Deborah Cramer's 'Narrow Edge': Ecological tale of threat, hope

The Narrow Edge

nolead begins A Tiny Bird, an Ancient Crab and an Epic Journey nolead ends

nolead begins By Deborah Cramer

Yale University Press. $28. 304 pp.

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Deborah Cramer's riveting story of a small shorebird begins with loss: loss of large numbers of birds, of beach and mudflat, of its food, "and a slide toward extinction."

Grim stuff. But in Cramer's able hands, the story of the red knot - a bird inextricably linked with the Delaware Bay and its horseshoe crabs - becomes a scientific page-turner, full of intricacies and astonishment. Exhaustively researched and elegantly written, The Narrow Edge is a must for anyone interested in the natural world, our relationship to it, and our stewardship of it.

The red knot, weighing no more than a stick of butter, has one of the longest avian migrations on the planet, nearly 10,000 miles from the tip of South America to its breeding grounds in the Arctic.

One of its main stopovers is the Delaware Bay, which every May hosts a wildlife spectacle: the largest concentration of shorebirds on the Eastern Seaboard. The bay also is the population epicenter for horseshoe crabs. Just as the birds arrive, their final reserves depleted, the crabs set the buffet, emerging from the underwater muck to lay their fat-rich eggs in the sand.

Overall, shorebirds have declined, none so much as the red knot, whose population has plummeted as much as 70- 90 percent. Cramer takes us on a personal odyssey to explain why. She travels by boat, plane, ATV, SUV. She slogs across Patagonian mudflats and bundles up in the harsh Arctic. She shows us that the tiny shorebird faces many threats, from development to sea-level rise. Declared threatened in 2014, the red knot was the first species to be listed specifically because of the threat of climate change.

Bird and crab occupy an intricate, complex, and fragile web. Cramer's account is embroidered with rich asides - although the relevance of a few escaped me - and sumptuous scientific tidbits. (Example: At night, the sensitivity of the crab's eyes to light increases by a factor of one million.)

In this cautionary tale for our times lie hard questions, "questions of how or whether humans and wildlife will share our increasingly fragile shore," Cramer writes.

If the story begins with loss, it ends with a qualified optimism: "In the resilience of shorebirds . . . I find hope and faith that we can face even our most difficult challenges and that a healthier Earth supporting a multitude of species is still possible."