Mudanças climáticas vão favorecer Gramíneas exóticas sobre espécies engenheiras nativas em áreas úmidas da Amazônia

Abstract

The Amazon Basin has suffered several anthropic impacts, such as deforestation, fires, and construction of roads and dams. These factors in synergy with climate change lead to an increase in extreme events, such as floods and severe droughts. Along the Amazonian rivers, aquatic herbaceous plants, mainly from the Poaceae family, are very abundant and produce up to three times more biomass than the flooded forest. Some species such as Echinochloa polystachya (Kunth) Hitchc and Paspalum fasciculatum Willd. ex Fluggé are key species due to the high carbon contribution to the floodplain ecosystem, being considered engineers given its structuring role in the early stages of succession of these environments. In the last decades, invasive grasses such as Urochloa brizantha (A. Rich.) R. D. Webster and Urochloa decumbens (Stapf) R. D. Webster have spread through the Neotropics and are gradually entering the Amazon through the arc of deforestation. These invasive species often reach high coverage, suppress other species, and become dominant in disturbed and, pristine habitats. This work aimed to analyze the pattern of distribution of two native engineer species and two invasive species in the Amazon Basin. In addition, the effect of different climate change scenarios on areas potentially suitable for their occurrence was evaluated. Five scenarios were chosen, current, SSP1 2.6, SSP2 4.5, SSP3 7.0 and SSP5 8.5 for the years 2040, 2060, 2080 and 2100 to project the suitable areas. The modeling to create the consensus model, using eight algorithms, was performed in the R program using the ‗biomod2‘ package. It was used 19 bioclimatic layers available in the Wordclim website for the current period, and the global circulation model - CNRM CM6 was used to project the future scenarios. The species presented a low number of unique records (E. polystachya, 69, P. fasciculatum 69, U. brizantha 79, U. decumbens 97) in the Amazon Basin at a 10 km2 resolution. The current climatically suitable areas for the engineer species was estimated at 22% of the Amazon Basin, while the invasive ones have 23% of potentially suitable areas. A decrease in the areas of suitability of the two engineer species was observed in almost every scenario and year, with losses of up to 5,4% of area in a high emission scenario (SSP 8.5) for the two species combined. On the other hand, invasive species showed an increase in suitable areas, with an area gain of up to 5.2% in a high emission scenario (SSP 8.5). These results raise a concern about the invasion of grasses with high aggressive potential that could result in the exclusion of native engineer species