SOIL T E C H N O L O G Y vol. 2, p. 301-311 Cremlingen 1989

RISQUES D ' E R O S I O N A U TIERS M O N D E : LE P O I N T D E V U E DE L'UTILISATEUR E R O S I O N H A Z A R D M A P P I N G IN THE

T H I R D W O R L D : A L A N D USERS PERSPECTIVE

Y. Biot, P. Blaikie & M. Stocking, Norwich

R ~ u m ~

L'analyse des 6checs de nombreux pro- grammes de conservat ion des eaux et des terres a r6v616, entre autres, des lacunes sev~res dans les processus d ' identif icat ion des causes et des cons6quences de la d6gradat ion des terres. Ces lacunes sont bas6es, n o n point sur une analyse sci- entifique erron6e, mais sur un point de d6part qui ne tient sufl isamment compte du point de vue de l 'ut i l isateur des terres au Tiers Monde.

Les auteurs pr6sentent une approche diff~rente bas6e sur l ' identif ication de l ' env i ronnement social, poli t ique et ~conomique de l 'ut i l isateur en deux par- ties: l '6tude des liens entre la d6gradat ion des terres et le d6veloppement des soci6t6s humaines et l '6tude du d+clin de la productivit6 des terres r~sultant de l'6rosion. Les m&hodes propos6es dans cette communica t i on rendent pos- sible l '6 laborat ion d 'une strat+gie de con- servation des eaux et des terres qui tient compte du savoir, des condit ions de vie et des possibilit6s de l 'ut i l isateur et de la soci+t6 qui l 'enveloppe.

ISSN 0933-3630 (~)1989 by CATENA VERLAG, D-3302 Cremlingen-Destedt, W. Germany 0933-3630/89/5011851/US$ 2.00 + 0.25

Summary

Recent studies of failed soil and water conservation programmes in the Third World have revealed, amongst others, serious flaws in the process of identification of the causes and consequences of land degradation. These flaws are not caused by an erroneous scientific analysis, but originate in a theoretical framework which is not targetted at the user of the land.

The authors propose an alternative approach to the analysis of land degradation problems. The method is based upon the identification of the so- cial, political and economic environment of the land user and can be divided into two parts:

(i) a study of the relationship between land degra- dation and development and

(ii) a study of productivity decline caused by ero- sion.

It is believed that this methodology permits the design of soil and water conservation programmes which take into account the knowledge, present day conditions and prospects of the land user and the society which supports him/her, hence be more likely to succeed.

I Introduction

L'~tude et la cartographie des risques d'~rosion ont ~t+ jusqu '~ r+cemment le domaine de la gbomorphologie, hydrolo- gic et agronomic. L'6chec des pro- grammes de conservat ion des eaux et des terres de par le monde a instigu6 un effort de recherche accentu~ au d6but des ann+es 80. Cette recherche co-

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302 Blot, Blaikie & Stocking

incide avec l'initiation d'une concep- tion nouvelle en l'+tude des probl+mes agricoles au Tiers Monde: l'6tude des syst~mes de production (Farming Sys- tems Research) et la recherche participa- tive (Farmer Participatory Research) qui mettent l'accent sur les besoins, le savoir et les capacit6s des utilisateurs du terroir plut6t que sur l'application de quelque th~orie macro-~conomique ou politique de dbveloppement.

C'est dans cette perspective que se situent la m+thodologie d'incorporation du savoir de l'utilisateur des terres dans les programmes de conservation des eaux et des terres propos6e par ROOSE (1988) et les btudes par BONVALLOT (1986), MAR C HAL (1986), MIETTON (1986) et ROOSE (1986).

Le parti pris pour l'utilisateur des terres permet aussi l'+tude et la car- tographie des risques d'6rosion d'un, ou plut6t de plusieurs angles diff+rents, dont deux sont le sujet de la communication pr~sente:

• l'~tude des liens entre la d6gradation des terres et le d~veloppement des soci6t~s humaines,

• l'6tude (plus restreinte) du d~clin de la productivit+ des terres r+sultant de l'~rosion.

Le but de cette communication est de r+sumer le savoir acumulb par les au- teurs pendant les derni~res ann~es, et d'ouvrir le d6bat sur l'6valuation de la d6gradation des terres ~t de nouvelles per- spectives.

Introduction

Until recently, both the study and mapping of ero- sion hazards have been restricted to geomorphol- ogists, hydrologists and agronomists. The failure of soil and water conservation programmes world- wide has prompted renewed research in the early

'80's. This effort coincides with the initiation of new concepts in the study of the agricultural problems of the Third World: Farming Systems and Farmer Participatory Research - approaches which empha- sise the needs, the know-how and the capabilities of the land user rather than macro-economic or political theories of development.

The methodology of incorporation of farmers' knowledge within soil and water conservation pro- grammes proposed by ROOSE (1988) and the re- cent studies by BONVALLOT (1986), M A R C H A L (1986), MIETTON (1986) and ROOSE (1986) are examples of Farming Systems and Farmer Partic- ipatory Research in soil and water conservation planning.

The emphasis on the land user also allows the study and mapping of erosion hazards from two different angles:

• the study of the relationships between land degradation and development,

• the study of productivity decline caused by ero- sion.

The present paper summarises the authors ' past experience in such studies in an attempt to open up the debate on land degradation assessment and land conservation planning to new perspectives.

Etude des liens entre la d~gradation des terres et le d~veloppement des soci~t~s hu- maines

Les probl6mes d'brosion dans les soci6t~s en voie de d6veloppement ont tendance

~tre plus importants que dans les com- munaut6s en ~quilibre plus ou moins stable. Malgr~ les ann+es de recherche en la nature physique du probl+me et son arret, voire renversement, l'+rosion acc616r6e est toujours pr6sente, sinon am- plifi+e: les images provenants des terres de montagnes en Ethiopie et des plaines d+sertiques du continent Indien en sont t~moins.

L'analyse des 6checs des programmes de conservation des eaux et des ter- res a d6montr6 l'importance de nom- breux facteurs regroup+s en trois niveaux d'organisation humaine :

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1. le niveau politique national et interna- tional,

2. le niveau de l '~conomie politique r6gionale,

3. le niveau des d6cisions prises par l 'utilisateur des terres vis ~t vis de l '6conomique et du social.

Au premier niveau, plusieurs domaines ont trait aux probl6mes d'6rosion au Tiers Monde : la conservat ion de l 'eau et des terres, l 'aide ext6rieure, le gouverne- ment national, les activit6s des bureau- crates, les activit+s des services coloniaux.

Au niveau de l '6conomie politique r6gionale la recherche a d~montr+ l ' importance de l'acc+s et l 'utilisation des ressources naturelles des soci~t~s agraires, ainsi que de l 'al location des ter- res, du cr6dit, du capital et des droits coutumiers.

Au niveau le pus bas ce sont les d6cisions prises par les utilisateurs vis ~t vis de l '~conomique et du social qui d&erminent surtout le risque d'+rosion des terres. Ces d+cisions sont influenc~es non point par la nature du terrain seule, mais par l'effet des d+cisions prises aux niveaux sup6rieurs: le village, la r6gion, la nation, le jeu des nations puissantes et des compagnies trans-nationales (fig.l).

Deux examples d6montrent l'utilit6 de ce genre d 'analyse:

• Au N6pal une des causes de l ' abandon des syst+mes de conservation des ter- res a ~t~ at t r ibute au d6cimage de la popula t ion la plus active par le biais du service des Ghurkas dans l 'arm6e bri tannique (BLAIKIE , 1985).

• L'infusion d 'argents gagn6s en de- hors du cercle de la famille et du village a des effets tr~s n~fastes sur la fa~on dont le terrain est prot~g~ contre l '~rosion et aug- mente consid~rablement les risques

de d6gradat ion des terres - - les ex- amples de d~gradation des p~turages et des terres agricoles au Botswana et au Zimbabwe en sont les plus r~cents (ABEL et al., 1987; A B E L et B L A I K I E , 1988).

Plusieurs 6tudes par les auteurs ont d~montr+ que l'6rosion, et le d+clin des rendements s'ils s'en suiv- ent sont la consbquence d 'un ou d 'une s6rie de d6s6quilibres au niveau social, ~conomique et /ou politique l '6rosion n'est donc que sympt6me d 'un ou de plusieurs d6sordres qu'il se faut bien conna~tre avant de d~cider de la strat6gie de conservation des eaux et des terres. Les diff6rentes strat6gies possibles sont illustr6es dans la fig.2. I1 n'est pas im- pensable, par example, qu 'une diminu- tion du poids des dettes ~trang~geres soit plus efficace ~ arr~ter la destruction syst+matique du couvert v6g&al de larges r6gions tropicales au Tiers Monde qu 'un p rogramme de plantat ions d'arbres.

Study of the relationships between land degradation and development

Erosion problems in developing societies are usu- ally more acute than in communities which live in a more or less stable equilibrium with their environ- ment. The images of land degradation coming from the mountains in Ethiopia and the barren lands in the Indian continent remind us constantly that de- spite the many years of research in the physical nature of erosion and in methods of conservation, erosion still occurs, often at an even faster pace than before.

The failure of many soil and water conservation programmes has been explained at three levels:

1. at the level of national and international politics,

2. at the level of the regional political economy,

3. at the level of the decision making by the land user.

Several factors within the level of national and international politics have been demonstrated to

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have serious implications with regards to the ex- tent of land degradation: soil and water conser- vation strategy, foreign aid, national governments, activities of the bureaucracies and of the colonial powers.

At the level of the regional political economy, the access of agrarian societies to natural resources, land allocation, land tenure, credit and capital all have a potential impact on the ways in which land is managed - hence on erosion.

At the lowest level, the risk of land degradation is determined mainly by the decisions taken by the land users as conditioned by economic and social considerations. These decisions are not only influ- enced by the physical attributes of the environment, but especially by the effects which decisions taken at higher levels have on his/her life: the village, the region, the nation, and the powerful nations and transnational companies (fig.l).

Two examples illustrate how political and socio- economic processes may influence land degrada- tion :

• Several traditional soil conservation systems have deteriorated since the onset of European expansion. In Nepal, BLAIKIE (1985) partly attributes the abandoning of soil conservation practices to the selective removal of a most ac- tive component of society through the Gurka service in the British army,

• The infusion of money earned outside the con- fines of family and village has dramatic impacts on the way in which land is traditionally pro- tected against erosion, and is a major cause of enhanced land degradation - see, for instance, the degradation of rangeland and arable land in Botswana and Zimbabwe (ABEL et al; 1987; ABEL and BLAIKIE, 1988).

Past studies by the authors have demonstrated now and again that erosion and productivity de- cline (if it occurs), are most often the result of a (se- ries of) stress(es) operating at the social, economic and/or political dimensions of society. Erosion is often only a symptom of a (number of) disorders which need to be uderstood fully if an efficient strategy of soil and water conservation is to be devised. Possible strategies are illustrated in fig.2. According to this reasoning, it could, for instance, be argued that a reduction in the foreign debt bur- den of certain Third World countries could lead to a more effective protection of tropical forest than re-afforestation programmes.

3 Etude du d~clin de la producti- vit~ des terres r~uitant de l'~- rosion

Le deuxi+me sujet de cette commu- nication a trait ~ l'appr~ciation de l ' importance des symptrmes physiques, non point en termes physiques (p.e. t/ha/an), mais en termes financiers et/ou ~conomiques. I1 se peut, en effet, que l'+rosion, m~me acc~lrrre par, disons, un changement des pratiques culturales, n'a que peu de consequences financi+res n+gatives pour l'utilisateur et son en- tourage imm~diat et lointain.

Au Tiers Monde l 'apprrciation des pertes financi~res et ~conomiques dues l 'rrosion est effecture fr~quemment dans le domaine de l'analyse de factibilit+ des programmes de barrages (problrme de s+dimentation des rrservoirs). Des ~tudes rrcentes par la FAO (STOCKING, 1984; 1985 et 1986) ont trait au d+clin de la productivit6 des terres agricoles ~t cause de l'+rosion.

La revue par S T O C K I N G (1984) de la recherche pass~e a d+montr+ que:

• la relation entre le d~clin de la produc- tivit6 et l'+rosion cumulative est d'une forme exponentielle n~gative (fig.3). Cette fonction est d&ermin+e surtout par le sol et l'utilisation que l'on en fait: certains sols perdent leur ca- pacit+ productive plus rapidement, cer- taines cultures r+sistent mieux ~ la d+nudation que d'autres;

• les +l+ments nutritifs perdus ~ cause de l 'rrosion peuvent ~tre remplac+s et que la perte de la capacit6 de r+tention en eau est irrempla9able.

La revue de la recherche passre a permis l '~laboration d'un protocol de recherche adopt6 rrcemment par un

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Erosion H a z a r d - Risques d'Erosion 307

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r6seau mondial coordin6 par la FAO (STOCKING, 1985).

Au Zimbabwe (STOCKING, 1986), les pertes en azote, phosphore et mati+re organique du sol sont d6termin6es princi- palement par le taux d'~rosion et par les charact6ristiques du sol. Des fonctions &ablies pour 2058 6v6nements de ruis- sellement ont permis le calcul th6orique du cofit de l'apport d'engrais n6cessaire au remplacement de l'azote et du phos- phore perdus. Ce cofit a 6t6 estim6 ~t 1.5 milliard de dollars am6ricains par an.

L'analyse financi6re effectu6e pour le Zimbabwe est tr+s simplifi6e, et la recherche actuelle a 6t6 dirig6e vers la mod6lisation du syst+me productif sous l'influence de l'6rosion, permettant ainsi la pr6vision du d6clin du poten-

tiel productif et le calcul de l'aptitude r6siduelle des terres agricoles (ELWELL et STOCKING, 1984; STOCKING et PAIN, 1983; BLOT, 1988a; b e t c). Un mod61e d6velopp~ pour l'&ude du d6clin de la productivit~ des p~turages naturels au Botswana, THEPROM (fig.4) (BIOT, 1988b; 1989), a permis la pr6diction du d6clin de la productivit6 du sol (fig.5) dont il est facile de d6duire l'aptitude r6siduelle en projetant les niveaux de l'aptitude actuelle et l'aptitude minimale d6termin6e par l'6conomique, le social et/ou le politique.

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Study of productivity decline caused by erosion

The second topic of this paper deals with the anal- ysis of the importance of the physical symptoms of degradation, not in physical (e.g. t/ha/year), but in financial and economic terms. It is possible, indeed, that erosion, whether enhanced by human interference with the non-human processes of the environment or not, causes only limited damage to the land user, and his or her near or remote neighbour.

In the Third World, the estimation of financial and economic losses caused by erosion is usually confined to feasibility studies of dam projects (i.e. siltation problems). Recent studies by the FAO

(STOCKING, 1984; 1985; 1986) deal with pro- ductivity decline of agricultural land caused by erosion.

STOCKING' s (1984) review of past research has demonstrated

1. the negative exponential shape of the relation- ship between productivity and cumulative ero- sion (fig.3). The shape, or rather the curvature of the relationship, is mainly determined by the soil and the land utilisation type: some soils lose their productive potential rapidly; some crops are more resilient than others;

2. that in most past experiments nutrient losses are usually recovered, whereas losses in the soil's capacity to retain water are irreplaceable.

Based on these findings, STOCKING (1985) has

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Erosion H a z a r d - Risques d'Erosion 309

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designed a research protocol for the determination of productivity/erosion curves which has recently been adopted by a research network coordinated by FAO.

In Zimbabwe, losses in soil Nitrogen, Phospho- rous and Organic Matter are mainly determined by rates of erosion and soil type. Relationships established for 2058 runoff events have permitted the theoretical computation of the cost of fertiliser needed for the replacement of the lost Nitrogen and Phosphorous. This cost has been estimated at 1.5 billion US S/year (STOCKING, 1986).

The financial analysis carried out for Zimbabwe remains simplified, and presently research has been directed towards the modelling of the productive system as influenced by erosion, thus allowing the forecasting of productivity decline and the calcula- tion of the residual suitability of agricultural land (ELWELL and STOCKING, 1984; STOCKING and PAIN, 1983; BlOT 1988a, b and c). THE- PROM (rigA), a model developed for the study of productivity decline of rangeland in Botswana (BLOT, 1988b; 1989) - forecasts the decline in pro- ductivity (fig.5) from which it is possible to deduce the residual suitability on the basis of the present day and minimum allowable suitability levels.

4 Conclusions

Vus d 'un angle social, ~conomique e t /ou pol i t ique, les p rob l rmes d ' r ro s ion ne sont souvent que s y m p t r m e s de d rs rqu i l ib res

plusieurs n iveaux d ' o rgan i sa t i on du

genre humain. La ca r tograph ie des r isques d ' r ros ion est incompl+te sans une analyse app ro fond ie des re la t ions so- ciales, ~conomiques e t /ou pol i t iques qui engendren t la d~grada t ion des terres.

L ' impor tance financi~re e t /ou ~cono- mique de l '~rosion n 'est pas nrcessaire- ment p ropor t ione l l e ~ l ' impor tance phy- sique des phrnom+nes d '~rosion locaux. La recherche en les drc l ins de product iv i - t6 des terres au Tiers M o n d e a 6t6 ini t i re r rcemment .

Les conclusions d 'ana lyses des causes humaines de l '~rosion et du co~t de la d r g r a d a t i o n des terres effectures r r cemmen t peuvent &re r r sumres en qua t re poin ts :

1. ce n 'est pas l ' r ros ion qui compte , mais l 'effet de l '~rosion sur la product iv i t6 des terres,

2. la re la t ion entre ~rosion et drc l in de la product iv i t6 n 'est pas une re la t ion simple, mais est fonct ion du sol et de l 'u t i l i sa t ion que l 'on en fait,

3. l ' r ros ion n 'est pas un probl~me mais la consequence d'un probl&ne - - s 'a t ta- quer ~ l ' r ros ion seule est un emplSt re

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sur une jambe de bois. Le vrai probl+me est la gestion des terres,

4. la gestion des terres, et donc aussi l'+rosion, est largement influenc6e par les facteur +conorniques, sociaux et politiques aux niveaux de la famille, de la r+gion, de la nation et du march6 mondial.

C o n c l u s i o n s

When looked at from a social, economic and/or political viewpoint, erosion problems are often per- ceived as symptoms of stresses operating at several levels of organisation of humans. It is contended that the mapping of erosion hazards is incomplete without an in-depth analysis of the social, eco- nomic and/or political dimensions of land degra- dation.

The financial and/or economic impact of soil erosion is not necessarily proportional to the phys- ical dimension of land degradation. Research in productivity decline caused by erosion in the Third World has been initiated recently.

To conclude, the results of recent analyses of the human causes of soil erosion and of the cost of land degradation can be summarised in four points as follows:

1. It is not erosion which is important, but the impact of erosion on the productivity of land,

2. The relationship between erosion and produc- tivity decline is not a simple rationship but a function of the soil characteristics and the land utilisation type,

3. Erosion is not a problem, but the result of a problem - to fight erosion directly is often a misguided strategy. The real problem is land management,

4. Land management, hence erosion, is largely de- termined by economic, social and political fac- tors at the family, regional, national and inter- national levels.

References

ABEL, N.O.J. & BLAIKIE, P.M. (1988): Man- aging common property resources in rural devel- opment: the case of Zimbabwe and Botswana. Research Scheme ESR 322/348/01, ODG/ODA, Norwich/London.

ABEL, N.O.J., FLINT, M.E., HUNTER, M.D., CHANDLER, D. & MAKA, G. (1987): Cattle keeping, ecological change and communal man- agement in Ngwaketse. International Livestock Centre for Africa (ILCA) and the Integrated Farming Pilot Project (IFPP) and the Over- seas Development Group (ODG), Addis Ababa, Gaborone and Norwich.

BIOT, Y. (1988): Calculating the residual suit- ability of agricultural land based on routine land resource surveys. Paper presented at the Sym- posium on Land Qualities in Space and Time, Wageningen, August 1988.

BLOT, Y. (1988): Forecasting productivity losses caused by sheet and rill erosion in semi-arid rangeland: a case study from the communal areas of Botswana. PhD thesis, School of De- velopment Studies, University of East Anglia, Norwich.

BLOT, Y. (1988): Modelling productivity losses caused by erosion. In: Proceedings of the Fifth International Soil Conservation Confer- ence, Bangkok, Thailand.

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BLAIKIE, P.M. (1985): The Political Economy of Soil Erosion in Developing Countries. Long- man, London and New York.

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SOIl, I 'ECHNOLOGY A cooperating Journal of CATENA

Erosion H a z a r d - Risques d'Erosion 311

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Address of authors: Yvan Biot, Piers Biaikie & Michael Stocking School of Development Studies University of East Anglia Norwich NR4 7TJ U.K.

SOIL TECHNOLOGY A cooperating Journal of CATENA