Impacts of climate warming and carbon intensity on rice yield: Implications for adaptation strategies in the Mekong Delta, Vietnam

Abstract

Importance of the work: Rice yield response to warming exhibits non-linear threshold
behavior dependent on rhizosphere biogeochemical status.
Objectives: To identify thermal tipping points and quantify carbon intensity (CI)
moderation of temperature-yield relationships.
Materials and Methods: A balanced panel dataset (1995−2024, n = 180) across six
Mekong Delta provinces was analyzed using data envelopment analysis and Hansen’s
threshold model, with temperature data from the Ca Mau hydrological station and
emission factors from the Intergovernmental Panel on Climate Change guidelines.
Results: A statistically significant threshold was identified at γ = 27.5°C (95% confidence
interval: 27.3−27.7°C, p < 0.01). Below this threshold, each 1°C increase raised yields
by 0.18 t/ha, whereas above it for each 1°C, yields declined by 0.24 t/ha. Systems with
CI >1.2 kg CO2e/kg had 35% greater yield volatility and 82% larger thermal penalties at
supra-threshold temperatures than low-carbon systems.
Main finding: This study provided the first regional-scale, panel-based quantification of
a 27.5°C thermal tipping point governing rice yield in the Mekong Delta, demonstrating
that CI functions as a biophysical stress multiplier. Specifically, high-emission systems
(CI >1.2 kg CO2e/kg) suffer 50% larger thermal yield penalties above the threshold
than their low-emission counterparts. Achieving CI <1.0 kg CO2e/kg (as mandated
by Decision No. 1490/QD-TTg by the Prime minister of Vietnam) confers the dual
co-benefits of a reduction in CH4 and N2O emissions, as well as enhanced thermal
resilience, providing a biophysical basis for differentiated provincial adaptation strategies
under National Assembly of Vietnam Resolution No. 202/2025/QH15.