Locust (40 page)

The grazing by cattle, in particular, was heavily concentrated along rivers and streams, precisely the habitats utilized by the locusts. Many of the breeds of cattle raised in the West were developed in the pastures of Europe, where water was in abundance. Unlike bison, these were thirsty animals, accustomed to plentiful water. The typical beef cow needed ten to fifteen gallons of water daily, and a dairy cow required nearly twice as much. The aggregation of cattle in the valleys dramatically altered these ecosystems.

Based on modern studies, we know that it does not take many livestock to rapidly degrade riverside vegetation. Cattle may not be the brightest creatures, but they know what tastes good. So while hanging out along the streams, they pick out their favorite plants and leave behind an odd and dysfunctional assortment of species. With the loss of deeply rooted vegetation that anchors the riverbanks, the soil begins to erode. And as the banks collapse into the river, the water becomes shallow and silty. In this manner, the falling banks and rising riverbed generate a self-perpetuating process. Through these mutually reinforcing activities, the structure of the channel degenerates, and the river is freed from its established borders.

Like a feral animal, the deep, calm river is transformed into a wild, churning flood. With chronic trampling by cattle and the acute surges of spring meltwater, the channel erodes into a broad, silty floodplain. This transformation is accelerated by the effects of cattle even far from the river valley. The compacted soils and overgrazed vegetation in the uplands renders the land incapable of absorbing and transporting the spring melt and summer rains. This runoff feeds an already bulimic watershed that binges on the winter snowpack and then purges the spring runoff. Without the capacity to buffer the inflow, a river becomes prone to spectacular flooding. According to Clarence Forsling, who headed the Department of Interior’s Grazing Service, the West has been plagued by “disastrous floods since the turn of the century because of overgrazing in the mountains.”

Although Riley spent years observing the Rocky Mountain locust and generated thousands of pages on the natural history of this species, he conducted only one set of experiments on the locust—and these related to the effects of flooding on the survival of the eggs. It was clear from his records during that winter of 1876 that Riley was not a research scientist, as his experiments followed no systematic design. He tried a haphazard set of conditions, submerging eggs for various durations and frequencies. His experiments also lacked controls, which is the sort of flaw that would be fatal to a junior-high science-fair project. That is, he failed to keep any of the eggs in natural or dry conditions during the winter to understand what the normal rate of hatching would be without his efforts to drown the embryos. Most of his experiments showed that submerging the eggs in the midst of winter, when the embryos were not developing, had little effect on survival. Of course, flooding egg beds in January would have been impractical, even impossible, throughout most of the locust’s range. In the mountain valleys, the rivers would have been frozen over and there would have been no potential for the inundation of the overwintering eggs.

Riley conducted only a few experiments in the early spring, but these results were most revealing. While locust eggs are in diapause (an entomological term for a state of lowered metabolism and arrested development analogous to vertebrate hibernation), they are not much harmed by flooding. But once development recommences in the spring, the embryos become sensitive to environmental conditions. As many as four-fifths of the eggs that were periodically submerged in March and April failed to hatch. Riley concluded that springtime flooding, when the eggs were near hatching, would be particularly detrimental to the locust. However, he never extended this conclusion to the Permanent Zone. Springtime would have been precisely the season in which the peak vulnerability of the locust coincided with the maximal likelihood of inundation in the degraded river valleys. For the Rocky Mountain locust, the conversion of the serene river valleys into churning floodplains would have been devastating in terms of both the erosion of soils that sheltered the eggs and the flooding of these habitats.

Riley also was confident in the effects of livestock trampling on the locust’s eggs. Thinking in terms of the farmers of the Great Plains, he recommended, “In pastures or in fields where hogs, cattle, or horses can be confined when the ground is not frozen, many if not most of the locust-eggs will be destroyed by the rooting and tramping.” In fact, locusts were reasonably willing to deposit their eggs in grazed fields, so they would have been particularly prone to this crushing and churning. Surely the eggs laid in the river valleys of the Rockies fared no better under the pounding hooves of livestock.

 

In his seminal paper on the phase transitions of locusts, Sir Boris Uvarov saw beyond the immediate biological meaning of his theory to its potential application in the realm of pest management. Although Uvarov was a consummate taxonomist and brilliant naturalist, he was firmly grounded in the practical world of agriculture. Toward the end of his 1921 paper, he speculated that suppressing the solitary phase of locusts might be more effective than pouring resources into battling the overwhelming swarms that swept across Africa and Central Asia. Uvarov wrote, “The theory of phases suggests the theoretical possibility of the control of
migratoria
by some measures directed not against the insect itself, but against certain natural conditions existing in breeding regions which are the direct cause of the development of the swarming phase.”

He clearly saw that the weakest link in the locust’s life history was between outbreaks. The time to strike was when the creature was hiding out in refuges. Uvarov briefly reviewed the situation in the Black Sea basin, where the river valleys had spawned immense swarms of locusts for centuries. After the 1880s, however, these breeding grounds had not generated another outbreak. Uvarov attributed this change in locust population dynamics to agriculture: “This is easily explained by the fact that the valleys of the Don, Kuban and Dnieper [river valleys in south-central Russia and Ukraine] were during the end of the last century more or less cultivated or, at any rate, their natural conditions were entirely changed by the persistent grazing of herds of cattle.” The failure to apply Uvarov’s insight to the case of the Rocky Mountain locust probably reflected both a mistaken sense of ecology (that studies of the Old World locusts had no relevance to North
America) and a regrettable sense of arrogance (that Russian scientists had little to offer their American counterparts).

It seems that in the waning years of the nineteenth century, in river valleys 8,000 miles apart, the sanctuaries of locusts were being destroyed by farmers who were converting these habitats into fields of crops and grazing lands. The people who had been plagued for decades on the prairies of North America and for centuries on the steppes of Central Asia were simultaneously altering their landscapes in ways that would utterly transform the ebb and flow of life. Perhaps the only difference is that the river valleys of the Black Sea basin were ultimately more expansive than human industry could completely alter, whereas those of the Rocky Mountains were far more concentrated. And so today, while the farmers of the Great Plains know of locusts through the journals of their great-grandfathers, the farmers of Kazakhstan and Uzbekistan still know the visceral panic that comes on a summer day when the sky takes on the queer, dirty yellow hue of an impending storm, whose true nature is revealed by the shimmering flecks of 10 billion wings.

The most difficult element in solving a century-old homicide—or would it be an “insecticide”?—is ascertaining the motive of the killer. Often, dozens of people have the means and the opportunity to have done in the victim, so the case hinges on the element of motive. In the extinction of the Rocky Mountain locust, however, there appears to have been only one suspect present at the time and place of the creature’s disappearance and with the means to dispatch the victim. Therefore, pinning the blame on the settlers of the montane river valleys does not depend on finding a motive that separates the farmers from a collection of other suspects. However, we are rarely satisfied with simply knowing what happened. As humans we desperately seek to grasp
why
.

Of course, some events appear to occur randomly with no rational explanation. We don’t try to explain why a boulder careens down a slope and crashes onto a passing car or why a meteor smashed into
the earth and snuffed out the dinosaurs. These seem to have been natural deaths, although rather tragic (in the case of the people in the car) or cataclysmic (in the case of the creatures at the end of the Cretaceous). Other events appear to originate from intentional acts—the assassination of John F. Kennedy, the serial murders of Son of Sam, the Columbine killings, and the extinction of the passenger pigeons, moas, and dodos. In these instances, understanding the motive helps us make sense of the world, and such insights might even allow us to avoid similar events in the future. The passing of the Rocky Mountain locust appears to fall into this latter category.

Although farmers might well question whether a pest should be protected, in the case of
Melanoplus spretus
we lost a keystone species that affected ecosystem processes on a scale equivalent to that of the bison. The locust was a “living fire” sweeping across the western lands, altering the nutrient cycle on a continental scale; a single swarm metabolically burned 4,000 pounds of vegetation an hour. The normal ebb and flow of energy, carbon, and nitrogen across the plains was lost along with the locust, and the ecosystem may not have yet recovered—given what we’ve learned about the consequences of altering fire regimes in western forests. What species may have been dragged down or critically weakened with the loss of the locust cannot be known because we have such a poor understanding of the biological diversity of the mountains and plains when
spretus
was thriving.

Conversely, the loss of this ecological lynchpin may well have created explosive opportunities for some species; perhaps this is why the grasshopper outbreaks of the twentieth century were so severe. We can be sure that the structure and productivity of plant communities changed in the absence of the locust, but again, sorting out the winners and losers is impossible without baseline data. What we do know is that many western birds and mammals have been in a long-term decline. A colleague in Montana has suggested that the Eskimo curlew (a migratory bird of the grasslands and tundra that is now on the brink of extinction) may have depended on the eggs of
spretus
to fuel the northern leg of its intercontinental journey—its decline coinciding with that of the locust. We also know that some habitats within the West are hypersensitive to livestock grazing, weed invasions, and
erosion. Perhaps these are the legacies of having robbed an ecosystem of one of its vital components. Finally, with the passing of the Rocky Mountain locust we have lost a cultural icon—a reminder that we are ultimately dependent on natural processes more sweeping and eternal than the most clever human contrivance.

The motive underlying the ecological transformations that drove the Rocky Mountain locust to extinction might be expressed in terms of either “hope” or “greed”—depending on one’s reading of the past. History is a continuous stream of overlapping episodes, upon which we impose a retrospective system of discrete organization in an effort to interpret the world. And if there is a discrete event that marks the beginning of the end for
spretus,
it would be the Homestead Act of 1862. From the early days of our nation, the federal government wrestled with the disposition of public lands. For years, various groups had called for the free distribution of land to the people, in accordance with Jeffersonian ideals. This policy was opposed by the southern states, as they surmised that it was a thinly veiled approach to stopping the spread of slavery into the territories. With the secession of the South, the notion of “free land” became law. Any head of a household who was at least twenty-one years old could claim a 160-acre parcel of federal land. Newly arrived immigrants, former tenant farmers, single women, and freed slaves found this land grant program to be a gateway to hope. Unfortunately, there was not as much open land as was generally assumed because the federal government had given away millions of acres to the states and the railroads. This tactic stimulated the rapid building of both railroads and financial empires. However, railroad magnates did not become wealthy by building railroads but through selling the land along the rail lines. This acreage was extremely valuable because the trains provided a ready means of transporting commodities to distant and lucrative markets. The combination of homesteader hope and railroader rapacity generated the social motivation that would put humans on a collision course with the Rocky Mountain locust.

A tremendous boom in homesteading was seen along the 100th meridian, the imaginary line defining the Minnesota-Dakota-Nebraska-Kansas frontier. In 1871, there were more than 20,000 homestead entries
staking claim to 2.5 million acres of land. According to historian Gilbert Fite,

New York financier Jay Cooke bought the Northern Pacific Railroad hoping to convert rails to riches. However, he failed to consider that the land along his rail line from Minneapolis to Seattle was marginal for agriculture—and that it was smack in the migratory path of the Rocky Mountain locust. In the tried-and-true tactic of crass commercialism, Cooke hired a gaggle of publicity men to deceive the public as to the desirability of his lands. False advertising can be a very effective strategy, but it is essential to carefully time one’s hasty exit from the scam. When hopeful farmers found marginal lands and marauding locusts, Cooke’s duplicity was revealed and his business empire collapsed. The nation’s economic dominoes began to tumble. In short order, his investment bank—considered one of the strongest financial institutions in the country—tanked, the stock market plunged, more banks failed, businesses went bankrupt, and jobs disappeared. What became known as the Panic of 1873 was the worst economic depression in the young nation’s history. In the cities, hunger and homeless-ness spread. Unrest grew to the point where the country feared a second Civil War, this time between workers and industrialists.