Energy-sector commodities like natural gas and oil are going to rise in price, and will sweeten as investment opportunities even further as the global economy improves, says economist Marc Faber.

Emerging-market countries like China and India will continue to demand more commodities to feed their growing economies.

Weaker paper currencies also make commodities like gold good investments.

But oil, natural gas and other energy-stocks have room to grow in emerging markets as well as in the industrialized world, says Faber, publisher of The Gloom, Boom and Doom report.

Should the world slip into another slew of recessions, geo-political tensions would arise resulting in oil-supply cuts.

Either way, prices rise.

"The demand for oil will go up and drive up prices," says Faber, according to CNBC.

Oil prices recently hit $90 a barrel, their highest levels in two years, and should continue climbing along with other commodities including copper, gold, corn and soybeans, says global financial institution Morgan Stanley.

"Growing demand, together with a tightening supply side, provides the fodder for our broad constructiveness across the commodities space,” says Morgan Stanley analyst Hussein Allidina, according to Bloomberg.

“Declining inventories will not only lift spot prices, but will also improve roll returns” as falling stockpiles move prices into so-called backwardation, when nearby commodities trade above longer-term contracts, he said.