VALLE DE CASABLANCA, Chile, Nov 23 (Reuters) - Well into their drive to make Chile's wines less about bang-for-your-buck and more about premium vino, vintners in the world's fourth largest wine exporter are watching some of their promising vines wither with climate change.
Nestled between the Pacific Ocean to the west and the Andes mountain range on the east, Chile's vineyards have thrived in a Mediterranean-type climate, where hot days meet cool nights and soothing breezes.
But with average temperatures rising and rains becoming more scarce, producers are being forced to employ new techniques, or even uproot their vineyards and move to cooler, wetter climes further south before grape quality suffers.
While the shift threatens Chile's step-up in the competitive wine world, it is also opening up large swathes of land to viticulture, in places that were once too cold and rainy to grow decent grapes.
Winemaking in this long, skinny spine of a country dates back to the arrival of the first conquistadores some four and a half centuries ago.
It wasn't until the early 1980s that producers like Spanish winemaker Miguel Torres introduced methods that have made Chile a respectable New World wine producer, its bottles a staple of supermarket shelves from the United States to Europe and China.
But if temperatures keep rising, maintaining current grape varieties and improving quality in Chile is going to become increasingly difficult, said Miguel Torres, president of the namesake company, which has some 400 hectares (988 acres) of vineyards in the country.
"You can continue to plant tomatoes, beans, etcetera, if temperatures rise, but not the grape varieties we have today," said Torres. "We must find other varieties that are more resistant to high temperatures and drought."
This predicament for one of Chile's most prized industries is emblematic of how a hotter world is forcing a deep rethinking of economics and livelihoods as nearly 200 nations meet in Paris this month to try to work out a global accord to slow climate change.
Chile made its mark as a reliable producer of cabernet sauvignon, although it might be most proud of its signature carmenere grape, an old French variety rediscovered 20 years ago after being thought extinct. It also produces large amounts of sauvignon blanc, chardonnay, merlot and syrah.
So far, it's been a success story as more people around the world drink wine, thanks in part to budding wine aficionados in China and among millennials. Chile's production has doubled in the last 15 years and exports are forecast to reach $3 billion by 2020, up from $1.8 billion currently.
Chile's cluster of northernmost wine valleys - such as the verdant Elqui, some 500 kilometers (311 miles) north of the capital Santiago - face the biggest risk. Together they represent around 12 percent of the country's total plantings.
Areas near Santiago are also likely to see big changes in coming years, said Julio Bastias, chief enologist at the vineyard Matetic in the Casablanca Valley, where they are banking on novel techniques as well as the Humboldt ocean current to provide cool sea breezes.
"The merlot won't be able to withstand the heat and it will have to be harvested earlier," Bastias said, adding "clearly there is a desertification process that is pushing agriculture south."
A one degree temperature increase moves harvesting forward on average by 10 days, growers say. That means "you may have high sugar content in the grapes but the maturity of tannin may be incomplete," said enologist Cristian Aliaga. Tannins give complexity to wine and are particularly important for reds.
Winemakers in the northernmost valleys, reeling from an eight-year drought, sometimes forego watering chunks of their vineyards, leaving grapes to wither under the pounding sun. And what little water is available at times has quality issues.
"We have more saline waters in some basins and that also creates problems because there is greater accumulation of salts in the soil ... resulting in salty wines," said Alvaro Gonzalez of winemaker Concha y Toro's recently opened research and development center, which is working on new water management techniques.
These issues can still be kept under control and the impact thus far on its wines has not been "important," Gonzalez said.
President Michelle Bachelet has put forward a multi-million dollar plan to build dozens of river dams up and down the nation to shore up water reserves for use in agriculture, industry and homes. Winemakers, meanwhile, are implementing more advanced irrigation techniques.
"They have to try out different varieties, explore new valleys and develop adequate management practices," said Patricio Parra, the head of industry group Vinos de Chile's research and development wing.
But that complicates life for winemakers just as they were focusing more energy on developing premium wines. It takes years for new vines to grow and to adequately train field workers, especially if they have had scant experience in viticulture.
Cash-flush producers, like Torres, are taking the initiative of buying land in southern Chile, where high rainfall and cold temperatures have traditionally made winemaking nearly impossible.
But meteorologists say rainfall has already dropped by 20 to 30 percent in the southern regions in the last 50 years, while temperatures have become milder.
Unlike in France or Spain, where there is little room to expand into cooler areas, Chile's producers can plumb the southern depths of the string-bean shaped nation.
Therein lies the opportunity afforded by climate change, said Chile's Agriculture Minister Carlos Furche, who sees a new wine frontier opening up down south, such as the forested Araucania region, an area more known for logging.
"There have been two or three relatively successful attempts at producing white wines," said Furche. (Editing by Rosalba O'Brien and Mary Milliken)