There are multiple theories regarding how institutions change over time, but institutional change is often difficult to study and understand in practice. This is a theoretically driven agent-based model to explore two perspectives on institutional change, rational choice and cultural diffusion, in a rapidly changing social-ecological system in Chitwan, Nepal. The Chitwan region is urbanizing and facing a threat associated with the spread of an invasive plant, Mikania micrantha (Mikania). We focus on understanding how shared norms and strategies for Mikania management may change over time with each perspective of institutional change and the resulting impacts on the spread of Mikania. The model results are largely intuitive and consistent with previous studies. We find that rational choice is an unlikely candidate for institutional change in Chitwan and that the social learning and imitation mechanism modeled in the cultural diffusion perspective better replicates empirical patterns.