Using Multi-Layer Perceptron (MLP) and Similarity-Weighted machine learning algorithm (SimWeight) to reconstruct the past: a case study of the agricultural expansion on grasslands in the Uruguayan Savannas.

Changes in land use and land cover (LULC) have significant implications for biodiversity, ecosystem functioning, and deforestation. Modeling LULC changes is crucial for understanding anthropogenic impacts on environmental conservation and ecosystem services. While previous studies have focused on predicting future changes, there is a growing need to determine past scenarios using new assessment tools. This study aims to propose a methodology for LULC past scenario generation based on transition analysis. Aiming to hindcast LULC scenario in 1970 based on the transition analysis of the last 35 years (from 1985 to 2020), two machine learning algorithms, Multi-Layer Perceptron (MLP) and Similarity Weighted, were employed to determine the driver variables most related to conversions in LULC and to simulate the past. The study focused on the Aristida spp. grasslands in the Uruguayan savannas, where native grasslands have been extensively converted to agricultural areas. LULC data from the MapBiomas project were integrated with spatial variables such as altimetry, slope, pedology, and linear distances from rivers, roads, urban areas, agriculture, forest, forestry, and native grasslands. The accuracy of the predicted maps was assessed through stratified random sampling on reference images from the Multi-Spectral Scanner (MSS) sensor. The results demonstrate a reduction of approximately 659,934 hectares of native grasslands in the study area between 1985 and 2020, directly proportional to the increase in cultivable areas. The MLP algorithm exhibited moderate performance, with notable errors in classifying agriculture and grassland areas. In contrast, the SimWeight algorithm displayed better accuracy, particularly in distinguishing grassland and agriculture classes. The modeled map using SimWeight accurately represented the transitions between grassland and agriculture with a high level of agreement. By modeling the 1970s scenario using the SimWeight model, it was estimated that the Aristida spp. grasslands experienced a substantial reduction in grassland coverage, ranging from 9,982.31 to 10,022.32 km² between 1970 and 2020. This represents a range of 60,8 to 61,07% of the total grassland area in 1970. These findings provide valuable insights into the driving factors behind land use change in the Aristida spp. Grasslands and offer useful information for land management, conservation, and sustainable development in the region. The study's main contribution lies in the hindcasting of past LULC scenarios, utilizing a tool primarily used for forecasting future scenarios.