GHOST participation is by voluntary association. Participating organizations determine the tier(s) at which they choose to operate, and would commit themselves to:
providing all of the applicable variables at that tier within one of the hierarchies (terrestrial, freshwater or cryosphere);
accepting the other responsibilities associated with the tier.
At the central level, international and national support will be coordinated to ensure at least one tier 3 site per country, to provide national contact points. Where central resources are involved, major unsampled systems would take precedence over systems already represented. Once all major systems are represented, sample intensity proportional to the area (or volume) involved will be the guiding criterion. All else being equal, a long-term record, ease of access, and the presence of equal active research at the location are advantages.
