Arbor Day, the nearly-150-year-old holiday on which people plant trees, comes up later this month. Does anyone think planting trees is a bad idea? Anyone? Raise your hand. The fact that trees sequester carbon turns out to be a bonus. Or maybe, these days, the point. It’s one of the few anti-climate-change measures that virtually everyone can get behind. And why not?
In January, even the climate-denier-in-chief, Donald Trump, endorsed a tree-planting resolution — the Trillion Tree Initiative — at the World Economic Forum in Davos. He has put Jared and Ivanka in charge of the U.S. effort.
Yeah, yeah; if Trump is for it, how good can it be? But wait: The Davos initiative was evidently inspired by a Science article that calculated planting nearly a million hectares of trees — a task that would take decades — could absorb two-thirds of the carbon human beings had put into the atmosphere. Many scientists have begged to differ with the numbers and there has been a lively back-and-forth between scientific critics and the authors of the original study. But even people who dispute those original numbers suggest that the real number is pretty high — say, if not two-thirds then nearly one-third.
“Healthy ecosystems absorb and store carbon on their own. And if they are protected, restored, and managed sustainably, they can provide one-third of the emissions reductions needed to meet the Paris climate agreement’s goal for 2030,” writes The Nature Conservancy’s interim CEO, former Secretary of the Interior and former REI head Sally Jewell. “In other words,” Jewell writes, “nature is offering us an opportunity that we cannot afford to miss. . . .To secure a livable future on this planet, we . . . must commit to funding nature-based solutions.”
There’s certainly no lack of opportunity. Before people starting cutting forests down and starting fires that burned them up, suggests The Nature Conservancy’s science director for North America, Joe Fargione, there were a whole lot more trees. In fact, he says, research indicates “there are two and a half trillion fewer trees than there used to be.”
Here in the Pacific Northwest — at least the dank western part of the region — planting trees seems a natural. If there’s one thing we can do here, it’s grow trees. And we should.
But not every place is Western Washington or Oregon. And even here, there are caveats. As anyone who has ever stuck a seedling in the ground and watched it die can attest, where you plant and how you plant make a difference. There are places and methods of planting trees that make no sense. Last year, the Turkish government made a big deal of planting 11 million trees in one day. This year — although the government denies it — critics say that most of those trees have already died. In northern Scotland, people drained bogs to plant trees. The trees haven’t thrived. The peat was storing more carbon, anyway. Now, Scots are trying to restore the bogs.
And then there’s the question of what to plant. Knowing which trees to plant in which places is becoming trickier, explains David Diaz, a University of Washington Ph.D. candidate who is a member of the state Department of Natural Resources’ Carbon Sequestration Advisory Group. It’s no longer just a matter of looking around and seeing which species have done well in a given location so far.
What worked when nature did it 100 years ago may not work as well if we do it now. With a changing climate, Diaz says, it’s necessary to ask “what are the forests going to look like? What species should I be planting? The climate that’s going to be here in 50 to 100 years is going to be very different.” But no one knows exactly how different. How far down the road should we look? Diaz explains that a tree suited to conditions that will exist in 50 or 100 years may live much or most of its life in conditions to which it’s not suited. “Once you get out beyond 10 or 20 years,” he says, “you don’t know what the climate’s going to be.”
Growing plants absorb carbon, while decomposing wood and foliage release it. University of Washington associate professor of atmospheric sciences and biology Abigail Swann explains that the margin between absorption and release is narrow at best. As the world gets warmer, she says, decomposition speeds up, but so does tree growth. (On the other hand, if there’s not enough water, tree growth slows down.) There are so many unknowns that “it’s hard to figure out where the balance is going to end up.”
But given what we know now, preserving existing forests looks increasingly urgent. Scientists report that — because trees are dying at increased rates due to rising temperatures and drought — the Amazon and African rainforests are sequestering less carbon than they used to. Even if people stop logging tropical forests at their current rate, the Amazon forest may become a carbon source by the mid-2030s..
And some young American forests may also be sequestering less. New trees have grown up in the fields of abandoned farms, Fangione explains, and in their rapid growth have absorbed a lot of carbon. Now that they are nearing the ends of their growing lives, we should not expect them to absorb as much.
Even in this climate, “stopping deforestation is pretty much in all ways good,” Swann says. “As long as [carbon is] sitting there [in trees,] it’s carbon that’s not in the atmosphere.”
“Stopping people cutting trees down is the first thing,” Fargione agrees. “It doesn’t make a lot of sense to spend money [planting trees] in one place if you’re cutting trees in another.”
If a forest is logged commercially, a lot of the carbon it contains may be locked up long-term in 2x4s and other lumber. (If it winds up in cross-laminated plywood, it may displace much more carbon-intensive concrete and steel.) But much of the carbon is put back into circulation. Bark, branches, etc. are all burned or left to rot, and the carbon winds up back in the atmosphere. When a forest is logged, Diaz says, “the loss is between 30 and 50 percent of what’s in the tree.” That’s “a fairly big loss of carbon.” (The longer the growing rotation and the larger the tree, the more wood is likely to wind up as dimensional lumber.)
But not all logging is created equal. The temporary loss of trees in commercial forestry, when the land owner re-plants, does far less damage than converting forests to other uses. When trees are cut to clear space for buildings and pavement, the loss is, for all practical purposes, permanent. And there’s a lot of conversion going on. “We estimate roughly a million acres a year of forests are lost” in this country, Fargione says, and that loss represents “mainly conversion to urban sprawl.”
Not all the carbon in a forest winds up in trees. “Half the carbon storage is in the soil,” Swann says. In many places, it takes a century or two to get that much carbon into the ground. When a forest is logged, some of that carbon is lost.
“The Pacific Northwest is not seeing [carbon] accumulate [in soil] the way it would if forests were left alone,” Diaz says. There’s “evidence that the soil biology is really different” after logging.
As a way to sequester carbon, does it make sense to protect old growth forest , or to manage forests so that in a century or two they’ll attain old growth structure and complexity, as The Nature Conservancy is now doing on the Olympic Peninsula? “I certainly think it does” to do the latter, Diaz says. Like other people in the field, he makes it clear that storing carbon isn’t — or shouldn’t be — the only reason to preserve ecosystems. Old growth “is undeniably a good way to store carbon,” he says. Especially now that most mills aren’t even set up to handle big logs, “there’s no justification for cutting down an old growth forest.”
And there’s no justification for burning up a forest, old or new — but it has been happening spectacularly in eastern Washington, in California, in Australia. It’s tempting to say there’s no such thing as too much stored carbon, but as those fires demonstrate, that’s not true. In fact, Diaz explains, east of the Cascades, “we’ve got a lot more carbon in the forest now than we can sustain.” That carbon is locked up temporarily in the brush and litter of dead branches, dead and diseased standing trees, and the small trees and shrubs that can conduct ground fires up into tree crowns, where they become just about impossible to put out. A lot of that excess carbon has already gone up in smoke. It will continue to do so unless the state and others use smaller fires — as native people did here and elsewhere — or chain saws to reduce the amount of fuel. And a lot of it will probably fuel big fires no matter what.
“”It’s unsustainable,” Fargione agrees. When you reduce the fuel loads through thinning and prescribed fire, “you lose some carbon in the short run, but in the long run, the carbon that you stock is sustainable. If you look out over 50 years, there’s significant benefit.”
In Washington, the state and non-profits, including the Tapash collaborative, — the Department of Natural Resources, the U.S. Fish and Wildlife Service, The Nature Conservancy, and the Yakama Nation — have been working to remove fuel loads and restore forest health. Inevitably, money has been a constraint. Likewise the difficulty of setting controlled fires near towns and houses. If the federal government were to spend serious money on slowing climate change, that would be one place to drop a few more bucks.
Using forests — and grasslands and wetlands and peat bogs — to sequester carbon turns out to be one of those measures that is probably necessary but not sufficient. But something like the Trillion Tree Initiative can create the illusion that it is sufficient, reinforcing the — for some — comforting notion that we don’t have to stop burning so much petroleum and coal.
But it seems we do. “The best way to stop climate change is to stop emissions,” Swann says. Last year’s unprecedented Australian wildfires spewed out as much carbon as all Australia “I’d be surprised to hear any serious advocate of natural climate solutions say we don’t need to reduce emissions in the energy sector and elsewhere,” Lynn Scarlett, The Nature Conservancy’s chief external affairs officer, wrote earlier this year. “Campaigns that tout tree-planting without emission cuts should raise red flags,” Scarlett said. However, the “real distraction is presenting these two tactics—using nature to capture greenhouse gases and reducing our dependence on fossil fuels—as if they’re mutually exclusive.”
The good news, Fargione says, is that “the cheapest way to remove carbon dioxide [from the atmosphere] is plants. We have that technology. The bad news is we no longer have a choice. In order to meet the ambitious climate goals we have in the Paris agreement we will need both emissions reductions and investment in offsets. We’ve seen that bipartisan interest in tree planting because no one’s against planting trees. I hope that [a broader approach to] climate gets back to being a non-partisan issue.”
And maybe, just maybe, that will turn out to be a silver lining to our current distressing plague time. “The government can spend anything [in the context of the coronavirus pandemic], and they have socialized the economy,” Sir Michael Marmot, professor of epidemiology and public health at University College London, said recently. “Coronavirus exposes that we can do things differently. We must not go back to the status quo ante.” If the corona virus is worth a couple of trillion dollars and counting to this country, what is the climate worth?