When the Israelites had negotiated their difficulties with Pharaoh at the Red Sea, and gone forth from there into the wilderness of Sur, their rations were in short supply. Help, however, was at hand.
"The Lord said to Moses: `Behold, I will rain bread from heaven for you; let your people go forth and gather what is sufficient for the day.' " And so he did: "In the morning there was a layer of dew around the camp, and when the dew was gone thin flakes, like unto the hoar frost on the ground, appeared upon the desert floor." The Israelites duly gathered up the manna, and made bread. Some assert that this biblical manna may have been a lichen called Leconora esculenta. Lichens are a strange and unique form of life comprising a symbiotic pairing of a fungus and an alga. They form readily on the barks of trees and on rocks; they are often large and irregular in shape, and appear in many different pastel shades. Individuals may grow by as little as a millimetre a year, but they can survive for centuries.
More than 1,700 species of lichens inhabit the islands of Ireland and Britain, and if they are aesthetically questionable, they are at least a sign that the surrounding air is pure, being effective barometers of the level of pollution in the atmosphere.
Although they can endure the most extreme climatic conditions, lichens are very sensitive to airborne impurities, and a thriving population is an indication that the local air is clean. Conversely, their decline or absence signifies the opposite. Indeed, in recent years in Britain it has been found that certain species of lichen, thought to have been extinct, are re-emerging, a development probably connected to the decline in levels of sulphur dioxide pollution in the atmosphere. Leconora esculenta is a rather flaky lichen which peels easily from the rocks in the arid areas where it thrives, to blow freely in the wind. The biblical connection has been suggested by well-documented accounts of events in 1829 when, during a war between the Russians and the Prussians, a severe famine affected areas near the Caspian Sea.
During a violent windstorm, the countryside became littered with Leconora esculenta, and the local populace, noticing that their sheep could eat it without ill-effect, gathered the lichen. They made it into what was apparently a very palatable bread. Manna from heaven, could it possibly have been?