Trembley’s “tangled bank” on the Lehigh campus

Francis Trembley, pioneer ecologist, environmentalist, and professor of ecology at Lehigh University. In 1967, he convinced the administration to stop mowing the slope behind Williams Hall. The site was meant to be a place where students could observe secondary succession, righout outside (Image from

Francis Trembley (1904-1978), pioneer ecologist, environmentalist, and professor of ecology at Lehigh University. In 1967, he convinced the administration to stop mowing the slope behind Williams Hall. The site was meant to be a place where students could observe secondary succession, right outside the classroom (Image from

“It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us. . .” – Charles Darwin

Where is the tangled bank?

Snippets of what little I could recall of the above quote from Charles Darwin bounced around my head as I read labels on some herbarium specimens.

Label of a herbarium specimen that was collected from Lehigh's "Tangled Bank" in 1968.

Label of a herbarium specimen that was collected from Lehigh’s “Tangled Bank” in 1968.

My task was to reorganize this collection of carefully flattened and labeled dried plants, to make it more useful as a teaching resource.

According to the labels on these particular specimens, they were collected from the “Tangled Bank.” No other location information was given.  Where was this place? What was its significance? The labels indicated that they were all collected by a person named David J. Mazsa. Maybe I could track this person down…

Finding David Mazsa

Google is amazing. Within a minute of searching, I found a person by the name of David Mazsa with a degree from Lehigh Unversity. Perhaps he was the collector? I sent him an email and received a prompt response….

“You are in luck-  I am the guy you are looking for.

“Tangled Bank” is the sloped area right behind Williams Hall.  Dr. Trembley had an idea to allow that mowed and manicured area to proceed through natural succession and become a “tangled bank” (I think the term is from Charles Darwin).  Dr. Trembley convinced Lehigh to stop mowing and allow the area to begin to revert to it’s more natural state.  In his view this would be so much more attractive and diverse than the mowed lawn.  I honestly do not remember the exact chronology but my best guess is that they stopped mowing some time in 1967 and my samples were from the following year but I am not sure.  Dr. Trembley found some money for me to work on the bank and take samples to record changes in the plant species distributions.  I am amazed to learn that I left a mark!  I graduated from Lehigh in 1969 and although I visited Dr. Trembley once or twice afterwards, I don’t know how long the project lasted or what additional data was collected.

Dr. Trembley was one of the people responsible for my career path.  I was born and raised in Bethlehem and he wrote a lot in the local newspapers.  He was one of the reasons I chose Lehigh.  He was a combination of an old time naturalist who loved the diversity of living things and was eternally curious about how they interacted.  Walking on a field trip with him was like having a window to the world of nature.  We hung on his every word and loved his stories.  But he was also politically astute and he was in the middle of Environmentalism of the 60s and 70s.

He taught Ecology with a set of note cards that were at least thirty years old.  When we asked him if it was boring teaching the same stuff over and over again, he noted that the Ecology material was much the same, but the students changed every year and his interaction with them made it different every year.  I have just finished my 40th year as a high school teacher and now I understand how right he was about the difference in students from year to year.

I also remember that our grade in Ecology was determined by a semester exam and that the question was “Describe life in, on, and around inland waters.”  Although that was the only science course at Lehigh that I didn’t ace (I got a B I think), That course and Dr. Trembley are certainly one of the big reasons I have spent much of my life teaching and working toward making the world a more sustainable place.

I hope I helped identify the location for you.  Thanks for bringing back some very fond memories.

David Mazsa”

So the “tangled bank” is the slope behind Williams Hall!

Of course! This is the only non-manicured place on the Asa Packer campus. And before the Department of Earth & Environmental Science moved from Williams Hall into the STEPS building, my office used to face it. For five years I looked directly out my window at the “tangled bank.” And I agree with Trembley, it is more beautiful and diverse than a mowed lawn. An aerial photograph from 1971 shows that much of the slope was still characterized by low-growing vegetation four-years after they stopped mowing.

The "tangled bank" on the slope behind Williams Hall in 1971 and today. In 1971, four years after the mowing stopped, low-growing vegetation on much of the slope is seen in the photographs. A few trees remained on the southern margin.

The “tangled bank” on the slope behind Williams Hall in 1971 and today. In 1971, four years after the mowing stopped, low-growing vegetation on much of the slope is seen in the photograph. A few trees remained on the southern margin, which is the top of the slope.

After David’s email, I also found mention of the “Tangled Bank” in a book on the history of education at Lehigh University (Yates 1992, page 238):

“The biologist Fran Trembley was speaking and writing on the dangers of technology long before the subject became popular with the general public. In 1951 he had his title changed to professor of ecology. Students flocked to his classes. In order that they might have a nearby spot in which to study ecosystems, he asked that the slope above Williams Hall be left in a wild state – a tangled bank, he called it, using a term coined by Darwin. The administration complied with the request and put up a sign, “Tangle Bank,” to identify the place.”

The “tangled bank” today
The "tangled bank" behind Williams Hall.  Trees are higher than the building today.

The “tangled bank” behind Williams Hall. Trees are higher than the building today.

Today, the “tangled bank” is a small, diverse woodlot, with an overstory that includes tulip poplar (Liriodendron tulipifera), American beech (Fagus grandifolia), black cherry (Prunus serotina), several species of maples (Acer spp.), as well as several other deciduous species. Various shrub species occur throughout, particularly along the margins, and poison ivy (Toxicodendron radicans) and Virginia creeper (Parthenocissus quinquefolia) are common. It is a very different place than it was in 1968. A few more photographs are below (click on one to view as slides).

What can students learn from the tangled bank?

This fall, students in general ecology (EES-152) at Lehigh University, will revisit Trembley’s “tangled bank.” Forty-seven years of ecological succession have passed since the mowing was stopped, and because of David Mazsa’s collections we know many of the pioneer species that grew on slope after just one year.

Francis Trembley on the cover of the Lehigh Alumni Bulletin in 1970.

Students in the ecology class will complete a botanical inventory of the slope, and the data will be used to introduce and explore the topic of secondary succession. Furthermore, the students will use modern databases to research and compare information on the functional traits (e.g., seeds per plant, energy content per seed, growth habit, mode of dispersal) of plants in early succession versus mid-succession (i.e., today). We will report our results on this blog later in the fall semester!

Trembley’s last lesson.

Unfortunately, this will probably be the last lesson taught by Trembley’s “Tangled Bank.” A renovation of Williams Hall is planned to begin later this year, and as part of this effort the area will be relandscaped…removing the “tangle” from the bank.

Perhaps only this ecologist would be saddened by such a thing.


Posted on July 12, 2013, in Ecology (EES-152), Fieldwork, Original Posts, Teaching and tagged , , , , , , , , , , , . Bookmark the permalink. 5 Comments.

  1. Excerpt from an email I received from Lehigh Alumnus Dick Brugam:

    “I was in one of the last ecology classes taught by Fran Trembley before he retired. He was failing pretty badly. He did not go on our field trips. One good thing that he did for me is introducing me to Silent Spring. I was a high school student in the “Junior Engineers and Scientists Summer Institute” in 1963. We had an hour with Trembley. At that time he was amazing. He made a strong case against pesticides. The state was spraying forests against gypsy moth. He was furious about it. He mentioned that Rachel Carson had a book about pesticides that would change things. He urged us all to get a copy. I read the book and it changed my outlook. That summer institute is why I chose Lehigh.

    I remember the tangled bank. It is located where you wrote in you blog. I am very sorry to here that some campus landscapers are going to wreck it. I did always think that the space was really too small to fit Trembley’s purpose. The advantage is that it is a mini-wilderness area in the heart of campus.”

  2. Excerpt from an email I received from Lehigh Alumnus Judy Brook:

    “I just received from my first husband a link to your blog on the tangled bank. Thank you for a trip down memory lane. We met in l966 as graduate students at Lehigh playing “kneesies” under the lab benches in an invertebrate lab that looked out over the tangled bank. I remember parking back there and enjoying a “fix” of wildflowers before I headed to classes and labs. Fran Trembley was a one-of-a-kind character and friend. Thanks to him and others at Lehigh I went on to be a field ecologist doing EIS studies and for most of my career a teacher of biology and ecology in high schools and colleges. I’m sorry to learn that such a great, local, longitudinal study site will be razed. It takes foresight to create such a treasure and unique research lab.”

  3. Excerpt from an email I received from Lehigh Alumnus Abe Eastwood:

    “Actually, the first course I took at Lehigh was with Dr. Trembley. I had been an undergraduate at Muhlenberg, initially as a chemistry major. I did very poorly in that major and eventually had to switch. I picked biology, and discovered I loved it and got all As and Bs that pulled my GPA up enough to graduate. With that less than stellar record, most of the graduate schools I applied to rejected me despite my good graduate record exam scores. Lehigh accepted me on the condition that I do well in the ecology course Dr. Trembley taught that summer. I got an A.

    In that course we had several field trips to Hawk Mountain, and I continued to go there often during my time at Lehigh. Dr. Trembley wrote a weekly article for the Morning Call newspaper. In one article about Hawk Mountain he featured a photo I took of a child standing on the top of the lookout holding a massive (compared to the child) pair of binoculars.

    One of the things I remember most about Dr. Trembley was his ability to help and counsel students. I know he helped give me insight into some of the problems my parents were having.

    By the way, I think it is ridiculous to take down the tangled bank to make room for a building. It really doesn’t take up that much space, and it is a wonderful learning location right in the middle of the campus.”

  4. Reblogged this on In the Forgotten Forest and commented:
    Another interesting bit of forest succession history on Lehigh’s campus!

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