Botswana - suite

Jeremy Burgess

5. RESSOURCES PASTORALES

Les ressources en pâturages du pays sont essentiellement constituées de parcours naturels. Des recherches sur l'amélioration de ces ressources ont été conduites, de 1970 à 1990, en particulier en encourageant l'introduction d'herbacé et de légumineuses natives à haut potentiel en même temps que celle de légumineuses exotiques. D'autres recherches ont été conduites sur les effets des applications d'engrais sur les pâturages pour en augmenter la productivité. Ces recherches et d'autres, sont analysées dans la Section 6.

Parcours naturels
Les parcours naturels couvrent presque tout le pays (on se reportera, pour les détails, à l'analyse des types de végétation et de paysages donnés dans l'annexe 1)

De nombreuses espèces herbagères ont une période végétative courte, ce qui traduit une adaptation aux incertitudes des précipitations. Le lourd piétinement de la végétation par le bétail, particulièrement dans les sols sablonneux, tend à déraciner les plantes qui ont un système radiculaire peu profond, ce qui crée de larges plages de sols dénudés jusqu'aux pluies suivantes. Ces parcours contiennent aussi de nombreuses légumineuses (de la famille des Papilionoideae) des espèces arbustives, parmi lesquelles des légumineuses comme les arbres du genre Acacia.

Limitations des ressources fourragères.
La principale contrainte limitant la productivité des ressources fourragères est celle de la pluviosité, dont les occurrences sont faibles et irrégulières. Les parcours naturels sont ainsi soumis à des variations extrêmes, aussi bien sur une base quotidienne que sur une base saisonnière ou inter-annuelle. Les températures diurnes varient avec des amplitudes atteignant 20 ºC tout au long de l'année.

Au cours des saisons, les ressources pastorales ne sont, le plus souvent, disponibles, que sur des périodes courtes, ce qui contraint le cheptel à se déplacer sur de grandes distances pour trouver d'autres pâturages, en attendant de nouvelles pluies. Trop souvent, un pâturage ne peut être utilisé qu'une seule fois dans l'année, bien que, par besoin, les animaux soient amenés à revenir sur les aires déjà pâturées et raser les plantes résiduelles après consommé toutes les meilleures espèces.

De nombreuses espèces sont annuelles, en particulier dans le sandveld où les touffes de végétation sont physiquement arrachées du sol par les animaux aux pratiques de pâture non sélective comme les bovins. Ainsi, durant un nombre limité de périodes pluvieuses, de nombreuses espèces herbagères ne peuvent pas concurrencer, pour l’humidité et la lumière, les espèces ligneuses qui ont établi leur système radiculaire. Les rendements des herbages sont donc extrêmement faibles, de l’ordre de seulement 1-2t/ha.

On observe que de nombreuses espèces végétales ne sont appétibles ni pour le cheptel ni pour la faune sauvage herbivore. On pense que ce rejet est du à des concentrations acides élevées, à de fortes contenances de silicates, à un excès de lignification, à des goûts peu appréciés, comme dans le cas de la présence de la composante aromatique terpenes. Il est intéressant de noter que les espèces animales monogastriques (comme les équidés et les ânes) sont les mieux adaptées à cet environnement (pour autant qu'ils aient accès à l'eau), alors que les ruminants sont moins favorisés.

Certaines espèces buissonnantes sont appétées mais beaucoup d'entre elles sont défendues par des systèmes épineux, par un fort taux de tannin, ou encore par des saveurs aromatiques qui les rendent peu appétibles. D'autres sont tout simplement trop en hauteur pour que le cheptel puisse les atteindre. Les feuilles sont généralement appétées lorsqu'elles sont tombées en hiver ou au début de la saison sèche estivale.

Une autre contrainte réside dans la faible dotation des sols en phosphate, une caractéristique de tout le pays. Les éleveurs commerciaux remédient à cette carence en donnant du phosphate au cheptel sous forme de pierres à lécher et en ajoutant de l'urée (principalement fourni par les déchets des élevages de volaille) aux compléments alimentaires fournis au cheptel. Une autre contrainte provient de l'éradication progressive des meilleures plantes des parcours, par suite du surpâturage continu.

La répartition des pluies concentre la production des espèces pastorales et des autres fourrages pendant la brève période pluvieuse de l'été. Dès la fin des pluies, les herbages cessent aussi de croître. Dès que les ressources ont été utilisées, il n'y a plus rien jusqu'à la saison des pluies suivantes.

Les zones sableuses les plus sensibles à la dégradation sont celles qui environnent les campements (cattle posts) et les points d'eau. Ces zones tendent à être couvertes de petits épineux denses qui s'étendent jusqu'à 1-1,5 km autour du point d'eau.

L'eau de surface manque presque totalement et l'élevage doit dépendre essentiellement de l'eau des forages profonds. Les études hydro-géologiques ont montré que pour conserver les équilibres des nappes, les forages doivent, dans la plus grande partie du pays, respecter des écartements d'au moins 8 km. Cette contrainte signifie que la plus petite dimension possible pour un ranch est de 8 km sur 8 km.

Les facteurs les plus importants qui limitent la productivité des parcours sont relatifs à la brièveté de la saison pluvieuse, le taux élevé d'évapotranspiration, la percolation rapide de l'humidité des sols, à des profondeurs que les racines ne peuvent pas atteindre. Ces contraintes encouragent une forte compétition entre les espèces végétales pour l'humidité résiduelle du sol. A cela s'ajoute la compétition entre les animaux pour les ressources fourragères. Ceux-ci, d'ailleurs ne se concurrencent pas seulement entre eux mais ils doivent aussi entrer en compétition avec les termites, les rongeurs et la faune herbivore sauvage.

6. AMÉLIORATION DES RESSOURCES PASTORALES

Pâturages améliorés et fourrages semés
Des recherches ont été conduites sur les pâturages améliorés et sur les cultures fourragères semées mais on ne trouve que rarement d'applications se leurs résultats, sauf dans les stations de recherche, dans les petites exploitations laitières et dans les élevages d'autruches.

Les résidus de récolte
Ceux ci sont couramment utilisés dans les élevages sur terres tribales collectives. Le bétail est admis après récolte sur les terres cultivées dans les zones agricoles.

Bilan des recherches sur les pâturages pendant la période 1970-1990
L'Unité de Production Animale et de recherche (APRU) a effectué un bilan des recherches entreprises pendant la période 1970 to 1990.

Facteurs limitant la productivité des parcours naturels 1972-1973 .La recherche sur les parcours au Botswana se poursuit depuis 1937. Un programme plus ambitieux a été lancé en 1972 et il s'est proposé de rassembler sur tout le pays des données de base sur la productivité des parcours et sur le poids des animaux. La digestibilité est apparue comme le principal facteur limitant les gains de poids à partir des ressources des parcours, ce facteur étant suivi par les carences en protéines durant la saison sèche. Les parcours des ranchs du hardveld ont les plus hauts taux de phosphore tandis que les herbages du sandveld ont les taux les plus bas. D'une façon générale, les taux de calcium et de phosphore dans les herbages tendent à augmenter durant la saison humide et sont plus bas durant la saison sèche. La supplémentation avec du phosphore des jeunes bovins montre des gains de poids de 0,2 kg/jour. Dans neuf ranchs de recherche, on a observé des rendements du pâturage variant de 4 kg à plus de 60 kg de matière sèche par kg de poids vif. La variation inter-annuelle des précipitations est la principale cause de ces écarts de rendements. La sélectivité des ressources fourragères par les animaux tend à être plus forte quand le niveau de protéines est inférieur à 5 %.

Evaluation des espèces herbagères 1974-1977.
Les types d'herbages (voir tableau 7) que l'on trouve dans le hardveld sont rarement présents dans le sandveld et vice versa. Les espèces sont ainsi très différentes et ont des caractéristiques très différentes en saison sèche.

Cymbopogon excavatus a un taux élevé de protéines mais il n'est pas appété par le cheptel en raison de son amertume.

Le défrichement des zones buissonnantes (le "bush") de 1974 à 1979. On attendait du débroussaillage du bush un effet bénéfique sur la composition botanique, en particulier du fait d'une meilleure insolation et d'une meilleure capture des eaux de pluie. Une expérimentation comparative entre des zones débroussaillé, partiellement débroussaillé et non modifiées (voir tableau 8) a montré que les zones débroussaillé ont, de façon régulière, un rendement en matière sèche supérieur (de quelque 20%) au rendement des zones non défrichées. En outre, on a observé une amélioration du couvert végétal ainsi qu'un meilleur rendement des espèces les plus convoitées.

L'importance de l'effet bénéfique du débroussaillage doit cependant tenir compte de l'effet inverse de suppression du pâturage aérien dans les arbustes. On en retire la leçon que l'éradication totale des arbres devrait être contrôlée de façon à ne pas éliminer les ressources fourragères arbustives appréciées par le bétail.

Techniques de défrichement et de gestion du "bush" Cette recherche fut conduite pour évaluer l'impact économique et biologique de méthodes alternatives de contrôle et d'éradication des espèces arbustives du "bush".

1. Les méthodes mécaniques (bulldozer) et chimiques d'éradication des arbres et arbustes se sont révélées coûteuses. Des considérations environnementales se sont en outre imposées en raison des risques des traitements chimiques sur les animaux et sur la végétation native.

2. Le feu. Des feux contrôlés, à des intervalles de sept à dix ans, permettent de gérer la végétation du bush et de détruire les arbustes jusqu'à une hauteur de deux mètres. Des contrôles sont cependant nécessaires pour gérer les repousses. Cette technique exige en outre assez de matériel ligneux pour être efficace.

3. Les caprins. Les chèvres jouent un rôle efficace pour réduire la densité du bush en pâturant les repousses après incendie. Une chèvre par ha peut, sur une période de quatre à cinq ans, réduire de 70% la capacité de repousse des acacias et des espèces ligneuses associées.

Systèmes de conduite du parcours. 1975 (suite). Le recours à des systèmes de rotation de parcs de pâturages pour améliorer les performances de l'élevage, conserver les espèces les plus appétées et contrôler les envahissements d'espèces non désirées, a fait l'objet de recherches. Les études initiales, conduites en 1975-1979 montrent peu de différences dans les performances animales, la composition de la couverture végétale. Il faudrait identifier des avantages plus évidents pour justifier les coûts de clôture qu'imposent ces systèmes de rotation par parcs. De nouveaux essais, lancés en 1979 ont comparé trois systèmes d'utilisation des parcours: le pacage continu; une rotation en trois parcs par troupeau (un mois de pacage et deux mois de repos); neuf parcs par troupeau (4 jours de pacage et 32 jours de repos).

Lors d'une expérience pur contrôler la charge animale et les systèmes d'utilisation des parcours dans les zones collectives /tribales, la proposition fut faite d'établir 12 cellules de pâturages.  Le contrôle technique et le suivi devaient être effectués par l'APRU. Deux cellules de contrôle furent établies à cet effet. Ce projet ne put cependant pas atteindre las objectifs qu'il se proposait et les leçons suivantes furent tirées de cette expérience: des projets de ce type ne peuvent fonctionner qu'au travers d'institutions locales; l'identification et la reconnaissance de l'aire pastorale utilisée par la communauté ou le groupe est indispensable pour qu'une gestion volontaire de la charge animale puisse réussir; le concept de "cellule de parcours"  a été perçue comme bénéficiant à une minorité tandis qu'elle réduisait les accès au parcours des éleveurs exclus de ce système. Le travail sur l'une de ces cellules (Makhi II) se poursuit actuellement.

Etudes écologiques des reliefs du Kalahari occidental 1975-1979. L'établissement de ranchs commerciaux devant être loués à des éleveurs dans la zone de Ncojane a constitué une composante importante du premier projet de Développement de l'Elevage lancé en 1972. Un  projet d'écologie des parcours fut ensuite lancé pour suivre l'impact écologique du cheptel bovin dans la zone du projet.

Bien qu'aucune conclusion définitive ne puisse être tirée après seulement cinq ans de projet, quelques recommandations purent être faites en tirant les premières leçons de l'expérience:

1. Le facteur de la charge animale s'est révélé être plus important que les systèmes d'utilisation des pâturages. On en tire la conclusion que le pacage continu est acceptable s'il est accompagné d'une charge animale modérée.
2. Le contrôle de la pression pastorale est d'autant plus efficace qu'il s'accompagne d'une bonne distribution spatiale des points d'eau, sans toutefois dépasser 5 km entre les points d'eau.
3. Le délestage des parcours durant les sécheresses est indispensable
4. Des moyens sont nécessaires pour pouvoir contrôler effectivement le respect de la charge animale sur chaque parcours pour éviter le sur pâturage.

Essais de systèmes de pâturage de Makhi II 1980 (suite). Les résultats de ces essais n'ont pas de cohérence sur plusieurs années. La première année le pâturage, utilisé de façon continue, s'est révélé plus pauvres que ceux utilisés avec d'autres systèmes mais une amélioration fut constatée l'année suivante. Au cours des trois années suivantes, le système de la rotation en neuf parcs s'avéra meilleure que les deux autres systèmes. Ces résultats furent suivis par de meilleures performances en pâturage continu Ce dernier système est sensible à des effets négatifs en année de sécheresse et affecte les gains de poids. Le système, en effet, ne permet pas de période de repos pour la repousse de la végétation.

Essais sur la charge animale 1980 (suite). Des charges animales de 2, 4, 6, 8, 10 et 12 ha/par unité (LSU) furent expérimentées comparativement. Les résultats préliminaires ont montré que la densité des herbages de qualité augmentait avec des charges animales décroissantes. Comme on s'y attendait, les gains de poids augmentèrent de la même façon. On attend de l'étude qu'elle analyse aussi les implications économiques sur la production à long terme d'une variation des charges animales.

Le problème de la charge animale se rattache au concept de capacité d'accueil des pâturages que l'on doit apprécier sur de longues périodes. Sur de telles périodes, en effet, il y a des années de bonnes pluies au cours desquelles des ressources de biomasse ne sont pas utilisées et, par ailleurs, des années sécheresse ou de pluviosité insuffisante au cours desquelles des charges excessives apparaissent. Il semble ainsi préférable de gérer la charge pastorale sur la base du potentiel de chaque année et de contrôler ainsi les situations d'excès ou de déficit de la charge par rapport aux ressources.

Restauration des parcours dégradés 1982 (suite). On attribue la dégradation des parcours à une carence des systèmes de gestion de ces ressources et au manque de contrôle de la charge animale sur les parcours, particulièrement dans les parcours communaux. Des essais furent conduits dans le ranch de terres communales de Morale, dans le Kalahari occidental (Tshane) afin d'étudier les processus de dégradation, de proposer des modes de restauration et de gestion plus efficients et d'évaluer les effets sur le tapis herbacé et sur les performances des animaux. L'essai de Tshane concernait la restauration d'une zone dégradée tandis que les essais de Morale s'attachaient surtout à suivre et comprendre le processus de dégradation.

Les essais de Tshane ont démontré la possibilité d'une augmentation de la densité des bonnes espèces en proportion de l'éloignement du point d'eau tandis que la végétation non graminéenne (forbs) semblent décroître avec l'augmentation de la distance de l'eau dans les parcs (exclosures) protégés du pâturage pendant la période de croissance de la végétation. Des différences significatives dans la densité du couvert végétal ont été observées à la fin de la période de croissance, selon qu'il s'agissait des exclosures ou des parcours adjacents ouverts au pâturage.(jusqu'à une distance de 14 km du point d'eau) Les différences furent cependant moins marquées lorsque l'on s'éloignait davantage du point d'eau (jusqu'à18 km et plus).

Essai de simulation d'un système de pâture communale dans le ranch de Morale 1984 (suite). La mauvaise gestion et la dégradation des parcours collectifs laissent planer de sérieux doute sur la durabilité à long terme des systèmes d'utilisation de ces ressources. Une étude a été lancée en 1984 dans le ranch de Morale, sur les aspects de la dégradation des parcours et sur les apports possibles d'une supplémentation en phosphore. Le but recherché était de trouver des réponses pour restaurer les parcours dégradés, établir des normes de charge animale, définir de meilleurs modes de conduite du troupeau. A cet effet, des bovins furent introduits sur deux parcs utilisés en continu avec des taux de charge de 3, 6, et 9 ha/unité (LSU). Les effets de cette charge animale furent évalués sur la base de la qualité de la couverture végétale et sur celle des gains de poids vif. Les effets sur la végétation en 1985 furent les meilleurs avec la charge de 9 ha/LSU. La perte de matière végétale fut plus forte avec une charge de 3 ha/LSU qu'avec 6 et 9 ha/LSU. La même tendance fut observée en 1987, 1988 et 1989. Le poids vif du cheptel, augmenta, comme on s'y attendait, avec les taux de charge les plus bas. Les gains les plus forts furent observés avec une charge de 9 ha/LSU accompagnée d'une supplémentation en phosphore. Cette dernière semble donner plus de résultats; en condition de faibles précipitations, avec un taux de charge encore plus faible - plus de 9 ha/unité animale.

Plantes fourragères et pâturages 1976 (suite). Les cultures fourragères et les pâturages dans les zones a forte ou moyenne pluviosité présentent plus d'intérêt quand elles sont développées dans des systèmes intensifs ou semi intensifs, comme par exemple, les exploitations laitières. Des travaux conduits avant l'indépendance, furent à l'origine de l'introduction du "saltbush", du melon fourrager et du cactus fourrager; ils encouragèrent également la culture de quelques plantes natives et de quelques légumineuses fourragères tropicales. Les résultats de ces expériences ne furent pas bien exploités et, faute d'information, ils ne furent pas adoptés par les éleveurs.

Introduction d'espèces fourragères 1977 (suite). Des expériences d'introduction d'espèces ont été faites à Sebele, Mahalapye et Pelotshetlha. 25 espèces herbagères et 77 légumineuses ont été ainsi introduites. Graminées indigènes Cenchrus ciliaris, Panicum coloratum, Eragrostis curvula, Urochloa mosambicensis, Chloris gayana, Cynodon dactylon. Légumineuses indigènes Glycine wightii, Indigofera sp., Desmodium, Dolichos lablab, Sesbania. Les légumineuses présentant un intérêt potentiel comprennent: Indigofera , Tephrosia, et Siratro

7. ORGANISMES DE RECHERCHE ET DÉVELOPPEMENT IMPLIQUÉS DANS LE PASTORALISME

APRU - Botswana College of Agriculture. L'Unité de Production Animale et de Recherche (APRU) est l'institution de référence pour tout ce qui concerne la recherche sur les parcours, les pâturages et les cultures fourragères au Botswana. Cette unité est localisée auprès du Collège d'Agriculture du Botswana, Sebele, Gaborone.

L'APRU dispose de plusieurs stations de recherche dans le pays. Ces stations conduisent des recherche sur l'élevage et les parcours dans différents types de parcours en s'adressant à une diversité d'espèces animales et de systèmes de production. Les personnes ressources clés de l'APRU sont les suivantes::

BRIMP – Ministère de l'Agriculture. Le Programme du Botswana pour l'Inventaire et le Suivi des Parcours, (Botswana Range Inventory and Monitoring Programme), localisé dans la Division d'Ecologie des Parcours, Department of Productions et des Forêts, Ministère de l'Agriculture, Gaborone est aussi une institution clé. Il fonde son travail sur des banques de données très riches et est équipé pour interpréter les images satellitaires. Il utilise également les prévisions météorologiques pour interpréter les tendances de la productivité des parcours sur une base saisonnière.

Contacts auprès de BRIMP

Représentant de la FAO au Botswana
Le représentant de la FAO à Gaborone, dont le siège est basé au College of Agriculture du Botswana, Sebele, est M. Poloko Nkepu, Tél: 3928 715.

8. RÉFÉRENCES BIBLIOGRAPHIQUES

Etudes d'ensemble

APRU, ~1991. Twenty Years of Animal Production and Range Research in Botswana. 1970-1990. Ministry of Agriculture.

APRU, 1978. An Integrated Programme of Beef Cattle and Range Research in Botswana, 1970-1977. Animal Production and Research Unit, Ministry of Agriculture, Gaborone.

Bhalotra Y.P. R., 1985. Drought in Botswana. Dept. Met. Services. Ministry of Works, Communications & Transport. Republic of Botswana.

BRIMP Botswana Range Inventory & Monitoring Project. Ministry of Agriculture, Gaborone, Botswana. Jointly funded by DFID, UK.

Carney J. N., Aldiss D. T., and Lock N. P., 1994. The Geology of Botswana. Bulletin 37. Geological Surveys Department, Ministry of Natural Resources and Water Affairs, Republic of Botswana. Govt. Printer, Gaborone.

Cook H. J., 1978. Botswana’s present climate and evidence for past change. Proc. Of Symposium on "Drought in Botswana". The Botswana Society, Gaborone, Botswana.

CSO, 1996. Agriculture Statistics:1996. Central Statistics Office, Gaborone. Republic of Botswana.

DHV Consulting Engineers, 1980. Countrywide Animal and Range Assessment Project. Seven Vols., with Maps. DHV, PO Box 85, 3800 AB, Amersfoort, The Netherlands.

Ecosurv, 1997. Strategic Assessment of the South Western Wildlife System of Botswana: Rehabilitation Measures. IFAD funded programs on SW Strategic Environmental and Countrywide Assessments.

Environmental Consultants, 1991. Central District Planning Study. Main Report, Vol. 1. MLGL&H/Central District Administration. Gaborone.

FAO, 1990 a. Soil Map of the Republic of Botswana. . Soil Mapping and Advisory Services Project. AG:DP/BOT/85/011. Ministry of Agriculture, Gaborone Botswana/FAO/UNDP.

FAO, 1990b. Explanatory Note on the Soil Map of the Republic of Botswana. Soil Mapping and Advisory Services Project. AG:DP/BOT/85/011, Field Document #30. Ministry of Agriculture, Gaborone Botswana/FAO/UNDP.

FAO, 1990c. Land Systems Map of the republic of Botswana. Soil Mapping and Advisory Services Project. AG:DP/BOT/85/011. Ministry of Agriculture, Gaborone Botswana/FAO/UNDP.

FAO, 1991. Contribution to the Vegetation Classification of Botswana. Soil Mapping and Advisory Services Project. AG:DP/BOT/85/011. Field Document #34. Ministry of Agriculture, Gaborone Botswana/FAO/UNDP.

FAO 1992. Map of Land Suitability for Rainfed Crop Production, plus the Explanatory Note and Legend. TCP/BOT/0053, Field Document #3.

FAO/UNDP Soils and Land Utilisation documents and maps:

Ministry of Agriculture, 1993. Monitoring and Progress Report 1991-1992/3. Ministry of Agriculture.

Moyo S., O’Keefe P., & Sill M., 1993. The Southern African Environment: Profiles of the SADC Countries. EARTHSCAN. ISBN 1353331719.

National Development Plan 8, 1997/98-2002/03. Ministry of Finance and Development Panning. Govt. Printer, Gaborone.

Roe E., 1973. Development of Livestock, Agriculture & Water Supplies before Independence, in Botswana: A short History and Policy Analysis. Cornell University and Ministry of Agriculture. Rural Development Committee, Occasional Papers #10.

Sims D., 1981. Agro-Climatological Information, Crop Requirements and Agricultural Zones for Botswana. Land Utilisation Divisions, Ministry of Agriculture, Gaborone.

Smith R. A. 1984. The Lithostratigraphy of the Karoo Supergroup in Botswana. Botswana Geological Survey Bulletin. 26. 239 pp.

Thomas, D.S.G. and P.A. Shaw 1991. The Kalahari Environment. Cambridge University Press.

UNDP/FAO, 1982. Co-ordinator, Animal Production and Range Research. BOTS. AG:DP/BOT/74/002 Internal report. Rome 1982.

Weare, P.R. and A. Yalala. 1971. Provisional Vegetation Map of Botswana (First Revision). Botswana Notes and Records 3:131-147.

WMA studies including - various National Parks and Game Reserves,

Etudes générales

Botswana Notes and Records, published by the Botswana Society in Gaborone. (These journals cover issues on the environment - plants and wildlife, agriculture, society, culture and cultural history, and new research findings on Botswana related topics.)

IUCN 1990. The Nature of Botswana: A Guide to Conservation and Development. IUCN, Field Operations Division, Gland, Switzerland.

Tlou T & Campbell A, 1984. History of Botswana. Macmillan, Botswana.

Etudes récentes

• Management of Indigenous Vegetation for the Rehabilitation of Degraded Rangelands in the Arid Zone of Africa - Botswana, Kenya, Mali. A joint UNEP/GEF funded program , combining inter-regional programs from the three countries, working through the three Governments. The study is a progression from the Kalahari-Namib study within Botswana.
  www.unep.org/unep/gef/biokalahar.htm

Documents sur les poltiques

Ministry of Agriculture, 1974. Draft Livestock Development Policy. National Land Management & Livestock Project. Animal Production Division, Ministry of Agriculture.

Conventions

• RAMSAR www.ramsar.org/
• Convention de Lutte contre la Désertification (CCD) < http://www.iisd.ca/linkages/vol04/enb04118e.html >
• Convention Internationale sur la Biodiversité: www.biodiv.org/
• CITES www.cites.org/
• Projet Kalahari-Namib www.unep.org/geo2000/english/0147.htm

9. CONTACTS

Jeremy Burgess est un écologiste indépendant qui a acquis une grande expérience du Botswana.
Plot 560, Lenganeng, Tlokweng - Gaborone.
Tel: 3930972, Cell: 71755933
e-mail: jburgess@info.bw

Remerciements
De nombreuses personnes ont apporté volontairement leur temps et leur savoir et sans leur aide, ce profil n'aurait pas pu être réalisé. Des remerciements particuliers sont adressés aux personnes suivantes: (1) l'équipe du BRIMP pour leurs contributions et pour leur information sur les sources de documentation, dont, notamment, Victor Tlhalerr, Principal Range Ecologist et Assistant de la Range Ecology Section, Ministère de l'Agriculture qui nous a également fait part  de commentaires éditoriaux particulièrement utiles; également David Stimela (GIS section) qui nous a fourni les cartes digitalisées (2) M. S "Bings" Bingana, du Botswana National Productivity Centre, qui nous a accordé son temps et donné des matériaux sur les aspects socio économiques ainsi que les graphiques relatifs à la BMC (Botswana Meat Commission). (3) Dr. Wanda Mphinyane, qui nous a donné des documents et des résumés de recherches (4) Enfin nos remerciements vont à Raymond Kwerepe, Chef de la Division "Forestry, Range Ecology and Beekeeping", pour le temps qu'il a consacré à l'édition et à la relecture de ce document.

[Ce profil a été préparé en 2002 par l'auteur et il a été mis en forme par J.M. Suttie et S.G. Reynolds qui ont apporté les touches finales en janvier-mars 2003]
[Le profil a été traduit en francais por Anouchka Lazarev]

APPENDICES

APPENDIX 1. Detailed Regional Vegetation Associations

The following sub-sections describe the vegetation according to region, as provided on the associated map.

Figure 14. Vegetation Regions as Taken from the FAO Soils Map
[Click to enlarge map]

Region 1. Extreme South-West

Sandveld - Extremely Arid

This region forms a narrow zone along the Nossop and the Molopo from the Gemsbok National Park via Bokspits to Khuis.

Along the Nossop bare rolling dunes are present.

Undulating to rolling dunes found further inland are covered by a vegetation mosaic varying in structure from grassland to low shrub savanna and shrub savanna with as most conspicuous species Acacia haematoxylon and the grasses Stipagrostis amabilis, S. uniplumis and Schmidtia kalahariensis. The interdunes mainly support a shrub savanna characterised by Acacia haematoxylon and Rhigozum trichotomum. The vegetation of this dune-interdune complex has an association of Acacia haematoxylon and Rhigozum trichotomum.

Region 2. South-West

Sandveld - Arid

Region 2 extends north from Region 1 and from the Molopo River via Phitshane, Jwaneng and Kang to the Tropic of Capricorn.

Due to higher precipitation rates to the north, the shrub savannas of Region 1 gradually change into savannas in Region 2.

The largest part of this sandveld region is characterised by a savanna with an Acacia mellifera, A. luederitzii, Boscia albitrunca association.

Frequent pans are observed in the central and northern section of this zone. The pans are fringed by a dense savanna and have a central area that is bare or is covered by grassland with species from genera such as Sporobolus, Panicum, and Eragrostis.

In the south-east of the region a (open) shrub savanna has been established, belonging to the same sandveld association. There the grass layer varies in coverage from 10-70%, and is dominated by Eragrostis lehmanniana, Stipagrostis uniplumis and Anthephora pubescens.

In the west of this region (open) shrub savannas are found, which form part of a Catophractes alexandri, Rhus tenuinervis association.

The most eastern land systems are characterised by open shrub savannas and open savannas. They occupy a floristic intermediate position between the Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba sandveld association and the eastern hardveld associations Peltophorum africanum, Acacia tortilis, / A. karroo, Ziziphus mucronata and Peltophorum africanum, Acacia tortilis / Terminalia sericea.

Throughout the region several zones with superficial aeolian sand deposits can be recognised. These areas are mainly characterised by shrub savannas and savannas which fit in the Acacia mellifera, A. luederitzii, Boscia albitrunca association.

In the north, some isolated patches of shrub savanna and savanna occur that belong to a Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba association (see Region 3).

Region 3. Mid-West

Sandveld - Arid to Semi-arid

This region is enclosed by the Tropic of Capricorn in the south, the Okwa/Quoxo valley system in the north and east and the Namibian border in the west. A small zone extends southwards along the international boundary to the Nossop.

In this region the vegetation structure ranges from low shrub savannas to dense savannas. The vegetation of the whole area is part of a Terminalia sericea, Lonchocarpus nelsii, Acacia erioloba and A. leuderitzii association. Predominant grass species include Anthephora pubescens, Eragrostis lehmanniana, Schmidtia kalahariensis, S. pappophoroides, Stipagrostis uniplumis, Aristida congesta, Pogonarthria squarrosa.

Region 4. Okwa/Quoxo valley system

Sandveld - Fossil Valley Systems

This fossil river system, located in the centre of the country, is mainly covered by a shrub savanna and savanna mosaic, which floristically belongs to the Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba association. The grass layer is dominated by Aristida congests, Eragrostis lehmanniana, Pogonarthria squarrosa, Schmidtia pappophoroides, Stipagrostis uniplumis.

Region 5. Mid-East

Sandveld - Shallow with Hardveld Interface

Region 5 is confined by the Quoxo in the west and the hardveld in the east and is roughly situated between Letlhakane in the north and Dibete in the south. This region mainly consists of sandveld vegetation types. Towards the boundary between the sandveld and the eastern hardveld transitional vegetation types and one hardveld association occurs.

The principal vegetation structure in the sandveld is savanna. The savannas belong to the Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba association.

Hardveld land systems are located at the eastern fringe of the sandveld. They support a transitional vegetation with elements of the sandveld association and species of the hardveld associations Peltophorum africanum, Acacia tortilis / Terminalia sericea, and Combretum apiculatum, Acacia nigrescens, and A. tortilis. A system of superficial aeolian sand deposits, mainly surrounded by hardveld consists of the hardveld association Colophospermum mopane, Acacia nigrescens / Combretum apiculatum, Acacia tortilis (see Region 6). The grass layer is dominated by Aristida congesta, Digitaria milanjiana, Eragrostis pallens, Stipagrostis uniplumis., with 10-30% basal cover.

One land system is covered by a transition community with elements of the sandveld association and the hardveld association Colophospermum mopane, Acacia nigrescens / Combretum imberbe, forming an association of Colophospermum mopane, Terminalia sericea / Combretum imberbe. Part of this land system is also characterised in places by a vegetation transition between sandveld and hardveld resulting in a Colophospermum mopane, Terminalia sericea / Sclerocarya caffra association. The grass layer here is dominated by Anthephora pubescens, Digitaria sp., Eragrostis pallens, and Stipagrostis uniplumis, with 10-70% cover.

The mopane-line roughly follows the boundary between sandveld and hardveld. It crosses land and divides it in a southern part with typical sandveld vegetation and a northern zone with an association of Colophospermum mopane and Terminalia prunioides. The grass layer is dominated by Cenchrus ciliaris, Digitaria milanjiana, Eragrostis sp.

Region 6. Eastern Hardveld

Hardveld - with Minor Sandveld Intrusions

The eastern hardveld extends from approximately 26º south to 20º south and is confined by the sandveld in the west and the international boundary in the east.

The hardveld has a vegetation cover ranging from shrub savanna over savanna to tree savanna. In comparison with the sandveld, the hardveld is typified by a denser and taller vegetation. This difference can be contributed to the heavier texture and higher nutrient content of the hardveld soils.

From south to north shrub savannas decrease and tree savannas increase. This tendency is probably due to the increase of the precipitation towards the north.

In the hardveld two provisional alliances consisting of two and three associations respectively and three independent association have been distinguished.

From 26º south to 23.5º south a Peltophorum africanum, Acacia tortilis alliance is found, consisting of two associations:

• The southern association is characterised by structures varying from shrub savanna and savanna to tree savanna and the species Peltophorum africanum, Acacia tortilis / Acacia karroo, Ziziphus mucronata.
• The northern association is typified by shrub savannas and savannas, marked by Peltophorum africanum, Acacia tortilis / Terminalia sericea.

Between 23º south and 20º south a Colophospermum mopane, Acacia nigrescens alliance is present, which consists of four associations:

• The southern one is predominated by savannas, which form a Colophospermum mopane, Acacia nigrescens / Combretum apiculatum, A. tortilis association.
• The eastern central section of this zone is covered by relatively tall (12-16m height), close-canopy woodlands that are dominated by Acacia nigrescens and Sclerocarya birrea, with a secondary woodland storey of (4-10m height) dominated by Combretum apiculatum. This vegetation association coincides with shallow-basalt-derived soils that overlie a granitic parent geology.
• The eastern land systems are covered by an association of open tree savannas typified by Colophospermum mopane, Acacia nigrescens / Burkea africana. B.africana is usually associated with sandy soils, but occurs here, in pockets of deep sand, which are generally old drainage lines and erosion surfaces that have infilled with sand.
• In the north-western area of the hardveld and in some patches of the north- I east savannas and tree savannas are found, which belong to a Colophospermum mopane, Acacia nigrescens / Combretum imberbe association. The grass layer is dominated by Aristida congests, Eragrostis lehmanniana, E. rigidior, E. superba, with 10-70% basal cover.

The hardveld land systems situated between 23.5º and 23º south, predominantly consist of savannas, which form an independent association of Combretum apiculatum, Acacia nigrescens, A. tortilis.

There is an intermediate land system between the Peltophorum africanum, Acacia tortilis / Terminalia sericea association and the Combretum apiculatum, Acacia nigrescens, A. tortilis association and can be classified as an Acacia erubescens, A. tortilis, Boscia albitrunca association. The grass layer is dominated by Bothriochloa insculpta, Chloris virgata , Perotis patens, and Setaria sp., with 30-70% basal cover.

There are two sandveld land systems that are included in this region, and which are typified by a range of vegetation structures from open shrub savannas to open tree savannas. One system is classified as an Acacia tortilis, Combretum erythrophyllum, Lonchocarpus capassa association, while the other is classified as an Acacia erubescens, A. tortilis, Boscia albitrunca association.

The mopane-line separates the Combretum apiculatum, Acacia nigrescens, A. tortilis association from the more northern located Colophospermum mopane, Acacia nigrescens alliance. The grass layer is dominated by Aristida congest a , Cenchrus ciliaris, Chloris virgata, and Eragrostis lehmanniana, with 10-30% basal cover.

Region 7. Letiahau, Ghanzi, Hainaveld area

Northern Sandveld

Region 7 extends from the Okwa to the Boteti and is confined by the almost flat fossil lagoon in the east and the international border in the west.

Both on the eastern and western side of the Ghanzi ridge, the sandveld is mainly characterised by shrub savannas and savannas belonging to the Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba association. Typical grass species include Anthephora pubescens, Aristida meridionalis, Cenchrus ciliaris, Digitaria eriantha, Enneapogon cenchroides, Eragrostis lehmanniana, Pogonarthria squarrosa, Rhynchelytrum repens, Schmidtia bulbosa, Stipagrostis uniplumis, Tragus berteronianus and Urochloa mossambicensis.

Part of the land system consists of parabolic dunes and fossil rivers. The parabolic dunes carry a continuity of Terminalia sericea, Lonchocarpus nelsii, Acacia luederitzii. The fossil rivers provide carbonate rich soils and favour the occurrence of the species Catophractes alexandri and Acacia tortilis. The vegetation is dominated by Terminalia sericea, Lonchocarpus nelsii, Acacia tortilis, Catophractes alexandri association.

The Ghanzi ridge has a complex vegetation, which ranges in structure from shrub savanna and open savanna to tree savanna. A compilation of the floristic characteristics leads to an association of Acacia mellifera, A. erioloba, Terminalia prunioides, Catophractes alexandri.

Region 8. North-West

Northern Sandveld - Western Delta Fringes

This region is situated in the north-western corner of the country and extends from Lake Ngami in the south to the Caprivi Strip in the north. Its eastern boundary is formed by the Okavango Delta, while the Namibian border forms its western limit.

The area is predominated by savannas and dense savannas, although shrub savannas and tree savannas occur as well.

In spite of the different parent materials (sandveld, alluvium and limited hardveld) the vegetation of the region developed in a rather uniform way, according to associations on massive fossil sand dunes.

On the sandy soils of the dune system and the fossil alluvium the Terminalia sericea, Lonchocarpus nelsii / Acacia erioloba association is found. Associated grass species include Anthephora pubescens, Aristida meridionalis, Eragrostis sp., and Stipagrostis uniplumis.

There is an apparent division in the vegetation on the western side of the Delta with the boundary occurring along a parallel with the Tsodilo Hills (Tlhalerwa, Pers. Comm.). The northern part is predominated by the Miombo tree savanna on very deep sands, similar to the one found east of the delta pan handle; e.g. the Pterocarpus angolensis association found along the Tamacha to Tsodilo road. The vegetation described here is found south of the Miombo tree savanna. Ihe grass species Anthephora pubescens is generally found south of the Nokaneng to Xangwa road, which is generally the boundary between the Miombo tree savanna and the vegetation described here.

Lake Ngami only contains water during wet years. The lake shore and the lake bed (in dry years) consist of a forbland of Sesbania sp., and Asclepias fruticosa. The forbland merges into a zone of shrub and tree savanna on the flats, belonging to the Terminalia sericea, Lonchocarpus nelsii I Acacia erioloba association. Associated grass species include Aristida congesta, Cenchrus ciliaris, Cynodon dactylon, and Panicum repens.

The mopane-line enters the region just north of Lake Ngami and runs around the Okavango Delta to the north in the direction of Nokaneng. From Nokaneng up to Shakawe Colophospermum mopane only occurs in a 5 - 15 km wide zone along the Okavango Delta and the Panhandle.

East of the mopane-line a mosaic of savanna and woodland is recognised typified a by Combretum imberbe, Acacia erioloba, Colophospermum mopane association. This association is found on the fossil delta floodplain towards the mainland edges. Associated grass species include Aristida congesta, Cenchrus ciliaris, Cynodon dactylon, Echinochloa pyramidalis and Setaria sphacelata.

Region 9. Makgadikgadi system, Nxai Pan area

Makgadikgadi Pan System

This region comprises the lacustrine land systems belonging to the Makgadikgadi Pans and their surroundings.

The Pans are dry and without any vegetation during the greatest part of the year. They are only submerged a few months each year. The shallow coastal zones support a swamp vegetation characterised by Scirpus maritimus. Grasslands typified by halophytic species such as Odyssea paucinervis and Sporobolus spicatus surround the pans. The catena is divided, with the grass Cenchrus ciliaris as a major dominant in the upper slopes of the catena, while Odyssea paucinervis and Sporobolus spicatus predominate in the lower parts of the catena.

South of the Makgadikgadi Pans land system the mopane-line divides this land system in a northern mopane free area and a southern mopane dominated zone.

The northern part is characterised by grasslands and occasionally open savannas. Clumps of Hyphaene petersiana and Catophractes alexandri are observed on calcareous substrates. Chrysopogon montanus is a dominant grass species part of this association (Tlhalerwa, Pers. Comm.). The grasslands with species Odyssea paucinervis, Sporobolus spicatus, Cymbopogon sp., Eragrostis rigidior and Enneapogon desvauxii belong to the Odyssea paucinervis association.

The southern area is covered by grasslands and savannas belonging to the Colophospermum mopane, Terminalia prunioides association, which is also found in the bordering Region 5.

East and north of the grasslands that surround the Makgadikgadi Pan system a variety of vegetation structures from shrub savanna to tree savanna are recognised. The vegetation belongs to a Colophospermum mopane, Terminalia sericea alliance.

The eastern part of the land system is typified by shrub savannas belonging to a Colophospermum mopane, Terminalia sericea Sclerocarya caffra association. This land system consists of five different zones:

• The grasslands around the Makgadikgadi Pans were mentioned above.

• South of 20º south Hyphaene petersiana and Adansonia digitata are frequently observed. In this area an association can be established, typified by Colophospermum mopane, Terminalia sericea I Hyphaene petersiana, Adansonia digitata, belonging to the Colophospermum mopane, Terminalia sericea alliance.

• In the north a range of vegetation structures from shrub savannas, savannas to tree savannas is found, belonging to a Colophospermum mopane, Terminalia sericea I Combretum imberbe association.

• Nxai Pan is covered by an open tree savanna. The landscape is characterised by grasslands of Cenchrus ciliaris, Panicum repens, Odyssea paucinervis and Cymbopogon sp. and clumps of Acacia tortilis trees.

• East and west of the Boteti River a zone is found, which is covered by shrub savannas and savannas belonging to the Terminalia sericea, Lonchocarpus nelsii Acacia erioloba sandveld association.

• The floodplains and courses of the Boteti River are typified by a swamp vegetation and sedge- and grasslands of Phragmites australis, Scirpus inclinatus, Cyperus articularis and Typha capensis. The banks and terraces are covered by shrub savannas and savannas with Acacia tortilis, A. erioloba, A. mellifera and Terminalia prunioides. An association of Acacia tortilis, Phragmites australis, A. erioloba, Terminalia prunioides could be established for this land system.

Region 10. Mid-North

Northern Sandveld Bordering on Eastern Hardveld and the Delta in the West

This region, mainly sandveld, extends from Maun to Basotho and is located north of the Makgadikgadi Pans system and south of the Chobe area.

Savannas with a Colophospermum mopane, Terminalia sericea alliance are predominantly found in the east and the centre of the region. The communities of the land systems Ar3 and Sa17 south are classified as a Colophospermum mopane, Terminalia sericea, Dicrostachys cinerea association. The vegetation is part of a Colophospermum mopane, Terminalia sericea I Lonchocarpus nelsii association.

There is a 10 km wide fringe along the Thamalakane River with woodland of the same alliance which can be classified as a Colophospermum mopane, Terminalia sericea I Dicrostachys cinerea association.

A variety of structure types from shrub savanna and savanna to tree savanna and forest forming a Colophospermum mopane, Combretum sp., association. Grass species found here include Aristida sp., Cenchrus ciliaris, Chrysopogon montanus, Digitaria milanjiana, Eragrostis rigidior, Schmidtia bulbosa, and Urochloa trichopus.

The north-western area is covered by shrub savannas and savannas belonging to a Terminalia sericea, Lonchocarpus nelsii I Combretum sp. association.

In the north-eastern part of the region shrub savannas and savannas are found. Miombo species as Pterocarpus angolensis and Ricinodendron rautanenii are invading from the north forming a Terminalia sericea, Lonchocarpus nelsii I Pterocarpus angolensis association.

Region 11. North-East

Sand Forest Region

This region occupies the north-eastern part of Botswana. It comprises the Chobe area, Kasane and the Mpandamatenga plains.

The Chobe area is basically characterised by sand plains supporting savannas, tree savannas and woodland with a floristic association of Pterocarpus angolensis, Baikiaea plurijuga in which Colophospermum mopane frequently occurs.

This vegetation forms a transition between the northern miombo woodland, found in Zambia and Zimbabwe, and the southern Kalahari savannas. Other typical miombo species occurring in the Chobe area are Ricinodendron rautanenii, Croton gratissimus, Guibourtia coleosperma, Burkea africana, Brachystegia boehmii, Julbernardia globiflora and Isoberlinia sp.

The Mpandamatenga plains are characterised by grasslands, shrub savannas and open savannas fringed by open savannas and tree savannas. The savannas are part of a Colophospermum mopane, Acacia nilotica, Combretum sp. association. Grass species found here include Andropogon sp., Cenchrus ciliaris, Chloris gayana, Cymbopogon sp., Digitaria eriantha, Eragrostis sp., Hyparrhenia filipendula, Panicum maximum, Perotis patens, Setaria sphacelata, and Sporobolus sp.,

The vegetation varies in places from (open) savanna and tree savanna to woodland, and can be classified as part of the Colophospermum mopane, Terminalia sericea Combretum imberbe association.

A gently undulating basalt plain in the far east supports an open savanna and savanna vegetation, which forms part of the Colophospermum mopane, Acacia nigrescens I Combretum imberbe hardveld association.

Along the Chobe River grasslands are found on the floodplains. Savannas and forest, in literature often described as riverine woodland, are recognised on the banks. The riverine woodlands have a Combretum imberbe, Acacia erioloba, Colophospermum mopane association with associated species Lonchocarpus capassa and Croton megalobotrys. Grass species found here include Andropogon sp., Aristida sp., Cymbopogon sp., Dichanthium annulatum, Digitaria eriantha, Eragrostis sp., Hyparrhenia filipendula, Panicum maximum, Perotis patens, Schmidtia bulbosa, Setaria sphacelata, and Sporobolus sp.,

The Chobe Enclave is a marshy area with floodplains and islands. The islands are predominantly covered by savannas with an association of Hyphaene petersiana, Lonchocarpus capassa, Phoenix reclinata, while the floodplains carry grasslands.

Region 12. Mababe, Kwando-Linyanti, Okavango

Alluvial Flood Plains

Region 12 is located in the north of the country and includes the Mababe Depression in the east, fossil alluvium in the centre and longitudinal dune systems in the west. The region is bordered by the Caprivi Strip in the north and by the Okavango Delta in the south.

The Mababe Depression can be divided in a clay rich central depression, a sandy terrace in the east and a beach ridge in the west.

The centre is covered by a shrub savanna of Acacia tortilis, surrounded by shrubland and woodland with associated species Colophospermum mopane, Acacia erioloba , A. nigrescens, Lonchocarpus capassa, resulting in a Colophospermum mopane, Acacia tortilis association. Grass species include Grass species found here include Aristida meridionalis, Digitaria eriantha, Eragrostis sp., Schmidtia pappophoroides and Stipagrostis uniplumis.

On the terrace a dense shrub savanna with an association of Colophospermum mopane, Combretum sp. is recognised. The beach ridge is covered by a sandveld savanna belonging to the Terminalia sericea, Lonchocarpus nelsii, Acacia erioloba association.

The Savute Marsh, which only floods in extremely wet years, is covered by grassland dominated by Cynodon dactylon, surrounded by Acacia erioloba and A. nigrescens, forming an Acacia tortilis, Cynodon dactylon, Cenchrus ciliaris, Combretum imberbe association.

The fossil lagoon sands around the Mababe Depression have a typical sandveld vegetation with savannas consisting of the Terminalia sericea, Lonchocarpus nelsii Acacia erioloba association.

The fossil alluvium from the Okavango Delta and the fluvially eroded longitudinal dune systems are covered by shrub savannas, (dense) savannas and tree savannas, which are part of the Colophospermum mopane, Terminalia sericea Lonchocarpus nelsii association.

On the longitudinal dunes along the Caprivi Strip (dense) savannas with Terminalia sericea and Baphia massaiensis are well developed.

The interdunes are typified by an open savanna with as most characteristic species Peltophorum africanum and Combretum hereroense. The vegetation of the entire dunefield can be classified as an association of Terminalia sericea, Baphia massaiensis, Peltophorum africanum, Combretum hereroense.

The floodplains of the Kwando and Linyanti Rivers and of the Savute Channel are covered by grasslands. The river banks and terraces support savannas and forests, which can be classified as the riverine woodland association of Combretum imberbe, Acacia erioloba, Colophospermum mopane.

Region 13. Okavango Delta

Okavango Delta and Associated Floodplains

Region 13 comprises the Okavango River (the Panhandle zone) and the Okavango Delta.

Five land systems have been observed in this region: permanent swamp, delta- floodplain, river floodplain and two types of fossil alluvium respectively.

• The permanent swamp and the delta-floodplain are characterised by the land elements swamp, floodplains and islands. The swamp is typified by emergent, floating and submerged vegetation communities, consisting of hydrophytic grasses, sedges and aquatic species. The floodplains consist of grassland.

The swamp and floodplain communities can be grouped in an alliance of Cyperus papyrus, Phragmites australis, Imperata cylindrica. This alliance comprises three associations: a permanent swamp association of Cyperus papyrus and Miscanthus junceus, a delta-floodplain (seasonal swamp) association of Phragmites australis, Schoenoplectus corymbosus, Cyperus articularis and a floodplain association of Imperata cylindrica, Setaria sphacelata, Hyparrhenia rufa.

• On the islands a variety of structural vegetation types is found: grassland, (dense) savanna, tree savanna, woodland and forest. The central part of the islands may consist of halophytic grasslands or savannas, while the fringes support a much denser riverine vegetation.

The island vegetation can be classified in a Hyphaene petersiana, Garcinia livingstonei alliance, which consists of two associations.

• In the perennial swamp a Hyphaene petersiana, Garcinia livingstonei Phoenix reclinata, Ficus verruculosa association is found.
• The islands of the delta-floodplain belong to a Hyphaene petersiana, Garcinia livingstonei Lonchocarpus capassa, Acacia nigrescens association.
• Peninsulas and large islands as the Mopane Tongue and Chief's Island are mainly covered by a mosaic of savanna and woodland, which form part of a Colophospermum mopane, Terminalia sericea Lonchocarpus nelsii association.
• On both sides of the Panhandle a zone of fossil river floodplain is recognised. The vegetation structure is varying from savanna to tree savanna, supporting a Terminalia sericea, Lonchocarpus nelsii Baphia massaiensis association.
• Along the Okavango River, floodplains and scattered islands occur. The floodplains are covered with grassland belonging to the Imperata cylindrica, Setaria sphacelata, Hyparrhenia rufa association. The islands resemble the permanent swamp islands and support the same Hyphaene petersiana, Garcinia livingstonei I Phoenix reclinata, Ficus verruculosa association.
• Along the borders of the Okavango Delta patches of riverine woodland occur, characterised by the species Ficus sycomorus, Garcinia livingstonei, Diospyros mespiliformis, Acacia erioloba, Combretum imberbe and Colophospermum mopane. Grass species found here include, Aristida stipoides Eragrostis sp., Hyparrhenia rufa, Hyperthelia dissoluta, Imperata cylindrica, and Setaria sphacelata.

APPENDIX 2.

A brief palaeo-history of the land formation processes that have created the current land-systems
Thomas & Shaw (1991) have written a fascinating book on the pre-historic land formations of Botswana, with hypotheses on how the present land-forms have been derived from these.

Much of the Makgadikgadi pans area was a lake which was fed by several rivers including the Okavango, Kwando, Chobe and possibly even the Zambezi. The lake then drained out through what are now the Shashe and Motloutse river systems, that run eastwards into the Limpopo River. The major rivers brought in massive quantities of sand from upstream, which began to fill the lake bed.

The western Kalahari Region was also once a massive, shallow inland lake, that also drained into the Limpopo River through the Serorome Valley, on the tropic of Capricorn.

With a gradual change to a much drier climate (but with several periods of heavy rainfall interrupting this period), and some major geological upheavals to the south east of the Makgadikgadi Pans, the ancient lakes gradually dried up. Additionally, several major geological upheavals resulted in all but the Okavango river turning to the North-east, to join the present Zambezi River, which is their current alignment.

After going through a process of looking rather like the Okavango Delta does today, the Pans cover an area of open white sands with saline rich waters lying below the surface. It is this sub-surface salinity that is a major determinant in the current landscape and vegetation associations that characterise the Pans.

To the west, climate change resulted in fine sands being blown in from the west, and deposited in an almost flat layer of sand over several thousands of square kilometres. This layer was then reshaped by subsequent wet and dry cycles to form the flat to rolling countryside, which is broken in places by fossil drainage lines, ridges and ancient sand dunes. The sand dunes form in two ways, as linear dunes, and as elliptical dunes, around existing major pan systems, in the South-west of the country.

The eastern side of the country is generally more broken with hills and drainage lines due to surface uplifting. Many of the drainage lines, however, are dry for much of the year, and rivers and streams only run during the rainy season.

Contribution of the land formation processes to the existing landscape
The Western portion of the country, is covered by a great depth of sand over a large part, and which is up to 200m deep in places. In these areas, ground water is generally found at great depths, from 40m to below 200m. The ground water is also very often too salty for people, and often even for livestock, to drink safely and survive in the long term.

The inherent salinity of the ground water associated with rising and falling ground water levels through long-term wet and dry cycles, over a very long period, has resulted in the formation of sub-surface lenses. These lenses, have formed as water levels rise and fall, and minerals have been deposited and then hardened into solid rock. The lenses are made primarily of calcrete (a form of limestone) and silcrete (a form of limestone which has hardened by silica from the sand deposits). These lenses then form a barrier to rainfall percolating down through the sand, which leads to the creation of scattered pans and outcrops of exposed calcrete, mainly around the pans and along the rim of the fossil drainage lines.

The combined landscape formation factors have resulted in the development of vegetation systems that can survive on very little rainfall, and livestock production strategies have historically been mostly nomadic, to capitalise on localised rainfall and vegetation growth particularly in drainage lines, and around pans.

In the east and northern parts of the country, people have been more settled, as rainfall is generally higher, and surface water is available in places. In other places water can be found by digging shallow wells in the sandy river beds, of the major drainage lines, or by drilling shallow boreholes into the banks of these rivers.

More recently, deep boreholes have been drilled in the western and southern portions of the country and these have enabled "cattle posts" to develop.

As more and more boreholes develop, however, there has been increased pressure on the range resources. Ground water resources, are also becoming depleted in places, as extraction rates exceed replenishment rates, and salinity levels increase as removal of fresh water layers result in an increase in the levels of dissolved salts.

APPENDIX 3. THE DEVELOPMENT OF THE LIVESTOCK SECTOR IN BOTSWANA, 1895 to 1965

[From Roe (1973)]

Chronology of Major Events, 1895-1965

1895/96. A devastating epidemic of rinderpest occurred, estimated to have killed up to 95% of the cattle in the Protectorate. This decrease in the supply of cattle resulted in their price rising to new levels in certain areas of the country.

1905.The Veterinary Department was established with a small staff; in 1913/14 there were still only one veterinary officer and one stock inspector.

1910. The Bechuanaland Protectorate, Basutoland, Swaziland, and South Africa entered into a new Customs Agreement (in force until 1969) which was to provide the Protectorate with access to the South African markets for its main export, cattle.

1909-1912. A quarantine on the export of cattle from the Protectorate to South Africa was imposed because of lung sickness. Some easing of these restrictions occurred with the opening up of the Johannesburg municipal abattoir in 1912, but quarantine restrictions continued in some form until 1923. The 1911 national census estimated the Bechuanaland cattle population to number 323,911 beasts, an increase of 133% over the estimated herd size of 1904.

1911-1919. The steady recovery in the national herd after 1895 was ended by recurring drought, considered at that time to be the worst ever experienced by some tribes. It is thought, for example, that one-third of the Bangwaketse livestock died in 1914.

1920-1924. A worldwide economic depression, a severe drought and a series of locust attacks served to reduce cattle exports. The 1921 national census put the Protectorate cattle population at 495,062, an increase of 53% over the 1911 figure.

1922-1923. The staff of the Veterinary Department was increased to a chief veterinary officer, one veterinary officer, a laboratory assistant, two stock inspectors, one scab inspector, and a clerk.

1924-1941. Cattle exports from the Protectorate to Johannesburg were subject to a number of severe weight and supply restrictions, limiting the Protectorate's ability to export. However, a number of new markets opened sporadically during the period--Northern Rhodesia in 1930, Southern Rhodesia commencing 1939, Angola between 1926-1930, Italy between 1925-1936, and the Belgian Congo between 1921-1932--which reduced the overall impact of restrictions to the Johannesburg market.

1925. An agreement was signed between the Protectorate administration and the Imperial Cold Storage and Supply company to erect a storage and refrigerating unit at Lobatse and the new factory was opened in August, 1927, at a cost of some £40,000.2 Abattoir activity did not really commence until 1934/35, primarily due to the restrictions and weight regulations on Protectorate cattle exports. Veterinary restrictions, low producer prices, and weight and supply restrictions were constantly to plague the operation of this Lobatse abattoir and by 1941 it had ceased operations altogether.

1926. A dairy inspector was engaged by the Protectorate administration, leading to a rapid development in African dairy production up to the Great Depression.

1931-1938. These eight years were the worst in the economic history of the Protectorate. Between 1931-38, there occurred not only the worst drought up to that time (1933-35) and an as-yet unparalleled economic depression, but also major outbreaks of foot and mouth disease (1933-34) and locust attacks (1934-35). The cattle export industry basically collapsed. The amount and value of official cattle exports from the Protectorate plummeted in the early 1930s, primarily as a consequence of foot and mouth disease embargoes. The national cattle herd may have fallen from levels as high as 1.2-1.4 million head in the early 1930s to 540,00 to 640,000 in the mid- and late 1930s. It has been estimated that some 400,000 cattle died between 1933 and 1936 because of the drought, while at least a further 250,000 were lost due to illegal smuggling of cattle to the Union between 1935-38. The foot and mouth disease embargoes on official cattle exports placed an incredible hardship on African producers. Tax rates were reduced and tax collections fell.

During this period, the activities of the Veterinary Department increased. Over a million head of cattle were inoculated during the foot and mouth campaign of 1933/34. In 1936, 66 African cattle guards were appointed in order to detect and control outbreaks of disease. Livestock Improvement Centres were started in several tribal areas, beginning in 1936. Similarly, in the late 1930s the Department appointed a hide-and-skins officer to improve African production. Much of this development owed its impetus to the recommendations of the Pim Report of March, 1933, on the economic and financial position of the Protectorate.

1939-1950. The value of African livestock exports began increasing again, as the average price of cattle began rising, with World War II further stimulating demand. In response, the Union of South Africa lifted its weight restrictions on cattle imports from the Protectorate which grew substantially thereafter. In 1939, net revenue from the major livestock exports was roughly £215,000; by 1950, it exceeded £1.4 million. Tribal innovations such as local cattle auctions became increasingly popular among a few tribes during the 1940s. World War II and the post-War increase demand for livestock products profoundly altered the structure of the territory's livestock industry. After 1950, the aggregate value of livestock products exported from the Protectorate never fell below £1.5 million.

1951-1959. This was a period of rapid and substantial infrastructure development within the Protectorate's cattle industry. In 1954, the Colonial Development Corporation completed a new export abattoir at Lobatse and, thereafter, the value of carcasses exceeded the value of live cattle exports. Between 1951 and 1957, the Veterinary Department field staff expanded considerably; a veterinary school was established at Ramatlabama; and a system of cordon fences and quarantine camps was constructed across the territory. In 1956, the European Advisory Council gave consideration to the need for a second abattoir in the north of the Protectorate. In 1958, the Adviser on Cooperatives to the Secretary of State for the Colonies visited Bechuanaland to investigate the feasibility of cooperative cattle marketing.

While foot and mouth disease outbreaks occurred, reducing cattle exports and offtake at particular times, the value of livestock exports increased between 1951 and 1959, from approximately £1.8 million to £2.5 million. Cattle auctions became less popular during the 1950s, both because they were viewed as too risky by Botswana and because the recurrence of foot and mouth disease tended to discourage cattle speculation.

1960-65. This period included not only continued outbreaks of foot and mouth disease, but also the worst drought in the Protectorate's history. Some 400,000 head of cattle were said to have been lost in the drought of 1965/66. In the early 1960s, U.K. veterinary authorities had agreed for the first time to the importation of Protectorate cattle carcasses and by 1965 the value of these carcasses from the Lobatse Abattoir had reached an all-time high of over £2.9 million, with an official record offtake of 14.2% of the national herd. In 1965 the Abattoir was nationalized, thereafter becoming known as the Botswana Meat Commission. Livestock marketing Cooperatives were officially organized during 1965 as well.

Click to return to first page