Should we genetically engineer carbon-hungry trees?

These scientists are looking toward genetically modified trees to sponge up the world’s excess carbon.

Charles DeLisi was in grade school when he first had an inkling his environment was changing. At the time, he loved to play in the forest. Lucky for him, he lived in a very wooded area. Trees filled his neighborhood. But, by the time he entered high school, many of his beloved trees were gone — cemented over, which he describes as one of the saddest events of his adolescence. 

Now DeLisi says we are approaching another tipping point where large swaths of nature’s playgrounds will disappear, like his beloved forest, but on a grander scale. Humankind is releasing 40 billion tons of carbon dioxide into the atmosphere every year — a rate that, left unchecked, could have serious consequences.

“Even if we stopped, went to zero (carbon emissions) today, another .4 to .5 degrees Celsius would be added to the temperature at some point. It is going to be a disaster. There’ll be a whole collapse of the coral system,” he says. “And that’s a huge, huge loss of life — the whole ecology and all the fish and whatnot that rely on coral reefs.”

Jay Mantri / Upsplash

DeLisi, a biomedical engineer at Boston University, says the government’s goal to reach zero net carbon emissions by 2050 is ambitious. But even if we hit it, there will still be some emissions that will need to be offset. Dozens of countries, including the U.S. Japan, the U.K., and Germany aim to offset any remaining greenhouse gas emissions with carbon captured by methods, such as direct air capture — giant machines that vacuum carbon from the atmosphere.  

But DeLisi says that breaking even isn’t enough. We must find a way to suck even more out of the atmosphere — much more.

“If you don’t do both, you’re not going to get very far,” he says. He wants to bring “carbon drawdown” technologies into the conversation with genetically modified trees. 

Last year, DeLisi organized a workshop with a team of heavy hitters — Sir Richard Roberts (biochemist, Nobel laureate, and staunch advocate for GMOs), Val Giddings (a geneticist at the Information Technology and Innovation Foundation), and researchers from Oak Ridge National Laboratory — to create solutions, like genetically modifying carbon-hungry trees.

And they are close. 

Supercharged Trees, Nature’s Natural Remedies

The idea is simple: use trees to combat climate change by enhancing something they already do well — suck carbon dioxide out of the atmosphere. 

Trees take atmospheric carbon dioxide and transform it via photosynthesis into oxygen and carbon. Then they release the oxygen into the air we breathe and store the carbon in their leaves, roots, and trunk. 

But natural carbon storage isn’t permanent. Deforestation and forest fires can release it all back into the atmosphere. Even insect infestations can cause forests to decay and release carbon. 

A perfect world would balance the process — carbon that goes into the atmosphere comes out, and vice versa. But add in the surplus of carbon dioxide humans emit through industrial processes, like burning fossil fuels or expansive agriculture, and the system is overwhelmed. Nature can’t keep up.  

DeLisi and his team say, why not supercharge trees so they can keep up, by genetically engineering the trees to grow faster or have deeper roots? 

When it comes to carbon sequestration, age and size matter. The carbon absorption rate accelerates as the tree ages, accumulating most of its stored carbon in the last stage of its life. Large, old-growth trees are some of the biggest carbon storehouses on Earth. The largest 1% of trees house 50% of the carbon trapped in trees worldwide. But it could take hundreds or even thousands of years for a new tree to reach that age and size. 

Now, these scientists want to use genetic engineering to accelerate their growth rate so they could reach “old growth” status in just 20 to 50 years, absorbing more carbon in less time. Additionally, carbon stored in roots is trapped beneath the soil even if the tree is chopped down, dies, or burns. Trees enhanced with extra-deep roots could stow away more carbon.    

A bonus: DeLisi says that genetically modified trees could even be programmed to transform captured carbon into a white calcium carbonate substance, which could prevent the carbon from being released again if the tree rots. This material could even be collected and used as a natural source of raw material for plastic or other durable materials. 

The idea is simple: use trees to combat climate change by enhancing something they already do well — suck carbon dioxide out of the atmosphere. 

DeLisi says the biological pathways to transform carbon dioxide into calcium carbonate are already well understood — in corals. Theoretically, scientists could transfer these pathways to trees, sequestering carbon and turning tree trunks into ultra-hard wood, suitable for buildings and other structures. 

“If you’re cutting (the trees) down to provide structural wood for buildings, that’s going to lock the carbon away for quite some period of time,” says Val Giddings, a geneticist at the Information Technology and Innovation Foundation, a think tank working on technological innovation and public policy. 

“That attenuates the existing carbon reservoir in the atmosphere and buys time for additional, more permanent geological repositories to be developed. There’s no question that this is an improvement over the status quo.” 

Creating economic alternatives to fossil fuels will become essential, according to DeLisi. But while he says that while the U.S. could switch to renewable energy, it will be difficult for developing countries to make the switch. They depend on fossil fuels because they are cheaper. 

Other solutions, like industrial scrubbers that suck carbon out of the atmosphere, are costly and less efficient. Solar geoengineering — spraying sulfuric acid into the atmosphere to block out the sun’s heat — could have unintended consequences and doesn’t address the carbon buildup in the atmosphere. Why not soup up nature’s natural remedy instead?

Some people are already working on making it happen

Maddie Hall is the founder and CEO of Living Carbon, a startup growing genetically modified poplars and pines capable of soaking up more carbon dioxide than ordinary trees. 

She says her startup, which is less than two years old, is operating in “stealth mode.” They’ve already raised millions in venture capital funding. Their work is mostly proprietary, but she says they already have seedlings in the ground, and the trees will be ready before the end of the year.   

Risky Business

But genetically modified organisms have a history of conflict. Some scientists are concerned about the environmental risk and worry about irreversibly changing the forest ecology. The human species has already tinkered with the planet enough, they say. 

Ricarda Steinbrecher, a molecular geneticist, says that even with the advancements like CRISPR, which she regards as an “excellent research tool to learn more about genes, their function(s), regulation, interactions and inter-dependencies,” there are risks with genetically engineered trees. 

“The possibilities of investigation and understanding are limited, especially when taking into account the complexity not just of trees, but the ecosystems they are part of, and that across time and space,” she said in an email.

Because trees take so long to grow and are linked with many systems in nature, they are so complicated that “currently, no meaningful and sufficient risk assessment of  GE (genetically engineered) trees is possible,” she wrote in 2008 — and she says it still holds today.

Biologist William Powell, the director of the American Chestnut Research & Restoration Program, appreciates these concerns. He says that it is essential to look at the ecological context of a genetically modified tree (and it is required for approval by the USDA, the department that regulates what GMO trees can be released into the wild). 

Andy Newhouse and Vanessa Gravenstine working on the American chestnut trees in the greenhouse. SUNY College of Environmental Science and Forestry

Powell’s work on the American chestnut tree began in 2006. A fungus had wiped out the American chestnut, but many roots remained because the fungus can’t penetrate the soil. Now, a new tree can sprout from a root system, but if they ever grow taller than a shrub, the blight kills it to the ground again.

To save the species, Powell had transferred an essential gene from the wheat plant to the American chestnut cells. The gene enhances resistance to the fungus that causes the blight. 

He is conducting a series of environmental tests to ensure his modified American chestnut is a bona fide American chestnut: the nuts are just as nutritious, the fallen leaves don’t harm insects, etc. 

So far, so good, he says. 

But Powell is concerned about the bad rep GMOs have. Many Americans are wary of GMOs, primarily in food, despite a nearly unanimous scientific consensus that GMOs are safe. In fact, Powell says, genetic engineering and gene editing have fewer unintended consequences than the old-fashioned way of modifying plants — hybrid breeding. 

“We basically have everything upside down here. The safer way is the one that once people are more afraid of,” he says.

Before scientists could do genetic engineering and gene editing, farmers and scientists changed a plant’s genes by interbreeding them. But doing so could introduce thousands of extra genes, new variants, and unintended changes. With CRISPR and other new methods, they can focus on changing one specific gene at a time.

“There are less unintended consequences than the old methods of people breeding, especially breeding hybrids, where you take two species and you cross them. That causes all kinds of mutations. It mixes genes on species that developed in different environments,”  he says.  

“(Modern methods are) actually better for things like conservation because you’re keeping the integrity of the tree you’re making the same and just making very small changes,” adding that the same is true for GMO crops. 

Initially a GMO skeptic, Val Giddings, one of DeLisi’s team of geneticists, spent four decades “being careful” — looking for hazards and assessing risks associated with genetically modified trees. Ultimately, like Powell, he hasn’t found any concerning consequences. 

“I can say that despite an enormous amount of blood and treasure invested in looking for novel problems associated with the use of these genetic engineering techniques to make improved varieties of crops or livestock, nobody has come up with a novel problem,” he says.

“There are potential issues that might arise that would be related to safety. But none of them are new to us. All of them are familiar from stuff that we’ve done with classical plant breeding,” explaining that if you plant a tree in a drought area, and it sucks up too much water, then that is a problem. 

But it is the kind of problem we are familiar with already. 

“The principle risk that I see is of not moving fast enough to exploit this opportunity,” he says.

Crops vs. Forests 

Martin Bunzl, professor emeritus at Rutgers University, reiterates Steinbrecher’s sentiment about unknown risks. He says we should be concerned about potential knock-on consequences of new varieties of trees. 

“We don’t know what the interdependence is and what adjusting the timescale of that interdependence does,” he says. But he’s not anti-GMO —  he actually favors genetically modified crops as a solution to climate change, instead of trees. 

Because crops are planted and harvested each year, the timescale is shorter, and, therefore, studying and assessing the risks involved is more feasible. Additionally, farmers buy and plant crops each year, so genetically modified crops already have a built-in distribution plan. 

The Harnessing Plants Initiative at the Salk Institute for Biological Studies leads the charge for genetically modified crops that target climate change. Recently, they made inroads into understanding the genetic secrets behind duckweed, the world’s fastest-growing plant. They hope to create next-generation plants optimized to combat climate change — with unique features like uber-deep roots, pest resistance, and rapid growth rates.  

Seedlings of the model plant Arabidopsis thaliana, growing in one of Salk’s climate-controlled growth chambers. Salk Institute

Wolfgang Busch, a plant biologist with the initiative, says that even when crops are harvested, their roots remain in the ground, locking carbon beneath the soil for longer. 

He’s non-partisan when it comes to the crops vs. trees debate. He says there is considerable potential to use nature to solve the climate crisis by enhancing these natural processes. 

“The more hands-on-deck in this area to use genetic engineering to mitigate climate change, the better,” he says.

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