About 97% of flower-rich meadows have been lost over the past 50 years, Mr Warren added.
Butterfly Conservation and the Centre for Ecology are calling for reforms in the countryside to protect butterflies after a joint survey suggested some of the nation's traditional species were in danger of collapse.
There are serious concerns for the status of the high brown fritillary, the wood white, the pearl-bordered fritillary and the marsh fritillary.
Changes in farming methods and woodland management have destroyed habitats vital for the butterflies' breeding, said Martin Warren of Butterfly Conservation.
The last 100 years have shown a massive change in butterfly species, he said.
"Over half of our resident species have declined quite substantially and five have become extinct," Mr Warren told BBC Radio 4's Today programme.
Ploughed fields
Ploughing of unfertilised meadows and the use of herbicide and fertiliser has wiped out wild flowers which are popular with the insects, he said.
About 97% of flower-rich meadows have been lost over the past 50 years, Mr Warren added.
Butterfly recorder Douglas Goddard, of Butterfly Conservation and the Wildlife Trusts, said the species most at threat were ones that required special habitats.
"We've got some species for which we have very serious cause for concern like the high brown fritillary and the silver-spotted skipper which are down to a small number of colonies," he said.
Move north
Mr Douglas said corridors were needed to enable butterflies to spread to more suitable areas. But it is not all bad news for butterfly spotters.
The survey shows that about 15 species of butterfly, including the Essex skipper and the brown argus, are spreading northwards, due to the warmer climate.
"Butterfly Conservation is determined to do what it can and make this century better than the last one," said Mr Warren.
"We will need the co-operation of conservation bodies but also some big reforms in agriculture and forestry to encourage much more sympathetic and environmentally sensitive management."