27 Oct 2003
Sahelian Desertification, Landuse


  • Hulme and Kelly 1993 Exploring the links between desertification and climate change. Environment 35(6):4-45
  • Adams, William M. 1991 Large scale irrigation in northern Nigeria: performance and ideology. Trans. Inst. British Geographers 16:287-300 (New Series)
  • Adams, W.M. and M.J. Mortimore 1997 Agricultural intensification and flexibility in the Nigerian Sahel. The Geographical Journal 163:150-160.
  • Mortimore, Michael J. 1993 The Intensification of Peri-urban Agriculture: The Kano Close-Settled Zone, 1964-1986. In Population Growth and Agricultural Change in Africa, edited by B.L. Turner II, Goran Hyden, and Robert W. Kates, pp. 358-400. Univ. of Florida Press, Gainesville.
  • M. Mortimore (1998:17-37) Roots in the African Dust.
  • C. T. Agnew 1995 Desertification, drought, and development in the Sahel. In People and Environment in Africa, ed. T. Binns, pp. 137-149. Wiley & Sons.
  • Otterman 1975 Baring high-albedo soils by overgrazing Science 186:531-33
  • Charney, and P. Stone (1974) Drought in the Sahel: Biogeophysical feedback mechanism. Science 253:299-301.
  • P. Little, 1994 The social context of land degradation ("desertification"). In Population and Environment: Rethinking the Debate, edited by L. Arizpe, M.P. Stone, and D. Major, pp. 209-251. Westview Press, Boulder.
  • C. Tucker, H. Dregne, W. Newcomb (1991) Expansion and contraction of the Sahara desert from 1980 to 1990. Science 253:299-301.
Harmattan in central Nigeria, photographed in January. G. D. Stone

Sahel desertification: History of an idea

  • early 70s are critical time; peak of major Sahel drought, emergence of desertification as major env issue, and development of scientific theory attributing the problem to human misuse
  • but fear of desertification had long history
  • concern on this goes well back into colonial Africa of creeping desert (Palmer on Bedouins: "To call him a 'son of the desert' is a misnomer; half the desert owes its existance to him")
  • Stebbing, 1930s British forester in W. Africa, estimates desert marching 1 km/year for last 300 yrs; recommended forest belt, 15 mi wide and 1400 mi long,
  • Aubreville, considered by some father of desertification concept; 1949 book described how forested regions were transformed into savanna and savanna into desert-like regions.

Emergence of the Desertification Industry

  • Sahel drought 1964-74, peak in 1972, upsurge in interest
  • 1974: "internal biogeophysical feedback" model, attributing desertification to land cover removal (by farming and grazing); by Otterman in Negev desert and Charney in Sahel
  • landcover being removed by
    • cultivation by farmers like Hausa
    • livestock overgrazing by pastoralists like Fulani
  • removal raises albedo; reduces convection; reduces rainfall; reduces plant growth --image from popular pub.
  • hence positive feedback cycle producing desert
  • Charney, others simulations that did show creeping desert
  • theory was huge hit, and quickly became received wisdom.
  • desertification emerges as major env issue.
  • UN Env Program develops a desertification branch; Desertification Control Bulletin established;
  • major scientific orgs give much attention (e.g., Nat Acad Sci 1975 Arid Lands of SubSaharan Africa)
  • Popular env writers like Lloyd Timberlake (1985, Africa in Crisis) and Paul Harrison devote chapters to "the desertification problem"
  • claims appear all over for rate of desert encroachment; 5.5 km/yr, 8 km/year, up to 1972 USAID claim of 30 mi/yr


  • Problem is lack of evidence for any of this. People wanted to believe it, so dropped their standards of evidence. So 1972 drought accepted as part of trend, and localized studies used as indicators of general desertification
  • e.g. Lamprey 1975 in Sudan defined desert edge using 1958 rainfall figures, compared to desert defined by air photos in 1975, concluded desert advancing 5.5 km/yr; this figure repeated often (but methodlogical problems, plus assuming 1975 to be part of trend rather than secular fluctuation)
  • by around 1990 the lack of evidence was starting to pile up. Although Otterman working along Israel-Egypt border in (Sinai & Negev deserts) found the overgrazed Egyptian side had both higher albedo (0.37) and cooler temperatures than the better-covered Israeli side (albedo = 0.25), a later study on Arizona-Sonora border showed overgrazed and devegetated areas on Mexiacn side were warmer than vegetated areas on the Arizona side -- both soil and air (Balling, 1988). Landuse increased rainfall runoff and increased soil evaporation by increasing soil temperature through removing shading vegetation.
  • as Hulme & Kelly point out, observed changes in albedo have been localized & often short-term, not widespread and sustained as assumed in Charney theory
  • also, long-enough-term sequences of satellite data were becoming available and didn't support encroachment (although not conclusive)
    The higher the red line, the more loss of vegetated area; the higher the blue line, the lower the precip
  • Tucker et al. study using satellite data; consolidated chart in Hulme & Kelly. Shows fluctuations including great increase in 1984 almost totally recovered in 1988
  • expansions in desert correlate w/secular changes in env
  • definitely no correlation w/population growth (Caldwell 1984)
  • Dregne & Tucker [1988] review the evidence, say "Attractive though the encroaching Sahara idea is, it is no more credible now than it was in Stebbing's day"
  • Mace (1991 Nature article, "overgrazing overstated"):

    "Sometimes we are so sure of something that we don't need to see the evidence. That Africa's rangelands are being reduced to desert through overgrazing by domestic livestock is received wisdom. But, as became plain at a recent meeting, such a view may be seriously flawed."
  • Global Env Change 2001 special issue has more recent evidence of fluctuating desert. E.g., Kjeld Rasmussen, Bjarne Foga and Jens E. Madsenb, Desertification in reverse? Observations from northern Burkina Faso. Global Environmental Change 2001 11:271-282. Abstract:
    The idea of degradation of arid and semi-arid lands, often termed desertification in its irreversible form, due to human impact and/or climatic change has been much debated since the mid-1970s. From the time of the UN Conference On Desertification in Nairobi, 1976, certain areas of northern Burkina Faso have been pointed out as examples of severe desertification. Several studies demonstrated that revitalization of a series of E_W oriented fossille dunes in the Oudalan province was ongoing. The present study includes an analysis of the trends of vegetation development in the region, covering the period 1955 to 1994, with emphasis on the fossile dunes. It is demonstrated that desertification and revitalization of dunes were phenomena associated with the period between the early 1970s and the mid-1980s, and that the decline in vegetation cover on the dunes seems to have been reversed in recent years. The analysis is based upon time series of aerial photos and satellite images, field studies of vegetation, interviews with local people and review of relevant literature. The findings are discussed with reference to the debate concerning desertification and land degradation, as well as to the current revisions of the `range management paradigm'. The observations indicate that the environmental history of the region is complex and cannot be boiled down to `human-induced irreversible degradation'. Rather they support the idea of semi-arid cultural landscapes undergoing constant change in response to both human impact and climatic trends and fluctuations.
  • update, paper by Tucker, abstract: "Satellite data and ground rainfall measurements have been used to study variations in the size of the Sahara Desert from 1980 to 1997. Through a combination of the satellite and ground data, the 200 mm/yr precipitation boundary was mapped for the Saharan-Sahelian region by year. Although highly significant year-to-year variation in the size of the Sahara Desert has occurred, no systematically increasing or decreasing trend from 1980 to 1997 was evident. The area of the Sahara Desert varied from 9,980,000 km2 in 1984 to km2 in 8,600,000 1994 and had an average 1980-1997 area of 9,150,000 km2. "
  • in fact, deserts in "spectacular retreat"
  • but it's still widely perceived as problem; Nat Geog as baramoeter of sci/public interest
  • and still scientific support in Africa and elsewhere
  • recent twist: indications that rainfall decreases may be caused by Western Pollution

    Case study: intensive agriculture around Kano

  • Back to the Afgricans and their landuse; now know more info on behavior of indigenous land-users

    • south edge of Sahel; rain avg 822 mm but quite variable
    • cultural group is mainly Hausa (agricultural); also pastoral Fulani

    • Kano ancient Islamic city around, very dense agricultural population surrounding; "Close Settled Zone" by definition, pop > 141/km, runs 65- 100 km out of city
    • smallholders, dispersed farms, much land in annual cultivation
    • repeated claims that pop here was stripping landscape of treecover

      Taki from urban Kano, cleaned for use in Kano Close-Settled Zone. G. Stone
      Ancient shaduf.
      Managing fertility

    • families keep stock for manure but need much more
    • ancient manure trade from free-ranging sheep-goats in city; taki is brought to country on donkeyback (or now in pickups) in exchange for firewood & other commodities
    • many economic trees in CSZ; planted, maintained, lopped, sold
    • predictions that fuelwood would be gone by 80s; 1984 statement of near-collapse. But number of trees INCREASED be/1972-81

      Managing water

    • most of CSZ is rainfed agric
    • indigenous drought-resistant varieties
    • multi-crop millet (short-season, least sensitive to drought) and sorghum (long-season, most productive)
    • other crops include N-fixing legumes like peanuts
    • when yields very low, backup strategies (below)
    • along streams, garden irrigation called fadama
    • traditional pump was shaduf; in 1980s World Bank subsidizes small gas pumps for surface water or effluent; productive, but even these have broken down, and farmers relying on shaduf again






    Why is African Desertification So Popular? (Sinat: Everybody Loves A Good Drought)

    1. Fit American env consciousness perfectly, after env awakening + drought. Became (still is) darling of Nat Geographic -- picturesque, exotic people, countryside. Can also be tied into the Population Bomb (Ehrlich 1968 book predicting massive famine in 70s-80s due to exceeding planet's productive capacity). E.g. Nat Geog image of Maasai settlement attributing their spread to pop growth. Also Hardin's "Tragedy of the Commons" article asserting self-interest leads to degradation of communal resources, using pastoralists as example.
    2. Scientists found appealing model -- people actually changing climate. Also seemed to be explanation for pressing env problem, with built-in implications for solution. Charney & Stone (1974), Otterman (1975) both appeared in SCIENCE
    3. NGO's, international org's like UN, national aid agencies, all like because it's perfect problem for raising funds or deploying funds on high-profile, effective schemes. Little (1994:213) describes

      how "science" was invoked to justify the excessive funds and projects allocated to such an elusive issue. Projects were hastily designed and implemented, with little clear understanding of the nature of the problem or agreement over what constituted desertification; many of them received strong political and financial support from multilaterals (e.g., UN bodies and the World Bank) and bilateral foreign aid programs (e.g., US, French, and Nordic aid agencies). Henry Kissinger, the former US Secretary of State, spoke in the 1970s of "rolling back the desert" in Africa, while as recently as 1986 a member of the European Parliament "declared that aid must go to the sahel, because the desert was advancing at 8 km a year."
    4. African governments like for several reasons
      • history of ignorance & disdain for sustainable indigenous adaptations; government ministers like to distance themselves f/their own peasants, say they're modernizing age-old practices (even though they don't understand the practices)
      • like to erect monumental projects as solutions, and large top-down development projects are favored when desertification is being attributed to indigenous landuse (e.g. Kano Dam, described below); opportunities for graft as well
      • may find an environmental catastrophe good excuse to strengthen their own control. e.g.: 1984, President of Niger used encroaching Sahara as justification for shelving plans to liberalize the political system, saying "We cannot talk politics on an empty stomach".
    Large-Scale Hydraulic Projects are Partly the Result of Desertification Industry
  • e.g. Kano dam
  • confiscated large amounts of land
  • cost benefit analyses greatly underestimate indigenous production (inc. downstream fishing) and overestimate potential output of scheme
  • produces rice & wheat but can import f/Louisiana & Kansas cheaper
  • one analysis (Salau 1986) points out that nationally the River Basin Development Authority claimed to produce crops worth 215 mill naira, but received 430 mill naira from Fed Govn! (and the crop figure is probably way overestimated)
  • env. effects: physical & chemical deterioration of soil; fine fraction washed out of profile, pH rises, salinization
  • social costs: displaced farmers and Fulanis; transferred land ownership from smallholders to wealthy farmers
  • Bakolori massacre