This specimen of creeping crow’s foot was collected May 2, 1850, and preserved in the scrapbook of Mary Clark, the Ann Arbor teacher who often brought her young charges to study botany in Schoolgirls’ Glen. (Image: Papers of Mary Clark, courtesy of U-M’s Bentley Historical Library.)

This 19th-century lithograph, published in an 1871 edition of Scribner’s Magazine, captures the glen’s sublime appeal.

Schoolgirls today would see this drain, which appears at the top of the glen. (Image: R. Grese.)

This image is looking down from the drain outlet. (Image: R. Grese.)

The eroding soil has exposed myriad rocks and stones. (Image: R. Greese.)

Years of erosion have taken their toll. (Image: R. Greese.)

The glen once grew an extraordinary mixture of shrubs, ferns, wildflowers and trees. (Image: R. Grese.)

This drainage pipe carries water from the drain at Washington Heights to the base of the channel. (Image: R. Grese.)

This second pipe carries water from the outlet down to the channel as a way of preventing further erosion. (Image: R. Grese.)

After the Second World War Schoolgirls’ Glen began to wash away. (Image R. Grese.)

The diversity of flowers and trees in the glen was known to attract an extraordinary range of insects and birds. (Image: R. Grese.)

The glen can never look as it did in the 1800s — too much soil is simply gone. (Image: R. Grese.)

In the early 2000s, SNRE students studied what decades of unchecked stormwater had done. (Image: R. Grese.)

When they began to assess damage in the area, SNRE students estimated about a cubic yard of soil had washed out of the glen every day for some 35 years. (Image: R. Grese.)

Erosion in the glen has been slowed, thanks to concerted efforts. (Image: R. Grese.)

Glacial boulders hidden underground for millenia now sit exposed on the ground. (Image: R. Grese.)

Birdwatchers have followed the birds to other, more hospitable spots in the Arb. (Image: R. Grese.)

Erosion has exposed these pre-glaciation sediments at the base of the ravine. Geology students at U-M are able to study these samples; the glen is one of few local places where they can be seen. (Image: R. Grese.)

“No person with any poetry in his soul can walk from the second railroad bridge north to Schoolgirls’ Glen without rhyming all the way,” a 19th-century student once wrote. (Image: R. Grese.)

The glen has changed dramatically when compared to early images from the 1800s. (Image: R. Grese.)

It is expected the glen can reclaim its ecological integrity, but only if more is done, and soon. (Image: R. Grese.)