Summary:
Soils
Store water and solutes
Healthy spoils critical for agriculture and societal health
Soil security framework
Use soil indicators and utility graphs
Water capacity
Salinization
Key indicator: Soil organic carbon (SOC)
Many initiatives
GlobalSoilMap.net: bottom->up
ISRIC: top->bottom
FAO, 4Pour1000
Challenge: traditional approaches are static but soil properties change dynamically
E.g. SOC loss .04%-1.2%/year
Expansion of agriculture/forestry is threatening soils
Critical to integrate dynamic landcover changes in SOC assessment
Approach: SOC Monitoring at global scale
Baseline map
Landcover tracking: Where, when, change type, duration of change persistence
Baseline methodology: digital soil mapping
Based on covariates:
Soil properties
Climate
Organisms/landcover
Topography
Parent material/geology
Age
Geographic location
Trained ML model (Cubist) on dataset
Dynamics: Landcover tracking
MODIS MCF12Q1, 500m resolution
IGBP classification scheme
SOC amount: Depends on regional ecology and change in land cover type
Rate of change: depends on temperature and precipitation
Shape of change: gaining/losing SOC
Landcover tracking via Google Earth Engine
Key findings
Evolution maps of various regions of how changes in landcover types drive changes in SOC
Annual losses:
1.9Pg SOC / year (topsoil): 20% larger than annual production-based emission in US in 2018
Global total : 700-800 Pg
Tropic and sub-tropic : ~50% of global loss
Soil productivity:
Critical SOC limits:
1.1% tropical: 11 Mha/year
2% tropical: 6 Mha/year
Soil on these lands is very hard to recover (limited resource)
Towards a soil early warning system
500m-30m Landsat
Baseline for 1985
Future improvements:
Climate change effect, larger analytic window will make it possible to capture effect more clearly
Within-class changes
Different crops
Different management
Requires more soil data
Scenario analysis
Inform management and policy
Improve soil condition
Secure soils