The highest point in one of the world\u2019s foremost wine regions is just 131 feet above sea level. That is Listrac, in Bordeaux, France. Most of the region\u2019s famed vineyards lie far lower, from 33\u201366 feet.\r\n\r\nYet, wines grown at high altitudes always tout their superlative elevations. What difference does altitude make to a wine? Depending on location and climate, altitude has outcomes that can be decisive when it comes to wine style. Temperature and its variation, solar radiation and intensity, ventilation and drainage all come into play, and that\u2019s before you consider fog lines or climate change.\r\n\r\n\r\nLow-lying wine regions\r\nM\u00e9doc, also known as the Left Bank of Bordeaux, is one of the lowest-lying wine regions in the world. This enabled grapes like Cabernet Sauvignon and Merlot to ripen in a marginal climate for these varieties before climate change. Higher altitudes would have been too cool, and even low-lying vineyards often struggled to ripen grapes fully.\r\n\r\nFurther north on France\u2019s Atlantic coast, the vineyards around Nantes that produce light-bodied Muscadet rarely exceed 150 feet in elevation. The very cool vineyards in southern England barely rise above 320 feet, and those that do struggle with ripeness.\r\n\r\nVineyards in high latitudes and coastal regions that are marginal for their respective grape varieties tend to benefit from warmer, lower-lying land. This goes for a wide range of wines, from the light-bodied sparkling wines of England to the structured, ageworthy reds in the M\u00e9doc.\r\n\r\n\r\nExploiting differences\r\nIn most classic wine regions, like Napa Valley, California; Chianti, Italy; or Germany\u2019s Saar Valley, the differences in altitude between valley floor, hillsides and ridges can be marked.\r\n\r\nWinemakers exploit these differences for certain wine styles. Napa vineyards range from 200 feet to 2,200 feet above sea level, which allows producers to pursue different styles.\r\n\r\n\u201cFrom the soils, to the movement of air on the mountains, the angle and access to the sun, we deal with a very different environment on the mountains than on the valley floor,\u201d says Chris Carpenter, winemaker for Jackson Family Wines brands Cardinale, La Jota, Lokoya and Mt. Brave in Napa Valley. \u201cThe [mountain] grapes tend to have greater concentration of phenolics, higher natural acidity and a structural component that is unrivaled. The wines have incredible weight and texture, a lifting acidity and a backbone of structure.\u201d\r\n\r\nFlorian Lauer, of Weingut Peter Lauer in Germany\u2019s Saar Valley, farms the Ayler Kupp vineyard that rises from 490 feet to 790 feet. The difference in elevation has various effects.\r\n\r\n\u201cAir streams have more friction at the [base], but it is windier and slightly cooler at the top,\u201d says Lauer. His sweet wine styles are influenced by botrytis (noble rot), and less ventilation makes the lower hillside prone to the fungus. This allows Lauer to pick at the desired level of botrytis infection.\r\n\r\nSince cold air flows down, the lower parts of the vineyard are at greater risk of spring frost. The ridge, meanwhile, never freezes. Diminished water at the top, facilitated by natural drainage, also means less mineralization in the wines. It results in a lower pH level, which makes the wines \u201cfiner and more elegant,\u201d according to Lauer. Fruit grown lower down is slightly riper and makes wines which are \u201crounder and more melting.\u201d\r\n\r\n\r\nThe shifting magic of the mid-slope\r\nThe vineyards of Burgundy\u2019s C\u00f4te d\u2019Or, generally rise between 755 feet and 1,300 feet above sea level. Traditionally, the best vineyards were considered to be on the well drained mid-slope, an area elevated enough to catch most of the sunlight and be protected from frost, but not too high, windy or exposed. Most Grands Crus lie mid-slope.\r\n\r\nThis is also true in many other classic regions. However, climate change has begun to shift the emphasis. As global temperatures rise, growers look to greater altitudes to achieve classic styles.\r\n\r\n\r\n\r\nMarcello Lunelli, vice president of Ferrari, in Trentino, Italy, grows grapes that produce bracing, vivid sparkling wine in the Italian Dolomites at from 1,300 feet to 2,600 feet.\r\n\r\n\u201cAltitude is the most important factor because we need the right acidity for the long maturation of our wines,\u201d he says.\r\n\r\n\r\nDefining altitudes\r\nSome American Viticultural Areas (AVAs) in California also define themselves by their altitude. Here, elevation is crucial because it corresponds to the fog line.\r\n\r\nOn the Sonoma coast, Fort Ross-Seaview AVA stipulates elevations from 920 feet to 1,800 feet or higher. This allows the grapes, grown in close proximity to the cold Pacific Ocean, to get enough sunlight to ripen in the cool climate. They bring forth pristine, red-fruited Pinot Noirs and Chardonnays with real tension.\r\n\r\nSome vineyards, outside the AVA and just within the fog line, make wines even more nervy, bright and taut. The Mendocino Ridge AVA requires elevation of at least 1,200 feet, and its highest vineyards can even ripen distinctive Zinfandels.\r\n\r\n\r\nHigh altitude vineyards\r\nHigh altitude means lower temperatures and more ventilation, which slows ripening and preserves acidity.\r\n\r\nIn Europe, elevations above 1,650 feet are considered high. Austria\u2019s Steiermark, France\u2019s Savoie and Italy\u2019s Valle d\u2019Aosta are all known for fresh wines that are slender yet expressive.\r\n\r\nThe world\u2019s highest vineyards are in South America. Bodega Colom\u00e9\u2019s Altura Maxima vineyard rises from 9,500 feet to 10,200 feet. Winemaker Thibaut Delmotte warns of the \u201cextreme conditions\u201d at this altitude. Due to frost in spring and fall, the growing season is short, says Delmotte.\r\n\r\n\u201cIt would be impossible to ripen varieties like Cabernet Sauvignon or Petit Verdot,\u201d he says. For earlier-ripening varieties like Malbec, he says the benefits outweigh the problems.\r\n\r\n\u201cWe have ozone in the atmosphere and therefore, more UV radiation,\u201d says Delmotte. \u201cThe fruit has to protect itself from this high radiation, producing thicker and darker skin. So the wines have darker, deeper color and great tannic structure.\r\n\r\n\u201cThe extreme conditions produce high-quality fruit and give us a great paradox: very dark and concentrated wine, but elegant, fresh and harmonious at the same time,\u201d he says.\r\n\r\nAltitude, just one of numerous viticultural aspects, means different things in different climates. It\u2019s a key element in site selection, and it has a direct impact on wine styles, ripeness, freshness and the development of flavor.\r\n\r\nAs the world of wine expands, the low-lying slopes of southern Sweden can be as compelling as the Himalayan heights of Bhutan.