Drylands: Variation in Net Primary Productivity
| Analytical Overview |
Map Projection
Interrupted Goode's Homolosine
Map Description
Researchers have used eight years of NDVI (Normalized Difference Vegetation Index) data (1982-1989) to analyze interannual variation of Net Primary Productivity and to determine the coefficient of variation (ratio of the standard deviation of annual totals to the long-term mean) from the Global Production Efficiency Model (GLO-PEM) developed by the University of Maryland Department of Geography. Interannual variation in mean NPP can reveal the complexity of spatial variation in species composition and biomass that is caused by climate, topography, soil types, and human-induced change.
This map of variation in NPP illustrates that some regions have stable NPP values from year to year while other regions have highly variable values. Generally, the regions of lower NPP correspond to areas with the largest percentage variation in productivity from one year to the next. Many of the areas with high variability in NPP are found in drylands on all continents-- the Great Plains of North America, southern Patagonia, the Sahel, Southern Africa, and much of central Asia and Australia. This variation may affect human behavior and household decisions. It may influence whether people migrate on a seasonal or permanent basis or whether they abandon livestock herding for a more sedentary, agrarian existence.
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Citation:
WRI. 2002. World Resources Institute. Drylands, People, and Ecosystem Goods and Services: A Web-based Geospatial Analysis. Available online at: http://www.wri.org
Sources:
- United Nations Environment Program/Global Resource Information Database. Prepared by U. Diechmann and L. Eklundh. 1991, Global Digital Datasets for Land Degradation Studies: a GIS Approach. Nairobi, Kenya:UNEP/GEMS and GRID.
- GLCCD, 1998. Loveland, T.R., B.C. Reed, J.F. Brown, D.O. Ohlen, Z. Zhu, L. Yang, and J. Merchant. 1998. "Development of a Global Land Cover Characteristics Database and IGBP DISCover from 1-km AVHRR Data" In International Journal of Remote Sensing21(6-7): 1303-1330.
Available On-line at: Source Link.Global Land Cover Characteristics Database, Version 1.2.. - Goetz, S.J., S.D. Prince, S.N. Goward, M.M. Thawley, and J. Small. 1999. Satellite remote sensing of primary production: an improved production efficiency modeling approach.Ecological Modeling122:
- Prince, S.D., and S.N. Goward. 1995. Global Primary production: a remote sensing approach.Journal of Biogeography22: