Over the past five decades, OPEC has earned a reputation for being a powerful cartel that controls the world's oil production and prices - but there are limits to OPEC's influence and wealth. In fact, many OPEC countries face grave problems, which are to some extent the result of their oil-income dependence. EARTH examines OPEC's past, current and future place in this world. Will OPEC continue to control the planet's oil for the next 50 years?