Commentary, St. Louis Post-Dispatch
By Jeffrey P. Bonner

There is a beautiful, albeit slightly bizarre, fern found in the far northern forests of the United States, up in Wisconsin, Minnesota and Michigan. It's called the goblin fern because it hides in the leaf litter of the forest floor.

Occasionally, it sticks its pale form an inch or two above the surface; most of the time, it lies buried, invisible, among the dead leaves. Scientists think it might draw nourishment from fungi in the soil during the time it's hiding.

The goblin fern is considered endangered. Never easy to find in the first place, it appears to be dying out, and it is dying in a peculiar pattern. The areas of the country where it's found are dotted with little lakes and ponds, and the goblins are dying in circles that radiate out from these ponds.

Why are they dying? Why in such an odd pattern? Scientists think they know the answer, but before I share it with you, let's talk about worms.

The first thing you should know about worms is that they aren't native to most of the United States, and those that are native to America are just tiny little things. But night crawlers and big red wrigglers alike came over with the early colonists. Some came in the soil that was used as ballast in ships' holds, and some probably came in crates that were carefully packed for the long ocean voyage.

The European colonists knew that earth worms are good for the soil, as any gardener will tell you. They convert dead organic matter, like leaves, into rich humus. As they move through the soil, they take in little bits of dirt along with the leaf litter, grind it into a paste and excrete it as a "cast" that is super rich in nitrogen, phosphates and potash. It is, in other words, a perfect fertilizer.

The average worm produces about ten pounds of casts a year, and it keeps the soil aerated and improves drainage. Long story short: Any gardener with a lick of sense loves the little guys, and that's why the colonists brought them over.

Of course, gardeners aren't the only folks with a fondness for these slimy little wigglers. Fishermen like them, too. And although fishermen like to joke about "drowning some worms," here's something they may not know: Worms can survive in a pond for weeks if there's enough oxygen in the water.

I always thought worms came out of the ground after a rainstorm because they couldn't breathe, but I was wrong. The real reason is that the moist ground allows them to travel quickly over the ground, instead of having to tunnel through it, getting to new areas faster (although not nearly so fast as they traveled here by boat).

In fact, worms would move through America very slowly if we humans weren't shipping them to gardeners all around the United States from the worm farms where they're bred.

By now, those of you who appreciate a good Halloween mystery already may have figured out why the goblin ferns are dying in circles radiating out from the lakes and ponds of our lush northern forests. It's because of the worms.

Fishermen bring them into the forest when they fish in the ponds. Rather than haul the yucky worms home with them when they're done, they dump the extras in the lake or along the shore. The worms hightail it into the forest where they find what must seem like paradise to them: a forest floor covered with several inches of delicious, nutritious dead leaves.

The worms chomp to their heart's content - a night crawler has five pairs of hearts, so there's a lot to be contented - gradually getting rid of all the leaves and leaving rich soil in their place.

But this leaves no place for our little goblin fern. No leaf litter, no habitat. No habitat, no ferns.

So, our scary Halloween mystery comes down to this: Slimy 10-hearted alien invaders from another country are eating our reclusive ghostly ferns out of, well, out of house and home. But don't blame the fishermen. The worms would have got there eventually. The fishermen just helped speed the process along.

If you were in charge of colonial immigration, would you have let the worms in? Do worms do more good today than harm? I can't answer that question myself. I like to fish and to garden in my spare time, so you won't get an unbiased answer from me. But it's a question worth pondering today.

Happy Halloween!

Jeffrey P. Bonner is president and chief executive of the St. Louis Zoo.

Republished with the permission of the St. Louis Post-Dispatch
Copyright 2006 St. Louis Post-Dispatch
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