Sayre applied the “Page 99 Test” to his new book, The Politics of Scale: A History of Rangeland Science, and reported the following:
Page 99 of The Politics of Scale concerns a global issue that most people know almost nothing about: the conversion of vast areas of grasslands to shrublands. “Shrub encroachment” was first documented scientifically in southern Arizona and New Mexico, where the US government had located its earliest research stations following episodes of severe overgrazing during droughts at the turn of the 20th century. Sometimes referred to as “desertification,” it is most commonly found in semi-arid regions, which are too dry for crop agriculture but wet enough to grow highly nutritious forage grasses for livestock—as long as the grasses aren’t displaced by shrubs, that is.Learn more about The Politics of Scale at the University of Chicago Press website.
Why does shrub conversion happen, and can it be reversed? These questions stymied scientists for most of the 20th century. The landscapes in question were huge—tens of millions of acres in the Southwestern US alone—and the loss of grass was seen as a regional and even national crisis. But the lands were not actually very productive in money terms—30, 40, or even 80 acres being necessary to support a single cow for a year—so any solution would have to be very low-cost to make the investment economical.
Fire was the only real solution—indeed, recurrent fires were why grasses had dominated for centuries prior to the arrival of Europeans and their livestock. But the government agency most responsible for rangeland science in the early 20th century—the US Forest Service—considered wildfires a mortal threat to itself as well as its lands, and the scientists it employed were disallowed from studying the possible benefits of burning rangelands.
The scientists were also blinded by the assumptions on which rangeland ecology was founded. The theory of plant succession held that overgrazing was the cause of shrub invasion, and that grasses would return “naturally” if livestock were controlled or removed. Even when data clearly refuted these ideas—as described on page 99—the Forest Service “rejected the plain story written on the face of Nature,” to quote from Aldo Leopold.
In the US, agencies and ranchers have fought each other for a century without resolution because they shared a flawed mental model of how rangelands work. Overseas, pastoralists in Africa, Asia, the Middle East and the Americas have been erroneously blamed for desertification and compelled to give up their time-tested management practices. The Politics of Scale explains why.