(Wine-Searcher) - A new report shows the increasing "internationalization" of the world's vineyards at the beginning of this century.

The global vineyard is shrinking and so is the choice of wines as available grape varieties become more homogenous, according to a new study.

The report in the Journal of Wine Economics compared vineyard area and the diversity of grape varieties planted throughout the decade 2000-2010 and found that both were getting smaller.

The study, which claims to cover 99 percent of global wine production, showed that the world's vineyards have shrunk by almost 6 percent in the first decade of the century, despite hefty increases in plantings in United States (up 30 percent), Czech Republic (up 40 percent) and New Zealand, which more than doubled its vineyard area.

Those increases were offset by declines in countries with large vineyard areas like Spain (down 13 percent) and Portugal (down 20 percent). Reliable information for the year 2000 was not available for vineyard areas in some countries, such as China.  

Within the vineyard, red grape plantings increased strongly, accounting for 56 percent of all plantings, and up from 49 percent in 2000, although the dominance of red grapes varied wildly from country to country. In 2010 China's vineyards contained 96 percent red grapes, while red varieties made up just 24 percent of New Zealand plantings.

The increasing focus on just a few grape varieties was marked. Cabernet Sauvignon and Merlot increased in popularity during the decade to be the two most-planted grape varieties, while Tempranillo plantings more than doubled. Chardonnay continued to boom, as did Syrah, Sauvignon Blanc and Pinot Noir. The big loser was the Spanish workhorse Airén, plantings of which fell by a third over the decade.

The research also found that, while popular varieties had become even more popular, there was increasing similarity in the world’s vineyards, with the major wine-producing nations becoming more homogeneous. In France researchers found 285 main varieties across the country's vineyards in 2000. By 2010, that number had fallen to 96.