This document outlines the process for creating the first country-driven global map of salt-affected soils (GSSmap). It describes guidelines, training materials, and capacity building to support national mapping efforts. It also discusses challenges countries face in mapping salt-affected soils and plans for regional gap-filling, compiling the global map, and reporting on the status of salt-affected soils worldwide.

2. GSSmap
• First country-driven global map
of Salt-Affected Soils
• Follows same framework as
GSOCmap – harmonized capacity
building and mapping on
national level
• Started in 2019 –> 1st version to
be published by the end of 2020

3. GSSmap process
• Guidelines and Technical Specifications
• Technical Manual and training materials
• Capacity development
• National mapping
• Regional gap-filling
• Compilation of the final map
• GSSmap Technical report
• Report on the global status of salt-affected soils
In progress
In progress
Done
Done
Done
Pending
In progress
Pending

4. GSSmap process
Guidelines and Technical specs
• 3 indicator maps at 1 km resolution:
• Electric conductivity from saturated paste
extract(ECe)
• pH (water)
• Exchangeable Sodium Percent (ESP)
• Classification (severity of salinity/sodicity)
• Uncertainty estimation for each map
• 2 Depth: 0-30 cm and 30-100 cm
Done

5. GSSmap process
Training materials
Lessons starting from the basics:
• Software introduction: R, QGIS, ILWIS
• Data preparation: soil data, predictors
A basic set of standardized predictors at 1km
resolution based on global datasets was prepared
for each country to complement national predictors
and data :
• MODIS spectral bands
• DEM (GMTED 2010)
• ESA landcover
• Temperature and precipitation from
worldclim.org
Done

6. GSSmap process
Technical Manual
• For different user levels: from basics to advanced
• Basics of soil salinity drivers and indicators
• R scripts + preparatory steps in GIS:
• Data preparation: soil data, predictors
• Harmonization of EC measurements from different
solutions (1:5, 1:2, 1:1, etc.)
• DSM modelling and mapping in R
• Validation and accuracy assessment in R
• Uncertainty assessment (width of the 95%
confidence interval obtained by bootstrapping)
Done

7. GSSmap process
Capacity development
• 8 regional training:
• NENA, Eurasia, Asia, Pacific, Africa,
Caribbean, Latin America, Europe
• 2 Local trainings:
• Kazakhstan (CACILM-2 project)
• Armenia (ArSIS project)
• More than: 270 national experts
from 117 countries
Done

8. GSSmap process
• 21 countries already submitted their final maps
• Secretariat in contact with 40 more countries that are working on their maps
submitted
in contact with GSP
others
GSSmap submission status:
In progressNational mapping

9. GSSmap process
Examples of maps: EC map + uncertainty map
In progressNational mapping

10. GSSmap process
Examples of maps:
• Classification of salt-affected soils
• Validation of the classified map
In progressNational mapping

11. GSSmap process
Metadata collected from the countries:
• Data provider name and institution
• Number and age of samples
• Analytical methods used to obtain
primary data
• Conversion formulas and pedotransfer
rules (if any)
• Predictors used for mapping
• Mapping method (model)
• Validation results: mean error, RMSE, R2
• Authors and contact information to be
used for a scientific publication
In progressNational mapping

12. GSSmap process
Common challenges for many countries:
• Lack of salinity data (especially ESP); data fragmented in many institutions;
• Old legacy data – requires a lot of effort to digitize and georeference;
• Different methods: e.g. TSS (total soluble salts) measured instead of EC;
• Biased data – EC and ESP available only from saline regions, but not from the whole
country – need to add expert-based pseudo-observations for non-saline regions;
• Lack of national predictors relevant for salinity (e.g. geology, irrigation, climate);
• Modelling does not reflect real situation in the country due to biased or insufficient data;
• Lack of computer capacity to run prediction and Monte-Carlo simulations to estimate
uncertainty (for big countries)
In progressNational mapping

13. GSSmap process
In progressRegional gap-filling
Data sources for regional gap-filling:
• World: WoSIS 2019
• Europe: LUCAS Soil 2015
• Africa: AfSIS
• Latin America: SISLac
• Other: regional initiatives by
countries to share their data
EC (green) and pH (blue) data in WoSIS 2019

14. GSSmap process
In progressRegional gap-filling
Example of regional gap-filling with
WoSIS (2019) data
Sub-Saharan Africa:
• National maps from Cameroon,
Ghana, Ethiopia, Lesotho, Nigeria,
South Africa, Sudan, Zimbabwe
• Regional model for the rest
0.75
2.0
4.0
8.0
16.0
EC (0-30cm)
dS/m

15. GSSmap process
In progressRegional gap-filling
Challenges for regional gap-filling
• Lack of ESP or Na data in WoSIS
• For certain areas few global data is
available, e.g. North Africa, Middle
East, Central Asia.
• Regional model may not fit with
national maps in case of lack of data
0.75
2.0
4.0
8.0
16.0
EC (0-30cm)
dS/m

16. GSSmap process
In progressReport on the global status
of salt-affected soils
• Joint GSP publication with country
chapters written by national authors
• Includes:
• Overview of salt problems in the country
• Methodology of salinity mapping
• Assessment of SAS based on mapping results
• Practices for managing SAS

17. GSSmap way forward
• Continuing to support national mapping efforts
• Compilation of the global GSSmap
• Review and publication of the global GSSmap online
• Publication of the GSSmap technical report and communication materials
• Continuous update and improvement (similar to GSOCmap)
• Finalization and publication of the Global Status of Salt-Affected Soils Report