UNITY -- An hour's walk brought a group of about 25 Unity College biology students to the center of the lake's surface. The acidic water beneath them was at least 40 feet deep, but a spongy network of moss supported them -- for the most part.

On occasion, the soggy peat had given way underfoot, and students found themselves suddenly sinking knee- or hip-deep into the slough before being pulled out to safety. Even in the firmer spots, ripples spreading from the feet of a student bouncing on the floating mat visibly moved his classmates who were standing 15 feet away on the surface of Kanokolus Bog.

Throughout the trek, Unity College professor David Potter explained how a sphagnum bog works and how certain species depend upon the unique habitat it provides.

"Could we (humans) get by without bogs?" he said. "Sure. But a lot of ecologists would say 'no.'"

Potter said that while humans would probably survive without the existence of bogs' unique habitat, several species of plants and animals might not. Several creatures and plants, such as the Ringed Boghaunter dragonfly, Bog Lemmings, several varieties of bog sphagnum, Bog Rosemary and Bog Laurel are found exclusively in sphagnum bogs; cranberries and blackberries also grow well there.

"These are extreme habitats out here," Potter said. "We're talking Arctic conditions, we're talking Mohave Desert equivalent conditions."

Potter said harsh conditions such as high acidity provide a safe harbor to certain species simply by cutting down on the number of predators that can survive in the bog. Ducks congregate to the relatively safe center of the bog when they lose their flight feathers after molting, Potter said.

Skyrocketing fuel costs might threaten the existence of bogs if they ever reach the point at which people would find it economical to harvest peat as they do in Ireland and other parts of the world, he said. This would mean draining the lake beneath the bog, and would destroy centuries of nature's work.

The bog on which the group walked was ancient. It took 10,000 years for sphagnum moss to form a "dome" across the surface of the lake, Potter said, growing ever thicker to the point that it could support the weight of creatures walking on it.

After pausing for a moment's reflection at the center of the lake, students scribbled down their observations about sights, sounds and even tastes they had encountered in the bog, and then slowly crept back in single file, leaving the unique ecosystem nearly as they had found it.