The ancient flood meadows of Clifton Ings and Rawcliffe Meadows to the north of the City of York have been confirmed as a site of special scientific interest (SSSI) this week, following a four month consultation period.

The site supports rare species-rich grassland, is the last stronghold of the critically endangered tansy beetle (Chrysolina graminis) in the British Isles.

Floodplain meadows are one of the most diverse habitats in the UK. They are rich in flowers and grasses such as great burnet, meadowsweet, common bistort, meadow rue and meadow foxtail and are home to a great many insect species including butterflies, dragonflies, damselflies, spiders and moths.

The site at Clifton Ings and Rawcliffe Meadows is home to the critically endangered tansy beetle – an iridescent green beetle which relies almost entirely on the tansy plant Tanacetum vulgare for its entire life cycle in England. Noted at Clifton Ings since Victorian times, it is thought that a stretch of the River Ouse (which runs adjacent to the site) near York supports the last known population of this species in the British Isles.

Lowland grasslands are vulnerable to agricultural improvement and it is estimated that there has been a 97% decline in semi-natural grassland in England and Wales in the 50 years to 1984, with losses continuing during the 1980s and 1990s. Clifton Ings and Rawcliffe Meadows is an unusually large area of intact floodplain grassland that has avoided fragmentation or agricultural improvement. The continuation of traditional management over several hundred years, involving the harvesting of hay followed by the grazing of the aftermath growth, has maintained the biodiversity value of the site which now receives statutory protection.

The Ings also play a vital role in flood management and are used as temporary flood storage area at times of high flow in the River Ouse. With a capacity of 3.3 million cubic metres, Clifton Ings and Rawcliffe Meadows are critically important in preventing flooding in York and Rawcliffe.

David Shaw, area manager for Yorkshire and North Lincolnshire at Natural England said: "It is fantastic to confirm Clifton Ings and Rawcliffe Meadows as a SSSI as it protects a large area of rare habitats and species so close to the thriving city of York. We look forward to working with the Environment Agency and other interested parties to ensure this vital floodplain is managed appropriately to ensure its biodiversity is maintained and enhanced whilst utilising the site as a flood storage area when needed for flood prevention."

Steven Kirman, communications officer at the Environment Agency, said: "This is great news for the tansy beetle as well as many other important species of plants, birds, animals and insects. SSSI designations are a hugely successful way of helping to conserve natural habitats, and as well as helping wildlife they are of huge benefit to people in many ways. The maintenance of Clifton Ings and Rawcliffe Meadows is especially important to us because of the role the site plays in flood alleviation in the city of York."