There was a day when most doctors were generalists, but they didn’t know they were. They just dealt with sick people and people who were hurting, whatever the cause. There were very few doctors who dealt exclusively with one form of sickness or one kind of body part. Today, we’re often sent to a specialist if we’re sick or hurt. These specialists tend to cluster in a few large centers, but are rare elsewhere. We’re fortunate to be relatively close to several of these large clusters of specialists here in Central Iowa. Because the “habitat” in these centers seems to be right to support them, we can usually see one (eventually) if necessary. We benefit from having access to the very complex medical machinery, and wide array of drugs and techniques that require the training and knowledge that specialists provide in these very specialized “habitat centers” We lost something, though, when a generalist could provide at least some level of treatment and relief for whatever problem you came in the door with; even if you had several issues to deal with at the same time, as many of us do. There’s comfort, stability and assurance when there are a few good generalists still around.
The situation we face today with much of our native wildlife has some similarities. Generalist species that can cope with a wider range of foods and habitats are hanging on and even thriving. Specialists that have very narrow food and habitat requirements face a very difficult future as their various specialized habitat niches become more rare and isolated. The monarch butterfly is a classic example of a specialist. Although the adult butterflies can feed on a wide variety of nectar-bearing flowers, their caterpillar young can feed only on plants from the milkweed family. North America is home to many species of milkweeds, and almost all parts of temperate North America once hosted several species of milkweeds in good numbers. The once-common milkweed family has nearly disappeared in vast areas of America over the past 30 years, though, due to sweeping changes in the way we use the land. As milkweed populations have become more rare and isolated, the monarchs that once fed on them have nearly disappeared as well. This migratory species is doubly vulnerable because their only winter habitat is a small, isolated stretch of mountain forest in Mexico that is now increasingly threatened by changing land use there and changing climate.
Generalist species like starlings, house sparrows, and even robins and red-winged blackbirds continue to thrive with their ability to adapt to a variety of habitats and foods. They can even cope with highly altered environments like much of Iowa is today. Wild creatures and their habitat needs occur across the full spectrum, from highly specialized to very generalized, though, with more species somewhere in the middle. The highly specialized ones are already threatened, endangered or gone. The somewhat less specialized ones are becoming threatened as the landscape continues to lose the diversity of habitat types necessary to support them. It will take a great deal of thoughtful effort on our part if we are to keep much of the species diversity we still enjoy. Continuing down the path we’ve been on will eventually leave us with only a relatively few generalist species.
My wife, Sue, and I enjoyed walking along a rocky ridge in Floyd County on Easter Sunday. Seeing the pale blue pasque flowers, purple avens and prairie violets blooming on this rather rare habitat type is a spring ritual we have missed for a couple of years, and it was good to be there again. We hope to enjoy another of our spring rituals later today as we look for a large and beautiful yellow-headed blackbird. Though they eat most of the same things, they are much more specialized than their common red-winged cousins. They nest only over standing water in tall marsh vegetation. We’ve found them in the past, but will be lucky to find even one this year. Although a few wetlands still exist, vegetation in them changes from year to year. The kind of vegetation and water levels that yellow-heads need to nest and raise young can be hard to find.
Steve Lekwa is a former director of Story County Conservation.