When faced with a decline in resource availability, the first action a project manager should take is to refer to the project’s resource management plan. This plan outlines the approach for how resources will be identified, acquired, and managed throughout the project. It provides guidance on how to address resource shortages and includes strategies for alternative solutions. By consulting the resource management plan, the project manager can assess the impact of the declined resources on the project schedule and scope, and determine the best course of action to reallocate resources or adjust project plans accordingly.