Monitoring Reforestation and Vegetation Recovery Using NDVI
Summary
In this activity, students use ArcGIS Pro to visualize and analyze long-term vegetation recovery in Hawai'i's Hakalau Forest National Wildlife Refuge. Students calculate the Normalized Difference Vegetation Index (NDVI) using Landsat satellite imagery from the years 2000, 2014, and 2024 to assess changes in tree cover over time. A defined NDVI threshold is applied to classify forested versus non-forested areas, and students calculate the percentage of tree cover for each year. In the second part of the lab, students validate their findings using high-resolution Sentinel-2 imagery. Through this hands-on activity, students develop skills in raster analysis, multi-temporal image interpretation, and geospatial data validation, while gaining insight into forest succession and ecological restoration.
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Context
Audience
This activity was designed for an upper division "Fundamentals of GIS for Environmental Science" course. The lab builds upon foundational concepts in ecology and remote sensing, focusing on vegetation indices and forest succession. It assumes some GIS experience and requires familiarity with ArcGIS Pro but offers step-by-step guidance for newer users.
Skills and concepts that students must have mastered
Students should have some understanding of GIS principles, especially relating to ArcGIS Pro. Students should also display familiarity with basic ecological concepts such as succession, tree cover, and disturbance.
How the activity is situated in the course
This lab is typically assigned in the second half of the course, once students have been introduced to raster data, vegetation indices, and basic classification techniques. It supports course objectives related to spatial data interpretation, image processing, and environmental monitoring. This activity is particularly valuable in hybrid or online courses where students are unable to perform fieldwork, as it enables analysis of real-world ecological change from remote sensing datasets. NDVI serves as a conceptual and practical bridge between ecological theory and quantitative spatial analysis.
Goals
Content/concepts goals for this activity
Students should be able to:
- Explain the NDVI formula and interpret what it represents
- Use NDVI values to identify vegetation presence and health
- Apply Boolean classification to distinguish forested areas using a threshold
- Compare satellite imagery across three different years to detect landscape change
- Interpret differences between Landsat and Sentinel-2 datasets in terms of resolution and accuracy
- Validate NDVI-based results with higher-resolution Sentinel imagery
Higher order thinking skills goals for this activity
- Calculate and interpret changes in vegetation cover over time
- Critically assess and validate remote sensing outputs using multiple datasets
- Reflect on the limitations of satellite data and how classification thresholds affect interpretation
- Draw inferences about the environmental and human-driven factors influencing forest change
Description and Teaching Materials
Students will use ArcGIS Pro to calculate NDVI from Landsat imagery (2000, 2014, and 2024) and classify the results into forested and non-forested areas using a defined threshold. After calculating the percentage of forest cover in each year, students will quantify the change over time and examine trends in reforestation. In the second part of the activity, students will validate their Landsat-derived classification with Sentinel-2 NDVI imagery, comparing spatial patterns and exploring discrepancies. The lab includes guided processing steps and a worksheet with critical thinking questions designed to encourage scientific interpretation and ecological reasoning.
The required datasets (Landsat and Sentinel-2 imagery) are provided in advance and prepared for use in ArcGIS Pro. Students must have access to the ArcGIS Pro desktop application.
Student Worksheet (Microsoft Word 2007 (.docx) 95kB Jul16 25)
GIS Files (Zip Archive 402.8MB Jul16 25)
Teaching Notes and Tips
Student worksheet answer key is found here:
Lab Worksheet Answer Key -- educator-only file
HideAssessment
Students will be assessed on:
- Completion of raster processing steps (NDVI calculation, thresholding)
- Correct application of Boolean classification and interpretation of symbology
- Accuracy of percent forest cover estimates across years
- Visual comparison with Sentinel-2 imagery
- Responses to critical thinking questions provided in the lab worksheet
References and Resources
- ArcGIS Pro (ESRI Desktop GIS Software)
- Landsat and NAIP/Sentinel-2 imagery (USGS EarthExplorer, ArcGIS Online )