Any natural or human-induced factor that directly or indirectly causes a change to a given system.

Note: A direct driver is a driver that unequivocally influences ecosystem processes, such as climate change, and can therefore be identified and measured to differing degrees of accuracy.

An indirect driver is a driver that operates by altering the level or rate of change of one or more direct drivers. [Important indirect drivers include changes in population, economic activity, and technology, as well as socio-political and cultural factors.]