<![CDATA[Abstract. Trung TV, Chau NT. 2026. Declining carbon intensity of rice production in the Mekong Delta, Vietnam, as a consequence of yield growth rather than emission reduction. Asian J Agric 10 (2): g100230. https://doi.org/10.13057/asianjagric/g100230. Rice production in Vietnam's Mekong Delta is a focal target of the national low-emission agenda, with Decision No. 1490/QD-TTg setting a carbon emissions intensity ceiling below 1.0 ton CO2e per ton of paddy. Carbon emissions intensity under the IPCC Tier 1 inventory framework, the accounting basis used for provincial reporting, is examined here to clarify what such intensity targets measure. A provincial panel of 13 Mekong Delta provinces over 1995 to 2024 (N = 381 province-year observations) is analyzed. Because Tier 1 accounting assigns a constant per-hectare emission factor, provincial carbon intensity reduces to a fixed constant divided by yield, an identity confirmed empirically (log-log yield elasticity of carbon intensity = -1.00, within R-squared = 1.00). The reported decline in carbon emissions intensity over three decades is therefore a reduced-form consequence of rising yields rather than measured mitigation. Two-Way Fixed Effects models with Driscoll-Kraay standard errors indicate that, once province and year effects are absorbed, mean temperature and rainfall are not significantly associated with yield, and the strong raw yield-intensity correlation is largely attributable to shared temporal trends. A separately reported Tier 2 scenario simulation, with low, medium, and high assumptions, indicates carbon intensity reductions of 25 to 53 percent from alternate wetting and drying combined with improved straw management across the technically feasible area, with the water-management component alone accounting for 23 to 47 percent. The principal implication is that intensity targets defined on a Tier 1 basis are met arithmetically through yield gains and, by construction, cannot reflect field-level emission reductions, so certification-grade monitoring requires a shift to Tier 2 or to measured emission factors.]]>
