Analysis of the lower Volga floodplain landscapes burning according to active fire and burnt areas satellite data

Abstract

Landscape fires have significantly intensified in the last two decades. A lot of research is devoted to forest fires, while much less attention is paid to the analysis of the burning of non-forest lands. The floodplain landscapes of the arid zone, which include the Volga-Akhtuba floodplain with the Volga delta, are practically not covered by studies of the fire regime. The aim of the work is to establish the spatio-temporal regularities of the burning of the floodplain landscapes of the Volga in its lower reaches according to the detection of active burning and burnt areas based on Earth remote sensing technologies. The work used MCD14ML (FIRMS), MCD64A1, FireCCI51 and GABAM data for 2001–2020, the first three of which are based on MODIS data, the last one is based on Landsat data. Each of the products has both omissions and false definitions and artifacts. Nevertheless, a joint analysis of all the data makes it possible to obtain a fairly reliable assessment of the flammability. In total, during the study period, the total area of burned areas ranged from 2.9 million hectares to 4.8 million, according to estimates of different products. The average long-term flammability is 9.2 % of the study area. The maximum burning rate was noted in 2019 (15.4 %), and the minimum—in 2016 (2.8 %). These years are characterized by the shortest and longest duration of periods of maximum flood flow, respectively. The influence of the hydrological situation on the burning of floodplain landscapes is confirmed by the correlation analysis. A significant correlation between the fire rate and the flood level and its duration has been established. The higher the maximum flood level of the floodplain and the longer the water stays on the floodplain, the lower the flammability. This is especially pronounced in the Volga delta, where, due to the reduction in flood costs and the drop in the level of the Caspian Sea, the drying of floodplain landscapes is intensifying. This leads to the intensification of fires. In addition to the hydrological situation, the weather affects the flammability. At the same time, the main climatic factor is atmospheric moisture. The more rainfall, the less fire. The air temperature does not affect the size of the burnt area, since the temperatures remain quite high throughout the entire warm period. Trends in hydrological changes are aimed at reducing the water content of the flood, which will lead to the drying of the floodplain against the backdrop of a continuing drop in the level of the Caspian Sea. With the existing system of fire prevention, we should expect a further increase in the burning of landscapes.