Global sourcing ??? - Purchasing function or SCM responsibility

Global sourcing activity is on the rise across the world admist challenges of fluctuating currencies, rising input cost, difficult transportation and supplier management. However the question remains if global sourcing is an activity of just the Purchasing function or is it more SCM ????

If it is considered as a purchasing activity how are these issues addressed?

1. When the companies move from a transaction cost & cost competitiveness based sourcing to value based global sourcing - Can this be handled just by the Purchasing function?
2. When shorter product life cycles are coupled with market volatality - the longer leadtimes in global sourcing is a hinderance for responsiveness - Can purchasing function alone increase the responsivness or is it a Supply Chain problem?
3. The hidden cost of global sourcing are enormous like lost opportunity cost, logistics & transportation issues - Can these costs be evaluated just by the purchasing function in global sourcing decisions?
4. When you involve new actors like TPL companies o take care of the coordination - you change the supply chain structure affecting the organisation of activities and processes in the supply chain - Can purchasing function alone tke responsibility for this.

It is evident that the responsibility of the purchasing function is at the highest in the initial stages of global sourcing. But to have sustainable global sourcing with a longer time frame it needs integration through coordination across different functions and also to the external supply chain. Global sourcing is considered strategic for a company and decisions in terms of targets are taken by the top management. However process of global sourcing seems to be typically run by the purchasing function with perfomance monitoring from the top management. The question is for sustainable global sourcing it needs a move from top management monitoring to top management involvement along with other function to take a supply chain approach rather than a purchasing function approach.