When nature-based solutions meet their limits: rethinking urban water resilience under climate extremes

Nature-based solutions (NbS) for urban stormwater management, including bioretention systems, constructed wetlands, green roofs, and permeable pavements, are increasingly promoted as climate adaptation tools that enhance water resilience while delivering ecological co-benefits. However, most NbS are designed and validated under historical or moderate climate conditions, raising a critical question: will these systems perform reliably under the compound climate extremes they are ultimately intended to buffer? This Perspective argues that climate change is producing unprecedented combinations of stressors, including prolonged droughts followed by high-intensity rainfall, consecutive heatwaves, and shifting precipitation seasonality, that may push NbS beyond their functional thresholds. I identify three underappreciated vulnerability pathways: (1) hydrological failure under compound drought-deluge sequences, where soil cracking and hydrophobicity bypass infiltration capacity; (2) microbial community collapse, where heat and desiccation degrade the biological processes essential for pollutant removal; and (3) design obsolescence, where NbS engineered to historical rainfall statistics are structurally inadequate for projected extremes. I propose a tiered resilience framework that integrates hybrid grey-green infrastructure, real-time adaptive management, microbial health monitoring, and climate-forward design standards. Without confronting the operational limits of NbS, cities risk an “adaptation illusion”: investing in green infrastructure that fails precisely when it is most needed.