The more we hear about the terrible things we've done to the Earth - the defrosting ice caps, the Great Pacific Garbage Patch - the more we try to redeem ourselves through recycling. You practically have to apologize to the supermarket cashier if you show up without your own bag, preferably made from biodegradable hemp. These days, the quickest path to virtue is to reuse those high-numbered plastics and shop your closet.

It's strange how much we obsess about these small eco-minded gestures when the real elephant on the planet is our habit of wasting perfectly good buildings. What's really bloating our carbon footprint isn't all the plastic grocery bags, it's the plastic houses.

Those thoughts came to mind after hearing that a buyer in Lower Merion has purchased one of the region's finest mansions as a tear-down - the turreted Mediterranean villa known as La Ronda. Completed in 1929, the house was the last commission carried out by Addison Mizner, a popular society architect who single-handedly defined the look of Palm Beach, Fla. La Ronda is one of the few Mizner houses outside the Sunshine State.

Unlike some historic buildings targeted for demolition, La Ronda isn't a wreck. Several people who toured the house recently said they were astounded by its pristine condition. After 80 years, even the sliding porch doors still work perfectly. The stained glass in the Great Hall's Venetian windows continues to turn the afternoon light into a kaleidoscope of color. The pink stucco exterior doesn't have a wrinkle on it.

No one can claim the house is too small for modern life, either. At 18,000 square feet, there's enough space to provide separate wings for Jon & Kate Plus 8 - more than plenty for a statistically average family to spread out.

While it's hard to get an exact room count, estimates put the number between 40 and 50, including a library, dining room, and ballroom. There are plenty of closets and numerous bathrooms. Imagine the lucky kids who get to roam the Great Hall's secret mezzanine and host sleep-overs in the turret. Yes, the house needs an air-conditioning system and a general freshening, but what new purchase doesn't need work?

The new owners aren't likely to be overwhelmed by such expenses. Having bought the three-acre property on Mount Pleasant Road for $6 million, they plan to construct a very large new house. The replacement would cost from $3 million to $10 million to build. That suggests that the buyers - who have declined to divulge their identity - are tearing down La Ronda because they can.

Even the township's groundbreaking preservation law can't stop them from wasting a good building. Because preservation remains a touchy issue, Lower Merion decided in 2000 to make the designation voluntary. Though La Ronda was always eligible, it was never included on the protected list.

So when the house was acquired as a tear-down this spring, the best the township commissioners could do was stay the demolition for 90 days. The hope is that preservation groups, like the Lower Merion Conservancy, will find an alternative buyer. But unless an angel appears by Sept. 1, the mansion is headed for the landfill.

One angel is hovering overhead, but he hasn't gotten much response.

Benjamin Wohl, a Palm Beach-based real estate executive who lives in a 10,000-square-foot Mizner house, says he offered a six-figure sum Tuesday for the right to move La Ronda. He would shift the structure to a neighboring site occupied by its former carriage house. That 1.6-acre property is for sale. Wohl has yet to hear from La Ronda's owners.

Meanwhile, the clock ticks. Workers have been seen removing original fixtures, perhaps to give the owners a head-start on demolition. During a visit to La Ronda this week, I saw several contractors' trucks parked in the garden behind "No Trespassing" signs and heard crashing noises inside the house. It was a little like watching a madman rip away at Thomas Eakins' Gross Clinic.

The mention of that great Philadelphia painting isn't arbitrary. It depicts a pioneering Philadelphia surgeon at work. Yet, part of what makes it great is that it distills a chunk of the region's history into a single image.

While La Ronda was built for the pleasure of a single manufacturing titan, Percival Foerderer, who made his money in kid gloves, it, too, has the memories of the whole region embedded within. La Ronda, which originally sat on 233 acres, came into being as the result of the wealth created by the region's industrialization in the early 20th century. The new rich shuttled between the Main Line and Palm Beach. Mizner was the thread connecting their stories.

Of course, more than history is ingrained in La Ronda's stucco walls. All the energy that was expended to produce the wood for its joists, quarry the stone for its walls, and craft the handmade tiles that cover its floors remains bound up in the building today. Think of the way a debit card is embedded with existing value.

It's reasonable to assume that the construction of a replacement house will consume an equal amount of energy. The U.S. Green Building Council calculates that construction aborbs 40 percent of the world's natural resources. That's a huge expenditure of energy when plenty of buildings sit vacant.

Of course, it's understandable that a quirky house like La Ronda might not suit the buyer's lifestyle or taste. That's fine. So, buy a different house, or an empty lot.

Then there's the issue of quality. We don't know which architect the buyer has hired, but if the surrounding homes are any guide, La Ronda will be replaced by a pallid, Colonial-Victorian hybrid of clunky proportions. La Ronda is over-the-top, but it's over-the-top with aesthetic rigor.

Given the weakness of Lower Merion's preservation law, we can expect more La Rondas. There is nothing to protect Glenmede, a great house from 1902 by architect Will Price, now up for sale, and nothing to guarantee that Paul Cret's Barnes Foundation or Furness & Evans' Gerhard Building at Bryn Mawr Hospital will survive. A great old building is a terrible thing to waste.

Contact architecture critic Inga Saffron at 215-854-2213 or isaffron@phillynews.com.