FORMA Alert Thresholds

Dataset Availability
Dataset Provider
Earth Engine Snippet
daily deforestation forest forma gfw modis monitoring wri


NOTE from WRI: WRI decided to stop updating FORMA alerts. The goal was to simplify the Global Forest Watch user experience and reduce redundancy. We found that Terra-i and GLAD were more frequently used. Moreover, using GLAD as a standard, found that Terra-i outperformed FORMA globally.

FORMA alerts are detected using a combination of two MODIS products: NDVI (Normalized Difference Vegetation Index) and FIRMS (Fires Information for Resource Management System). NDVI updates are processed every 16 days, while fire updates are processed daily. Models are developed individually for each ecogroup to relate the two inputs to the area of clearing, using the Hansen annual tree cover loss data to train the model. The minimum threshold to qualify as an alert is 25% of the pixel cleared, though thresholds vary by ecogroup to minimize false positives. Here is an example script for a quick introduction to the FORMA datasets.

This image contains the thresholds at which, when crossed, a FORMA alert is produced. The values are equal to max(25,40%*RegionalMax), where RegionalMax is the historical maximum clearing for a pixel in this ecogroup.


250 meters


Name Units Min Max Description
delta_bound % 25 40

The thresholds at which, when crossed, a FORMA alert is produced

Terms of Use

Terms of Use

The FORMA datasets are available without restriction on use or distribution. WRI does request that the user give proper attribution and identify WRI and GFW, where applicable, as the source of the data.

Explore with Earth Engine

Code Editor (JavaScript)

var dataset = ee.Image('WRI/GFW/FORMA/thresholds');
var thresholds ='delta_bound');
var visParams = {
  min: 0,
  max: 50,
Map.setCenter(26, -8, 3);
Map.addLayer(thresholds, visParams, 'Thresholds for FORMA alerts');
Open in Code Editor