Biophysical Drivers and Spatiotemporal Dynamics of Maize Productivity Decline in Kenya: A Review of Climate Impacts and Environmental Planning Responses

Abstract

Maize (Zea mays L.) is the cornerstone of Kenya's food security and agricultural economy, yet productivity across the country's diverse agro-ecological zones is declining under the compounding pressures of climate change. This integrative review synthesizes evidence from 36 studies published between 2015 and 2026 to examine the biophysical drivers and spatiotemporal dynamics of maize productivity decline in Kenya, and to critically evaluate the alignment between these biophysical realities and existing environmental planning responses. The analysis identifies three primary biophysical pathways underpinning productivity decline: phenological compression, driven by rising temperatures that shorten the growing cycle by 34–38 days in highland zones; thermal stress and pollen sterility, with each 1°C above optimal thresholds reducing yields by approximately 5%; and soil-climate synergism, wherein declining soil organic carbon amplifies moisture stress and nutrient deficiency, with productivity losses of 20–50% in unfertilized systems. These pathways interact across a stark agro-ecological gradient that is being progressively flattened by climate change, as high-potential western highland regions contributing over 80% of national output experience accelerated degradation while arid and semi-arid lands face intensified climatic extremes. Temporal dynamics reveal a shift from predictable seasonality toward heightened inter-annual and intra-seasonal variability, undermining traditional farming calendars and amplifying production uncertainty. Despite an elaborate environmental planning architecture including the Climate Change Act (2016), National Adaptation Plan (2015–2030), and Kenya Climate Smart Agriculture Strategy (2017–2026) planning responses remain structurally decoupled from mechanistic biophysical realities. Critical disconnects persist in spatial targeting, temporal horizon alignment, monitoring and evaluation capacity, and institutional coordination between national and county levels. County plans are structured around administrative wards rather than agro-ecological zones, are constrained by five-year political cycles that mismatch decadal biophysical trends, and rely on climate information too coarse to capture farm-level variability. The review concludes that addressing these disconnects requires planning frameworks restructured around agro-ecological realities, nested across multiple temporal scales, grounded in high-resolution biophysical monitoring, and coordinated through unified institutional mechanisms. Without such reorientation, substantial investments in climate adaptation risk being misdirected toward interventions that fail to protect the most nationally significant production zones, undermining Kenya's food security in an era of accelerating climate change.