Prominent oil industry executives said that demand for energy in the long term will rise and urged investors to invest money into the industry.

The statements were made despite of the current economic downturn that has dropped crude oil's value. Prices closed at $33.97 a barrel on the New York Mercantile Exchange Thursday. Oil has shed over $110 since it reached a record high of $147 a barrel in July 2008.

The challenge for all of us is to not allow this cyclical fall to pitch us into a structural loss in capacity, said BP chief executive Tony Hayward this week in a speech at the CERAweek energy conference in Houston.

We must continue to invest in technology to achieve greater energy efficiency across the board and to bring new sources of energy to market, Hayward added.

Presenting figures, Hayward said energy producers must invest more than 1 trillion dollars every year, in order to meet future global energy demand. He also said BP expected to invest an average of $6 billion a year in the United States over the next ten years.

Hayward's counterpart at Royal Dutch Shell, Jeroen van der Veer, also raised a the concern.

To invest or not to invest . . . that's the question, he said at conference.

I believe that continued investment - within reason - is in the best interest of our industry, and in the best interest of the world as a whole, Van der Veer said, clarifying that a considerable part of that within reason depended on government policies: consistent tax regimes, faster permitting and a hard CO2 price.

He advised that by the time the global economy recovers, the industry should stave off a supply crunch of hydrocarbons.

In the same way, BP CEO addressed that the industry must support the development of hydrocarbon resources in the US and around the world.

Even with the rapid growth of biofuels, solar and wind -- fossil fuels will continue to provide most of the energy we consume for the foreseeable future, Hayward added.