Climatic trends in the tropics - the role of human interference [drought, Sahel, Venezuela]

affectation de ressources africa africa south of sahara afrique afrique au sud du sahara alimentation alimentation des animaux america animal feeding catastrophe naturelle clima climat climate condiciones ambientales condition de milieu deforestation desarrollo de recursos desastres naturales disponibilidad del agua drought eau disponible energia energie energy environment environmental conditions environnement feeding feeding systems forestry operations grazing land use lluvia medio ambiente methode methods natural disasters nutrition operaciones forestales pastoreo pluie precipitation rain resource allocation resource development sahel site factors south america technique d'alimentation unrestricted feeding utilisation du sol venezuela water availability zootechnie zootechny zootecnia