Long-term study reveals devastating loss of British flora

The results of a major new study have revealed a shocking statistic: non-native plants now outnumber their native counterparts in the British and Irish countryside.

Thousands of botanists from the Botanical Society of Britain and Ireland (BSBI) have spent two decades collecting data on changes in the British and Irish flora, with the results now published in the Plant Atlas 2020.

Non-native species outnumbering their native counterparts is likely to have "huge implications for insects and other species" that depend on our plants, BSBI said.

The results also revealed that more than half (53%) of native species have declined in Britain due to impacts such as agricultural intensification and climate change. There were also notable distribution changes linked to climate change. For example, many montane plants have declined, while warmth-loving species, such as Bee Orchid, have benefitted and spread north.

Many non-native species are benign, but some – such as New Zealand Pigmyweed and Sitka Spruce – have become invasive, disrupting ecosystem function and outcompeting native species.

Harebell is one of the many native plant species to have declined significantly in recent decades (Dr Kevin Walker).

Plant Atlas 2020 is the most in-depth survey of the British and Irish flora ever undertaken. It builds on two previous Atlas surveys undertaken by the BSBI in the 20th century. 

Julia Hanmer, BSBI Chief Executive, said: "Plant Atlas 2020 presents a powerful and concerning insight into the changing distributions of our wild plants. More than 30 million plant records of 3,445 species, collected by almost 9,000 botanists, fed into the Atlas project. The dedication and expertise of our recorders, combined with the in-depth knowledge of scientists at BSBI and BRC/UKCEH, provides a unique contribution to the evidence base needed to underpin nature recovery and highlights the urgent need for action to ensure that going forwards our wild plants thrive and are valued."

Many of the habitats our wild plants depend on have been impacted by changes in agriculture since the 1950s. Nitrogen enrichment, habitat degradation and changes in grazing pressure have led to the decline of species such as Heather and Harebell. Damp meadows have been drained, leading to substantial declines in species such as Devil's-bit Scabious. Traditional grasslands have been reseeded or over-fertilised, and consequently 62% of our ancient arable wildflowers, such as Corn Marigold, have declined.

Climate change is likely to be the primary cause of the declines of some mountain plants such as Alpine Lady-fern, Alpine Speedwell and Snow Pearlwort which depend on areas where the snow lies late in the spring and summer. Peatland habitats will be essential as we strive to combat climate change, but they are being impacted by species such as Sitka Spruce, which is able to regenerate into moorlands and peatlands, reducing their ability to sequester carbon. Sitka Spruce has shown the most significant increase in range of any species recorded for Plant Atlas 2020.

Sitka Spruce ably regenerates on moorland and peatland, reducing these habitats' ability to sequester carbon (Dr Kevin Walker).

Dr Kevin Walker, BSBI Head of Science and Plant Atlas 2020 co-author, commented: "There's lots we can do to reverse these declines, but the most important are to increase the protection plants receive, extend the habitat available to them, and to place their needs at the very heart of nature conservation5. We also need to ensure that our land, water and soil are managed more sustainably so that plants, and the species which rely upon them for food and shelter, can thrive. Plant Atlas 2020 provides the evidence we need to do this important work, but we'll need even more research and monitoring6 to help better conserve our wild plants and their vitally important habitats in the decades to come."

Craig Bennett, Chief Executive of The Wildlife Trusts, which helped fund the publication by Princeton University Press of Plant Atlas 2020, added: "The decline of our beautiful native plants is heart-breaking and has consequences for us all. The loss of natural habitats due to modern farming methods over the last 70 years has been an unmitigated disaster for wildflowers and all the species that depend on them including insects, bats and birds. But it's not too late to stop this catastrophe9. The Government's new farm environment schemes must do what was originally promised and reverse the decline of nature in our agricultural landscape. Also, protection for Local Wildlife Sites needs to be increased, and the promise made by the Government at the recent UN biodiversity summit to halve nutrient pollution by 2030 must be honoured."

Find out more at plantatlas2020.org.