Lakes for all seasons and reasons

kw: book reviews, nonfiction, limnology, lakes

I considered starting with a definition, that limnology is the scientific study of lakes, but I realize that "scientific" adds a redundancy. "Study", all by itself, is scientific. Whether we then draw conclusions scientifically, or some other way, is another matter.

Still Waters: The Secret World of Lakes, by Curt Stager, helped me understand that lakes are like the proverbial duck: seemingly serene on the surface, but paddling like mad underneath. Thus, a duck gliding along expresses the reality of the pond. A lot is going on under there!

"Lake" refers to the larger water bodies that are not oceans. The related words "pond", "pool", and even "tarn" refer to smaller ones, but I know of no clear dividing line. The state of Minnesota is called "The land of 10,000 lakes". Perhaps for that reason, in the area around Lake Minnetonka, a pretty big lake at 23 square miles, almost everything big enough to float a canoe and paddle around in is called a lake. By contrast, one of America's most famous lakes, Walden Pond in Massachusetts, has an area of 61 acres and is something over half a mile long. Yet it is called a pond. My own criterion is this: a pond is small enough for an ordinary person to own in its entirety. So if it fits on a farm, for example, I think of it as a pond.

At the upper range of sizes, the largest lakes are too big to see across. The largest, the Caspian Sea, is 745 miles long and has an area of 143,000 square miles. However, its water is brackish; it used to be an arm of an ocean. The largest freshwater lake is Superior, centered on the US/Canada border. Its length is 383 miles, and its area nearly 32,000 square miles. The deepest lake, Baikal in Russia, is more than a mile deep. While it is of similar length to Superior (395 miles), it is much narrower, but because of its depth, contains more than twice as much water.

The largest lake of my experience is Erie, between northern Ohio and Canada. With length of 241 miles and area of 9,900 square miles, it seems oceanic to me. It is not possible to see across it. From points west of Cleveland, Ohio across to Point Pelee, Ontario, the distance is about 33.5 miles. The curvature of the Earth makes the water midway across "rise" 187 feet above shoreline points at either end. There aren't any near-shore hills high enough to see over that; there would have to be one at each end of the sight line.

The author's studies of lakes are pretty comprehensive. I used to joke that the bailiwick of geophysics, my primary area of expertise, is "from the center of the Earth to the edge of space, and a little beyond." However, geophysics has little to do with life. Limnology, on the other hand, encompasses not only the geology and geomorphology and geophysics of the land under a body of water, but also its biology and chemistry and hydrology (how water moves).

One aim of the book is to show the impact people have had on lakes. We tend to think of human impact in Eurocentric terms, as though every lake on Earth was pristine until the colonial empires were formed between 500 and 200 years ago. The fallacy of this was brought home to me when I visited relatives in North Carolina, some 50 years ago. My uncle-in-law has collected arrowheads and other prehistoric stone tools in every one of the fifty United States. We went to the shore of a pond near his home, where he dug around a bit, sifted some of the soil, and brought forth a few yellowish flint arrow points. He said they were about 8,000 years old. He told the story he could read in the shape of the landscape. He had known where to dig because it was a good spot to put a tent or cabin above the shoreline, with good sight lines. He pointed out another few places that would probably have been repeatedly visited by the people of that time, plus or minus a few thousand years. The people that lived in the area would have fished in the pond and used it and connecting streams for transportation via whatever kind of small boats they had. Their wastes also ended up in the pond, changing its chemistry, often in seasonal ways.

The author of Still Waters uses seven lakes or lake areas to tell the stories of how lakes change through time, in particular, how the fish, insects, and other living things in a lake go about their business...or not, if some humans happen to decide to poison a lake and replace the fish with some they'd rather have there; or if they decide to drain a shallow lake; or build a dam to raise its water level. All these things happen to thousands of lakes. The "game fishing" business is especially troubling, because people would rather fish for trout, bass, or even crappie, rather than the things they call "trash fish". It is pretty well known (finally!) that many, perhaps most, lakes contain one or a few fish species that are endemic, meaning that they occur nowhere else. A chapter on Heritage Lakes tells us of one of them, one that hasn't been (yet!) poisoned out or "over-loved".

The deadest of dead lakes, the Dead Sea of Israel and Jordan, has no fish or insects living in it, but it does have a few species of extremophile bacteria (or archaea) that occur nowhere else. A project being considered by the two countries, to create a hydropower facility that uses Red Sea water, flowing more than 1,100 vertical feet over the 100 mile distance to the Dead Sea, is certain to change or eliminate them.

I have ruminated too long of matters that are mostly peripheral to the author's concerns. He aims for more people to realize just how much we have changed every one of the hundred-plus million lakes on this Earth, and how much we continue to do so. The fascinating stories of the lakes, and their histories as told by studies of the sediments that line them, underscore first, just how dependent we are on lakes, and secondly, just how dependent they are on us. The lakes of Earth, even the most remote, are much different from what they would be were we not here.