The Narrow Edge: A Tiny Bird, an Ancient Crab & an Epic Journey by Deborah Cramer. New Haven, Yale University Press. 2015. 293pp. ISBN: 978-0-300-18519-5
Cramer put a lot of effort into this book. She embedded herself with researchers studying an array of natural history all stemming from the symbiotic relationship of the red knot shorebird and the horseshoe crab. It is pretty detailed and includes the kinship of much of the food chain and that is what makes the story important.
The red knot migrates from Tierra del Fuego to northern Canada. Then back again after nesting. It’s about a 9500 mile one way trip and is quite a tribute to this little bird that it has been making the trek for millions of years.
For many birds their plight as a species is increasingly imperiled. No reader needs a lecture about it from these quarters. What Cramer does is provide a link about the importance of many species to others and what is going on that is damaging those connections.
While we are eroding our salt marshes, hewing our carbon dioxide receptacles, warming our atmosphere and melting ice caps other species feel the heat too. This is all about the chain of life and Cramer provides much detail with observations and working with professionals who explain their works through her.
Her prime subjects are the horseshoe crab and the red knot shorebird but they are symbolic of a bigger plight that endangers those two but the rest of life as well. Horseshoe crabs, if all goes well will lay their eggs in the spring. In the Delaware Bay where Cramer focused, this event occurs when the migration from Bania Lomas to northern Canada has the red knots land for a mid-trip respite. There are fewer of both of them annually.
The crabs (they are not true crabs and she explains that in the book) are selected by the medical industry who bleed them for a sterilizing component found in their blood. The component-LAL stands for Limulus amebocyte lysate, and it is a test required on all blood transfusion (and more) tools. It must be passed by the FDA or those products cannot be used. Only the horseshoe crab (family Limulidae) can provide the chemical required for this sterilization process. In her story she indicates that something like 18% of the crabs that are bled actually die in the process. The others docile, go back to the sea where they slowly recoup but do not mate-thus no eggs.
The discovery of this sterilizing component came years after the horseshoe crab was harvested for fertilizer and bait. Despite the fact that that they still exist in the millions, wherever they are found it is in increasingly smaller numbers. That means that one part of the red knot ecosystem is dwindling. They too still have large numbers but they decrease annually at an alarming rate.
Why should anyone care about crabs that are inedible for humans and a tiny shorebird? Cramer continues her quest to teach the reader about symbiosis by following a chain that leads to Midwestern prairie farmers and how the reduction of one part of a food chain goes all the way to its impact on crops in the field. You will need to read the book for those details but she makes a case not only for an impact on foods that you and I eat but also the financial strain placed on farmers. As I like to say, “We are all (the flora and fauna) in this together.” The extinction of red knots is not going to starve humans but it is one more chink in the armor of the food chain.
Through 12 chapters Cramer presents a good case about the sanctity of symbiosis and then she finishes the book with an epilog. The last few pages were tepid and filled with suggestions that are so generic that they require a yawn. “Be good to the earth” might be one way of putting it. We already knew that. There is a saying that I can only paraphrase here and essentially it says “my grandfather saw millions of them, my father hundreds. I see tens of them and my children see a few.” Those of us with an interest in ecology and natural history already know what the epilog suggests.
She did present a sound argument about the critical nature of symbioses and the chain of life in the 12 chapters and in all it was quite a good book.