The Little Ice Age spelt the death knell of northern viticulture. The vine disappeared from northern Germany and Baden, and the maximum altitude for viticulture descended to 220 metres. Hans-Jürgen Otto noted that: "all the vineyards suffered and decreased in area".Forest Ecology, Hans-Jürgen Otto and Matthis Kempf, 1 December 1998, Google Books, Institut forestier pour le développement, , page 54, consulted on 4 June 2010 In EnglandThe "bubbly", the equal of champagne, Marco Evers, 3 December 2009, consulted on 4 June 2010 the vine also disappeared. The less early vineyards preferred to select white varieties of grapes because, even if unripe, white grapes allowed wine that was a little sour to still be consumable, while red grapes do not give enough colour and green tannins make the wine bitter. The interruption of the fermentation by a cold winter led to the discovery of the process of secondary fermentation of champagne.The Sparkling mysteries of champagne, Mathieu Perreault, 31 December 2009, cyberpresse.ca, on line 31 December 2009, consulted on 4 June 2010
