High altitude wines

There is a lot of talk about high altitude wines. Does it really matter? The short answer is yes but don´t get dragged into believing that “higher is better” or much of the rest of the hype.

Let´s start with the definition. CERVIM (Centre for research, environmental sustainability and advancement of mountain viticulture) defines high-altitude wine as wine produced from vineyards above 500 m ASL (Above Sea Level), on minimum 30% slopes and terraced/embanked vineyards.

The reason why these wines are different is because:

1. Temperature drops. The greater the height, the more the average temperature drops, and this means potentially lower alcohol and higher acidity, both increasingly sought after for fresher, lighter wines. The diurnal changes in temperature (difference between day and night levels) are greater, slowing down the grapes ripening process, which in turn increases the flavour compounds in the skin and preserving the acidity. The freshness can also be increased by wind chill in a vineyard on a mountain slope (not essential for high altitude, but often the case).

2. Drainage. Mountain slopes often have rocky soils which whisk rainfall way from grape routs, forcing the vine to grow deeper. These low-yielding vies give each surviving berry more character and higher quality. It also brings out notes of minerality.

3. Intense sunlight. The vines are subject to intense, direct and concentrated sunlight, especially UV-B radiation. This gives grapes more antioxidants and thicker skins, equating to more colour, tannin and flavour intensity in reds, and longer aging ability too – all desirable attributes.

4. Increasing average temperatures. Climate change has made climate more unpredictable. Furthermore, the world’s traditional grape growing areas are warming giving higher sugar and lower acidity levels in the grapes leading to unbalanced, over-alcoholic wines. Moving the vineyards higher up leads to longer growing seasons and higher acidities in the grapes.

The altitude of a vineyard on its own does not mean much unless the latitude is indicated as well. Latitude is important because the close to the equator, generally the hotter it is, hence both the permanent snow line and the tree line are higher. For example, in Europe 500 m is high because there is year-round snow above 2800 m (wine growing latitudes are around 40-50o North) and very few vineyards reach even 1000m. While in South America most vineyards are at 1,500 m or more because they are much closer to the equator at latitudes 25-30o South with the snow line well above 4,500 m.

So, what is the ideal altitude? Professor Hans Schulz, president of Hochschule Geisenheim University, links the two parameters altitude and latitude in the following manner:  “Sea level is the reference for altitude, but it should be the baseline temperature at sea level for grape growing. In the Northern Hemisphere, between April and October you need a baseline temperature, average minimum 12°C. In Germany, at 15°C, you can lose 0.8°C per 100m, so 400 m above sea level would be 11.8°C. Therefore 400m ASL is close to the limit for an area such as Rheingau. In northern Italy, where the April to October average temperature is 17-18°C, you can grow grapes at 600-800m altitude.”

High altitude ASL for any given region becomes the limit of being able to grow and ripen grapes. Any higher and the average growing season temperature becomes so low that cultivation is not possible. Some other considerations of high altitude wines:

  • Temperature decreases by about 0.6°C to 0.8°C (depending on latitude) per 100m increase in ASL
  • Diurnal temperature range increases with higher altitude ASL. Lower night time temperature reduces respiration rate, particularly of malic acid, of grapes.
  • UV radiation increases with increasing altitude ASL. Increased photosynthesis: thicker skins, more anthocyanins and polymerised tannins.
  • Growing seasons shorten between 2 and 4 days per ~100m increase in altitude ASL. Vine growth can still be strong because of greater UV and higher diurnal temperature range
  • CO2 uptake is lower at higher altitude ASL, which limits photosynthesis. Vine growth may be stunted.
  • Risks such as frost, hail, winter hardiness, winds and higher production costs increase with higher altitude ASL.
  • Prevailing winds can also affect temperature and humidity.

The combination of low soil nutrients, larger temperature variation, and fierce sunlight alter the growing season, giving high altitude vineyards a later spring bloom and earlier harvest period. By adapting and differentiating with darker skins, incredible structure, and bright acid, their fruit forms the basis for wines that fantastically express their individual terroir. The obstacles elevation creates for agriculture forces these grapevines not to work harder, but to work smarter.

The rewards are a terrific freshness for reds and whites, together with a delicacy of floral and fruit characters along with an intensity of flavour, deep colours and big tannins for certain reds.

References

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