Global VGT burnt area product 2000 -2007 (L3JRC)

Global burned area products are in high demand from research groups and communities interested in modelling the carbon cycle, understanding the relationships between fire regime and climate, atmospheric emissions and pollution resulting from fires and the impact of vegetation burning on land cover change. Burned area is a crucial component in the computation of gas emissions. Currently, global burned area products have been limited in time. As its name suggests, the GBA2000 product was limited to the year 2000. This was also true of the European Space Agency (ESA) GlobScar product.

Recent initiatives by ESA to implement a number of regional algorithms from the GBA2000 product combined with GlobScar results over the period 1998-2007 has resulted in some problems caused by scaling up of the algorithms. At this time, we still await the MODIS global burned area product. Whilst these global products provided the user community with strong evidence of the scale of global vegetation burning, multi-annual products are needed to strengthen the arguments of relationships between vegetation, climate and fire.

It is in this context that the L3JRC (pronounced L-three-J-R-C) product has been developed. Its name refers to the consortium of academies involved in the development: the University of Leicester (UK), the Université Catholique de Louvain (BE), the Instituto de Investigação Cient’fica Tropical, Lisbon (PT) and the Joint Research Centre of the European Commission (EU).

A single algorithm was used to classify SPOT VGT S1 data to burned areas. Originally developed by D. Ershov and colleagues under contract to the Joint Research Centre, the algorithm has been subsequently modified by the L3JRC consortium. After considerable pre-processing to remove cloud shadow and other unwanted data, the algorithm makes use of a temporal index in the near infrared (NIR) channel. The output is then post-processed to remove some over detections. Post-processing of the data is largely based on the land cover information provided by the GLC2000 product.

It is assumed that a global fire year starts on the 1st April of every year and that a surface cannot be burned more than once in the same fire season. If we started our fire season on the 1st January every year the second assumption is not valid for northern hemisphere sub-tropical regions. For each fire year (2000-1, i.e. 1st April 2000 to 31st March 2001) a binary product is available in geographic coordinates. The pixel value indicates the Julian date that a burned area was first detected. In addition an ASCII text file is available for each fire year giving the geographic coordinate of the centre of each pixel that has been detected as being burnt. The pixel size in these geographic products is 0.0089285714 degrees.

Africa subset of the L3JRC global data

The frequency of burnt area detection between the period 1st April 2000 and 31st March 2007 for the Africa subset of the global data is shown in the figure above. The following colour scheme applies: white is not burnt, green is burnt once, pea green is burnt twice, yellow is burnt three times, orange is burnt four times, red is burnt five times, maroon is burnt six times and purple is burnt seven times. Light blue is water, black is no data and grey indicates non-vegetated land.

The variation in global annual burned area is shown below. It shows that global burned area estimates exceeded four million km2 in fire years 2001-2, 2003-4 and 2006-7. It shows that there is a difference of almost one million km2 between the year with the greatest amount of burnt area detected (2006-7) and the year with the least amount detected (2002-3).

Global annual burned area based on L3JRC

The L3JRC product has been evaluated against a large number of Landsat TM and ETM+ image pairs and a number of regional products derived from in situ or remote means. We evaluate the product in its ability to correctly quantify the amount of burnt area by computing comparative values over a global hexagonal grid with a cell spacing of 60km. This is done over a number of different vegetation cover types and also geographical regions.

The provisional version of the global product and the validation results are made available for download and evaluation. This will allow the user community to provide comments and suggestions.

For more information on this topic, please contact Jean-Marie Gregoire (JRC), Pierre Defourny (Université Catholique de Louvain), Kevin Tansey (Leicester University) and José Miguel Pereira (Instituto de Investigação Cient’fica Tropical, Lisbon)

KEY PUBLICATIONS:

L3JRC - A global, multi-year (2000-2007) burnt area product (1 km resolution and daily time steps). Tansey, K., Gregoire, J-M., Pereira, J.M.C., Defourny, P., Leigh, R., Pekel, J-F., Barros, A., Silva, J., van Bogaert, E., Bartholomé, E., Bontemps, S. Remote Sensing and Photogrammetry Society Annual Conference 2007. Newcastle upon Tyne, UK, 11-14 September 2007  

A new, global, multi-annual (2000-2007) burned area product at 1 km resolution and daily intervals. Tansey, K., Gregoire, J.M.C., Defourny, P., Leigh, R., Pekel, van Bogaert, E., Bartholomé, E., Bontemps, S. 2008. Geophysical Research Letters, VOL. 35, L01401, doi:10.1029/2007GL031567