Assessment of vegetation vulnerability to ENSO warm events over Africa

The study investigates the vulnerability of vegetation over Africa to El-Niño Southern Oscillation (ENSO) events using the moving window statistical correlation analysis technique. The correlation analysis was done between Normalized Difference Vegetation Index (NDVI) data from Advanced Very High Resolution Radiometer (AVHRR) and an ENSO index, namely Multivariate ENSO Index (MEI). The study develops a new monitoring approach (ENSO vulnerability assessment system) to quantify the relationships between monthly maximum NDVI anomalies and their month-to-month correlations with the ENSO indices for the vegetative land areas of Africa. The data used in this study was for the period 1982–2006. The new monitoring approach was used in the assessment of the long-time vegetation sensitivity to the ENSO warm events that occurred during the study period. A map of Africa indicating the vegetation vulnerability to ENSO is produced. Different areas of vegetation vulnerability are identified within the main vegetation cover classes. For the African vegetative land, 16% of the total area was characterized by moderate vulnerability of vegetation to El-Niño, whereas 1.18% showed high vulnerability. Results suggest that the vulnerability of vegetative land surfaces across Africa to climate extremes, such as ENSO depends considerably on the vegetation type. In particular, results show that areas of equatorial rainforest are more resistant to drought stress than the wooded and non-wooded vegetation categories.