Detecting changes in vegetation and climate that serve as early warning signal on land degradation using remote sensing: a review

Abstract

Desertification and land degradation have severe negative effects on land-use, water resources, soil stability, agriculture and biodiversity. Especially, drylands cover 33.8% of northern Mediterranean countries: approximately 69% of Spain and 66% of Cyprus. The European Environment Agency (EEA) indicated that 8% of the territory of the European Union (mostly in Bulgaria, Cyprus, Greece, Italy, Spain and Portugal) experience a ‘very high’ or ‘high sensitivity’ to desertification. For Cyprus Island, 9.68% of the land area was found to be susceptible to land degradation. The objective of this literature review is to provide a detailed synthesis of the main contributions of the global vegetation phenology research to the development of environmental knowledge, based on land degradation/ desertification and Earth observation (EO)-based science and technology. The study identifies the current fields of research and possible research gaps. To achieve this, more than 700 scientific papers were screened from which approximately 549 papers were reviewed, identifying and the state of land surfaces and vegetation phenology with remote sensing data. Most of the studies have as a central research object direct human-induced land degradation or the degradation of anthropogenic-modified landscapes, without having considered long-term un-altered natural vegetation, in order to assess the impact and the level of climate change. Hence, a detailed EO-based time-series monitoring and analysis of un-altered natural vegetation could provide indicators that may serve as early warning signals for the scale and level of climate change induced effects on vegetation and ecosystems that might lead to land degradation and even to desertification.