Assessing land use and land cover (LULC) change is essential for the sustainable management of natural resources, biodiversity conservation, monitoring food security, and research related to climate change and ecology. With increasingly rapid changes in LULC in response to human population growth, a better assessment of land use changes is more necessary than ever. Although a multitude of LULC assessment methods exists, none alone provides a clear understanding of changes and their underlying factors. This study analysed historical LULC changes over a temporal extent of 42 years (1974–2016) in the Togodo Protected Area and its surroundings, in Togo, by associating intensity and trajectory analyses, that are complementary but rarely associated in the literature. Our results show that LULC change in our study site is linked to the combined effects of human activities, climate, and invasive plants, particularly Chromolaena odorata. While each type of analysis provides useful insights, neither intensity nor trajectory analysis alone provides a full picture of changes and their causes. This study highlights the usefulness of associating intensity and trajectory analyses when implementing any management policy.

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Sheep and goat production is the main and sometimes only agricultural activity available to populations living on rangelands in the arid regions around the Mediterranean. Desertification threatens large areas of Mediterranean arid rangelands but remains difficult to describe, quantify and accurately locate for management purposes. A methodology is described which estimates a Spatial Rain-Use Efficiency Index (SRUEI) and its potential use to evaluate rangeland condition at a large scale. It is based on an Aboveground Net Primary Production (AGNPP) map generated from field herbage mass measurements and a rainfall spatial distribution map derived from local elevation–rainfall gradients with the whole resulting from satellite imagery processing and GIS technology. The area of the case study was in the Nâama–Mecheria region located on the High Plateau south of Oran (Algeria). It covers ~215 000 ha, receiving ~200 mm year–1 of winter and spring precipitation. The Nâama–Mecheria SRUEI-derived map clearly shows the degradation gradient declining away from the settlements. The Mecheria AGNPP 2007 map and associated grazing rings indicate that the Mecheria cooperative flocks may ingest 48–57% (Range Use Factor) of the rangeland’s seasonal plant production, which is barely compatible with sustainable rangeland use. When adding the effect of fuel wood collection by local residents and rain-fed arable cropping, the Nâama–Mecheria region is undoubtedly heading towards a slow but certain desertification of its fragile arid rangelands unless correcting measures are implemented. The SRUEI and associated results are powerful tools that allow rangeland conditions to be mapped, and which can be employed in planning and pursuing sustainable management of rangelands in such arid areas.

Acacia seyal cassé par un éléphant (a). Éléphant au pâturage sur un Balanites aegyptiaca (b). Photo P. Poilecot. De Pierre SUMMARY DRY-SEASON GRAZING STRATEGY OF AN ELEPHANT POPULATION IN ZAKOUMA PARK IN CHADDuring the dry season, Acacia seyal stands in the savannah areas of southeastern Chad are one of the main food sources for the elephant population of Zakouma National Park. Forming a more or less dense mosaic, this tree savannah is an essential additional source of nutrition for these huge herbivores. This note does not set out to estimate the aerial grazing potential of the savannah for the elephants in the park, but to identify, through remote sensing, the areas that are either essential or marginal in terms of their food needs. Satellite imagery was used to establish quantitative and spatial values for these vegetation resources, whose use does not appear to be related to food quality or palatability, but to result from several concomitant physical and edaphic factors, i.e. a permanent water network and the fact that tree densities of more than 400 trees per hectare limit access for the elephants to these dry-season food resources.Keywords: savannah, elephants, Acacia seyal, satellite imagery, Zakouma, Chad. RESUMEN ESTRATEGIA DE PASTOREO DE UNA POBLACIÓN DE ELEFANTES EN LA ESTACIÓN SECA: EL CASO DEL PARQUE DE ZAKOUMA EN CHADLos rodales con abundancia de Acacia seyal de las sabanas del sudeste del Chad son uno de los principales recursos alimenticios durante la estación seca para la población de elefantes del Parque Nacional de Zakouma. Estas formaciones arbóreas, según mosaicos más o menos densos, constituyen un complemento nutricional indispensable para el equilibrio alimentario de estos grandes herbí-voros. En esta nota no se trata de estimar el potencial de los pastos aéreos de estas sabanas, sino de identificar mediante un enfoque espacial las áreas que resultan determinantes o marginales para su alimentación. Es así como gracias a las imágenes satelitales, se lograron determinar los valores cuantitativos y espaciales de este recurso vegetal cuya utilización no parece que esté relacionada con la calidad alimentaria o la apetencia, sino que es el resultado de diferentes factores físicos y edáficos concomitantes. Dichos factores son la permanencia de la red hídrica y el hecho que una densidad superiora 400 árboles por hectárea limita el acceso de las manadas en la estación seca.Palabras clave: sabana, elefantes, Acacia seyal, imagen satelital, Zakouma, Chad. P. PoilecotParachevé par : S. Saïdi et P. Daget