The battle to save the red squirrel will continue for many years
Red squirrels, whose future had been threatened by a killer virus, have doubled in numbers on Merseyside.
A successful breeding season has helped rejuvenate the blighted population, which had been wiped out in some areas.
Since 2006, the number of red squirrels has been decreasing in the Ainsdale and Crosby areas. In 2008, hundreds perished in Formby pinewoods.
The devastating disease, squirrel pox, is carried by grey squirrels and is lethal to the red squirrels.
The epidemic began in the urban area of Ainsdale and quickly spread to the Ainsdale National Nature Reserve, where it wiped out the entire red squirrel population.
Monitoring carried out by volunteers showed the red squirrel population had fallen by more than a third by March 2009 and their future was looking uncertain.
However, productive breeding over the summer has seen the numbers rise from between 100 to 200 in October 2008 to between 200 to 400 in October 2009.
It is hoped that if the same level of breeding continues then the healthy population of 2002, which was when the red squirrel population was at strength in the area, can be seen within five years.
Fiona Whitfield, the Lancashire Wildlife Trust's conservation officer, said: "This staggering recovery is testament to the hard work and enthusiasm that the Red Alert partners, volunteers and staff have put in.
"It is vital that we continue to commit to the recovery of the red squirrel in this area."
She did warn the battle to save the red squirrels continues and it is of "utmost importance" the grey squirrels are kept apart from the reds.
People are urged to report all sightings of both grey and red squirrels in the Sefton area to the Wildlife Trust.