ISIL's Libya bastion is a problem for Africa and Europe just to the north.
In addition, the bastion could be a fall-back position if the main front in Syria and Iraq collapses:
“Libya is the affiliate that we’re most worried about,” Patrick Prior, the Defense Intelligence Agency’s top counterterrorism analyst, said at a recent security conference in Washington. “It’s the hub from which they project across all of North Africa.”
The leadership of the Islamic State, also known as ISIS or ISIL, is now clenching its grip on Sirte so tightly that Western intelligence agencies say they fear the core group may be preparing to fall back to Libya as an alternative base if necessary, a haven where its jihadis could continue to fight even if it was ousted from its original territories.
Like I've been saying since the Paris massacre when France indicated it finally felt at war, France should take the lead to destroy the Libya portion of ISIL.
Success there would provide a lot of advantages to the war on terror in addition to adding glory to France by being their front rather than being a slightly larger force in the coalition of scores who do nothing in the fight against ISIL in Iraq and Syria but who get their name on the credits.
And it is really just finishing the job that France was eager to start back in 2011.