A Fence That Affects the Weather

BY AWAKE! WRITER IN AUSTRALIA

IT ONCE split the state of Western Australia from top to bottom. When completed in 1907, this 1,139-mile [1,830-km] wall of wood and wire was the longest structure of its kind in the world. Its official name was the No. 1 Rabbit Proof Fence.

As its name implies, the fence was first built as a bulwark against the plague of rabbits that swarmed westward across Australia during the late 19th century. Today much of this hundred-year-old barricade is still in place. In recent years, however, it has become the focus of scientific interest for an unlikely reason. It seems that this man-made barrier is indirectly affecting local weather patterns.

Before we explore how a fence that stands little more than three feet [1 m] high could have such an effect, let us learn some of the history of this remarkable construction.

Fighting a Losing Battle

In the war against invading rabbits, up to 400 workers labored from 1901 to 1907 to build the No. 1 Rabbit Proof Fence. “Some 8,000 tonnes of materials were carried by ship and then railed to depots, before being hauled overland by horse, camel and donkey teams to the remote fence construction sites,” according to the Western Australia Department of Agriculture.

On either side of the fence, workmen cleared a ten-foot-wide [three-meter-wide] swath through the vegetation. Some of the felled timber was used for fence posts, and where there were no trees, metal posts were imported. On completion, the fence line served not only as a barrier to rabbits but also as a rugged road that spanned the continent.

By funneling the advancing rabbits into holding yards, where they died, the fence acted like a giant net. The rabbits, however, climbed over parts of the fence. How? As they pushed relentlessly westward, they climbed over the dead bodies of other rabbits piled high against the wire and thus swarmed across. Two additional fences were built radiating off the first fence. The combined network of fences stretched for 2,023 miles [3,256 km].

A Tribute to Human Endurance

A handful of boundary riders, such as F. H. Broomhall, patrolled this massive barrier. In his book The Longest Fence in the World, Broomhall says: “The duties of the patrolman . . . were to keep the Fence and the track running alongside it in repair . . . , to cut scrub and timber to the required width on both sides of the Fence [and] to keep gates, which were situated roughly every 20 miles [32 kilometers] along the Fence, in good order and to empty the trap yards [of rabbits].”

The boundary rider’s job must have been among the loneliest occupations in the world. With only his camels for company, each patrolman was charged with tending miles of fence line, which seemed to stretch endlessly toward the horizon. Some patrolmen lacked even the companionship of camels, since they were required to bump their way along their assigned fence line on a bicycle. Today what remains of the fence is patrolled in the relative comfort of four-wheel-drive vehicles.

Not a Total Failure

While the fence may have failed to halt the rabbit plague, it has proved to be an effective barrier against another mischief-maker​—one of Australia’s native birds, the emu. In 1976 more than 100,000 of these giant flightless birds decided to migrate toward the fertile croplands west of the fence. The fence halted their progress, and although 90,000 birds had to be destroyed, much of that year’s harvest was saved from disaster.

Since this crisis, 725 miles [1,170 km] of the fence has been reinforced or realigned to protect Western Australia’s vulnerable farmlands from migrating  emus and roving packs of wild dogs. * As a result, the fence has become a line of demarcation. To the east lies the disheveled wilderness of Australia’s heartland. To the west spread the manicured fields of man-made agriculture.

An Unexpected Weather Wall

It is this drastic contrast in vegetation that may explain the fence’s apparent effect on the weather. The science magazine The Helix says: “Incredible as it seems, rainfall has increased east of the fence and decreased west of the fence.” Thus, the native vegetation in the east enjoys a consistent natural water supply, while farmers in the west must increasingly rely on irrigation. Providing one possible reason for these changes, the magazine explains: “The shallow-rooted crop plants in the farmed areas don’t transpire as much water as the more deeply rooted native vegetation.”

Commenting on another factor, Tom Lyons, a professor of atmospheric science, says: “Our thesis is that because the native vegetation is so much darker than the agricultural land, it releases more heat to the atmosphere leading to . . . turbulence which in turn assists in cloud formation.”

The Rabbit Proof Fence may not have saved the farmers of Western Australia from the rabbit plague, but its apparent effect on the weather and the lessons this teaches about the need for farsighted land management may yet prove valuable.

[Footnote]

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No. 1 Rabbit Proof Fence

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Rabbits

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Patrolling the fence, early 20th century

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Emus

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Stretching 1,139 miles [1,833 km], the No. 1 Rabbit Proof Fence was once the longest unbroken fence line in the world. The fence separates wilderness from farmland, thus creating a weather wall

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All color pictures: Department of Agriculture, Western Australia; top center: Courtesy of Battye Library Image number 003582D