Opinion editor's note: Star Tribune Opinion publishes letters from readers online and in print each day. To contribute, click here.

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What a moving, thorough and thoroughly heart-breaking story you have told in the article "Can they come back?" (an installment of the occasional series "Vanishing North," Oct. 9) about the disappearance of the Poweshiek skipperling butterfly from the Minnesota landscape. How touching the efforts of Cale Nordmeyer and Erik Runquist to care about these tiny creatures and want to save them.

The ways the human race has altered the Earth so carelessly, as if cutting down forests, paving over prairies, draining wetlands, using harmful chemicals in our air, soil and water, as if this would never catch up with us: Well, it has.

It has baffled me that conversations about climate change seem to focus, however late and however little, on reducing carbon emissions. And yet that is only one part of the problem. Habitat loss for countless creatures, cutting down trees needed to soak up CO2 and provide shade, all contribute not only to species extinction but also to the heat island we now call the Twin Cities. Yet major construction sites continue to eat up habitat, adding asphalt and cement by the acre.

This last year I watched a big tract of land in Champlin, where my grandson and I used to see turkeys and red-tailed hawks, get eaten up by many one-story industrial buildings and their parking lots. Farewell to the turkeys and hawks.

I hope I see a Poweshiek skipperling butterfly someday. But I tried to enjoy this morning by getting out for my walk while the big full moon was still in the sky. I love the moon — it's one of my favorite elements of nature. And I love that we can't ruin it. It's already barren.

Karen Jeffords-Brown, St. Paul

I would like to answer an Oct. 9 letter writer's question of whether someone can explain why crypto mining with its massive use of electricity is a good thing.

Bitcoin mining represents less than 0.5% of the world's electricity consumption and secures a worldwide digital network that has never been hacked and that now has more than 100 million users, many of whom live in countries with double-digit or triple-digit inflation and where their personal property may be subject to seizure by authoritarian regimes. It is also important to note that bitcoin mining's sustainable energy usage is growing every year. The Bitcoin Mining Council now estimates the energy mix is up to 59.5% renewable. Other research ranges from 40% to 75%.

Bitcoin mining is extremely competitive, and miners can locate their rigs anywhere in the world where power is cheap or stranded: for example, hydroelectric power in Iceland, or wind and solar power in Texas. Miners there will buy excess wind and solar energy when prices are cheap and will turn off their operations during high demand periods, thus stabilizing and incentivizing the expansion of the renewable energy electrical grid. Exxon and others are mining bitcoin with methane gas, a byproduct of oil production that would normally be vented or flared into the atmosphere.

Bitcoin has been the best-performing asset in the past decade, it has changed the lives of many underprivileged people throughout the world and its mining operations provide a valuable service to the network. Please welcome those miners if they come to a town near you.

Nat Robbins, Minneapolis

Concerning the Oct. 9 front-page article "Cashing in on going cashless," every U.S. bill clearly states: "This note is legal tender for all debts, public and private." In view of this, I was under the impression that every business that held itself out to do business with the public legally had to accept U.S. greenbacks if offered in payment. Apparently, I am mistaken! What is the law on this?

In any case, if my money is not good enough for a place, I'm not going to do business there.

Don E. Scheid, Northfield

Opinion editor's note: To "tender" is to offer. Currency defined as "legal tender" under Section 31 U.S.C. 5103 is a valid and legal offer of payment. According to the Federal Reserve at tinyurl.com/faqs-tender, "there is no federal statute mandating that a private business, a person, or an organization must accept currency or coins as payment for goods or services." Some states do have laws requiring businesses to accept cash (tinyurl.com/states-cash).

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I read "Cashing in on going cashless" with some amusement. A couple of weeks ago, I was running errands with my 7-year-old grandson. He asked for a couple of quarters to buy candy from a dispenser. I agreed. Later, he asked if I would buy him something from a nearby store. "This time, would you use real money, Grandpa?" he asked. "I'm not sure what you mean," I replied. "You know," he said, "the money on your iPhone!"

Vince Therrien, Burnsville

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Do many people know that using a card or an app adds up to 5% to the cost? Guess who pays this. This is why many small busineses give a cash discount. I may be paranoid, but I don't want my transactions tracked and my data sold. Big business likes cashless, as most people spend more. If you want to use a card, do so, but don't take away my freedom to use cash.

David Newville, Coon Rapids

I have a modest proposal for chief executives of Comcast/Xfinity. It might be useful for senior execs at Xcel, CenturyLink, Verizon and other utility-like organizations. It also might apply to senior managers in city, county and state government organizations.

Call your customer service line once a week.

I'd suggest doing it more often, but I realize you are busy people. Once a week. Make the call yourself from a personal phone. Have a problem ready to discuss — a common one or something a bit different. You can probably get suggestions from your existing customer service files (if you can find them).

You might want to budget more than a few minutes of your busy schedule — just like your customers have to do. You may discover everything is hunky-dory and get a warm glow of satisfaction because everything is working as you have planned.

If you're not satisfied, even after multiple attempts to resolve your problem, you could fire the proxy company you've hired to handle customer "service." Or fire whoever (eventually) answers the phone.

But it's a tight job market, and people at that level are hard to replace. If your call is frustrating, why not fire yourself? The job market for C-level positions is more robust.

Doug Wilhide, Minneapolis

An Oct. 9 letter writer ("Time's up) seeks to cancel the comic strip "Dilbert," which pillories corporate, interpersonal and political foolishness of all stripes, because, well, her political oxen are also being gored. This is an example of a sad and recurrent instinct by the left to purge and suppress imagined enemies. The same people who get misty-eyed over the sins of McCarthyism two, going on three, generations ago are the ones who are determined to quash any departure from, even parody of, the new left-wing orthodoxy.

Meanwhile, "Doonesbury" carries on, with some strips repeating from decades ago without any call for "off with his head" from conservatives. Let thousands of parodies and satires bloom, is my suggestion. The new McCarthyists on the left should be ashamed of themselves, and the Star Tribune shouldn't give in (as it unfortunately did with the "Mallard Fillmore" strip) to the would-be hecklers' veto.

Douglas P. Seaton, Edina