While the CRRF relates specifically to large refugee situations, population movements are not necessarily homogenous, and may be of a composite character. Some may be large movements involving both refugees and others on the move; other situations may involve refugees and internally displaced persons; and, in certain situations, external forced displacement may result from sudden-onset natural disasters and environmental degradation. These situations present complex challenges for affected States, which may seek support from the international community to address them. Support for appropriate responses could build on the operational partnerships between relevant actors, including UNHCR and the International Organization for Migration (IOM), engaging their respective mandates, roles and expertise as appropriate to ensure a coordinated approach.