Climate-State-Dependent Mortality Risk in Smallholder Cattle and Buffalo Systems: An Environmental Systems Model of Livestock Loss, Insurance, and Land Carrying Capacity in Thailand

Mortality in smallholder cattle and buffalo systems is climate-driven, but the signal is not uniform: heat and cold stress, flooding, and climate-sensitive disease act through different pathways, yet livestock loss models usually compress them into one elevated-mortality state. The paper builds a climate-state-dependent mortality model for the Thai national herd, separating an endemic baseline from a temperature-extreme and a moisture- and disease-driven regime. A 100,000-iteration Monte Carlo model, calibrated to the 2024 herd and a 2017 farmer survey at 2026 prices, generates the annual loss distribution and decomposes it by driver. The study is a calibrated scenario analysis, not an empirical estimation, so every result is conditional on the calibration and bounded by sensitivity analysis. Endemic mortality governs the average year, about 81% of expected loss but none of the extreme tail; the tail belongs entirely to the two climate regimes, with the moisture- and disease-driven regime carrying roughly 69% of losses beyond the 95th percentile and the temperature regime about 31%. This split holds across low-, medium-, and high-severity scenarios and a baseline range from 0.07 to 0.12, so it is structural: the driver of the typical year is not the driver of the catastrophe. Under a reduced-form behavioral layer with an assumed destocking response, generous payouts would raise stocking pressure 10% to 16% above a sustainable carrying capacity benchmark, so an adaptation instrument could degrade the rangeland it protects. The findings argue for regime-specific risk financing, for pairing insurance with heat and animal health adaptation, and for treating the carrying capacity externality as a design parameter.