Analysis of the vegetation trends using low resolution remote sensing data in Burkina Faso (1982–1999) for the monitoring of desertification

Abstract

After about two decades of dramatic rainfall deficits that started in the late 1960s, the Sahel of West Africa has experienced increasing precipitation since the early 1990s. The implementation of the United Nations Convention to Combat Desertification (UNCCD) needs the identification of areas that record declining vegetation productivity over long-time periods. In this scope, we analyse the state of the vegetation productivity using long-term time series of NOAA AVHRR NDVI data and compare it to rainfall data. For this, 128 rain gauge data (RR) were compared with the integrated NDVI during the growing period (iNDVI) values in Burkina Faso from 1982 to 1999. During the analysed period, most of the studied stations in the country were stable for the iNDVI/RR (57.8%). However, 39.8% showed a weak to strong negative trend in the iNDVI/RR while only 2.4% showed a weak positive trend. These negative trends may reflect ongoing desertification processes in Burkina Faso and could be a starting point for the identification of hot-spots areas to determine where to take action to combat desertification.

Assessing Land Degradation/Recovery in the African Sahel from Long-Term Earth Observation Based Primary Productivity and Precipitation Relationships

“…This causes the calculated RUE to remain highly correlated with precipitation ( Figure 8(A,B)) and the negative trends in rain use efficiency (RUE) (Figure 7(A,B)) may therefore be caused by a general increase in precipitation. The negative trends could be interpreted as land degradation, as has been done in Hountondji et al [62], but we would claim that precipitation variability has not been properly normalized for in the RUE calculation, thereby rendering RUE inappropriate for the purpose of assessing land degradation. The conversion of the GIMMS NDVI into NPP using per-pixel linear correlation between SPOT VGT NPP/GIMMS NDVI 1999-2010 monthly observations ( Figure 3) does not produce RUE time series data that are uncorrelated with precipitation time series due to a considerable per-pixel NPP offset when correlating NPP and precipitation; hence also RUE using this vegetation parameterization is deemed unsuitable for land degradation assessment.…”

Desert dust impacts on human health: an alarming worldwide reality and a need for studies in West Africa

“…Many studies carried out in West Africa emphasise recent increases in desertification processes (e.g. Hountondji et al 2006;Ozer et al 2006). This strengthens the need to deepen our knowledge of dust impacts on health in this zone.…”

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

“…Changes in precipitation were identified as the primary driver of the greening trend of the Sahel vegetation and its interannual variability between 1982 and 1998 (Hickler et al, 2005), although Anyamba and Tucker (2005) emphasize that the NDVI time series commenced ARTICLE IN PRESS during a historically intense drought (the early 1980s) and that the recent gradual recovery has likely not returned vegetation to pre-drought conditions of the 1950s and 1960s. However, the resilience of vegetation to rainfall is not evident everywhere and the idea of ''greening Sahel'' has been challenged by some authors (Hiernaux and Turner, 2002;Hountondji et al, 2006;Ozer and Ozer, 2005). But all these works are realized at a regional scale.…”