The Great Lakes

The Great Lakes

Blog post by Dean
Monday, July 17, 2017

My favorite genre is nature writing. I like reading about how the world works. The guy who writes about that best, for my money, is John McPhee. When a work mate recommended him to me in the early 80s, I went out and bought Basin and Range, and I’ve been reading natural history ever since.

Dan Egan has written a really enjoyable book of natural history, though on a lamentable subject: The Death and Life of the Great Lakes. Readers are comparing it to Silent Spring: a call to action and fascinating science. It describes wave after wave of invasive animals coming into the lakes, starting with lampreys that literally suck the life out of the trout; then alewives that overpopulate and die in billions and wash ashore in rotting gelatinous heaps. So salmon are released to control the alewives, and it works! The salmon gorge and grow huge and suddenly the fishing is spectacular! Until both populations crash, and then people want the alewives—formerly a stinking blight on the public beaches—restocked!

Currently a couple of mollusks are flummoxing biologists. Zebra and quagga mussels clog the lakes. They're filter feeders. They take in water, strip out its nutrients, and excrete it. There are now so many of these bivalves in Lake Michigan that they can turn over the entire lake in two weeks. That’s right: animals the size of sunflower seeds have reproduced so successfully that a few years after they arrived there are enough of them to filter all the water in Lake Michigan every fourteen days.

As a result, the lake is almost as clear as the Caribbean. Shipwrecks hidden by murky water for centuries are suddenly visible, which is delightful for swimming, but it means the lake is sterile. What clouded Lake Michigan when it was healthy was plankton, the base of the food pyramid and the origin of dinner for everybody.

The problems started in the early 1800s when humans built canals to bypass the rapids and locks to top Niagara Falls, the barrier that for eons had kept creatures and cargo from moving west onto the lakes. Ships got bigger and so did the canals until the locks could lift ocean-going vessels 60 feet up the Niagara Escarpment, bringing in animals from wherever those ships had been, lampreys and alewives from the North Atlantic and mussels from Ukraine. Only 2% of goods moving through the Great Lakes region ships on water. One long freight train could fill all those orders, but the shipping lobby is strong and the US and Canada are invested in the canals, and we are unlikely to change things in time to save the old ecosystem, if it isn’t already too late.

I’m trying to tell you the whole book in a half-page blog but it’s not possible. If you’re a fan of nature writing, you’ll want to hear it from Egan.