Silvopastoral systems as a sustainable alternative to mitigate the effects of climate change on farm level

Climate changes cause an increase in the duration and intensity of heatwaves and promotes a decrease in the time that cattle remain in thermal comfort zones. Silvopastoral systems can be considered a nature-based solution to mitigate the effects of climate change. The aim of this study was to estimate the thermal comfort of bovines during hot seasons (spring and summer) in a silvopastoral system compared to treeless pasture. The experiment was carried out between September of 2020 and February of 2021 in southern Brazil. Two pasture systems were evaluated (4 non-consecutive days per month): treeless pasture (TLP) and silvopastoral system (SPS) with trees along the border fences. Two sets of autonomous sensors were located in each system (TLP - center of the paddock and SPS - full sun and 2 m away from the trees), to measured microclimate variables used to calculate the bioclimatic indicators of black globe-humidity index (BGHI), radiant thermal load (RTL), and heat load index (HLI). All data were analyzed using a mixed model with days and hours as random effects using the statistical software R. There was an influence of the system (p<0.001) on the bioclimatic indicators. On average the SPS was ~80% (p<0.001) more likely to present lower values of bioclimatic indicators than the TLP. The average values of all bioclimatic indicators differed (p<0.001) between the systems; TLP: BGHI = ~78; RTL = ~581, and HLI = ~59; SPS: BGHI = ~72; RTL = ~439, and HLI = ~47. In TLP all bioclimatic indicators were above the threshold for heat stress for bovines, promoting a challenge thermal environment for pasture-based production. In conclusion, the SPS provided a better thermal environment for pasture-based systems when compared to TLP, indicating that it can mitigate the effects of heat during the spring and summer of subtropical climate.