Reuters: Smog from forest fires, which costs Southeast Asian economies billions in lost tourist dollars, could worsen as changing weather patterns cause an unusually dry spell, the region’s environment ministers warned on Tuesday. The effects of the La Nina weather phenomenon are expected to wear off in the third quarter of 2008, which could result in arid conditions, the ministers said, quoting a forecast from the ASEAN Meteorological Centre. "This could lead to drier periods …