Land degradation

Implemented in computer model

IMAGE land use model

Flowchart Land degradation. See also the Input/Output Table on the introduction page.

Key policy issues

• In what parts of the world have human-induced changes in land and soil conditions occurred?
• What are the future risks of soil degradation?
• To what extent are ecosystem functions lost by soil degradation, adding to local and global concerns about food security, biodiversity loss and climate change?

Introduction

Model intro

Input/Output Table

Input Land degradation component

IMAGE model drivers and variables	Description	Source
Number of wet days - grid (historical data)	Number of days with a rain event, per month; assumed constant after the historical period	CRU database
Land cover, land use - grid	Multi-dimensional map describing all aspects of land cover and land use per grid cell, such as type of natural vegetation, crop and grass fraction, crop management, fertiliser and manure input, livestock density.	Land cover and land use
Precipitation - grid	Monthly total precipitation.	Atmospheric composition and climate
Temperature - grid	Monthly average temperature.	Atmospheric composition and climate

External datasets	Description	Source
Initial land cover, land use - grid	Includes current state (intensive agriculture use, extensive agricultural use, no use) of land area and erosion protection represented by greenness index (NDVI = Normalized Difference Vegetation Index).	GlobCover database
Initial temperature, precipitation - grid	Global high resolution climate data from WorldClim.	WorldClim database
Slope - grid	Terrain slope index.	IIASA
Soil types and profiles (S-World)	Soil profiles based on the HWSD (Harmonised World Soil Database) and on the ISRIC-WISE international soil profile dataset	S-World database, HWSD database
Weighting factors for temperature, precipitation, land use and slope	Weighting factors for the contribution of temperature, precipitation, land use and slope on distribution of soil properties.	expert judgement

Output Land degradation component

IMAGE model variables	Description	Use
Erosion risk - grid	Risk of soil erosion caused by water.	Ecosystem services
Change in soil properties - grid	Change in soil properties, such as clay/sand content, organic carbon content, soil depth (topsoil/subsoil).	Crops and grass Land cover and land use