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.
References: The response is based on the principles of resource management as described in the PMBOK guide, which includes processes for planning resource management, estimating activity resources, acquiring resources, developing the team, managing the team, and controlling resources1. Additionally, the importance of the resource management plan is highlighted as it serves as a guideline, roadmap, and reference for project managers to allocate, manage, and control the resources required to complete the project work2.