Trees are essential for removing carbon and storing it in the ground in roots and wood. The most crucial factor for carbon storage is the remaining intact forests. Due to palm oil, soy, and agriculture, tropical forests are at critical risk of deforestation. The vast expanse of boreal forests is also vital; they are threatened by changing climates, insect infestation, drought, and now wildfire and permafrost thaw. Planting more trees seems logical to make up for losses of forest cover that we can take to reduce CO2 in the atmosphere. New England is a good example where forests were clear-cut for agriculture but have been rewilding for many decades. In some places, introducing trees does not help with carbon drawdown; the opposite occurs.
One of those areas is the Arctic tundra, where warming temperatures attract more woody plants. The consequence is the loss of albedo. Albedo in a cryosphere (ice- and snow-covered region), along with sea-ice and ice caps, reflect solar heat into space, keeping the cryosphere cold. When the ice and snow are absent, darkness on the earth and oceans absorb more heat. Arctic amplification is the best-known feedback loop of the phenomenon. Additionally, the woody plant roots migrating from Taiaga to the tundra can break up the permafrost, warming the soil, thawing the permafrost, and releasing CO2 and methane into the atmosphere.
Grasslands are disappearing at an alarming rate, and the primary drivers of this loss may surprise you. Land use conversion and tree cover expansion are increasing at the same rate – and that rate is beyond exponential. We have multiple tree species threatening the great plains grasslands: Eastern red cedar, Rocky Mountain juniper, Russian olive, and Siberian elm.A similar problem is now occurring in the great plains of North America, where native and invasive trees and other woody plants are migrating. Like the Arctic, these native and invasive plants darken the surface of the much lighter grasslands, changing prairie grasslands, including rangeland, shrubland, and savanna, with vast amounts of carbon stored underground. Only remnants of intact grasslands and prairies remain primarily due to agricultural and grazing by livestock land conversion.
Trees such as junipers darken the great plains, causing a loss of reflectivity that could become as dangerous as that seen in the Arctic. This reflectivity loss is significant. Losing prairies adds to biodiversity loss and aggravates climate change. As a result, the land becomes more fire-prone, CO2 increases, and local populations, ranchers, and wildlife suffer.
STRONG CITY, Kansas— Flint Hills rancher Daniel Mushrush estimates that his family has killed maybe 10,000 trees in the past three years.
It’s a start. But many more trees still need to fall for the Mushrushes to save this 15,000 acres of rare tallgrass prairie.
Whenever other work on the property can wait, Daniel and his brother, Chris, don helmets and earplugs, grab their tools and pick up where they left off.
“It’s a lot of old-fashioned chainsaw work,” Daniel Mushrush said. “Walking rocky ridges and cutting down trees.”
The Mushrush family is beating back a juggernaut unleashed by humans — a Green Glacier of trees and shrubs grinding slowly across the Great Plains and burying some of the most threatened habitat on the planet.
This blanket of shrublands and dense juniper woods gobbling up grassland leads to wildfires with towering flames that dwarf those generated in prairie fires.
NPR Kansas City writes: (A few images in this link highlight images of the greening that you may find interesting.)
Extensive portions of high-latitude grasslands worldwide have recently experienced increased vegetative productivity (i.e., greening) and have undergone a rapid transition towards woody plant dominance via the process of woody plant expansion (WPE). This raises the underlying question: To what degree are WPE and greening spatiotemporally linked? Given that these vegetative changes are predicted to continue, we seek to understand how recent changes in vegetation extent and productivity have interacted under recent climate change and anthropogenic disturbance to provide insights surrounding the future trajectory of temperate grasslands broadly.Why do trees backfire on the Great Plains?
It’s like standing in the sun on a hot summer day in a white t-shirt instead of a black one, Cook-Patton said. The darker your clothes, the more you’ll feel the heat.
The portion of sunlight that bounces back into space is called albedo.
Trees warm the planet in places where they reduce the ground’s reflectivity a lot, and don’t capture enough carbon to offset that problem.
Trees cool the planet in places where they pack away a lot of carbon and don’t change albedo very much, such as regions that aren’t very reflective anyway.
“Our work in general suggests that adding trees to Kansas grasslands provides limited to no climate mitigation,” Cook-Patton said.
Adding trees to some parts of eastern Kansas can have a cooling effect, but the trees change the color of the surface so much that this will “undercut the benefit of the carbon storage quite substantially.”
In the drier western half of the state, adding trees has a warming impact on the climate.
From the New York Times, a guest opinion piece by Carson Vaughn:
Like so many other certainties of the 20th century, however — American hegemony, ground water, Social Security, fossil fuels — Cather’s “great fact” is now in question. North America has already destroyed more than 60 percent of its native prairie. We’ve plowed the sod, left the topsoil to blow away, traded wildflowers for row crops, switch grass for suburbs, hay meadows for Home Depots. We’ve cleaved it apart with freeways, transmission lines, irrigation canals and oil pipelines. And now the Eastern red cedar tree is hungry for what’s left.
Thanks in part to roughly 100 years of fire suppression on the Great Plains, this drought-tolerant native tree — once primarily confined to river bottoms and rocky outcrops — has crept from the gullies to the grasslands, from the humid East to the arid West from Texas to South Dakota, and is now dismantling what little remains of one of the most endangered ecosystems in the world.
As both a journalist and native Nebraskan, I’ve witnessed this “Green Glacier” firsthand. I’ve watched the feathered hills of my childhood on the edge of the Sandhills — still the most intact temperate grassland on earth — turn black with cedar, slowly, in the beginning, then all at once. I’ve hiked through miles of redcedar woodland, the understory drowned in needles: silent, dead and dark. I’ve interviewed ranchers forced to cull their herds for lack of forage, fire marshals recounting uncontrollable flames and environmentalists mourning missing songbirds.
Between 1999 and 2018 alone, tree cover increased across 44 million acres of the Great Plains. Imagine the entire state of Oklahoma, from the Panhandle to the Ozarks, strangled in cedar. Picture so many prairie chickens dancing. Now picture them gone. The bobolinks, too. And the meadowlarks. And many other grassland species, avian and beyond, that have evolved over thousands of years not just to survive, but to rely on the open country. The black-footed ferret. The American burying beetle. And, of course, the grass itself: the side-oats grama, the big and little bluestem that bewildered the novelist in its galloping abundance.
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Ironically, Cather’s romantic vision, no matter how gripping, was rooted in the same settler-colonial mindset that ushered forth the Green Glacier. Ultimately, both were acts of erasure. For a host of ingenious reasons, Native people had long set fire to the prairie: to rejuvenate vegetation and attract bison herds, to ward off mosquitoes and snakes, to ease travel, even to hinder their enemies in battle. Intentionally or not, they were also keeping the Eastern redcedar at bay, confining the scrappy conifer to the prairie’s deepest wrinkles.
In a nutshell, Bauman said, the expansion of these species across the plains is now being dubbed the ‘Green Glacier,’ and the reality is that this expansion will continue to impact rangeland productivity and management.
“The most challenging message to come from recent research is that cedar invasion appears to be primarily a product of removal of fire from the grasslands,” he said. “While it is true that active planting of cedars will continue to create unnatural source populations, land management practices such as grazing do not significantly contribute to the spread of the plant.”
Simply put, Bauman explained that the grand expansion of cedars is the by-product of active planting and fire exclusion. “Where fire has been preserved or re-introduced as a management tool, the trees are generally controlled regardless of the other grassland management practices that occur,” he said.
Like all issues of biodiversity loss, climate change and ocean changes are incredibly complicated. This story is no exception. The pyrocene is likely to accelerate as the warming climate may cause more out-of-control grassland fires in the western states, which will suppress the invasion of trees and other woody plants. The difference between land managed by indigenous people and current management is telling.
Hell if you do, hell if you don’t.
