Deforestation of native forest, forest fires and flow of the Bio Bío river in the Province of Concepción from 1987-2021

Abstract

The importance of preserving the native forest has become relevant in the current context of drought and climate change, along with the relationship between native species and base flow in watersheds, as well as relative humidity. This study aims to review the evolution of the native forest cover, the trend in the flow of the Biobío River and the magnitude of the fires in the last 34 years. Through the processing and correction of satellite images from the years 1987, 2001, 2011 and 2021, in almost the entire province of Concepción in the Biobío region, we were able to define 8 types of land cover: native forest, bare soil, scrub, wetland , urban area, agricultural area, water and exotic plantation, and its variations over time with the Land Change Modeler tool. It is obtained that 34,034 ha of native forest have been lost, of which 88.87% migrated to forest plantation. Additionally, this loss of native forest is contrasted with the decrease in flow of the Biobío River, highlighting that 2017 is the year in which the most native forest is lost due to forest fires, and this coincides with the lowest average flow, reaching to observe 221.1 m3/s of flow at the mouth of the Biobío River, contrasted with the average for the period of time studied equal to 939.1 m3/s. This relationship becomes important due to the role of native forest cover and the available water in a basin. In parallel, an increase in the area affected by fire is observed, which favors the spread of exotic plantations over native. It should be noted that the lowest flow values coincide with the period with the largest area affected by fires. Equivalent to 2,706.9 occurred in 2017, according to the CONAF fire registry. Although there is a lack of rigor in the statistical analyzes that were carried out, it is undeniable that the high migration from native forest to forest plantation plays a relevant role in mega fires.