The Next Climate Change Science Experiment

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A California biotech company seeking to create fast-growing trees that can rapidly soak up atmospheric carbon dioxide has announced its first experimental results: the firm’s genetically enhanced poplars grew more than 1.5 times faster than unmodified ones in lab trials. Plant scientists applaud the news, but caution that much more work is needed before engineered trees can start to help curb climate change.

“It’s a great first step,” says Sophie Young, a plant biologist at Lancaster University who is not involved in the work. But, she adds, there’s “a big caveat”: The trees grew in a carefully controlled greenhouse as opposed to the outdoors.

Scientists and environmentalists have promoted tree planting as a promising and easily expandable way to draw down atmospheric levels of carbon dioxide, the primary cause of global warming. Trees, which are roughly half carbon by dry weight, absorb the gas from the air and turn it into stable forms of carbon such as wood and roots.

But how fast trees soak up carbon is limited by numerous factors. One key constraint is the rate of photosynthesis, the biochemical process trees use to convert carbon dioxide into sugars and ultimately wood. Nearly all trees use a relatively inefficient form of photosynthesis that produces a toxic byproduct called phosphoglycolate, which the plants must then remove through a process called photorespiration. That uses energy that could otherwise go toward growth.

To sidestep the problem, researchers with a company called Living Carbon used a bacterium to insert genes from pumpkin and green algae into poplar trees. The foreign genes enabled the trees to have lower photorespiration rates and to recycle carbon from phosphoglycolate into sugars essential to growth.

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