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CLIMATE CHANGE RESHAPES RANGE LIMITS, PHENOLOGICALSYNCHRONY, AND ECONOMIC THRESHOLDS OF COCOA MIRIDS IN WEST AFRICAN AGROFORESTRY SYSTEMS
Author(s): I. A. Aderolu and A. V. Oyedokun
Volume/Issue: Volume 6 , Issue 1(2026)
ABSTRACT:
Climate change is rearranging the spatial and temporal structure of pest pressure of perennial agroforestrysystems. More than 70 percent of the global cocoa is produced in West Africa, with the mirid bugs(Sahlbergella singularis Haglund and Distantiella theobroma Distant) being the main biotic factor limitingproduction stability. However, the dynamics of pest phenology and economic thresholds due to climatewarming are unknown. We combined 15 years of climatic data across cocoa-producing regions representinga north–south climatic gradient with longitudinal field surveillance, mechanistic phenological modelling,and recalibrated economic injury thresholds to determine how climate change alters cocoa miriddistribution, seasonal synchrony, outbreak risk, and intervention timing in West African agroforestrysystems. Peak mirid abundance had improved with the increase in minimum night temperatures (+1.2°C) by18-24 days and an increase in latitude northwards (87 km) corresponding to the climatic suitability envelopein 2008. The phenological theory of temperature attributed 71 percent of the variation in pest-cropintersection (R² = 0.71), in which there is increased synchrony between peak feeding and cocoa cherelleincrease. Climate-adjusted density–damage regression models revealed that conventional economic injurythresholds underestimated projected yield losses associated with Sahlbergella singularis infestations by 32%across West African cocoa agroforestry systems.Our results indicate that climate warming is not only causinga rise in pest abundance but also redefining geographical range boundaries, squeezing seasonal pest-cropinteractions, and disrupting most of the set economic decision rules. These findings make the cocoa miridsystem an example for studying how climate change alters pest risk and management thresholds in perennialagricultural systems worldwide.
KEYWORDS:
Climate Warming, Phenological Synchrony, Geographic Range Shift, Economic Injury Level,
Cocoa Agroforestry, Insect Pest Dynamics, Climate-Adaptive Management
