This document discusses using Google Earth Engine (GEE), a cloud-based platform, to analyze wetland degradation in the Tempisque Watershed in Costa Rica over time. The author creates a normalized difference vegetation index (NDVI) time series from Landsat and MODIS imagery to identify long-term drivers of wetland degradation. Results show increases in vegetation greenness following the abandonment of cattle ranging and invasion of cattails. GEE allows the custom analysis of temporal NDVI evolution to test hypotheses about vegetation changes.

1. WETLAND LANDSCAPE SPATIO-TEMPORAL
DEGRADATION DYNAMICS USING THE NEW GOOGLE
EARTH ENGINE CLOUD-BASED PLATFORM:
OPPORTUNITIES FOR NON-SPECIALISTS IN REMOTE
SENSING
Alec Popichak
25 April 2018

2. Background
 Importance of wetlands
 Carbon sequestration
 Biodiversity
 Important to map but difficult
 Google Earth Engine (GEE) becoming open for scientific use

3. Objectives
 Use GEE for wetland studies
 Demonstrate the capabilities of GEE
 Create a time series
 Create normalized difference vegetation index (NDVI)
 Based on vegetation absorbing red electromagnetic radiation

4. Materials and Methods
 Used Tempisque Watershed in Costa Rica
 Known for its biodiversity
 Runs through Palo Verde National Park (PVNP)
 Vegetative shift due to human involvement
 Cattails- decline in bird populations
 Severely degraded

5. Objectives Continued
 Identify long-term wetland degradation drivers
 Use time series analysis
 Set of hypothesized drivers
 Time series of Meteorological variables
 Time series of Hydrological variables

6. Preparing a Model
 Study area divided into eleven polygons
 PVNP divided into four sections
 Zones 1-3: combination of adjacent wetlands
 Zone four: dry land in PVNP

7. Finishing the Model
 Upper watershed divided into other seven
 Grouped by subwatersheds
 Generated with Hydrology Toolbox in ESRI’s ArcMap
 Final polygon created for irrigation district

8. Calculations
 rNIR = spectral reflectance recorded by near-infrared channel
 rred = spectral reflectance recorded by red channel
 NDVI generated from Landsat and MOTIS images
 GEE constructed and examined NDVI time series

9. Results
 Images with over 25% cloud cover excluded
 Led to lower usable images during rainy season

10.  Increase in vegetation greenness
 Abandonment of cattle ranging
 PVNP increase
 Cattail invasion

11. Landsat
MODIS

12. Conclusion
 GEE potential
 Create custom time series and maps
 Temporal evolution of NDVI
 Vegetation time series
 Tested against covariates to draw inferences
 Hindcast NDVI prior to 2000

13. Questions

14. References
 https://en.wikipedia.org/wiki/Normalized_difference_vegetation_index#/media/File:
NDVI_062003.png
 https://en.wikipedia.org/wiki/Normalized_difference_vegetation_index#/media/File:
NDVI_102003.png
 A. Alonso, et al., WETLAND LANDSCAPE SPATIO-TEMPORAL DEGRADATION
DYNAMICS USING THE NEW GOOGLE EARTH ENGINE CLOUD-BASED PLATFORM:
OPPORTUNITIES FOR NON-SPECIALISTS IN REMOTE SENSING.