Commodity prices are headed higher over the long term, Jeremy Grantham says, and investors would be wise to make sure they are exposed to them — though not through futures contracts.

“Risks abound, as always, in commodity investing. Despite them, Grantham advises, you should start getting in, ‘but keep a lot of dry powder,'” reports Forbes’ William Baldwin. “If there’s a crash, double up. If there’s no crash, add gradually to your positions over the next decade.”

Grantham finds commodities futures contracts overpriced, however, but is finding value in timberland and commodity producer stocks.

One risk to commodities in the short term is China’s growth. Commodity demand has been so great from China in recent years that a significant slowdown there could have a big impact. “The smart people I know who saw the [world] financial collapse coming–there are several dozen of them — are neatly divided on China,” Grantham says. “But almost nobody believes that China won’t recover. Their growth won’t stay at 10% a year, but at 5% they would be doing brilliantly. Demand [for resources] in 2020 will be much higher than it is today.”