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Towards an Integrated Early
Warning System for detec7ng the
onset of Deser7fica7on in Libya
Pauline Meyer
Supervisor: Stephen Hallett
Context
Introduc7on: Deser;fica;on represents
a serious environmental problem in arid
and semi-‐arid zones, caused by a
Study area
c o m b i n a ; o n o f c l i m a ; c a n d
anthropogenic factors.
Deser;fica;on cons;tutes an obstacle to urbanisa;on and
agricultural development, and impacts on the ac;vi;es in
Jeffara plain, Libya. The region also experiences the worst-‐case
for water-‐balance of the country due to Human pressures.
Aim: Describe a GIS model approach to evaluate the sensi;vity
to deser;fica;on and to analyse its spa;o-‐temporal evolu;on.
Objec7ves:
§ Iden;fy and integrate the driving factors of deser;fica;on
into the model using ArcGIS
§ Analyse spa;al and temporal trend using Remote Sensing
technique and MODIS NDVI ;me series data
§ Model applicable to Middle East and North African states
§ Classify the results into deser;fica;on risk levels
Methodology
§ Model approach and its components (MEDALUS method):
Rainfall
Aridity index
Climate
Quality Index
Vegeta7on
Quality Index
Soil
Quality Index
Fire risk
Erosion protec;on
Drought resistance
Plant cover
Parent material
Soil texture
Soil depth
Slope gradient
50,0
40,0
48,5
38,8
Area (%)
Results
Sensi7vity to
Deser7fica7on
Index
Slightly sensi;ve
Sensi;ve
Very Sensi;ve
30,0
20,0
§ Model results:
12,6
10,0
0,0
SDI = (CQI*VQI*SQI)1/3
(Sensi;vity to Deser;fica;on Index)
Slightly sensi;ve
Sensi;ve
Very Sensi;ve
Methodology
§ Assessment of MODIS NDVI* ;me series data products for detec;ng
deser;fica;on spa;al trend:
MODIS Terra Vegeta7on Indices
acquisi;on (250m 16-‐day NDVI)
*Normalized Difference Vegeta;on Index
Results
Random
sampling
Spa;al trend
analysis
Pixel reliability
check
Local Polynomial
Interpola7on
§ Time series analysis:
Discussion and Conclusions
Further work:
§ Include the socio-‐economic index due to significant pressures from human ac;vity in the
The vegeta;on index tends to be the most determinant factor of sensi;vity to deser;fica;on in this
region
study. The ;me series analysis shows a spa;al loss of vegeta;on over years during the dry season. These
§ Use of photogrammetry for vegeta;on mapping in order to produce a more precise index
results validate the GIS model developed in Jeffara plain. Coastal areas tend to be less sensi;ve to
§ Use of new satellite plakorms such as Copernicus with fast revisit ;mes can allow improved
deser;fica;on than the steppes in the Southern part where the loss of vegeta;on is clearly detectable.
method
Key literature references: Kosmas et al. (1999) “The MEDALUS project” ; Kibblewhite et al. (2007) “Environmental Assessment Of Soil For Monitoring Deser;fica;on In Europe” ; Salamani et al. (2012) “Evalua;on de
la sensibilité à la déser;fica;on en Algérie” ; Brandt et al. (2014) “Environmental change in ;me series – An interdisciplinary study in the Sahel of Mali and Senegal”
www.cranfield.ac.uk/courses/masters/geographical-informationmanagement.html
Cranfield University, Cranfield, Bedfordshire, MK43 0AL
Stephen Hallett - s.hallett@cranfield.ac.uk
MEYER.pdf (PDF, 2.11 MB)
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