Monitoring Deforestation Using Google Earth Engine: A Step-by-Step Guide with Landsat Data

Deforestation is one of the most pressing environmental challenges of our time. Whether it is driven by agriculture, logging, or mining, the loss of forest cover has profound consequences for biodiversity, climate, and indigenous communities. But thanks to modern remote sensing tools such as Google Earth Engine (GEE), we can now monitor forest changes in near real-time, from anywhere on the globe.

In this post, we will walk through how to detect deforestation over time using satellite imagery and a simple vegetation index, NDVI (Normalized Difference Vegetation Index) in Google Earth Engine.

🌍 Why Use Google Earth Engine?

Google Earth Engine is a powerful cloud-based platform for processing satellite imagery at scale. It provides free access to petabytes of remote sensing datasets (such as Landsat, Sentinel, MODIS), plus an interactive coding environment in JavaScript or Python.

You can run complex geospatial analyses in seconds, no need for heavy local software or downloading huge files.

🌲 Project Overview: Detecting Forest Loss

We will compare NDVI (a greenness indicator) from two different years (2015 vs 2023) over a forested region in the Amazon Basin. A drop in NDVI can indicate loss of vegetation—an early sign of deforestation.

Key Steps:

1. Define an area of interest (AOI)

2. Load Landsat 8 imagery for two dates

3. Calculate NDVI for each

4. Compute the difference

5. Highlight areas with significant vegetation loss

   
   

📊 What is NDVI?

NDVI is calculated as:

NDVI=(NIR−RED)(NIR+RED)NDVI=(NIR+RED)(NIR−RED)​

Where:

• NIR (Near Infrared) reflects strongly from healthy vegetation

• RED is absorbed by vegetation

NDVI values range from -1 to +1. Higher values (e.g., 0.6–0.9) indicate dense green vegetation, while lower values suggest sparse or no vegetation.

The following is an image of the results:

🔍 What the Results Mean

• NDVI 2015 & 2023 Layers: Help you visually compare vegetation density.

• NDVI Difference: Highlights areas of vegetation loss (red) and gain (green).

• Deforested Areas: Shows regions with NDVI drop > 0.2, likely signs of tree cover loss.

  
  

🌱 Conclusion

With Google Earth Engine, you don’t need a supercomputer or massive downloads to monitor Earth’s forests. In just a few lines of code, you can detect vegetation loss over time and take a small step toward protecting our planet.