I don't see any particular reason to believe that Lester's suddenly got his sh*t together after a 30 year losing streak ;) Ah, well. Even a broken clock is right a couple times per day, right? But you make a good point - such predictions have indeed been going on for a long time, and they've always been wrong.
You have to keep in mind where old Lester is coming from here. Famine is really a symptom of the real problem, overpopulation, as Lester sees it. In particular, Lester's very concerned with the overpopulation of all those brown and yellow people, if you catch my drift. And so the ultimate solution, as far as he's concerned, is population control - Lester thinks that China's one-child policy, and all that it entails, is just swell, for example.
I'm wary of Brown for two reasons - one, he's been wrong for thirty years running, as I've noted. But, two, I'm wary because his preferred solution is more or less to fly cropdusters carrying Ortho-Novum over Africa and Asia.... ;)