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de-naturalisation 129(iii) the cultivation of steeper slopes produces greater soil erosion andwater run-off than on less steep slopes.It’s precisely this kind of evidence-based hypothesis-testing in whichForsyth engages. In an essay entitled ‘Science, myth and knowledge’, hepresents research conducted in the village of Pha Dua, a settlement ofChinese and Laotian immigrants located in Chiang Rai (Thailand’s mostnorthern province). Settled in 1947, Pha Dua sits in an upland valley,straddling steep granite, quartzite and sandstone slopes and a gentler valleybottom. In 1995 it comprised 118 households and around 900 inhabitants.The main cultivars are rice, maize and soya (grown on unterraced, nonirrigatedslopes), with an increasing preference for irrigated rice terracesin the valley bottom. An influx of new residents, the establishment ofa government teak plantation, and the villagers’ decision to preserve aforested area for wood have together meant that agricultural land is scarcein Pha Dua. Conducted in the early to mid-1990s, Forsyth’s research wastriple-headed. First, he analysed aerial photographs of the village fromdifferent decades in order to assess whether steeper slopes were beingcultivated over time. Second, he took measurements of the isotope Caesium-137 that exists in soil profiles. By comparing these with measurementstaken from uncultivated soils, Forsyth could see whether erosion rates inPha Dua were significantly higher than natural rates. Finally, Forsyth undertooka questionnaire survey of Pha Dua residents. He asked them abouttheir land-use practices and about their perceptions of land-use change inPha Dua over time.When combined, the three sources of information could, accordingto Forsyth,‘be used to falsify assumptions about Himalayan degradation’(1996: 386–7). First, he discovered that Pha Dua farmers were aware thatsoil erosion is higher on steep slopes which is why they preferred to cultivateflatter slopes more often as time went by.This was confirmed by theanalysis of aerial photographs. Second, Forsyth’s isotope analysis suggestedthat soil erosion in Pha Dua was no greater that in similar non-cultivatedareas.Though farmers in the village suffered from declining soil fertilityover time this was a function of nutrient removal by crops rather thansoil erosion. Indeed, an analysis of gulley-formation in Pha Dua suggestedthat much of the sedimentation suffered in lowland areas of northernThailand might be natural: the result of gulleying on soils with granitebedrock. As a result of his study Forsyth concluded that environmental