What criteria require to be met prior to any proposed loss of green space in urban areas being referred to the Executive.

The extent of any Executive involvement in such matters will depend on issues such as the nature of the project leading to the loss of such space, any formal designation on the site and the particular consent procedures involved.
To take the planning system as an example, planning procedures do not contain a specific requirement for planning authorities to notify the Executive of planning applications involving loss of green space in urban areas.
However, there are a number of categories of proposal where notification of the Scottish ministers is required, and within which applications for development of such open space might fall. For example, applications for development on playing fields where sportscotland have advised against granting planning permission or applications where development is contrary to an approved structure plan because the land involved is designated green belt.
Details of these notification requirements are contained in the Town and Country Planning (Notification of Applications) (Scotland) Direction 1997, as amended. A copy of this direction is contained in Circular 4/1997: Notificationof Applications, which is available in the Parliament’s Reference Centre (Bib. number 33972).
Details of some of the amendments to the 1997 Direction which may be of interest in this context can be found in:
Circular 43/1997: The Town and Country Planning (Notification of Applications) (Scotland) Amendment Direction 1997 (Bib.number 33973)
Circular 15/1998: The Town and Country Planning (Notification of Applications) (Scotland) Amendment Direction 1998 (Bib. number 33974)
Notification of a planning application to the Scottish ministers allows them to consider whether or not the application should be called-in for their determination.