FORMA Alerts

Dataset Availability
2012-01-01T00:00:00Z - 2019-05-18T00:00:00
Dataset Provider
Earth Engine Snippet
daily deforestation forests 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.

The percentage of clearing takes a value of 0, no clearing detected, or in the range [ecogroup_bound:100), where ecogroup_bound is given by WRI/GFW/FORMA/thresholds . The time periods over which data is collected varies by N-days, where N is the number of days between the alert_date and the last MODIS NDVI update.


250 meters


Name Units Min Max Description
alert_delta % 0 100

Percentage of clearing which during the 6 MODIS periods (96 + N days) preceding the corresponding alert_date value for the pixel

alert_date ms

Timestamp in milliseconds since 1970/01/01

Image Properties

Image Properties

Name Type Description

Date, in "YYYY-MM-DD" format, of the last available data in this dataset

last_firms_date STRING

Date, in "YYYY-MM-DD" format, of the last available FIRMS data included in this dataset

last_modis_date STRING

Date, in "YYYY-MM-DD" format, of the last available MODIS NDVI data included in this dataset

nday INT

Number of days since last MODIS NDVI update

year INT

Year of the most recent data included in the dataset

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 in Earth Engine

var dataset = ee.Image('WRI/GFW/FORMA/alerts');
var formaAlerts ='alert_delta');
var formaAlertsVis = {
  min: 25.0,
  max: 75.0,
  palette: ['d65898', 'da68a2'],
Map.setCenter(6.746, 46.529, 6);
Map.addLayer(formaAlerts, formaAlertsVis, 'FORMA Alerts');