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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.

The images in this ImageCollection contain the raw FORMA data calculated after new MODIS FIRMS data becomes available, approximately every day.

Each band gives a percentage of clearing (from 0 to 100) for different accumulation periods. "N" is the number of days between the latest FIRMS update and the previous NDVI update. N is given by the 'date_delta' property.


250 meters


Name Units Min Max Description
nday % 0 100

Percentage of clearing in the last N days

delta_nday % 0 100

Percentage of clearing in the last 96+N days

near_term_delta_nday % 0 100

Percentage of clearing in the last 32+N days

Image Properties

Image Properties

Name Type Description
year INT

Year of the most recent data included in the dataset


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

date_delta INT

The number of days between date and previous_biweekly_date

previous_biweekly INT

The biweekly (every 16 days) period of the year associated with the latest MODIS NDVI

previous_biweekly_date STRING

The date associated with the latest MODIS NDVI update

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.ImageCollection('WRI/GFW/FORMA/raw_output_firms')
                  .filter('2018-08-01', '2018-08-15'));
var percentageOfClearing ='nday');
var visParams = {
  min: 0.0,
  max: 0.01,
Map.setCenter(26, -8, 3);
Map.addLayer(percentageOfClearing, visParams, 'Percentage of clearing');
Open in Code Editor