ALN logo; link to Arid Lands Newsletter Home page No. 49, May/June 2001
Linkages between Climate Change and Desertification

Human dimensions of carbon sequestration: A political ecology approach to soil fertility management and desertification control in the Old Peanut Basin of Senegal

by Petra Tschakert

"In this article, I argue that social science can help to broaden this emerging carbon agenda by introducing human dimensions in what otherwise risks being nothing more than a technical feasibility assessment."

The human dimensions of carbon sequestration

(Back to top)
Over the last decades, there has been increasing evidence of disruptions in the global carbon cycle. Carbon dioxide (CO2), the principal greenhouse gas emitted by the combustion of fossil fuels and by land use changes, has progressively accumulated in the atmosphere, thereby contributing to global warming. As this has progressed, essential terrestrial carbon sinks such as forests and soils have been consistently eroded, degraded, and depleted, resulting in reduced soil organic content, declining soil fertility, and significant cuts in productivity.

diagram of carbon sequestration cycle
Thumbnail link to diagram of carbon sequestration cycle

Carbon sequestration, advocated through the 1997 Kyoto Protocol to the United Nations Framework Convention on Climate Change, could offset portions of current carbon emissions by using vegetation to sequester CO2 from the air and store it in other pools.

Carbon sequestration in the soil pool, linked to improved management practices and land use change, has the potential to reverse land degradation and erosion of vital resources, particularly in semi-arid and sub-humid areas of Africa such as the Sahel (Lal 1999). Thus, carbon sequestration in soils could enhance people's food- and livelihood security while simultaneously combating desertification and mitigating global warming.

Considerable progress has been made on the technical side of soil carbon sequestration -- in terms of assessing current soil carbon contents, modeling maximum soil carbon storage capacities (Metting et al. 1999; Bruce et al. 1999; Post et al. 1999; Parton et al. 1994; Woomer et al. 2001) and identifying the most efficient sequestration techniques for specific agroecological environments. However, comparatively little attention has been paid to the social science components of this new research agenda. Especially in the African context, soil carbon sequestration is still largely perceived by most people as a technological abstraction outside of time and place.

Given the well-documented importance of involving local players to ensuring the success of technology transfer or other projects, this situation clearly needs to be addressed if soil carbon sequestration is to be a viable mitigation strategy for dryland Africa. Ultimately, after all, the success or failure of any climate change and/or desertification control effort rests upon the degree to which local understanding, acceptance and support exist for that effort. However, newly emerging research activities tend to overlook the social, economic, ecological, and political landscapes with their multiple human actors -- all with their own opportunities and constraints, their own knowledge bases and practices -- as well as the uneven power relations that determine access to and control over critical resources and decision-making processes.

In this article, I argue that social science can help to broaden this emerging carbon agenda by introducing human dimensions in what otherwise risks being nothing more than a technical feasibility assessment. The general objective should not be to aim automatically for the most favorable agroecological conditions under which sequestration activities would be easiest and amounts of carbon stored highest. I argue for a shift in rationale to identify areas where local populations can derive social, economic, and environmental benefits from sequestering carbon, while, at the same time, contributing to desertification control and climate change mitigation. In this sense, carbon sequestration in soils could be a true "win-win strategy."

Overall research design, Old Peanut Basin study

(Back to top)
This paper describes how ongoing research in one of the most degraded and also most densely populated areas of Senegal, the center of the Old Peanut Basin, addresses these human dimensions of carbon sequestration research. As the prime target area for peanut cultivation since colonial times, the central part of this western agricultural zone has been cleared of all natural forests. Overcultivation, overgrazing, and increasing population densities combined with unfavorable economic policies and reduced precipitation since the late 1960s have led both to considerable losses of biomass and to a decrease in agricultural productivity. As a consequence, outmigration has been playing an important role, particularly among the youth; but agriculture still represents the major source of income with millet, cowpeas, and peanuts as main food- and cash crops.

The political ecology framework of this study allows us to link soil fertility management practices and carbon sequestration potential with larger social, economic, and political factors that determine farmers' decision-making processes. The main objective of this research is to understand the various factors that determine how efficiently groups of small-scale farmers can invest in and benefit from improved soil fertility management to, inter alia, mitigate desertification and global warming. More specifically, this research intends to:

  1. assess local theories on soil formation/degradation and identify local soil management practices that also sequester carbon
  2. identify groups of small-holders that are more/less likely to participate in a soil carbon sequestration program;
  3. understand how national policies and action plans, primarily agricultural policies, laws on land tenure and resource management, and development priorities, will facilitate or hinder improved soil management/carbon sequestration techniques;
  4. assess potential costs and benefits for local stakeholders, particularly small-hold farmers as well as most appropriate avenues for sharing these anticipated costs and benefits in the most equitable manner;
  5. evaluate the institutional environment necessary to get local farmers, who are supposed to be the main beneficiaries of anticipated programs, organized as a group to better represent their interests.

Specific methodology and research results, Old Peanut Basin study

(Back to top)
Since December 2000, I have been working with three local research assistants in 14 selected villages in the Old Peanut Basin. The methodology used has been highly participatory, including village resource mapping, historical land use and management sequences, focus groups, and field visits as well as formal questionnaires. We used a total of 12 criteria during the sampling process in order to capture a maximum of the sociocultural and agroecological variation that exists in this part of Senegal. Criteria included soil type, degree of degradation, land cover change between 1968 and 1999 (based on remotely sensed imagery), ethnic groups (Wolof and Serer), religious groups (Moslems and Catholics), influence of an Islamic leader ("marabout"), activities other than rainfed agriculture, village size, and distance from nearest road and market.

farmer sieving soil
Thumbnail link to photo of farmer sieving soil

Field discussions have shown that local theories on soil formation and degradation are fairly uniform among villages, although rather different from our Western explanatory models. While most of the villagers, both men and women, conceive of soil fertility as being related to elements such as dirt ("saletés"), flavor ("cafko" as in a good "ceeb u jën," the national dish), vitamins, and strength ("doole") coming from trees, leaves, decomposed grasses, and animal manure, little is known about soil organic matter and even less about carbon as an essential component of soil fertility. Soil degradation is explained by the loss of the above elements through wind erosion, dissolution in the soil, the burning effect of the sun, and consumption by plants. If carbon sequestration through improved soil management is ever to succeed, these local, rather empirical explanations of soil fertility, formation, and degradation will necessarily have to be incorporated.

table of soil management practices
Thumbnail link to table of soil management practices

Most of the management practices encountered in the 14 selected villages increase soil organic matter content and, therefore, soil fertility. Local smallholders currently use practices that can be categorized as organic matter application, chemical fertilizer application, and physical management techniques. It should be noted, however, that approximately only one-third of these practices are applied on a scale significant enough to have a noticeable impact on soil fertility. Moreover, not all practices that increase soil fertility also automatically increase soil carbon content. Some of the important elements to consider in carbon sequestration efforts are appropriate nutrient ratios (nitrogen, potassium etc.), nutrient quality, and decomposition rates, all of which go beyond existing local soil concepts.

graph of total carbon in soil
Thumbnail link to graph of total carbon in soil

From a scientific standpoint, the amount of carbon sequestered per listed practice is still poorly understood, except for organic matter input from cattle, sheep, and goat manure, compost, fallow, Faidherbia albida ("kad," a tree much appreciated by local farmers for its ability to fix nitrogen) and some fertilizer combinations. Initial values that are available (nutrient ratios, nutrient quality and deposition rates), however, can be incorporated in a carbon model, such as the CENTURY model, to develop and evaluate scenarios that represent various management options for a given agroecological zone. The modeling component is important because it permits us to assess, on the basis of realistic historical carbon values, potential future carbon levels that may or may not be sufficient to warrant initiation of a carbon sequestration program in an arid, semi-arid, or sub-humid environment. An example of a CENTURY output for the Old Peanut Basin depicts historical carbon levels before agricultural exploitation (prior to 1850); a constant decline in soil carbon due to excessive clearcuts of the original tree savanna, natural fires, and continuous agricultural exploitation without replenishing inputs (1850 to 2000); and finally possible future scenarios (2001 to 2050) resulting in more or less satisfactory soil carbon levels.

One of the research challenges is to assess carbon gain values for all the other relevant soil management practices smallholders know and use, in order to expand model simulation and more precisely estimate carbon storage potential for a specific agroecological environment. Although one might argue that carbon modeling goes beyond a classic human dimensions assessment, I claim that social scientists, accustomed to the crosscurrents of complexity and diversity, can help to bridge the disciplinary gap that has been developing in this field of climate change research. We can elucidate the general principles of current soil fertility management, describe farmers' preferences and, if nothing else, provide this information to our colleagues from the biophysical sciences. In exchange, social scientists are probably the ones more attuned to assess how realistic the produced simulation outcomes are, from a social, economic, and political perspective.

Toward designing appropriate, site-specific mitigation strategies

(Back to top)
Preliminary research results indicate that carbon sequestration programs intending to implement best management scenarios, whether or not based on model simulations, will have to confront existing complexity and heterogeneity with respect to stakeholder groups and their options. In other words, there is no single best management package for any given area or group of people. To better adjust such "ideal" scenarios to the reality on the ground, the following questions, among others, will deserve greater attention.

"Who are the individuals, households, or groups of farmers that already invest in soil fertility management and how are they differentiated from others with respect to access to and control over resources?"

In the Old Peanut Basin, farmers who own or have otherwise access to multiple pieces of land, carts, draft animals, and sufficient labor to physically apply organic and inorganic matter input, prepare their land, plant trees, and protect fields and animals against theft, are those who are most apt to invest in soil fertility management. These individuals or groups are generally those with multiple sources of income. They are also likely to be the ones, given their relatively low level of risk, who will be the first to participate in any carbon sequestration activities. More than half of the interviewed villagers, however, lack one or more of these critical resources. Women or female-headed households, in particular, face considerably more constraints when it comes to efficient soil fertility management. In the case of the above-mentioned simulation scenarios, limitations with respect to access to fallow land, means of transportation, and labor will impede the feasibility of the proposed management options if not addressed on a large scale.

"How have management practices changed over time and what are possible factors that explain these changes?"

farmer explaining soil management practices
Thumbnail link to photo of farmer explaining soil management practices

Farmers were asked to rank the management practices according to their importance for three time periods: 1960-1980 (independence and era of Leopold Senghor, the first president), 1981-1999 (the era of Abdou Diouf, second president), and 2000 to present (era of Abdoulaye Wade, current president). Achieved results are primarily qualitative, based on the recollection and, sometimes, subjective perceptions of those who participated in the activity. Nevertheless, they represent clear trends: while, in the majority of cases, the use of fallow, chemical fertilizer, tillage, and stubble grazing has decreased during the last four decades, the application of animal manure and household waste, protection of trees, and the construction of living fences have increased.

Most of this variation over time can be explained by changes in agricultural policies during the three distinct time periods. The "Agricultural Program" initiated under Senghor, against the backdrop of African socialism, represented the glorious times for smallholders in the Peanut Basin: chemical fertilizer and agricultural equipment very heavily subsidized, peanuts seeds available on credit, and agricultural extension services, rural cooperatives, and investment in rural infrastructure flourishing. The Diouf era, on the other hand, brought significant changes for rural producers. Under pressure from World Bank and IMF structural adjustment policies, the state retired from its main duties while the private factor proved unable to fill the growing gap (Gaye 2000). Significant cuts in subsidies for fertilizer, seeds, and equipment, in combination with two serious droughts (1982- 84, 1996-97), during which many farmers were forced to sell their remaining animals and tools to purchase food, have reduced the enabling conditions for a profitable, productive, and sustainable rural sector to a bare minimum. Only recently has the state returned to credits for seed and fertilizer, although continuation of these efforts remains to be seen.

Another factor that explains changes in management practices, particularly reduced fallow and other longer-term soil fertility management strategies, is related to the centerpiece of Senegal's law on land tenure. According to "La Loi sur le Domaine Nationale," the large majority of available land belongs to the state, which grants usufruct rights to users rather than outright ownership. Soil management practices that were inherent to traditional land tenure systems (longer-term fallow, loans, rents, collateral, and gifts) are now officially limited to a duration of no longer than two years. Otherwise, usufruct rights can be withdrawn and allocated to a new user (Lo and Dione 2000).

Not surprisingly, this law discourages de-facto users in densely populated areas from letting "their land rest" (fallow) and temporary users from efficiently fertilizing plots they know they will have to return within a limit of two years. People have become more suspicious, but also more innovative. We have encountered farmers who fake cultivation, by sowing only 1/10 of their plot, and pretending a state of stubbornness close to mental illness -- with which administrative officials usually don't want to deal -- simply to let their land lie fallow. We have also met farmers who have lost precious land by voluntarily renting it out to needy neighbors who, after the critical period of two years, officially claimed the land and received it.

Without taking into account these and other policy issues against whose backdrop farmers have to make their daily decisions, best-bet scenarios for both increased soil fertility management and maximum carbon storage remain elusive. Concrete policy recommendations on how to achieve both objectives simultaneously would facilitate the implementation of carbon programs in Senegal that are in compliance with national development priorities and, at the same time, amplify possible synergies between the three conventions the country has signed and ratified: the Framework Convention on Climate Change, the Convention to Combat Desertification, and the Convention on Biological Diversity.

"How do management practices change with respect to distance between fields and a village's center?"

graph of soil mgmt practices vs. distance from village
Thumbnail link to graph of soil management practices vs. distance from village

Farmers in the Old Peanut Basin do not use management practices uniformly over their territory. Surveys from 75 fields demonstrate that plots close to the village compounds ("champs de case") usually benefit the most from household waste and crop residues. With increasing distance from the village, both crop rotation and protection of trees become more and more important whereas the application of manure, fertilizer, and household waste declines rapidly, due to constraints in transportation. These factors have proven to be critical for an appropriate soil sampling design on the basis of which basic soil parameters can be assessed and incorporated into an overall carbon model. At the same time, I expect that understanding such spatial complexity will lead to a much-needed shift in scale and give more emphasis to site-specific considerations when designing best-management scenarios.

"Will benefits to individual farmers be large enough to entice their participation in a carbon sequestration program?"

Given the current world market price for 1 metric ton of carbon ($11-20), it is highly unlikely that small-scale farmers will commit to carbon sequestration activities solely because of financial benefits. However, this study has shown that farmers are interested in any kind of support that would allow them to more efficiently manage their land, their most precious resource. To better evaluate potential benefits, this research will assess current financial returns from the major management practices in use and, based on results from the model scenarios, estimate both opportunity and transaction costs for the recommended, "best-bet" management strategies. The last component of this economic assessment will focus on most efficient ways to cover these costs -- possibilities comprise among others rural credit schemes; communal infrastructure such as wells, schools, and health clinics; and most-equitable channels and/or institutional networks for distributing anticipated benefits.


(Back to top)
These and similar questions will continue to be at the core of this ongoing research process. The contribution of social science to the new field of climate change research is not only to confront complexity and heterogeneity on the ground by illustrating the various social, economic and policy components that might facilitate or hinder actual project implementation. It is also, or even primarily, to establish important linkages within and among contexts ranging from field practices of local people to advanced laboratory experiments of biotechnologists and simulation modelers. This requires a truly interdisciplinary and collaborative approach. In the case of the research described herein, first steps have been taken by reinforcing communication and exchange among the local, regional, national, and international institutions and key players involved with the ultimate goal: to broaden our social and ecological horizons in the interest of more equitable and sustainable development of the world's drylands.


(Back to top)
Bruce, J., M. Fromme, E. Haites, H. Janzen, R. Lal and K. Paustian. 1999. Carbon sequestration in soils. Journal of Soil & Water Conservation 54(1):382-390.

Gaye, M. 2000. Politiques nationals affectant l'investissement chez les petits exploitants. Rapports entre politiques governementales et investissements paysans an Afrique semi-aride. Serie Sénégal. Drylands Research, Working Paper.

Lal, R. 1999. Potential soil C sequestration in Sub-Saharan Africa. Executive Summaries of the workshop "Carbon sequestration in Soils and Carbon Credits: Review and Development Options for Semi-Arid and Sub-Humid Africa". Sioux Falls, South Dak.: EROS Data Center, U.S. Geological Survey.

Metting, B., J. Smith and J. Amthor. 1999. Science needs and new technology of soil carbon sequestration. In Carbon sequestration in soils: Science, monitoring, and beyond. Proceedings of the St. Michaels Workshop, December 1998. Coordinated by Pacific Northwest National Laboratory, Oak Ridge National Laboratory, and the Council for Agricultural Science Technology. Ed. N. Rosenberg, R. Izaurralde and E. Malone. Columbus, Ohio: Batelle Press.

Lo, H. and M. Dione. 2000. Evolution des regimes fanciers. Rapports entre politiques governementales et investissements paysans an Afrique semi-aride. Serie Sénégal. Drylands Research. Working Paper.

Parton, W., D. Ojima, C. Cole and D. Schimmel. 1994. A general model for soil organic matter dynamics: Sensitivity to litter chemistry, texture and management. In Quantitative modeling of soil forming processes, ed. R.B. Bryant and R.W. Arnold, 147-167. SSSA Special Publication 39. Madison, Wisc.: Soil Science Society of America.

Post, W., R. Izaurralde, L. Mann and N. Bliss. 1999. Monitoring and verifying soil organic carbon sequestration. In Carbon sequestration in soils: Science, monitoring, and beyond. Proceedings of the St. Michaels Workshop, December 1998. Coordinated by Pacific Northwest National Laboratory, Oak Ridge National Laboratory, and the Council for Agricultural Science Technology. Ed. N. Rosenberg, R. Izaurralde and E. Malone. Columbus, Ohio: Batelle Press.

Tschakert, P., 2000. Soil carbon sequestration in semi-arid and sub-humid Africa. Brochure prepared for U.S. Geological Survey, EROS Data Center, Sioux Falls, South Dakota. Unpublished Document.

Woomer, P.L., N.K. Karanja and E.W. Murage, 2001. Estimating total system carbon in smallhold farming systems of East African highlands. In Assessment methods for soil carbon, ed. Lal et al., 147-166. Boca Raton, Fla.: Lewis Publishers.

bar denoting end of article text

About the author

(Back to top)
Petra Tschakert is a Ph.D. candidate in Arid Lands Resource Sciences at the University of Arizona. For her dissertation on human dimensions of soil carbon sequestration in Senegal, she works primarily with the Centre de Suivi Ecologique (CSE) in Dakar and the Centre National pour la Recherche Agronomique (CNRA/ISRA) in Bambey. Her main research partners in the US are the EROS Data Center/USGS in Sioux Falls, South Dakota and the Natural Resource Ecology Laboratory at Colorado State University. You can reach her for comment by email at

Additional web resources

(Back to top)
Carbon sequestration in soils: International Workshop, Dakar, Senegal, September 24-26, 2000

About the Arid Lands Newsletter

Link to ALN home page Link to index page for back web issues Link to index page for pre-web issue archive Link to this issue's table of contents