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Remote sensing technology has been applied to monitor anthropogenic changes in the landscape that produce impacts on natural resources, such as environmental degradation, changes in the hydrological cycle and in ecosystems structure and functioning. As digital change detection may be a difficult task to perform, this study proposes a simple and logical technique to display land cover changes using Landsat imagery. Open source geoprocessing tools were used to acquire information for mapping changes on the land surface. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) derived from satellite images of four dates between 1984 and 2016 were used in RGB composites. The method was used to map gains and losses of vegetation cover and liquid water content in a spatiotemporal scale. The results indicate that this change detection method can effectively reflect the variations occurred over the years. Although both indices have similar responses, NDWI may provide opposite information to NDVI in certain areas, such as in wetlands and riparian zones, presenting wetness losses even in places that exhibit gains in vegetation. This method has applicability to other regions for deriving historical changes.

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Pastures play a critical role in the global ecological system, covering approximately 20% of the global terrestrial surface. This paper aims to review the progress of research on pasture degradation in different countries. The main research methods for this study include bibliometric analysis, social network analysis and viewing analysis - covering the performance of publications, characteristics of related journals, countries, institutions and authors. The Impact Factor, the H-index and the number of citations are used to investigate the strength of active institutions, authors and scientific periodicals in the field of pasture degradation. Therefore, we intend to outline the research trends already made and point out to future studies. We found 1027 articles published between 1956 and 2018, but none of them has reviewed science in a systematically way. The majority of authors are from China, United States and Germany. These lines of research aim to show the dynamics of pasture in response to the climate, the changes in human activity, the estimates of degraded or healthy areas and the evaluation of public policy interventions. In terms of publication productivity analysis, we highlight the Journal of Arid Environments, the author Richard J. Dean and the institution Chinese Academy of Sciences.