Burning fossil fuels and other human activities have raised the amount of heat-trapping carbon dioxide in the Earth's atmosphere by more than 50 percent compared to 200 years ago. But that's a relatively small proportion of the total greenhouse gases that human civilization has emitted over that period. Plants, thankfully, have cushioned the blow by absorbing billions of tons of the greenhouse gas each year.
Some scientists see plants as a possible quill in the quiver of climate change solutions. As plants take in sunlight and turn it into chemical energy—a process called photosynthesis—they absorb carbon naturally and store it in the cells of their stems, trunks and roots. It may be possible to breed new strains of plants that are capable of sucking even more CO2 out of the air and storing it away.
That is the idea behind the work of Wolfgang Busch, a plant biologist, and his colleagues at the Salk Institute of Biology at San Diego. They hope to help slow, and perhaps even reverse, climate change in the years ahead by making food crops slightly better than they already are at absorbing carbon. Because the world grows such tremendous amounts of wheat, rice, corn and other crops, even a slight improvement could potentially remove significant amounts of CO2 from the atmosphere.
Over the past five years, Busch, one of the world's foremost experts on the biology of plant roots, has helped build Salk's "Harnessing Plants Initiative" into a massive effort involving more than 85 scientists, and multiple collaborations around the globe. HPI has received more than $85 million from high-profile donors, including Amazon's Jeff Bezos, Hess Corporation CEO John Hess and TED's Audacious Project. And this spring, Hess has agreed to kick in another $50 million.
Although Busch's team is using new gene editing technologies to search for the right combination of genes that can turbo-charge carbon absorption in crop plants, once they find those genes, the actual crop seeds could be produced with conventional breeding techniques, avoiding the taint of GMOs (genetically modified organisms) in Europe and other markets.
Removing carbon from the atmosphere permanently—known as carbon capture and sequestration—is, along with curbs on emissions, an important compoment of the larger effort to slow climate change. Busch spoke with Newsweek about his vision for the project and where things stand.
Newsweek: What's the idea behind this initiative?
Busch: To address the climate crisis, we will need to emit much less CO2. But we also need to somehow get as much CO2 out of the air as possible. There are very few approaches that can do that. Engineered carbon-capture technologies are very expensive and there's the question of how fast you could scale them.
Plants already take enormous quantities of CO2 out of the atmosphere every second. Every time a plant conducts photosynthesis, they take the energy of the sunlight and then take CO2 from the atmosphere and make it into biomaterials—that's the leaves, the stems and the roots of plants, everything we use as food, feed and fiber. If we could somehow make plants better at putting some of their carbon into the soil and keeping it there for longer, it would be an enormously scalable and powerful solution.
How would you do that?
We are focused right now on three different traits that would enable plants to put more carbon into the soil and keep it there for longer. All of them are related to the root system. Every gram of root material that plants make is about 41 percent carbon, even a little bit more.
One of the characteristics we are focusing on is size—we want to somehow grow these root systems bigger. We also want to make sure the carbon doesn't decompose as quickly so it stays in the soil for longer. One way to do that would be to make deeper roots. The deeper you go in the soil, the less oxygen is available to the microbes decomposing the roots. We also want to change the chemical makeup of the roots. One of the most stable forms of carbon that roots produce naturally in their tissue is called suberin, which you might know as cork. Suberin keeps water in and keeps microbes out. And it has been shown, in many circumstances, to stay longer in the soil.
By focusing on three characteristics—root mass, root depth, and suberin content—we think we can make a big difference in the amount and the duration of carbon that plants put in the soil.
How did you choose what plants to target?
When we look at our world, we see population growth and the need for more food, feed and fiber. So we thought if we do it in crop plants, we won't have to compete with the need to produce more food, feed and fiber when we fight climate change. We took six of the most prevalent: corn, rice, wheat, soybean, canola and sorghum.
This carbon sequestration solution doesn't take away any land out of production, but makes that land better by improving the soil content. It's a double win.
How much CO2 exactly do we emit each year? And how much would your plants reduce it?
Every year, we release about 37 gigatons—roughly 37 billion tons—of CO2 into the atmosphere. That sounds very dire. But nature itself turns around carbon at a tremendous scale, mostly due to plants and photosynthesis. Roughly 746 gigatons of CO2 is taken out of the atmosphere per year. The problem is plants die in the winter, and that decomposed matter releases 727 gigatons of CO2 right back into the atmosphere.
So essentially nature is a net absorber of CO2—absorbing 746 gigatons, then releasing 727 gigatons. In the end, we would actually normally be in a cycle where we reduce CO2 by about 19 gigatons a year.
Because humans release 37 gigatons of CO2 each year, every year about 18 gigatons accumulate in the atmosphere. Since the industrial revolution, about 900 gigatons have been added to the atmosphere due to human activity. If you [take] these 18 gigatons that are not taken care of by nature, and you compare it to the enormous amount—the 746 gigatons that nature already absorbs—it's actually very little. And so we realized if we made nature a little bit better, we could actually take care of the problem.
How much CO2 are you estimating that the harnessing plant initiative could take out?
We estimate we could store half of the excess emissions each year in the plants and soil, if we took six of the most prevalent crops that are planted everywhere: corn, rice, wheat, soybean, canola and sorghum. Of course, that is a very, very rough calculation, and we are working very hard to develop more accurate modeling. And that's a very, very ambitious goal.
How much progress have you made?
So far, we have identified more than a hundred candidate genes that we believe might confer an advantage. Initially, we are working in model plants, a species known as Arabidopsis thaliana, which scientists have worked on for almost a hundred years now. After we identify genes in this smaller species, we go to the crop species and ask what are the similar genes that, if we change them, will produce the same effect.
We are also working directly with the crop plants. We have hundreds of strains of crops from all over the world that present a high genetic diversity. And we characterize their root systems, to identify which varieties already have beneficial characteristics that are not in the most common strains that people use. By taking that approach, we have already found a number that have much deeper roots. Then we are using advanced genetics to identify what are the genes responsible and we can then make these genetic changes.
We are aiming for at least 50 candidate genes for each trait: deeper roots, size and increased suberin content. We are on a good track to achieve these numbers, hopefully in one or two years.
Are Monsanto, Bayer and some of these larger commercial seed distributors interested in this? What about farmers who buy their products and grow the crops?
Yes. Both big and small companies are excited. They know sustainability is important. I have also been talking to farmers in the Midwest and in other places, and they're also very positive, as are many politicians because it is such a win-win. The bottleneck is, how do you financially incentivize this for farmers? Seed companies only sell and develop products that they believe farmers will buy at a large scale. And so you need to find a way to incentivize farmers to sequester carbon, because otherwise, why would they change the seed material they're comfortable planting? Why would they take the risk of trying something new?
Carbon markets already exist in some places. The big issue is, how do you measure and report and verify the carbon that a farmer has stored in their field, and how do you account for the risk that it gets released? This is a solvable challenge.
What is the time frame on all of this?
One of our goals is within the next five years to have sequestered a million tons of CO2, probably in smaller, niche crops. The really large global impact, even if you're optimistic, is 13 to 15 years in the future. It depends basically on whether the carbon markets can be connected to agriculture soon enough that Big Ag and farmers have interest in these crops and demand them. Once that happens, we know that genetically improved plants can spread globally very, very fast. There's this example of herbicide-resistant soybean that within 10 years has gone on very substantial acreage.
What has to happen for that to occur?
The key is to identify ways to genetically improve these crops that still give the same yield or comparable yields so that farmers will plant them. And I'll get to our efforts there in a second.
We also need to be able to track progress. We've developed technologies that can efficiently measure these root systems so we can quantify the effect of genetic enhancements on their characteristics.
How does that work?
We have developed new imaging techniques that allow us to image hundreds of plants per day. And then we use AI and deep learning techniques to analyze hundreds of thousands of images in terms of the root character depth or root mass. So we have camera systems where we can put plants that grow in a transparent gel medium in cylindrical structures, that are put on a table that rotates. We take pictures from all angles as the plants turn around and we can, through computational approaches, reconstruct the 3D root system, which tells us a lot of how the root system will develop.
We also have an x-ray system on site where we can measure root systems in the soil. We also have operated multiple field research sites where we have plants that we had predicted would produce a deep and more macro root system in the field, and where we basically dug out the root systems and also use electronic devices to track the growth of the root system in the soil.
Would genetic modification hinder adoption in Europe?
Once we discover a gene, we can use modern breeding programs to get there. It just takes longer. For everything we are doing, you can get there using advanced breeding techniques that are accepted everywhere, which is how people have done breeding for many, many centuries.
Are you optimistic we can stop climate change?
It's very clear that the world will get warmer no matter what we achieve. And some areas of the world will have tremendous difficulties. But I truly believe that we can still limit global warming to 1.5 or 2 degrees Celsius. It will be very hard.
In 50 years, we still might have a livable world if the major economies get moving. But it is truly a minute before midnight.
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