Spatial and temporal scale issues in determining biomass burning regimes in Bolivia and Peru

Abstract

ATSR‐2 active fire data from 1996 to 2000, TRMM VIRS fire counts from 1998 to 2000 and burn scars derived from SPOT VEGETATION (the Global Burnt Area 2000 product) were mapped for Peru and Bolivia to analyse the spatial distribution of burning and its intra‐ and inter‐annual variability. The fire season in the region mainly occurs between May and October; though some variation was found between the six broad habitat types analysed: desert, grassland, savanna, dry forest, moist forest and yungas (the forested valleys on the eastern slope of the Andes). Increased levels of burning were generally recorded in ATSR‐2 and TRMM VIRS fire data in response to the 1997/1998 El Niño, but in some areas the El Niño effect was masked by the more marked influences of socio‐economic change on land use and land cover.

There were differences between the three global datasets: ATSR‐2 under‐recorded fires in ecosystems with low net primary productivities. This was because fires are set during the day in this region and, when fuel loads are low, burn out before the ATSR‐2 overpass in the region which is between 02.45 h and 03.30 h. TRMM VIRS was able to detect these fires because its overpasses cover the entire diurnal range on a monthly basis. The GBA2000 product has significant errors of commission (particularly areas of shadow in the well‐dissected eastern Andes) and omission (in the agricultural zone around Santa Cruz, Bolivia and in north‐west Peru).

Particular attention was paid to biomass burning in high‐altitude grasslands, where fire is an important pastoral management technique. Fires and burn scars from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM) data for a range of years between 1987 and 2000 were mapped for areas around Parque Nacional Río Abiseo (Peru) and Parque Nacional Carrasco (Bolivia). Burn scars mapped in the grasslands of these two areas indicate far more burning had taken place than either the fires or the burn scars derived from global datasets. Mean scar sizes are smaller and have a smaller range in size between years the in the study area in Peru (6.6–7.1 ha) than Bolivia (16.9–162.5 ha). Trends in biomass burning in the two highland areas can be explained in terms of the changing socio‐economic environments and impacts of conservation.

The mismatch between the spatial scale of biomass burning in the high‐altitude grasslands and the sensors used to derive global fire products means that an entire component of the fire regime in the region studied is omitted, despite its importance in the farming systems on the Andes.

Acknowledgement

The research was funded by the European Union (Grant number ERB IC18CT980299) and the Royal Geographical Society (with Institute of British Geographers), Slawson Award to AVB. The authors acknowledge the data providers: ATSR‐2 data were extracted from the European Space Agencies World Fire Atlas, TRMM VIRS data were downloaded from the Goddard Earth Sciences Distributed Active Archive Centre, GBA2000 data were acquired from Joint Research Centre's, Institute for Environment and Sustainability, AVHRR Pathfinder cloud cover data downloaded from NOAA National Environmental, Satellite data and Information service and Landsat data were downloaded from the University of Maryland's Global Land Cover Facility. The authors have benefited greatly from field trips and discussions with Carolina Casaretto (formerly of APECO, Lima) and Felix Huanca (UMSS‐Cochabamba). They are very grateful to Kevin Tansey (University of Leicester, UK), Ken Young (University of Texas) and Paul Laris (California State University – Long Beach) for commenting on earlier drafts of this paper, and to the detailed suggestions provided by two anonymous referees.