In an article by Fred Pearce that was posted on the website of New Scientist magazine on 16 September 2002 entitled "Africa's deserts are in 'spectacular' retreat," we were told the story of vegetation reclaiming great tracts of barren land across the entire southern edge of the Sahara. This information likely came as a bit of a surprise to many, since the United Nations Environment Program had reported to the World Summit on Sustainable Development in Johannesburg, South Africa in August of that year that over 45% of the continent was experiencing severe desertification. The world of nature, however, told a vastly different story.

Pearce began his eye-opening article by stating that "the southern Saharan desert is in retreat, making farming viable again in what were some of the most arid parts of Africa," noting that "Burkina Faso, one of the West African countries devastated by drought and advancing deserts 20 years ago, is growing so much greener that families who fled to wetter coastal regions are starting to go home."

And the good news was not confined to Burkina Faso. "Vegetation," according to Pearce, "is ousting sand across a swathe of land stretching from Mauritania on the shores of the Atlantic to Eritrea 6000 kilometers away on the Red Sea coast." What is more, besides being widespread in space, the greening was widespread in time, having been happening since at least the mid-1980s.

Quoting Chris Reij of the Free University of Amsterdam, Pearce wrote that "aerial photographs taken in June show 'quite spectacular regeneration of vegetation' in northern Burkina Faso." The data indicated the presence of more trees for firewood and more grassland for livestock. In addition, a survey that Reij was collating showed, according to Pearce, "a 70 percent increase in yields of local cereals such as sorghum and millet in one province in recent years." Also studying the area was Kjeld Rasmussen of the University of Copenhagen, who reported that since the 1980s there had been a "steady reduction in bare ground" with "vegetation cover, including bushes and trees, on the increase on the dunes."

Pearce also reported on the work of a team of geographers from Britain, Sweden and Denmark that had spent much of the prior summer analyzing archived satellite images of the Sahel. Citing Andrew Warren of University College London as a source of information on this study, he said the results showed "that 'vegetation seems to have increased significantly' in the past 15 years, with major regrowth in southern Mauritania, northern Burkina Faso, north-western Niger, central Chad, much of Sudan and parts of Eritrea."

Did these findings take us by surprise? Not in the least. In our Editorial of 15 Mar 1999, we had already reported that in a study of a series of satellite images of the Central and Western Sahel that were taken from 1980 to 1995, Nicholson et al. (1998) could find no evidence of any overall expansion of deserts and no drop in the rainfall use efficiency of native vegetation. And we further reported that in a satellite study of the entire Sahel from 1982 to 1990, Prince et al. (1998) actually detected a steady rise in rainfall use efficiency, suggesting that plant productivity and coverage of the desert had actually increased during this period.

That the greening phenomenon has continued apace is born out by the study of Eklundh and Olsson (2003), who analyzed Normalized Difference Vegetation Index (NDVI) data obtained from the U.S. National Oceanic and Atmospheric Administration's satellite-borne Advanced Very High Resolution Radiometer whenever it passed over the African Sahel for the period 1982-2000. As they describe their findings, "strong positive change in NDVI occurred in about 22% of the area, and weak positive change in 60% of the area," while "weak negative change occurred in 17% of the area, and strong negative change in 0.6% of the area." In addition, they report that "integrated NDVI has increased by about 80% in the areas with strong positive change," while in areas with weak negative change, "integrated NDVI has decreased on average by 13%." The primary story told by these data, therefore, is one of strong positive trends in NDVI for large areas of the African Sahel over the last two decades of the 20th century; and Eklundh and Olsson conclude that the "increased vegetation, as suggested by the observed NDVI trend, could be part of the proposed tropical sink of carbon."

Due to the stunning increase in vegetation over the past quarter-century in the Sahel, as reported in our Editorial of 11 Jan 2006, the African region was recently featured in a special issue of the Journal of Arid Environments entitled "The 'Greening' of the Sahel." Therein, Anyamba and Tucker (2005) describe their development of an NDVI history of the region for the period 1981-2003. Comparing this history with the precipitation history of the Sahel developed by Nicholson (2005), they found that "the persistence and spatial coherence of drought conditions during the 1980s is well represented by the NDVI anomaly patterns and corresponds with the documented rainfall anomalies across the region during this time period." In addition, they report that "the prevalence of greener than normal conditions during the 1990s to 2003 follows a similar increase in rainfall over the region during the last decade."

In another analysis of NDVI and rainfall data in the same issue of the Journal of Arid Environments, Olsson et al. (2005) also report finding "a consistent trend of increasing vegetation greenness in much of the region," which they describe as "remarkable." And they say that increasing rainfall over the last few years "is certainly one reason" for the greening phenomenon. However, they find that the increase in rainfall "does not fully explain" the increase in greenness.

For one thing, the three Swedish scientists note that "only eight out of 40 rainfall observations showed a statistically significant increase between 1982-1990 and 1991-1999." In addition, they report that "further analysis of this relationship does not indicate an overall relationship between rainfall increase and vegetation trend." So what else could be driving the increase in greenness?

Olsson et al. suggest that "another potential explanation could be improved land management, which has been shown to cause similar changes in vegetation response elsewhere (Runnstrom, 2003)." However, in more detailed analyses of Burkina Faso and Mali, where production of millet rose by 55% and 35%, respectively, since 1980, they could find "no clear relationship" between agricultural productivity and NDVI, which argues against the land management explanation.

A third speculation of Olsson et al. is that the greening of the Sahel could be caused by increasing rural-to-urban migration. In this scenario, widespread increases in vegetation occur as a result of "reduced area under cultivation," due to a shortage of rural laborers, and/or "increasing inputs on cropland," such as seeds, machinery and fertilizers made possible by an increase in money sent home to rural households by family members working in cities. However, Olsson et al. note that "more empirical research is needed to verify this [hypothesis]."

About the only thing left is what Idso (1982, 1986, 1995) has suggested, i.e., that the aerial fertilization effect of the ongoing rise in the air's CO2 concentration (which greatly enhances vegetative productivity) and its anti-transpiration effect (which enhances plant water-use efficiency and enables plants to grow in areas that were once too dry for them) are the major players in the greening phenomenon. Be that as it may, and whatever was the reason for the greening of the Sahel over the past quarter-century, it is clear that in spite of what the world's climate alarmists claim were unprecedented increases in the "twin evils" of anthropogenic CO2 emissions and global warming, the Sahel experienced an increase in vegetative prowess that was truly, as Olsson et al. write, "remarkable."

So is it Goodbye, Apocalypse and Hello, Paradise? Only time will tell, as will also be the case with the cause of whatever ultimately occurs. For the present, however, we're exuding more than a bit of confidence in the positive effects of elevated CO2. The elixir of life is looking good indeed.

References
Anyamba, A. and Tucker, C.J. 2005. Analysis of Sahelian vegetation dynamics using NOAA-AVHRR NDVI data from 1981-2003. Journal of Arid Environments 63: 596-614.

Eklundh, L. and Olssson, L. 2003. Vegetation index trends for the African Sahel 1982-1999. Geophysical Research Letters 30: 10.1029/2002GL016772.

Idso, S.B. 1982. Carbon Dioxide: Friend or Foe? IBR Press, Tempe, AZ.

Idso, S.B. 1986. Industrial age leading to the greening of the Earth? Nature 320: 22.

Idso, S.B. 1995. CO2 and the Biosphere: The Incredible Legacy of the Industrial Revolution. Department of Soil, Water & Climate, University of Minnesota, St. Paul, Minnesota, USA.

Nicholson, S. 2005. On the question of the 'recovery" of the rains in the West African Sahel. Journal of Arid Environments 63: 615-641.

Nicholson, S.E., Tucker, C.J. and Ba, M.B. 1998. Desertification, drought, and surface vegetation: An example from the West African Sahel. Bulletin of the American Meteorological Society 79: 815-829.

Olsson, L., Eklundh, L. and Ardo, J. 2005. A recent greening of the Sahel - trends, patterns and potential causes. Journal of Arid Environments 63: 556-566.

Prince, S.D., Brown De Colstoun, E. and Kravitz, L.L. 1998. Evidence from rain-use efficiencies does not indicate extensive Sahelian desertification. Global Change Biology 4: 359-374.

Runnstrom, M. 2003. Rangeland development of the Mu Us Sandy Land in semiarid China: an analysis using Landsat and NOAA remote sensing data. Land Degradation & Development Studies 14: 189-202.