An arborist report is a general assessment of tree health, condition, and management requirements, applicable across a wide range of purposes including council applications, property assessments, and risk management. An Arboricultural Impact Assessment (AIA) is a specific report type required for development applications where regulated or significant trees are present on or adjacent to a proposed site. AIAs quantify the impact of proposed works on tree root zones, calculate Tree Protection Zone (TPZ) and Structural Root Zone (SRZ) extents, and specify protection measures in accordance with AS 4970-2025.