My helpful neighbors are endlessly indulgent toward me: over the decades of our friendship, they have cared for all of my pets and animals when I’ve gone away. This menagerie over the years has included various dogs and cats, a budgerigar, fish, hamsters, chickens and goats (the latter of which I was, in turn, baby-sitting over a winter for another friend). It has also included as many as 50 houseplants at a time.

As I’ve said, they are endlessly indulgent and never demurred when I took in some new pet or got hooked on some new plant species I just had to propagate on the windowsill.

But when I went away last spring for several weeks, I somehow couldn’t bear to confess to Bob that I had pet worms. In the kitchen.

OK, so they are not really pets. I don’t pick them up and stroke them and talk to them in coo-ey little baby-talk phrases. They are workaholics anyway, and only care if they are fed well enough to turn the garbage into rich compost. I just pick up the top layer of mulch and peek in at them now and then when I give them vegetable peelings or egg shells or coffee grounds, and admire their wriggly, glistening, tiny pinky-red bodies. They look so happy.

When I left, I gave them a good feeding and trusted that the cooler temperature of the house would slow them down and they wouldn’t eat everything up and come crawling out of their bin looking for more food, which is what they do when they are hungry.

They didn’t, and Bob never knew.

These worms are much like but not the same species as earthworms that loosen up your garden soil or that you dig up to feed the fish you hope to hook for supper.

I found a clump in my compost heap. A friend has been keeping a worm farm she inherited in her cellar for several years, so I thought I would try a homemade version, and researched on the Internet to learn how to do it. Worm farms are simple to create and maintain (you can send away for commercial bins and the worms themselves if you don’t want the DIY route). You can turn vegetable and fruit scraps into fertile potting soil even if you can’t have an outdoor compost heap.

Composting worms can eat up to half their own body weight every day and can double their population every few months. They self-regulate their numbers when worm concentration in the container reaches capacity (about 15,000 to 20,000 worms) after 2 to 5 years. And then you can thin them out by giving some away to your undoubtedly eager friends.

It’ll be a while before mine reach that density, and in the meantime, they are a project that benefits me, provides the worms a happy home, and has a beneficial effect on the environment.

But when I began researching for this project, I was surprised to find out that our friendly garden worms may not be so beneficial. They are classified as a non-native, invasive species and are having a devastating effect on northern forests.

Native earthworms died out in the Ice Age. The ones we know are European imports, brought by colonists in balls of earth around plants they wanted to grow in the New World, or jettisoned when earth ballast in sailing ships was discarded.

Scientists at the University of Minnesota have been studying the effect of these foreign intruders on the ecosystems of hardwood forests. They seem to be especially damaging to sugar maple woods. The voracious appetite that make them so useful in compacted garden soil churns up leaf litter in the woods so rapidly that the nutrient cycle is changed and erosion has become a problem.

Anglers are now advised to refrain from dumping unused worms at the shore of a forested lake. The UM researches have discovered that earthworm damage radiates out around lakes where unused worms have been released at favorite fishing spots.

The worms advance slowly – five to 10 meters per year. Maybe this is a slow enough rate for the Minnesota scientists to figure out some way to deal with this damage – some way that won’t cause further unpredicted damage.

For that seems to be the message of our time about human interactions with the environment: what we do has an effect, perhaps one we won’t fully understand for years or even centuries, but one that nevertheless transforms the earth.

It’s not to say that we should stop living, but it is our responsibility to be conscious and conscientious about even small things we do, like dumping the contents of the worm can after a day of fishing. Like the physician’s oath, we must remember that as far as we can help it, our first calling is to do no harm.