Donald Dann’s March 16 letter about managing nature had many targets, ranging from Canada geese to cats. Some of his points were valid, and some were not.
Historically speaking, inviting humans, even “scientists,” to manage nature has often proved to be a mistake. Late last century, Dr. Spencer Baird, an expert with the Smithsonian Institution, brought carp to this country. In 1932, as one ornithologist reported, “It has become the duty of every state game warden to kill as many hawks and owls as possible, to destroy their nest and eggs and to preach the gospel of extermination.”
Today’s experts would not recommend eradicating hawks or releasing carp. Yet, a scant 20 years ago, college professors advised me to plant non-native multiflora rose and Russian olive to improve wildlife habitat. What will tomorrow’s experts recommend? Who knows.
Even biological control, as Mr. Dann suggests for purple loosestrife, has its risks. Biological control, such as releasing ladybugs to eat aphids, has been a popular trend in recent decades. The premise is that after careful testing, the new exotic beetle will dine only on the unwanted alien purple loosestrife and that harmless plants, such as the native species of loosestrife, will remain unscathed.
The following, reported recently in the journal Science, may be of interest:
From 1968-1972, after extensive prerelease screenings of host preference, the European flowerhead weevil was released in Canada and four U.S. states in hopes it would help control Eurasian thistles. This weevil is now found in 24 states, including ours. Researchers found that from 1992-1996, weevil damage to native thistles consistently increased. In particular, exotic weevil larvae were found developing within flowerheads of Platte thistle, a characteristic species of Nebraska’s Sandhills Prairie. Even though scientists’ tests “proved” these flowerhead weevils to be, in Mr. Dann’s words, “otherwise harmless,” nature proved otherwise.
All in all, Mr. Dann seems to overlook the true management problem that underlies many issues he addresses. He hints at the real cause when he refers to “misguided early settlers” and writes, “We have created ideal habitat to encourage the overabundance of Canada geese. . . .” As long as there are more and more of us creating goose habitat and letting cats run free, the problems will persist. In many of the cases he touches upon, I suggest it is the humans that need managing, not nature.
