Tourism is an optimistic industry by nature.

But as 2008 unfolds, businesses tied to hospitality and travel have fewer reasons to have high expectations. The consequences of the economic downturn can't help but spill over into travel plans. Right now, though, forecasting the impact is a moving target.

A few months ago, the state's tourism forecasting center was expecting little growth this year for the largest single sector of Maine's economy.

It wasn't a doom and gloom forecast, but Charles Colgan, associate director at Maine's Center for Tourism Research and Outreach, said the sour national economy just doesn't have the ingredients to give a boost to tourism spending.

One key indicator is lodging. Overnight guests leave behind the most money, and spending at hotels and inns grew by only a couple of percentage points in 2007, Colgan said. This year seemed to be shaping up flat.

But Colgan became even less optimistic in January. He issued an economic forecast that saw an increased likelihood of a recession. And he has been wondering if the slight overall growth he had been projecting for tourism revenue could end up with a loss.

The national picture may be somewhat better.

The U.S. travel industry is expected to post moderate gains in 2008, according to the annual Travel Industry Association forecast.

Travel spending by domestic and international visitors is forecast to increase 5.2 percent, to $778.2 billion. Domestic leisure trips -- the segment most important to Maine -- are expected to continue a modest upward trend, climbing 2 percent.

Maine could benefit if this forecast is accurate.

Northbound traffic counts on the Maine Turnpike give a clue about the tourism economy since the majority of visitors from the Northeast arrive by car. Colgan's projections have been calling for some year-round growth, as well as growth in the crucial summer season. The reason: Long-range forecasts show gasoline prices falling, and when the economy is bad, people tend to vacation closer to home. If that price decrease materializes, it could give Maine-bound drivers some relief by summer.

There are other bright spots.

The weak American dollar has made Maine a bargain holiday spot for Canadians. They mobbed Old Orchard Beach last year, just like old times. And bus loads of Canadian shoppers have become a common sight around the Bangor Mall and Aroostook Centre Mall in Presque Isle. They've even been spotted at the Maine Mall in South Portland.

Also helpful this past year was the weather. Summer was sunny, and autumn was warm. Early snow had snowmobiles on the trails and skiers on the slopes before Christmas.

Good weather this summer could make or break some businesses.