By gum, it might just be a solution

By gum, it might just be a solution
Email Print Normal font Large font July 19, 2007

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Selective crossbreeding to speed the growth of trees offers a breakthrough in meeting the increasing world demand for timber and at the same time saving forests, writes Louise Williams.

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AdvertisementIn a secure, sterile greenhouse just south of the Arctic Circle trees are flowering in four weeks that would otherwise have taken 10 to 15 years to mature. The genetically modified seedlings are a huge step forward in the race to produce bigger, faster-growing trees.

It's a race which must be won to meet insatiable global demand for wood and forest byproducts without pushing commercial logging even deeper into the world's dwindling native forests.

"The post-fossil fuel era will see human society turn back to its traditional dependency on wood," says Professor Ove Nilsson, the scientific co-ordinator at the Umea Plant Science Centre in northern Sweden.

But, he says, projected demand dramatically outstrips forest production. Soaring global consumption, especially in Asia, is colliding with new demands on forests for carbon-neutral biofuels for electricity, industrial furnaces, heating and vehicles.

"Everyone agrees that if we are going to solve this puzzle we have to make commercial forests more productive," Nilsson says. "We have to grow bulkier trees faster so we get much higher yields per hectare. Otherwise we risk cutting down every stand of rainforest left on the planet."

In China, the forest products industry grew from $US4 billion to $US17.2 billion in the five years to last year, paper consumption has doubled in a decade and forests, especially in Indonesia and Russia, are being rapidly felled to feed the Chinese industrial machine. Elsewhere, scientists are eyeing wood for biofuels because it is at least twice as "energy dense" as crops used to make ethanol for green vehicles, and trees require much less land and fertiliser.

The commercial forests of the future, Nilsson says, will be fast-growing plantations "tailor-made" for bio-energy, pulp and paper, new wood fibre products and sawn wood and logs for construction and furniture.

And it's not all science fiction; a plant enzyme has been identified in Sweden which makes paper highly water resistant, a potential replacement for petroleum-based plastics, and a wood fibre composite is being tested to replace plastic components in cars. Millions of cloned high-yield trees are being planted in the US, following decades of research and breeding to select the most productive trees. The most dramatic breeding gains have been achieved in Brazil, where massive eucalyptus plantations grow to 35 metres in seven years, a 300 per cent increase on the original Australian species. But most trees are still only 20 to 40 per cent bigger than their ancestors. Genetic engineering is the next frontier.

The futuristic seedlings are locked inside a pressurised greenhouse on the roof, to prevent cross-contamination of pollen and spores with native forests. Unlike work on crops such as corn and soy, the genetic modification of trees is in its infancy. In agriculture, extraordinary improvements in food crops have been achieved through millennia of selective breeding, irrigation, fertilisers and, more recently, the biotechnology revolution, which began in the US in 1995. Wild tomatoes were originally no bigger than a strawberry and corn was about the size of a finger.

"You could argue that biotech has an even bigger potential for trees than crops because crops were already greatly improved before GM, but in forestry we are still at the beginning," Nilsson says.

The trouble with trees is that, unlike crops, selective breeding takes decades. Many cold climate trees such as spruce and aspen take 10 to 15 years to flower, meaning superior trees can only be picked out and crossbred - in the hope of even more productive offspring - a couple of times in a forester's career.

Eucalypts have galloped ahead because they flower in two to three years, allowing rapid crossbreeding to emphasise favourable characteristics such as fast growth and straight stems, boosting harvests in Brazil from 20 cubic metres of wood per hectare to up to 60 cubic metres.

What Nilsson and his team have managed to do is to mimic one of the earliest flowering plants on the planet, the Arabidopsis, a member of the mustard family that flowers in four to six weeks. They discovered poplars and other trees have the same FT (flowering locus T) gene which triggers early flowering in the Arabidopsis, but in nature it is dormant for up to 15 years. By isolating the gene, activating it, then returning it to the seedling, they've turned on almost instant flowering in several of the slowest-maturing trees.

"The flowers are formed normally and they produce pollen," Nilsson says of the first batch grown last year, which created waves in the global scientific community.

The seedling themselves aren't much use in forests; they're not necessarily bigger or stronger. The idea is to use the GM early-flowering trees for cross-breeding; giving researchers the chance to select the best trees using molecular markers a couple of times every year, instead of once every two decades for cold forests such as those in Sweden.

The way the remotely activated FT gene has been delivered into poplars also opens the door for other genetic modifications from a bank of 250 tree genes identified at the Umea centre. The genetic delivery mechanism is a naturally occurring soil bacterium which readily infects plant cells, transferring part of its own genes into those cells. The bacterium has been hijacked by scientists looking for way into a tree's genetic structure.

"We just replace the bacterium's genes with the genes we want to introduce into the tree and the bacterium (or the plant) won't notice the difference.

"If you take the gene that controls the production of growth hormone and turn it off you get a bonsai, but if you make it more active you get a tree that produces almost twice the amount of wood fibres," Nilsson says.

An Australian PhD candidate, Jonathon Love, is at the Umea centre searching for his tree accelerator. His research focuses on how trees seek to correct a lean by generating more wood on one side to straighten the stem.

"If you identify the gene that is responsible for the localised growth stimulation, turn it on, then put it back, you can stimulate faster growth in the entire trees," he says.

Turning laboratory super seedlings into super forests is likely to rely increasingly on embryonic cloning. When genetically superior parents have been created, embryos can be excised from their seeds and grown in tissue culture, where they can be stimulated to make copies of themselves. The embryos can be stored in liquid nitrogen while the copies are planted out to identify which of the original seeds produced the best characteristics. Cloned tree embryos are not difficult to handle; they can be dried, shipped all over the world, and planted without a seed.

Love has worked in commercial forestry in Tasmania and says he's acutely aware of the pressure rapidly growing demand for wood products is putting on wilderness regions.

"The benefit of using forest sustainably is that you can have a carbon-neutral process. Wood is solar power harnessed by trees; you fix the same amount of carbon growing trees as you lose when you harvest them.

"Science can help with technical solutions to maximise productivity, but you still need good management and political commitment to replanting," Love says.

Umea lies in Sweden's biofuel region of vast forests. Wood waste from local timber industries fuels the power plant, providing carbon-neutral electricity, hot water and heating. Garbage is also tossed into the furnace. There's enough emissions-free hot water to run pipes under the city centre, keeping streets free from snow in winter, when the temperature plunges to minus 20 and the sea, lakes and rivers freeze over.

Forest industry waste is being used to generate electricity and heating in Europe, and in Brazil forest offcuts are replacing fossil fuels in the likes of smelting and food processing. Wood and wood composites must eventually replace high-emissions building materials such as steel, bricks, concrete and synthetic composites. In Sweden's south, Europe's first high-rise wooden apartment block is under construction.

Most significant, perhaps, are Swedish experimental factories turning wood and forest waste into second-generation automotive biofuels, raising the prospect of vehicles running on trees. GM trees are being tested in the US for biofuel production and New Zealand and Denmark are also investing in wood-to-vehicle fuel research.

How close we are to commercial GM forests is a matter of conjecture. China has planted out GM trees modified to resist pests, but many governments are cautious. Nilsson plans to use the fast-flowering mechanism only for breeding in sealed greenhouses. Once high-yield trees have been created, the gene can be bred out, leaving genetically normal trees to be cloned and planted.

GM eucalypts, he says, may be only five for six years away, but genetically modified hardwoods are unlikely in cold climate forests before 2015.

And there's still the contradiction between environmental demands for carbon-neutral biofuels and building materials to reduce greenhouse gas emissions and the traditional opposition to commercial forests from green groups concerned about biodiversity, especially with single-crop plantations.

But, says Nilsson: "The only way we are going to cope with rising demand is increase forest productivity. GM is one tool but this is a new way of thinking and working and we need more experience to fully understand its potential."

Louise Williams visited Sweden at the invitation of the Swedish Institute for the 300th anniversary of the birth of Carl Linnaeus, the world's first ecologist and the father of the binary nomenclature system of scientific classification.