In France, this winter's harvest comprised 20 tonnes of best quality black truffles -- half of what had been predicted.

"The bad harvest years, which used to be the exception, are becoming the norm," said Jean-Charles Savignac, President of the Federation Francaise des Trufficulteurs (FFT).

Prolonged droughts in France, Italy, and Spain -- the main truffle producing countries -- are devastating as the truffle cannot go more than three weeks without water.

Rising temperatures are also blamed for the drop in yields -- a situation that has pushed the prices up for truffles on the open market.

One kilo of black truffles can fetch as much as €1,000 (£794), three times the cost at the end of the 1990s.

Whilst high prices can be lucrative for producers, they are concerned about an uncertain future for their crops.

"There are a lot of plantations coming to maturity, but at the moment we cannot say what the future will hold for truffle production," said Jean-Pierre Audivert, President of the Departmental Federation of Perigord Truffle Producers.

Wholesalers are now trying to meet some of the shortfall by importing inferior truffles from China.

They may be similar in appearance to Europe's black truffle and cost a fraction of the price, but they are lacking in flavour -- the FFT has called on the European Union to ban imports.

Producers see their salvation in finding new ways to adapt to the weather and increase yields.

Researchers are now investigating ways in which truffles can be better protected from drought and frost.

"The idea is not to suffer, but to understand in order to react," said Jean-Marc Olivier, Director of Research at the French National Institute for Agronomical Research

"The production zones of the Mediterranean plain are on the frontline and will face further difficulties if we do not adapt."