He said the snails like very wet places in chalk areas – like those in south Wiltshire.
In the future, the trust wants to set up a captive breeding and release programme where it finds the right habitat for them.
Mr Stapleton-Goddard said changes in land use, with lots of river valleys being drained in the past, have led to a reduced population.
“The snails themselves are the base of the food chain. If you’ve got wetland and fenland supporting these snails then they’re going to be able support a lot more,” he added.