In reality migration decisions are complex, and choices are rarely made without constraint. For instance, when livelihoods are threatened by slow-onset events such as climate change and environmental degradation, the distinction between forced and voluntary migration may not be clear-cut. The term "survival migration" has sometimes been used to refer to migration induced by conditions of extreme economic difficulties. The important point is that in reality, migration decisions are complex and depend on multiple factors. They are best viewed as lying along a spectrum in which elements of choice and coercion intermingle and can be more or less predominant depending on circumstances and context. Totally forced migration generally occurs in the form of displacement (often over short distances) in response to direct threats to life caused by natural or human-made disasters or by armed conflicts.