Challenging Nature: Local Knowledge, Agroscience, and Food Security in Tanga Region, Tanzania (review)

This book synthesizes geographic, historical, social, and ecological processes to describe the shifting state of agrarian livelihoods in northeastern Tanzania. The author, a geographer specializing in cultural ecology, has developed a sophisticated computer model for simulating the dynamics of rainfall, soil mechanics, plant growth, and African farmers' decision making (available at http://www.geog.umn.edu/Faculty/Porter.html). Drawing upon an unusually rich set of rainfall data (1926–92), Porter shows that farmers' choices of cultigens, planting dates, spacing, and so on have, in general, been good ones. The computer models showed that the farmers' practices matched or surpassed the yields that they would have obtained had they followed the recommendations of Western agronomists. Scholars have long known that African farmers have extensive understandings of agricultural ecology; now we have quantitative data demonstrating the ability of these knowledge systems to cope with East Africa's notoriously patchy and unreliable rainfall.

Porter's modeling and analysis rely on two sets of survey data. In 1972 Porter surveyed farmers in eighteen villages throughout Tanga Region (mostly in the dryer lowlands). He returned in 1992–93 to repeat the exercise, interviewing 78 percent of the same individuals and averaging four days of fieldwork in each village. He is therefore able to confirm that as of 1993, material well-being and agricultural livelihoods in Tanga Region were much as they had been twenty years before. That such a status quo persists despite the fact that the region's population nearly doubled in this period testifies to the resilience and flexibility of African farming systems. Yet Porter does not applaud indigenous knowledge and practices as much as he castigates (unnamed) Western agricultural experts and Tanzanian policymakers for ignoring the fundamental fact that these farmers know how to manage their land. The book ends with a plea for more participatory agronomic research.

This book's major contribution to the literature on African farming systems is that it shows how to quantify familiar qualitative evaluations of agricultural practices and agrarian change. This is, at times, also one of the book's shortcomings. Much of the book is purely descriptive, and Porter often provides the quantitative data to demonstrate what we already knew, such as the fact that maize is the most important crop in Tanga Region (211). The book abounds with interesting tables, diagrams, and photographs that sometimes seem tangential to the argument (for example, a figure showing student researchers' impressions of the eighteen survey villages in 1972 [104]; a photograph of a woman who was not interviewed [126]). Another problem is that although Porter draws on regional histories to show how colonial policies did not improve the lives of Tanga's farmers, he uses postcolonial historical data in quite ahistorical ways. Throughout the book, Porter uses economic information in the present tense, which often means that he uses a 1972 fact to analyze 1993 data for a reader in 2006. This is likely a relic of the literature reviews Porter conducted before the 1972 and 1992–93 research projects, but it has the effect of flattening the very regional history that he is trying to map onto the topography of Tanga Region. Although the author advocates the approach of political ecology (11), the book provides little of the political processes of landholding and land use in the eighteen study villages (likely the consequence of his very brief stay at each site). Overall, then, students of African agriculture will benefit from this book's attention to farmers' fine-tuned ecological knowledge (of soil moisture, the water needs of crops, and planting dates), but many will find its demonstration that little changed for the farmers of Tanga Region between 1972 and 1993 frustrating for the purpose of understanding current agricultural dynamics.