New Church Life January/February 2016 | Page 28

new church life: jan uary/february 2016 oxygen on the planet. Although most of us have never heard of them, their loss would be even more devastating (I’m told) than that of all the rain forest. There are hundreds of thousands of species of them, all different, but they fall into two basic categories: so called “benthic” or bottom-dwelling diatoms, which are generally shaped like a feather and so are called “pennate”; and “planktonic” or floating diatoms, which tend to be round, at least seen from one angle, and are therefore called “centric.” Sherri devoted a lot of time to studying diatoms in the Chesapeake Bay. She found that they tell a very precise story year by year about ecological conditions in the distant past. And what she found was that for thousands of years there was a stable balance in the bay; the bottom was covered in hundreds of species of diatoms that happily coexisted and thrived through their diversity; there was plenty of sunlight for all, streaming through the clear water. Then in the 18th century the human land use inadvertently drove up the levels of nitrogen and phosphorous in the water, with the result that one of two species of planktonic or floating, centric diatoms became dominant. In what is rather kindly called a “bloom,” these floating diatoms reproduced wildly and upset the balance in the bay; they hogged the sunlight, killing all the benthic diatoms at the bottom; then ran out of silica and nutrients, died, sank to the bottom, and in the course of rotting, sucked all of the remaining oxygen out of areas of the bay, creating what is called “anoxia,” or lack of oxygen, which affects everything in the food chain. It is not an irreversible condition but an extremely dire one nonetheless. To Sherri I think the contrast between the heavenliness of a stable, longstanding condition of diversity, evenness and balance, and a deadness because just one species on land changed the land use, and just one or two others in the water became devastatingly dominant as a result, was highly instructive and attention-getting. And what about evenness? Even non-scientists know that diversity is important for a rich, vibrant ecosystem, but not as many of us are aware that it is not just the number of different species present, but how evenly they are distributed that matters. In formulas used by scientists to determine diversity, the evenness of each species is part of the equation. Having a hundred or even a thousand different species in a given environment does not supply much stability or balance if just one of those species hogs 75 percent of the space and controls 95 percent of the nutrients. Is this an issue among humans as well? Do humans sometimes want to exercise their will on each other and dictate how others should be? Do some take more than their fair share? It seems we sometimes do! I say this at the outset because understanding how crucial diversity, evenness and balance were to Sherri helps us understand the choices she made 24