Amateur collector rocks world of paleoentomology

David Kohls

BATTLEMENT MESA — This summer, Battlement Mesa retiree David Kohls will grab his sun hat and hammer, hop in his pickup and head to nearby highlands enough times to bring back perhaps 5,000 fossil-bearing rocks.

That will make it close to 80,000 that he’s collected during an amateur paleontological career that began less than 20 years ago and focuses on insect fossils.

“I’m trying to cut back, but when you’re addicted to something it’s hard to cut back,” Kohls said.

Kohl’s obsessive addiction to collecting so many fossils and contributing them to science won him the 2009 Harrell L. Strimple Award, given annually by the international Paleontological Society for work done by an amateur.

“People were really impressed with what his contributions were to the field,” said Dena Smith, an associate professor of geological sciences at the University of Colorado at Boulder and curator of invertebrate paleontology at CU’s Museum of Natural History.

Among those contributions:

Kohls is responsible for 90 percent of the more than 30,000 fossil-bearing rocks from the Green River geological formation in Colorado and Utah that are housed at the Smithsonian National Museum of Natural History. Kohls said the rocks he donated hold perhaps 110,000 fossilized insects, spiders and plant material.

Another 40,000 or so of his rocks are at CU’s museum.

The sheer breadth of Kohls’ collecting work is what makes it so important. He didn’t keep just the pretty specimens. He kept them all. The result is what the Smithsonian refers to on its website as an unbiased collection that is “perfect for statistical analysis and research.”

It says many notable entomological and paleontological scholars have visited the collection.

Smith describes what Kohls has assembled as “kind of a gold mine” that sheds light not only on the insect life but the overall ecology and ecosystems of the time period represented. It indicates the varying abilities of different species to become fossilized, which tells about the nature of fossil preservation itself, she said.

“To be able to get samples from multiple sites in the same area and to have that level of sampling day after day and year after year, you get a more complete picture,” Smith said.

She said Kohls shows the contributions amateurs can make to science. Whereas she is lucky to spend a month a year in the field, Kohls has devoted many months each year to collecting.

Rich fodder for research

Smith is contacted by paleontologists from around the world who are intrigued by Kohls’ collection.

“They all want to see these specimens, to work on them, to be involved with understanding this (Green River) ecosystem, and it’s because they’ve all heard about his work and what he’s found,” she said.

Interest is coming from experts doing evolutionary research in such specific areas as wasps, beetles, spiders and flies.

“His stuff is the foundation for a lot of those different studies,” Smith said.

That’s saying a lot for a man who didn’t begin to pursue paleontology until later in life. Kohls’ day job was as an administrator for Colorado Mountain College — he retired in 2002 — and it was in that capacity that he hired Bob Koper to teach a class in Colorado Plateau geology. Kohls, who long had harbored an interest in fossils, decided to take the class.

“We went out and found some fossils, some little worm burrows and some shells,” Kohls said.

They were the first fossils Kohls ever found.

“That just lit a fire that wouldn’t stop,” he said.

Not long afterward, he found a fossil fish. But it was the day he discovered a rich layer of insect fossils that set him on his course. Kohls soon discovered that insect fossils were all over the place in the Green River Formation, with numerous fossil-rich sites being within easy driving distance of his home and offering the opportunity to find hundreds of insect fossils in a day.

“I just stayed with (collecting) those,” he said.

The Green River Formation, found in areas including northwest Colorado’s Piceance Basin, is perhaps best known for holding world-class deposits of oil shale that energy companies long have been trying to commercially develop. But its fossil stash also is substantial, including in the realm of insect fossils.

“It’s probably the largest resource in the world of this type and age material,” Kohls said.

He explained that the Green River Formation was created when there were a number of big lakes in the region. The formation consists of layers of lake-bed deposits. Storms likely blew insects, leaves and other items into the lakes, and silt would cover and preserve them on the lake bottoms.

‘Like pages of a book’

When Kohls goes collecting, he merely separates layers to find fossils, with mirror images of insects often adorning the rock face on each side of a layer.

“They’re just like pages of a book … and that’s the way they’re laid down, and you just read through them,” Kohls said.

In this case, the book dates back about 50 million years. And as soon as Kohls started leafing through its pages, he decided every word — every fossil — was indispensable.

He likewise realized his collection should end up in the hands of scientists trained to make sense of it. So, he contacted the Smithsonian, which now is home to what he assembled from 1991 through 2002. Since then, he has been shipping specimens to the University of Colorado, which can involve driving to Boulder with flat rocks separated by paper towels and stacked in cardboard beer flats.

Kohls’ collection is focused entirely on the Eocene period, which he said ended around 36.5 million years ago. He said the Smithsonian specimens tend to date further back in that period, while the ones he has been collecting to deliver to Smith have been younger.

“So now she has the other half of the story, so to speak,” he said.

All the insects survived the great extinction event that claimed the dinosaurs about 65 million years ago. So they’re essentially the same insects living today, Kohls said.

Today, Kohl said, there are 36 orders of insects, and his work has gone far in helping scientists account for 22 of those orders in the Green River Formation. Six orders lived only in icier habitats than existed during creation of that formation, meaning scientists are closing in on assembling a complete record of Green River fossil insects.

Kohls’ diligence has resulted in discovery of new species, such as a fly that has eyes on the ends of stalks.

Smith said that by keeping everything, Kohls has introduced scientists to tiny but spectacularly preserved insects that might have been tossed by collectors interested in what looks good to the naked eye rather than under a microscope.

She said Kohls’ collection will keep researchers busy studying it for decades to come.

Past as prologue

While Kohls believes many a graduate degree will be earned by focusing on his work, he’s not sure how much practical value will result. Despite what his fossils reveal about past life, he doesn’t see them as having value in predicting the future.

Smith happily asserts otherwise. She said Green River insects reflect a time when the local climate cooled from tropical to more temperate. Studying its insects helps reveal which species survived, in some cases by moving elsewhere. She has been conducting just such studies in order to help predict how insects might respond to climate change today.

In the small world of paleoentomology — Kohls estimates that globally maybe 50 people make their living in that field — he has struck up friendships with foremost experts from places as far away as Russia. And Smith said Kohls helped connect paleoentomologists with each other and encourage them in their work.

“Everyone’s so scattered all over the world, and his work and his passion and his collection have kind of served as a focal point that has brought us closer together,” she said.

Kohls’ excitement for his hobby refuses to wane, even after collecting so many fossils.

“When I find a new fresh beetle, and I probably have found thousands of the same beetle, I still get excited at seeing that beetle,’ he said.


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