope in a darkened laboratory. Rather, they are the product of cross-pollenation of the best specimens of cottonwoods from different regions.

Planted in rows three metres apart, Mac-Blo 's poplars are fertilized with a standard, high- nitrogen urea fertilizer, but not, according to the company, in amounts great enough to be distributed in run-off water.

Scott Paper 's system is a bit different. With its smaller plantations (mainly in the Fraser Valley, on Fraser River islands), and a longer rotation period, it uses sewage sludge and pulp mill sludge to add organic matter to the soil, but that 's all.

There may be those who are concerned that the super-poplars will escape their plantations and offer unfair competition to indigenous species.

But both Mac-Blo and Scott Paper say there is no danger of unleashing an aggressive new species on the unsuspecting locals.

Ken Stenerson, Woodlands and Groundwood Pulp Mill Manager for Scott Paper, says he has seen no evidence of cross-hybridization with local trees, and that it 's not likely, since they come into flower at different times.

Bob Rogers, manager of Mac-Blo 's Poplar Farms Division, says it is possible for the hybrid trees to cross-pollinate with indigenous species, because they are, in fact, indigenous themselves. But they would need too much attention to succeed outside the plantations: for example, Short Rotation Intensive Culture requires weed control, fertilization, drainage control, and singling (a bit of tree surgery that concentrates growth in one stem).

In regard to weed control, MacMillan Bloedel says that for most of its plantations, there is not enough weed growth to worry about, and mechanical treatment is sufficient. In those cases where there is excessive growth, Roundup will be used before the poplars are planted, but only for persistent problems will the company use a "shielded application" of Roundup after planting.

After the poplars are about three years old, they produce enough shade to control weeds themselves.

Stenerson says Scott Paper uses only mechanical means for weed control. And he adds that the poplars provide a major benefit: "They fix more CO 2 than any other plant we know of."

They may have a few peripheral benefits too, as windbreaks, or shade sources for livestock operations. Rogers says they are so effective at removing leachates from soil that they can be planted along riparian areas to remove manure leachates, for example, before they enter streams.

Another benefit being touted is the natural, and potentially genetically enhancable, ability of the species to uptake toxic metals from the soil. Recent presentations by graduate students at the University of British Columbia in Vancouver confirm that tests for genetic modifications to improve poplar 's uptake rates are ongoing. Efforts are also underway to determine, and perhaps modify, the pathways of lignin biosynthesis in order to produce a plant that will be easier to pulp, and still stand up. The idea is to develop poplars that can be used for bio-remediation of metalliferous soils, and then be harvested and pulped.

In terms of the poplars that are intended for remediation of contaminated soils, current experiments do include trans-species genetic engineering. The hope is to cause metabolic changes in the poplar that will enhance the already significant ability of the trees to chelate or exclude metals.

There are several potential problems with this plan. One, there is always a risk of releasing trans-genic plants into areas where they could interact with natural communities. Tests have not yet been done to determine the potential for the genetically enhanced traits to be passed into other poplars, or related species. Second, the hope that metals can be recovered in the pulping process ignores the fact that process upsets from metals, and metals removal, are major stumbling blocks in current efforts to "close the loop" and eliminate liquid effluent at modern pulp mills. Lastly, the main area where poplars sequester metals is in the roots, a part of the tree not pulped, even if better metals removal were a possibility. This area of poplar experimentation, at least, has some serious questions to answer before it becomes a part of the standard procedure for the pulp and paper industry.

In an even grander scheme, industry and government are speculating about growing trees as a way to offset Canada 's disproportionate contribution to global greenhouse gas emissions. Forestry Canada studies suggest that about 7.3 million ha. of marginal agricultural land, woodlots, shelter belts, burns and NSR (Not Sufficiently Restocked) lands could be converted to hybrid poplar, producing five or six times the fibre of softwoods or other hardwoods. It is important to note that total agricultural land in Canada is 67.7 million ha., and forests (or plantations) occupy 417.5 million ha. Seven million ha. of hybrid poplar with a Mean Annual Increment of 12 cubic metres per ha. per year would produce about 84 million cubic metres of fibre - more than the entire annual cut (71 million cubic metres) in BC last year.

So. These poplars seem benign enough. How could they possibly be a problem? One problem, perhaps, might not be with the trees themselves, but whether or not they 're an appropriate crop to be growing on our land.

As Jim Cooperman, Forest Caucus Chair for the BC Environmental Network, so succinctly puts it, "If it 's good farmland, it 's a shame to be growing trees that will get turned into paper that will get thrown away. They 've pretty much trashed the natural forest, so now they 're forced to do this." (He adds, though, that if the trees are grown on marginal or private lands, then "it 's hard to find a lot wrong with it.")

In short, Cooperman 's concern is: if pulp companies follow a use-it-or-lose-it policy in regard to their annual allowable cut, will the poplars be used instead of natural-growth, or in addition to it?

Because even if a significant percentage of future pulp needs are met by the farming of hybrid poplars, if the demand for pulp, pulp, and more pulp increases at an even faster rate, then the overall benefits derived from the poplars will be greatly lessened.

Consider this assessment by the Rainforest Action Network: "Seventy-six countries have already lost all of their old-growth forests. Since 1950, global wood consumption has increased by 250 percent. The US has already lost 96 percent of its old-growth forests. The US and Canada consume three times as much wood as underdeveloped countries and twice as much as other industrialized nations. Seventy percent of the world 's remaining old-growth forests are in Russia, Canada, and Brazil."

To sum up, the potential for metals extraction is a seductive possibility, but hasn 't yet been proved to be a perfect solution.

And so long as research is being conducted into further genetic alteration, which makes it almost inevitable that further genetic alteration will be made, testing must keep pace to avoid any hint of a rabbits-to-Australia syndrome, and the more drastic the alteration, the more comprehensive the control must be.

What seems clear at the moment is that hybrid poplars will supply an increasing amount of pulp needs, and do not, so far, appear to present an environmental danger (depending, of course, on individual farming methods). But they will not ease the pressure on the use of farmlands or old-growth forests if the demand for pulp grows at a faster rate than even super-trees can satisfy.

Because if our reliance on pulp products increases unchecked, we 'll use up all the supplies available, from whatever source.