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<p>Climate change is expected to negatively affect dairy production, particularly in semi-arid environments such as that of Botswana, due to increased heat stress from the projected rise in ambient temperature. This study was carried out to investigate the potential impacts of climate change-induced heat stress on milk production in Botswana in the near-term (2030), mid-term (2050), and long-term (2070) under the high greenhouse gas emissions scenario (Shared Socioeconomic Pathway (SSP 5-8.5). The National Aeronautics and Space Administration Earth Exchange Global Daily Downscaled Projections were used to calculate the daily projected Temperature Humidity Index (THI). This dataset has been downscaled to a daily temporal resolution, derived from a daily variant of the monthly bias correction/spatial disaggregation. Milk yield loss per cow, due to heat stress, was estimated at a daily time step using the milk yield loss formula. This formula assumes that dairy cows lose 0.39&#xa0;kg milk yield for a unit increase in THI above the threshold. Results indicate increased exposure of dairy cows throughout Botswana to heat stress (THI &gt; 72) for most of the year ranging from 296 ± 20 days in 2030 to 364 ± 1 days in 2070. A progressive increase in THI was evident in all districts over time with a similar seasonal pattern of THI, recording high THI in the austral summer months and low THI during the cool winter months. There was a significant rise in THI in the projected years (all <i>p</i> &lt; 0.001) i.e., from 78.91 ± 0.67 in 2030, to 80.48 ± 0.67 in 2050 and 82.48 ± 0.67 in 2070 (mean ± se). Severe heat stress (79 ≥ THI &lt; 89) was projected to be the dominant (&gt; 60%) type of heat stress for all periods in all nine districts. Annual milk yield losses were projected to progressively increase from 2.9 ± 0.15&#xa0;kg/cow/day in 2030 to 4.2&#xa0;kg/cow/day in 2070 (mean ± se). These projected heat stress impacts are, however, subject to uncertainty as the bias-corrected, spatially disaggregated dataset used in this study may not fully represent local-scale climate variability. Future research should expand the multi-model ensembles as well as incorporate observational data to account for breed-specific responses and different dairy production systems.</p>

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Projected impacts of climate change-induced heat stress on milk production in semi-arid environments under SSP 5-8.5 scenario: a case study of Botswana

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Jonas Kwedibana,
  • Nnyaladzi Batisani,
  • Wame S. Boitumelo,
  • Cuthbert B. Banga

摘要

Climate change is expected to negatively affect dairy production, particularly in semi-arid environments such as that of Botswana, due to increased heat stress from the projected rise in ambient temperature. This study was carried out to investigate the potential impacts of climate change-induced heat stress on milk production in Botswana in the near-term (2030), mid-term (2050), and long-term (2070) under the high greenhouse gas emissions scenario (Shared Socioeconomic Pathway (SSP 5-8.5). The National Aeronautics and Space Administration Earth Exchange Global Daily Downscaled Projections were used to calculate the daily projected Temperature Humidity Index (THI). This dataset has been downscaled to a daily temporal resolution, derived from a daily variant of the monthly bias correction/spatial disaggregation. Milk yield loss per cow, due to heat stress, was estimated at a daily time step using the milk yield loss formula. This formula assumes that dairy cows lose 0.39 kg milk yield for a unit increase in THI above the threshold. Results indicate increased exposure of dairy cows throughout Botswana to heat stress (THI > 72) for most of the year ranging from 296 ± 20 days in 2030 to 364 ± 1 days in 2070. A progressive increase in THI was evident in all districts over time with a similar seasonal pattern of THI, recording high THI in the austral summer months and low THI during the cool winter months. There was a significant rise in THI in the projected years (all p < 0.001) i.e., from 78.91 ± 0.67 in 2030, to 80.48 ± 0.67 in 2050 and 82.48 ± 0.67 in 2070 (mean ± se). Severe heat stress (79 ≥ THI < 89) was projected to be the dominant (> 60%) type of heat stress for all periods in all nine districts. Annual milk yield losses were projected to progressively increase from 2.9 ± 0.15 kg/cow/day in 2030 to 4.2 kg/cow/day in 2070 (mean ± se). These projected heat stress impacts are, however, subject to uncertainty as the bias-corrected, spatially disaggregated dataset used in this study may not fully represent local-scale climate variability. Future research should expand the multi-model ensembles as well as incorporate observational data to account for breed-specific responses and different dairy production systems.