The rush of Wall Street dollars into green energy investments is a trend worth watching. But even more important is another trend that, in the near and medium term, could spell economic trouble: the under-investment in oil and gas production.

According to the Wall Street Journal, energy analysists think oil could reach $100 a barrel in the near term, reflecting economic rebounds at home and abroad. Typically, higher prices bring more supply online. But that may not happen this time:

…some analysts think production will struggle to catch up to demand, which the International Energy Agency projects will rise at least through 2026. Spending on oil extraction fell last year to about $330 billion, less than half the total from its 2014 record, according to research firm Wood Mackenzie. That figure is expected to rise just modestly this year and in the years ahead.

Leigh Goehring, managing partner at commodities-focused investment firm Goehring & Rozencwajg Associates, said he thinks prices will soar in coming years as consumption tops production capacity for a sustained period for the first time ever. His firm lifted its investments in energy producers during last year’s crash and has maintained those holdings.

“This is the basis for the next oil crisis,” he said. “We’re in uncharted territory.”

And we may remain so throughout the years-long transition between energy sources because despite the rhetoric, the internal combustion engine, and the oil powering them, is going to be with us for a very long time.