Discrimination between climate and human-induced dryland degradation
Citation
Jason Evans, and Roland Geerken, Discrimination between climate and human-induced dryland degradation: .
Summary
In this study we present a technique to discriminate between climate or human-induced dryland degradation, based on evaluations of AVHRR NDVI data and rainfall data. Since dryland areas typically have high inter-annual rainfall variations and rainfall has a dominant role in determining vegetation growth, minor biomass trends imposed by human influences are difficult to verify. By performing many linear regression calculations between different periods of accumulated precipitation and the annual NDVImax, we identify the rainfall period that is best related to the NDVImax and by this the proportion of biomass triggered by rainfall. Positive or negative deviations in biomass from this relationship, expressed in the residuals, are interpreted [...]
Summary
In this study we present a technique to discriminate between climate or
human-induced dryland degradation, based on evaluations of AVHRR NDVI
data and rainfall data. Since dryland areas typically have high
inter-annual rainfall variations and rainfall has a dominant role in
determining vegetation growth, minor biomass trends imposed by human
influences are difficult to verify. By performing many linear regression
calculations between different periods of accumulated precipitation and
the annual NDVImax, we identify the rainfall period that is best related
to the NDVImax and by this the proportion of biomass triggered by
rainfall. Positive or negative deviations in biomass from this
relationship, expressed in the residuals, are interpreted as
human-induced. We discuss several approaches that use either a
temporally fixed NDVI peaking time or an absolute one, a best mean
rainfall period for the entire drylands or the best rainfall period for
each individual pixel. Advantages and disadvantages of either approach
or one of its combinations for discriminating between climate and
human-induced degradation are discussed. Depending on the particular
land-use either method has advantages. To locate areas with a high
likelihood of human-induced degradation we therefore recommend combining
results from each approach. Published in Journal of Arid Environments,
volume 57, issue 4, on pages 535 - 554, in 2004.
