Beyond the thermostat: rethinking biological complexity, causation, and systemic constraints in plant science

Recent proposals that plants could be engineered to function as large-scale climatic “thermostats” reflect growing confidence in molecular biology, genomics, and synthetic approaches to environmental problem-solving. While technologically ambitious, such visions rest on mechanistic assumptions about biological control, predictability, and causal hierarchy that are poorly aligned with contemporary understanding of plant organization. Here we argue that plants are not centrally regulated devices but decentralized, modular, and historically contingent systems whose behavior emerges from multilevel interactions across developmental, physiological, ecological, and temporal scales. Drawing on concepts from systems biology, process ontology, and circular causation, we examine how emergent organization, phenotypic plasticity, epigenetic regulation, and stress memory constrain the predictability of molecular interventions. We further discuss how extrapolations from gene-level engineering to agricultural or planetary outcomes overlook systemic socio-ecological and biogeochemical constraints governing food security and climate regulation. Engineering strategies that treat plants as programmable components of global control architectures risk overestimating biological leverage while underestimating ecological complexity and scale dependence. Rather than rejecting molecular tools, we advocate embedding them within conceptual frameworks that acknowledge reciprocity across levels, historical contingency, and environmental embeddedness. Replacing metaphors of centralized control with systemic perspectives offers a more realistic basis for evaluating the role of plant science in addressing global challenges.