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Madagascar's highland region once was covered with an evergreen forest dominated by about 20 endemic tree species. This has been permanently replaced by a floristically impoverished steppe vegetation on ferrolitic soils. Human intervention has caused this deforestation, aided by a notable failure of highland forests to spontaneously regenerate. Beginning about A.D. 600, Indonesian settlers began removing forests in this region to create swidden fields. After A.D. 1000, zebu cattle introduced from Africa provided a strong motive for islanders to increase grassland at the expense of forest. By A.D.1600 the highland forest cover had mostly disappeared except for localized tract, patches, and strips. The historical record and contemporary observations point to the importance of fire in destroying the forest. This landscape conversion has had devastating outcomes. Tree and humus removal has led to massive erosion, floods, water shortages, and faunal extinctions or endangerments. Agricultural and pastoral production on upland soils is marginal. Re-establishment of long-term ecological stability to this region would require an end to burning as a form of pasture management, changes in communal land tenure, and reforestation of the highlands with native tree species. /// Les montagnes de Madagascar étaient dans le passé couvertes d'une forêt sempervirente dominée par 20 essences endémiques. Cette forêt a été remplacée en permanence par une végétation de steppe á flore appauvrie sur des sols ferralitiques. L'intervention humaine est à l'origine de cette déforestation, combinée avec un manque remarquable de régénération spontanée. Au début du VIIe siècle, les immigrants indonésiens ont commencé à détruire les forêts de la région dans le but de pratiquer l'agriculture sur brûlis. Au XIe siècle, l'introduction du zébu africain a beaucoup encouragé les habitants à augmenter les pâturages au détriment des forêts. Vers la fin du XVe siècle, la couverture forestière des montagnes avait pratiquement disparu, à part de petites étendues localisées. Le dossier historique et les observations contemporaines ont mis en évidence le rôle du défrichement par incendie dans la destruction des forêts. Cette conversion du paysage a produit des effets désastreux. La disparition des arbres et de l'humus a entraîné une érosion massive, des inondations, des pénuries d'eau et des extinctions ou menaces d'extinction de la faune. La productivité agricole et pastorale sur les sols de montagne est marginale. Le rétablissement de la stabilité écologique à long terme de cette région nécessiterait le renoncement à l'incendie comme forme de gestion des pâturages, un changement de régime foncier communal et la reforestation avec des essences indigènes. /// Früher war das Hochland von Madagaskar stark bewaldet und von hauptsächlich immergrünen endemischen Arten gab es mehr als zwanzig. Gegenwärtig sind die eisenhaltigen Böden nur mit einer dürftigen Steppenvegetation bewachsen. Die Entwaldung ist Folge von anthropogenen Eingriffen, und sie wird verstärkt durch die Tatsache, daß sich Hochlandwald sehr langsam regeneriert. Die Abholzung begann um etwa 600 a.D., als indonesische Siedler mit Brandfeldbau begannen. Ab etwa 1000 a.D. wurde Zebu Vieh aus Afrika eingeführt, was die Inselbewohner motivierte, die Entwaldung noch stärker zugunsten von Grassland voranzutreiben. Dies führte dazu, daß ab etwa 1600 a.D. der Waldbestand des Hochlandes bis auf vereinzelte, lokal begranzte Flächen verschwunden war. Alte Aufzeichnungen und neuere Beobachtungen zeigen, daß Waldbrand und nicht Abholzung dann den Wald endgültig vertilgt haben. Solch gravierende Land-schaftsveränderungen hatten verheerende Folgen. Der fehlende Baumbewuchs und der damit verbundene Verlust an Humusboden führte zu starker Erosion, Überschwemmungen, und Wassermangel und gefährdete außerdem die Tierwelt bis hin zum Aussterben einzelner Arten. Hochlandböden bringen der Land- und Weidewirtschaft nur noch geringe Erträge. Konsequenzen, die langsichtig zu ökologischer Stabilität führen, erfordern daß Brandfeldbau abgeschafft wird, daß Gemeindeland anders verwaltet wird, und daß das Hochland mit endemischen Baumarten aufgeforstet wird.

The geographical distribution of Babesia bovis and Babesia bigemina antibodies in communal herds in northern and eastern Zimbabwe was determined using the ELISA technique. The animals in different herds in the study region had different levels of natural exposure to B. bovis (mean 32 %, range 0-79%) and B. bigemina (mean 52%, range 5-92%) infections. The majority of herds (90%) were endemically unstable for B. bigemina and 62 % were unstable for B. bovis. Natural region 5 and Manicaland province had the highest seroprevalence of B. bovis infection, while natural region 5 and Masvingo province had the highest seroprevalence of B. bigemina infection.

Explores the problem forest degradation of communal lands. Shows that the way the regulation was devised gave rise to a discordant structure of property rights involving the government and the local inhabitants.

Ejidos are communal holding groups of redistributed land expropriated (generally without compensation) from large private landowners during Mexico's post-1910 land reform. The model in this study of the \"ejidal\" system's influence on fertility differs from DeVany and Sanchez in providing more current data and including the following more detailed variables: the land area of ejidos and the number of ejidos, the need for children, male income, female income share, and social security coverage. The data pertains to states rather than municipalities. DeVany and Sanchez found that the ejidal system encouraged fertility, because having more children helped an ejido family retain land rights, increased its chances of gaining additional productive land, and gave it increased political power. Children also provided a means of intergenerational transfer of resources. The estimation results of this study revealed that the total proportion of land held as ejidos had a positive, significant effect on fertility. The ratio of ejidos to total number of farms was negative and significant. There was support for the hypothesis that the impact of ejidos land holdings and area was diminished when ejidos were dominant in the state. Fertility declined with the increase in unpaid workers per hectare of land. Elasticity functions were small: 0.075 on ejidal land, -0.222 on ejidal farms, and -0.045 on workers. A positive significant demographic effect on fertility was illiteracy. Infant mortality and female income share each had a negative, significant effect on fertility. Insignificant variables were male income, social security coverage, and the dummy for northern states. There have been changes in the Mexican ejidal system. These changes and the availability of farm labor are expected to reduce urban and rural fertility differentials.