(AFP) - Can the world's most storied wine region adapt to climate change without losing its identity? This is the question haunting the Bordeaux region as the threat of global warming looms ever larger.

Concretely, it may boil down to this: Without Merlot, will it still be Bordeaux?

The dry, hot conditions that shaped the 2015 vintage, and are likely to prevail in coming years, "don't worry winemakers for now because the early harvests improve quality," said Bernard Farges, president of the Interprofessional Committee for Bordeaux Wines.

At the same time, they know that the most sun-sensitive grape varietals -- especially Merlot, by far the most planted in the region -- are headed for trouble.

"Within 20 or 30 years, Merlot will probably ripen in August, and that will clearly compromise the quality of the wines because they will lack freshness and have too much alcohol," said Kees van Leeuwen, a researcher at the National School for Agricultural Sciences.

And so Bordeaux winegrowers have turned to science to help them find ways to once again extend the maturation of this signature red grape -- as well as others -- into the crisp autumn nights.

The first counter-attacks against a warming climate are growing more bunches per vine, and partially shading the grapes from the sun.

A next step will be to identify and plant rootstocks -- the live root structure and trunk to which different varietals can be grafted -- that can better withstand warmer temperatures.

Both of these measures are uncontroversial and would buy winegrowers time. But eventually they would face tougher choices about how much of which grapes to use.

And this could subtly alter the signature aromas that have defined Bordeaux wines -- almost all of which are assembled from more than one varietal -- over the centuries.

- New grape varieties -

The region's prestige wines -- Margaux, Saint Emilion, Pomerol in red, for example, or Sauternes in white -- must be made of certain grapes in specific proportions to have the right to display their famous names.

Climate change may force a revision of these rules.

The Cabernet Sauvignon grape, which "corresponds well to the typical Bordeaux flavour," thrives under hot conditions, said van Leeuwen. "We need to plant more."

Petit Verdot, another grape that naturally matures late, is also present in Bordeaux, though currently only covers about one percent of vineyards.

In a few decades, it may no longer have such a marginal status.