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When Plants Migrate

The study of how plants moved north after the last ice age could mean new directions for conservation

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As a people, we Americans have decided that we want to preserve at least a part of our natural environment. We can't preserve everything, however, and that means we have to have some way of choosing between competing conservation strategies. This choice depends, in turn, on what we think it is important to conserve. When we thought the most important thing to do was to save a species, we concentrated on how to save a particular sand dune or prairie that was home to that species. Today conservationists are more likely to talk about preserving entire ecosystems: the Greater Yellowstone Region, for example, or the Everglades.

It may be time, however, to focus on a different goal. We should concentrate on preserving the ability of plants and animals to respond to environmental changes. "We should be thinking about establishing reserves that cross environmental gradients," argues Jablonski. "We should think of ecosystems as sets of living organisms that need to expand and contract and shift around."

Such shifting already occurs in nature, of course. The Hawaiian Islands have been created by progressively newer volcanoes rising above the sea surface. As the older islands slowly sink again, the corals that are able to migrate move upward so that they remain at the same depth. Not all of them move fast enough. (Other organisms, for various reasons, have had an even harder time: Hawaii has probably lost a greater percentage of its flora and fauna than any other place in the United States.)

The fossil record seems to be telling us that we should be thinking about preserving species by giving them room to maneuver. Jablonski suggests, for example, that if we make an environmental preserve in the Amazon, we should include some foothills of the Andes to protect this kind of flexibility. That philosophy could guide the creation of new parks and preserves in other parts of the world, too.

In the United States, unfortunately, our parks and preserves are often surrounded by expensive development. It is very difficult to change boundaries that have existed for decades, even when we find out we should have done things differently. Had we known a century ago what we know now, we might, for example, have extended the boundaries of places like Yellowstone Park to include greater ranges of elevation. We might have bought more inland acres when establishing coastal preserves, to maintain the ability of coastal ecosystems to migrate landward if sea levels rise in the next century. Even if our current choices are limited, I expect that these new ideas will have an impact on how we spend our conservation dollars in the future.

The implications go further. If the climate does warm, natural ecosystems are not the only ones that will be moving north: those associated with agriculture will be doing the same. We normally think of an Iowa cornfield as a monoculture, but as every farmer knows, all sorts of varmints, weeds and insects live in even that simplified system. If the Corn Belt moves north to Minnesota, the paleobots are telling us, the rest of the "community" may not move with it like one big unhappy family. Knowing what will happen in advance could be worth billions of dollars to American agriculture.

As I left that restaurant and walked out into the cold Chicago night, I felt strangely elated. For one thing, it seemed to me that this new understanding could move the entire environmental debate to a new and more realistic level. Perhaps even more important, though, it confirmed my belief in the value of basic research, which is sometimes portrayed as the pursuit of useless knowledge. We have much to learn from something as seemingly "useless" as ancient pollen grains in the mud at the bottom of an ordinary lake.

By James Trefil

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