Ash dieback: Field trial puts DNA to the test
20 November 2012 Last updated at 00:21 GMT
Europe's leading experts on ash dieback disease are warning that at least 95% of Britain's ash woodland will eventually fall victim to the fungal infection.
Scientists in Denmark - who have been studying the disease since it was first discovered in the country 10 years ago - say there is no known way to stop the spread.
But they say the few remaining ash trees - which appear to show natural immunity - could hold the key to replacing the millions which are likely to be lost.
The BBC's rural affairs correspondent Jeremy Cooke visited a University of Copenhagen field trial in Denmark which is trying to identify which genetic strains of ash tree prosper best in the wild.