Zoneamento bioclimático e impactos das mudanças climáticas para a bovinocultura de leite no Estado do Maranhão

Abstract

Bioclimatic zoning is an important tool for dairy cattle production, as it allows the identification of areas with greater vulnerability to heat stress and supports management strategies, territorial planning, and adaptation to climate change. Therefore, this study aimed to perform bioclimatic zoning and assess the impacts of climate change on dairy cattle production in Maranhão, Brazil. The spatial and temporal variability of environmental heat load and its effects on heat stress risk in cattle were evaluated using the Temperature-Humidity Index (THI), calculated from historical data (2012–2023) and future climate projections under the intermediate (RCP4.5) and pessimistic (RCP8.5) scenarios derived from the Eta/INPE model. Meteorological data on air temperature and wind speed were obtained from the TerraClimate platform. Decline in Milk Production (DMP) was also estimated for cows with production potentials of 10 and 25 kg cow−1 day−1. Spatial variability was assessed using geostatistical techniques, including experimental semivariogram fitting, ordinary kriging interpolation, and thematic mapping. The THI results revealed a decreasing thermal gradient from north to south, with the largest areas presenting THI values above 80 occurring in 2012, 2013, and 2015– 2017, indicating a higher risk of heat stress. Furthermore, DMP was more pronounced in high-producing dairy cattle due to their greater metabolic heat production and higher energy requirements associated with lactation. Climate projections indicated that, under the RCP4.5 scenario, more than 60% of Maranhão may present mean THI values between 78 and 81 by the end of the century, with losses exceeding 1.5 kg cow−1 day−1 for moderately producing animals and 4 kg cow−1 day−1 for high-producing animals in the long term. Under the RCP8.5 scenario, the expansion of areas with THI values above 86 is projected, corresponding to emergency heat stress conditions, with estimated losses exceeding 4 kg cow−1 day−1 for moderately producing animals and 9 kg cow−1 day−1 for high-producing animals. The results indicate high vulnerability of dairy cattle production in Maranhão to heat stress and reinforce the need for adaptation strategies, including the selection of animals better adapted to local climatic conditions, improvements in housing facilities, shading, ventilation, adequate water availability, adjustments in feeding management, and cooling systems. It is concluded that bioclimatic zoning can support the identification of priority areas and guide management and production planning strategies, contributing to increased resilience and sustainability of dairy cattle production under climate change.