William Blake saw heaven in a wild flower at the turn of the 19th century. But the poet-painter would not find the same flora in Britain today. The culprit is progress, the ills of which Blake vividly recounted. A healthier, wealthier society has emerged, but so has pollution, creeping conurbations and intensive farming. These threats have irrevocably changed the habitat for plants and the shifting composition of verdancy is seen in the botanical map of Britain in a 910-page New Atlas of the British and Irish Flora.

Remarkably, the carpet of wild flowers that once lay on Britain's floor is not so much being worn away as replaced. Despite meadows being ploughed and hedgerows cut down, only 10 species, like purple spurge and stinking hawk's-beard, have vanished since 1930. More worryingly, once-commonplace blooms such as pennyroyal are only to be found in protected sites. But for every loser there is a winner. The countryside is increasingly populated by pendulous sedge, wild leek and syringa. The reason for one flower's success, paradoxically, is often why another fails. Pollutants and fertilisers share nitrogen. This encourages nettles, docks, big rank grass at the expense of orchids and shortgrass downland plants that do best in poor soils. Britain's gardening obsession has also introduced new plants from far away such as buddleia - the butterfly bush - and laburnum. It will not be long before pampas grass, favoured by green-fingered townies, invades rural areas.

While Blake reminds us of past glories, the new atlas is a snapshot of the countryside today. Climate change means bigger changes in future. Safeguarding the nation's flora and fauna will not necessarily entail sacrifice but will mean changing how we build, farm and move around. The right outcome would ensure Britain is making an effort to retain wild flowers such as common fiddleneck, blue-eyed mary and autumn lady's tresses - the loss of which would harm language and landscape.