EarthTalk®
by Roddy Scheer & Doug Moss
Dear EarthTalk: Is it true that wastes left over from mining operations could be used to absorb carbon dioxide and help solve the climate crisis? -- D. Moore, Richmond, VA
Yes, mining wastes (“tailings”) could indeed be part of the solution to our climate woes. Researchers have shown that alkaline wastes—such as the slurries (semi-liquid mixtures), gravel and other industrial detritus that accumulate during and after mining projects—could be “reacted” with airborne carbon dioxide (CO2), which would not only sequester some of this most common of greenhouse gases but also neutralize the otherwise hazardous alkalinity of the waste itself.
This is good news because tailings in and of themselves can be a major environmental nuisance and health threat for those living nearby. Since most of this mining waste comes in slurry form means it often ends up in or near water, which causes contamination issues and destroys aquatic life. And because tailings can be transported by wind and/or water, they can easily expand their realm of contamination, spreading into nearby waterways and destroying larger and larger swaths of wildlife habitat.
If we can turn our mine tailings into carbon sinks (absorbers) on a large scale, it’s a win-win. Researchers at Canada’s University of Alberta seem to think so: Their March 2019 study found that the minerals in tailings naturally capture atmospheric CO2 if exposed to them, and the findings are backed up by similar research elsewhere. Harnessing this carbon sequestration (capturing) tool on a global scale would do wonders for our collective carbon footprint.
Meanwhile, an ongoing research project at another Canadian college, the University of British Columbia (UBC), is looking into how to facilitate so-called “direct capture” of atmospheric CO2 into mine tailings with the goal of at least offsetting the greenhouse gases generated as a result of the extraction work. In response to this challenge, UBC is identifying common traits among different types of mine tailings that excel at carbon sequestration in hopes of developing a set of protocols that mining operations anywhere in the world can call upon to reduce their impact and suck up at least the emissions their projects create.
“Incorporation of carbon sequestration activities into mine operations...will generate economic, corporate and societal advantages to mines and affiliated industries, including co-benefits such as tailings stabilization, dust mitigation and toxic metal immobilization,” they conclude. “Carrying this out on a global scale could trap between 310 million to 4 billion tons of carbon dioxide annually,” Robert F. Service reports in Nature. “That could provide the world with a much-needed means of lowering atmospheric carbon dioxide.”
It’s much easier said than done, and governments will need to offer incentives on a massive scale needed to make a dent in atmospheric carbon, Service says, adding: “And engineers will need to figure out how to harness the wastes while preventing the release of heavy metals and radioactivity locked in the material.”
CONTACTS: “CO2 Sequestration of Mine Tailings,” brimm.ubc.ca/slider/co2-sequestration-of-mine-tailings/; “Revaluing mine waste rock for carbon capture and storage, tandfonline.com/doi/pdf/10.1080/17480930902843102; “Scientists identify new minerals for carbon capture,” ualberta.ca/science/news/2018/december/carbon-sequestration-new-minerals.html.
Dear EarthTalk: I am sickened by all the death, destruction and misery resulting from the West Coast wildfires, but aren’t these blazes actually beneficial to the environment? -- B.T., Helena, MT
Some landscapes evolved with periodic wildfires as an influential force, and people have been using “prescribed burns” (the controlled application of fire under specified weather conditions) to restore health to certain types of ecosystems for millennia. But while some fires in some places might be beneficial, the wholesale torching of the forests of the American West right now is far from beneficial overall—not to mention a sure sign that our profligate ways with carbon emissions are coming back to haunt us.
On the plus side, forest fire does clear away the tinder-like overgrown understory that has resulted from years of forest management that avoided fire at all cost. Hundreds of years ago, many of the forests now on fire in California, Oregon and Washington had fewer yet larger and healthier trees. But these days, partly thanks to fire suppression regimes as well as other factors, forests are more crowded today with smaller, less healthy trees. It’s also harder for those remaining mature, established trees to compete for nutrients and space with all the undergrowth that’s built up in recent decades. In these situations, small manageable fires (or even better, prescribed burns) cannot only be beneficial, but can help prevent larger fires down the road by clearing the weaker, smaller trees.
Another benefit of wildfire is the clearing of overgrown underbrush to make room for new grasses, herbs and regenerated shrubs that provide food and habitat for many wildlife species. Also, the removal of thick stands of shrubs increases the water supply for the remaining larger plants and trees—and also allows streams and rivers to swell, further benefiting ever-thirsty native flora and fauna.
Yet another benefit of fire is that it kills off fungi, bacteria, viruses and insects that can decimate tree and plant communities and entire forest ecosystems. According to CalFire, California’s statewide wildfire management agency, more trees die from insect infestation and disease than from wildfire; some fire actually helps keep forests devoid of such pests and healthier overall than without fire. CalFire points out that vegetation burned by wildfire provides a rich source of nutrients that nourish surviving trees and soil.
And periodic fire can be an important way to keep certain ecosystems in balance. Many trees have evolved with fire and some even require it for seed germination; a few species even sport leaves covered with flammable resins (manzanita, scrub oak, chamise) to encourage fires that help seed the next generation.
National Geographic reports that, surprisingly, wildlife casualties tend to be low during wildfire events, as animals—especially those native to the areas on-fire and evolved to respond to the threat—either burrow in the ground or flee to safer areas instinctively. But invasive plants and animals may not fare as well given lack of genetic imprinting to be on alert for the threat.
Once the smoke clears on 2020’s horrific fire season, mass human and wildlife casualties could be the new normal. Global warming certainly has thrown the fire season into overdrive this year across California, Oregon and Washington, whether or not the Trump administration cares to admit it.
CONTACTS: CalFire, fire.ca.gov; “The Ecological Benefits of Fire,” nationalgeographic.org/article/ecological-benefits-fire.
Dear EarthTalk: How will global warming change the distribution of trees across the continental U.S.? Which types of trees and forests are most at risk?
-- Mike Powers, Golden, CO
It’s true that climate change is already affecting tree distribution and forest cover in the United States (as well as everywhere), but only time will tell which tree species are most successful at adapting and whether we will lose significant amounts of forest cover overall.
“A walk in the woods or a stroll on a tree-lined street could be a very different experience just a few decades from now,” says U.S. Forest Service researcher Stephanie Worley Firley. “Higher temperatures, altered precipitation patterns, and longer growing seasons predicted for the future could require that some tree species will have to move—or be moved—into new areas where habitat will be more suitable.” She adds that some tree species may be able to stay in place by adapting to new conditions, but many others are unlikely to be able to adapt and “may succumb to the pressures of climate change.”
One example of an iconic tree species that is already suffering from the effects of climate change is the Quaking Aspen, the most widely distributed tree species in North America. To day the tree is still common in higher elevation regions of Colorado and Utah as well as throughout the rest of the American West, but that might change in the coming decades. Researchers have been tracking the decline of aspens in Colorado for at least 20 years at the hands of climate change and related stressors. Given their shallow root systems, aspens are particularly sensitive to drought; warmer, drier weather overall as a result of global warming means more drought and more trouble for the trees moving forward. Researchers worry that aspens may be gone from the southern (and driest) band of its range within decades, and foresee drastic declines in the tree’s overall distribution as temperatures inch up, drought pervades and forest fires rage throughout the region.
Another iconic tree that has already been hit hard by global warming is the Sugar maple, famous as the source of Vermont maple syrup. Warmer winters have already shortened the syrup “tapping” season by more than 10% and if the trend continues there won’t be enough winter to sustain the $200 million/year Vermont maple syrup industry. Some other tree species on the ropes thanks to climate change include Balsam fir, Black ash, Paper birch, White pine, Tamarack and Red spruce.
Researchers from the North Carolina-based Eastern Forest Environmental Threat Assessment Center are using forest inventory and analysis data from the U.S. Forest Service to compare where tree species occur presently with a wider range of where they could move or expand given rising temperatures and other changing landscape conditions. By looking at how landscape, weather and temperature conditions will change over the next three decades based on a conservative model of climate change, the researchers can start to project where the most suitable conditions for different types of trees might occur across the country by 2050. This kind of knowledge can help land managers prepare for the changes coming and can help planners map out forward-looking, climate-friendly zoning patterns.
CONTACTS: A Review of the Potential Effects of Climate Change on Quaking Aspen (Populus tremuloides), fs.fed.us/psw/publications/documents/psw_gtr235/psw_gtr235.pdf; Eastern Forest Environmental Threat Assessment Center, forestthreats.org.
EarthTalk® is produced by Roddy Scheer & Doug Moss for the 501(c)3 nonprofit EarthTalk. See more at https://emagazine.com. To donate, visit https//earthtalk.org. Send questions to: question@earthtalk.org .
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