3 Policies Regarding CONSERVATION of World Heritage Properties
3.3 Impact assessments
Conservation of cultural and natural heritage is at the core of the Convention. Conservation includes effective and active measures that can be taken by States Parties to ensure the identification, protection, presentation and transmission of heritage.
There is no single definition of conservation in relation to both cultural and natural heritage. However, with regards to cultural heritage ‘all operations designed to understand a property, know its history and meaning, ensure its material safeguard, and, if required, its restoration and enhancement’ could be part of its conservation (Nara Document on Authenticity). Conservation of natural heritage refers to the protection, care, management and maintenance of ecosystems, habitats, wildlife species and populations, within or outside of their natural environments, in order to safeguard the natural conditions for their long-term permanence (IUCN).
The Conservation theme includes policies related to protection, management, monitoring, impact assessments, factors affecting the properties, tourism and sustainable development.
Synthesis based on relevant Committee decisions
The World Heritage Committee requests the States Parties to provide, in accordance with Paragraph 172 of the Operational Guidelines, detailed information on the planning and design of proposed and on-going projects, which may impact on the visual integrity of the World Heritage property or its immediate and wider setting, and undertake a visual impact study, for review by the Advisory Bodies, prior to approval and implementation and before making any decisions that would be difficult to reverse (Based on Case law on decisions on the State of Conservation). 
 See for example Decisions , , , , , , , , , , , , .