Land Degradation States and Trends in the Northwestern Maghreb Drylands, 1998–2008

Abstract

Abstract:States of ecological maturity and temporal trends of drylands in Morocco, Algeria and Tunisia north of 28˝N are reported for [1998][1999][2000][2001][2002][2003][2004][2005][2006][2007][2008]. The input data were Normalized Difference Vegetation Index databases and corresponding climate fields, at a spatial resolution of 1 km and a temporal resolution of one month. States convey opposing dynamics of human exploitation and ecological succession. They were identified synchronically for the full period by comparing each location to all other locations in the study area under equivalent aridity. Rain Use Efficiency (RUE) at two temporal scales was used to estimate proxies for biomass and turnover rate. Biomass trends were determined for every location by stepwise regression using time and aridity as predictors. This enabled human-induced degradation to be separated from simple responses to interannual climate variation. Some relevant findings include large areas of degraded land, albeit improving over time or fluctuating with climate, but rarely degrading further; smaller, but significant areas of mature and reference vegetation in most climate zones; very low overall active degradation rates throughout the area during the decade observed; biomass accumulation over time exceeding depletion in most zones; and negative feedback between land states and trends suggesting overall landscape persistence. Semiarid zones were found to be the most vulnerable. Those results can be disaggregated by country or province. The combination with existing land cover maps and national forest inventories leads to the information required by the two progress indicators associated with the United Nations Convention to Combat Desertification strategic objective to improve the conditions of ecosystems and with the Sustainable Development Goal Target 15.3 to achieve land degradation neutrality. Beyond that, the results are also useful as a basis for land management and restoration.

Comprehensive Research on Remote Sensing Monitoring of Grassland Degradation: A Case Study in the Three-River Source Region, China

“…It leads to overestimating of the severity of degradation in a poor harvest year and underestimating in bumper harvest year. In view of this problem, some studies have attempted to diagnose degradation by using rain-use efficiency (RUE) [16][17][18]. However, these indexes only focus on the water variation in suitable arid areas.…”

A 1973–2008 Archive of Climate Surfaces for NW Maghreb

“…This technique is based on archived vegetation density time-series and corresponding climate fields. The NW Maghreb was a case study for this approach [18]. The increasing demand for long-term, archived time-series of spatially explicit climate data forms the background for this dataset.…”

“…This technique is based on archived vegetation density time-series and corresponding climate fields. The NW Maghreb was a case study for this approach [18].…”

Relative quantification of wind erosion in argan woodlands in the Souss Basin, Morocco

“…Remote-sensing studies have revealed continuous degradation of the argan woodlands over recent decades, with increasing fragmentation of important stabilizing vegetation such as Genista pseudopilosa and Artemisia herba-alba (Kouba et al, 2018) and a drastic decrease in the population density of Argania spinosa (Le Polain de Waroux and Lambin, 2012). Most studies have found desertification clearly associated with high population and livestock pressure (del Barrio et al, 2016;Lahlaoi et al, 2017), including intensifying water scarcity due to declining aquifer recharge (Jilali, 2014) and the subsequent risk of water shortages (Johannsen et al, 2016), which is further aggravated by climate change (Van Dijck et al, 2006). Although Chakhchar et al (2015) found the genetic variety of inland argan ecotypes to be more drought tolerant compared with varieties from coastal areas, different approaches for rejuvenation of argan sites in the Souss Basin have not been successful for several reasons, the most important being a lack of sufficient protection against browsing herds and insufficient maintenance of young plants.…”