While we object to the needless destruction of non-native plants and trees, we are even more concerned about the destruction of non-native animals. Using the same justification, namely that non-native animals out-compete native species of animals, native plant advocates and their allies are equally committed to the eradication of non-native animals. The list of targeted animals is long: e.g., non-native frogs, turtles, fish, bees, foxes, opossums, squirrels, deer, pigs,etc. When populations of native animals increase in urban areas, they are called “subsidized predators” and added to the death list: e.g., raccoons, skunks, etc. A native animal can land on the death list if its range expands, such that it becomes a competitor for a preferred, rare native animal.
First we will indulge in a brief digression on behalf of the non-native European honeybee, one of the few species of bee in the United States that produces honey. If that’s insufficient reason to defend its existence, let us consider that the European honeybee is responsible for pollinating about one-third of all agricultural crops and orchards in our country(1). Even without eradication efforts, the honeybee is in trouble. In the past several years, about one-third of all hives have failed each year from multiple factors summarized as “Colony Collapse Disorder.” Despite the obvious value of this non-native creature, it is being eradicated by the Nature Conservancy on its “restorations” in the United States because it is non-native and it is considered a competitor to native bees, which are not capable of pollinating many agricultural crops or making honey(2). This seems to us a classic case of nativism shooting us in the collective foot.
Now we will turn to two efforts to exterminate animals that were both appallingly destructive, but more importantly, ineffective and clearly a waste of both lives and taxpayers’ money. The first example is historical, illustrating that man’s efforts to manipulate nature to serve his purposes are not new and undoubtedly can be traced as far back as the historical record can take us.
In this case, we will look at the efforts of the California Division of Fish and Game to increase the population of quail(3). Quail are native to California, but their population exploded with the arrival of Europeans whose agricultural and grazing practices increased the food supply of the quail. The population of quail in California reached its peak during the period 1860 to 1895 and thereafter began to decline as non-native annual grasses began to dominate the non-native herbaceous and leguminous plants that preceded them. Since man’s view of nature is rather narrow in time, limited by his brief lifetime compared to the more slowly moving forces of nature, the California Division of Fish and Game perceived the decline in the quail population as a problem requiring remediation. One of their proactive efforts was to exterminate all animals believed to be predators of the quail. This “predator control” effort was summarized for one six-month period as follows:
“…between January 1 and July 1, 1931, [deputies of the Division of Fish and Game] have destroyed…: 38 coyotes, 33 bobcats, 684 house cats, 35 foxes, 43 coons, 8 weasels, 2 opossums, 1 badger, 5 wild and unclaimed dogs…365 sharp-shinned and cooper hawks, 3972 blue jays, 293 magpies, 81 crows, 49 butcher birds, 2 great horned owls, and 47 snakes.”(4)
The Division of Fish and Game hired an army of 45 full-time men in 1948 to continue this war on the perceived enemies of quail. This extermination effort was not abandoned until 1957, when the Division of Fish and Game concluded that the quail population was not benefitting from this animal holocaust and that reduced food sources and cover, resulting from changes in land uses and consequent vegetation types was the reason for the declining quail population. In other words, hundreds of thousands of animals lost their lives over a period of over 25 years for no reason whatsoever.
So, did we learn anything from that experience? Clearly not. Today there are nearly as many programs to eradicate non-native animals as there are non-native species. We choose the brown-headed cowbird as an example of modern eradication efforts because it is occurring in California (5).
Although the brown-headed cowbird is native, it is perhaps one of our most reviled birds because it is a nest parasite, which means that it lays its eggs in the nests of other birds. Their egg is usually larger than the eggs of the “host” bird and it hatches earlier than its nest-mates. The result of these advantages is that the off-spring of the nest owner usually does not survive, but the cowbird chick survives to repeat this trick. Because the range of the cowbird has been expanding, it has been blamed for the declining population of songbirds.
But does the cowbird deserve to be blamed for the decline in the songbird population? Professor Stephen Rothstein (Department of Ecology and Evolution, UC Santa Barbara) says, “NO.” He tells us that the range of the cowbird is not larger than its historic range. At the time of the megafauna (e.g., wooly mammoths), about 15,000 to 20,000 years ago, cowbirds probably occupied their current range. When the megafauna disappeared, the range of the cowbird shrank. As in the case of the quail, we look to man for the explanation for why its range has expanded again: the introduction of large grazing animals by Europeans has provided the cowbird with a substitute for its prehistoric food source.
Professor Rothstein tells us of several efforts to exterminate cowbirds on behalf of declining populations of songbirds and concludes that although songbird populations may have recovered in some cases, the extermination of cowbirds is not the likely explanation for their recovery.
The recovery of the Kirtland’s Warbler in Michigan is a case in point. The warbler’s nesting habitat was well known to require periodic fire. Yet, the scientific managers of this recovery project preferred to kill cowbirds rather than to risk human life and property by not suppressing fire. Nearly 125,000 cowbirds were destroyed in a portion of a small peninsula in Michigan during the period 1972 to 2002. Although nest parasitism declined significantly, the population of Kirtland’s warbler did not increase until over 20 years later after a large accidental forest fire. In other words, the cowbird is a scapegoat for the choices made by man, in this case the suppression of fire.
Like the predator control project on behalf of the quail, cowbird extermination projects create jobs. The Kirtland’s Warbler project continues to cost about $100,000 per year, although there is no evidence that the warbler is benefiting from it. Rothstein speculates: ”The money spent on cowbird control every year may total more than one million dollars.” This creates a profit motive which Rothstein says results in a “control lobby” that advocates for continuing the program whether or not it is effective. He believes that this money would be put to better use by addressing the underlying problems, such as habitat loss to development or reduced water levels that change vegetation types, as in the case of the declining population of the Southwestern Willow Flycatcher.
These are familiar themes to the readers of Million Trees:
- That native plant advocates and their allies frequently confuse cause and effect, e.g., cowbirds are not responsible for declining songbird populations.
- That man finds it convenient to scapegoat plants and animals for changes in the environment that are caused by man.
- That people who make their living in these misguided “restoration” efforts have a vested interest in their continuation whether or not they are effective
- That the waste of money and scarce resources prevents us from addressing the real issues
- That choosing to replicate nature at some specific point in historical time is illogical because nature is constantly changing, not always in response to the actions of man
Postscript: Here is a link to a radio story about another episode in the attempt to save the Kirtland’s warbler. After killing 125,000 cowbirds (according to the ABA article), US Forest Service changed its mind about why the population of Kirtland’s warblers was dwindling. They decided that the problem was that the warbler required young trees of a specific species, which is germinated by fire. So, they set a prescribed burn that caused a wildfire on a windy day, burning over 20,000 acres, destroying 41 homes, and killing a young man who worked for the Forest Service. The population of Kirtland’s warblers rebounded. Now the Forest Service says they must continue to kill cowbirds and set prescribed burns every year forever if the Kirtland’s warbler is to survive. This radio program poses the question: does this make sense?
(2) “Bias Against Non-Native Species,” http://roomfordebate.blogs.nytimes.com/2009/09/02/saving-bees-what-we-know-now/
(3) A. Starker Leopold, California Quail, University of California Press, 1977. (N.B. A. Starker Leopold is Aldo Leopold’s son.)
(5) Rothstein, Stephen, “Brown-headed Cowbird, Villain or Scapegoat?,” Birding [journal of American Birding Association], August 2004, 374-384.