Unsupervised low-light image enhancement presents the challenge of preserving both local texture details and global illumination consistency. Existing methods often rely on uniform, predefined strategies within fixed neighborhoods (e.g., fixed convolution kernels or average pooling), which are limited in their ability to adaptively capture the dynamic interdependencies between pixels during the enhancement process. As a result, these methods may lead to oversaturation or the loss of fine details. To address these issues, we introduce PASD, a novel pixel-adaptive adjustment approach inspired by swarm dynamics. PASD establishes inter-pixel cooperative constraints that adjust pixel intensities based on dynamic neighborhood interactions, thereby forming a population dynamics system for image enhancement that ensures a balance between local enhancement and global consistency. Furthermore, a distributed multi-agent reinforcement learning mechanism is employed to optimize the interactions within the dynamic system, while a multi-scale coordination framework ensures strategy consistency and stability. Experimental results demonstrate that PASD significantly outperforms existing state-of-the-art methods, providing a more flexible and efficient solution for low-light image enhancement.