The Rainforest on Amersham’s Doorstep

The article “The rainforest on Amersham’s doorstep” by Marieke Bosman was written for the Society’s January 2022 Newsletter and underscores the importance of our local habitat.

Marieke is an Old Amersham resident who is passionate about wildflowers and their protection and enjoyment. Her wildflower art is @mrsbloem on Instagram.

Chalk grassland flora at Hartslock BBOWT reserve © Marieke Bosman
Chalk grassland flora at Hartslock BBOWT reserve © Marieke Bosman


Do you ever wonder why your Amersham garden seems to produce more flint than flowers? Have you noticed that footpaths in our area go white in summer? And why are there wild orchids in Amersham? There’s a simple answer to all of these questions. It’s a tale about geology, wildlife and humanity creating one of the most precious natural habitats in the world – right here on your doorstep.

Between 65 and 100 million years ago, warm tropical seas covered the area we live in today. Marine algae with calcite shells left a thick chalk sediment which, over time, developed into chalk rock in which other creatures became embedded and turned to flint. As seas retreated, weathering of this rock mixed with organic material to form soil on the rock surface. While in some places the soil was thick and stayed in place, on slopes and in river valleys only a thin layer managed to stick to the chalk, in which trees struggled to take root. Stone Age farmers arriving from 4,500 BCE used flint tools to fell these trees for dwellings and firewood and grazed their livestock on the cleared areas. Over time, farmers realised the chalky Chiltern slopes were not very productive: the lime-rich soil was too thin, warmed up too quickly, and rain and nutrients leached away into the porous rock below, making it too dry in summer. Much of this calcareous lowland grassland was used instead for low-intensity grazing: during Autumn and Winter sheep or hardy cattle cropped grasses and scrub but they were taken off the land in Spring and Summer.

Most wildflowers thrive on poor warm soil if dominant grasses and scrub are kept at bay. The lack of grazing in summer allowed plants to flower and set seed, and in winter the grazers would trample their seeds into the soil, ready for germination in spring. Thus farmers of old unwittingly created a habitat so biodiverse that it is often called ‘the European equivalent of the rainforest’: over 40 species of plant have been found in a single square meter of chalk grassland. This abundance of wildflowers supports many birds and small mammals as well as hundreds of rare species of invertebrates such as bees, hoverflies, moths, and butterflies; 35 out of 65 UK butterfly species occur here. In turn, they attract further birds, bats and reptiles. The mixed hedgerows that were grown along these fields provided nesting space and berries for birds and a refuge for amphibians, reptiles and mammals.

A walk through a traditional chalkmeadow is a feast for the senses. There’s a kaleidoscope of colour: yellow Rock Rose; magenta Knapweed, Red Campion and blue Milkwort. Odd shapes flutter in the breeze: ephemeral Harebells, Scabious pincushions, the lollipops of Salad Burnet, the lace of Wild Carrot, and the dried-flower look-alike that is Carline Thistle. The scent of Wild Marjoram evokes the Mediterranean, and odd names hint at historical, medicinal and folkloric connections: Granny’s Toenails, Ladies Bedstraw, Restharrow, Eyebright and Fairy Flax. And then there’s the beautiful orchids: Pyramidal, Bee, Common Spotted and many others. We even have our own unique local chalk grassland flower: the Chiltern Gentian. And this floral bounty is humming with the sounds of buzzing bees, scuttling beetles, chirping grasshoppers and singing birds.

Chalkland grassland is unique and wonderful and it is also internationally rare. It is only found in north-west Europe, with 50% in the UK, particularly in southern England, including the Chilterns. Alarmingly, chalk grassland has now become rarer still: it has been in serious decline since World War II as farmers were forced (through subsidies, policies and market forces) to bring every bit of land into intensive agriculture. Flat chalk grassland has been overgrazed, sown with uniform grasses; or ploughed, fertilised and treated with herbicides and pesticides for crops; and many hedgerows were removed. Elsewhere housing, roads, recreational areas, mineral extraction and landfill have replaced the habitat. Patches of chalk grassland too steep for farming or development have often been abandoned and become overwhelmed by scrubs or trees. Climate change is now adding to the pressure. As a result, by 1984, 80% of sheep-grazed lowland chalk and limestone grassland in the UK had disappeared and startlingly, today 97% of all traditional grassland in the UK has vanished. Only patches of traditional chalk grassland remain, usually in nature reserves or as military sites. Interestingly, as road side verges have never been ploughed or fertilised and are mown regularly, many are in fact strips of chalkland grassland.

Thus, the species-rich rainforest equivalent on your Amersham doorstep is now very rare, fragmented and unappreciated for its importance to local wildlife. Many species of bumblebees, butterflies, farmland birds and wildflowers have unique associations with chalk grasslands and cannot thrive or survive without it. For example, the beautiful Chalkhill and Adonis Blue butterflies feed on the horseshoe vetch, only found on chalk grassland. Fragmentation causes isolation of species that are then at risk of local extinction. Unfortunately, despite its international conservation status, many people simply have no idea about the importance and beauty of calcareous grassland. Conservation efforts often focus on iconic or large species, such as birds of prey, bees or woodland, rather than the intricate ecosystem of chalkland meadows.

So now you know: the flint in your garden is intrinsic to chalk soil; the footpaths go white due to the thin soil being scraped off the chalk; and orchids are a key indicator species of chalk grassland. This is the historic and cultural landscape of the Amersham area, which is beautiful, important and under threat.

Now you know about it, what can you do? Is there hope for these landscapes? The good news is that a number of local and national organisations such as BBOWT, the Chiltern Society, the National Trust, Prestwood Nature, the Chilterns AONB and Plantlife all champion calcareous grassland: they collect evidence; educate the public; and protect, expand and connect the chalkland in their own reserves and work with farmers and landowners to help them manage their land for productivity as well as nature. Amersham Town Council is increasingly leaving verges unmown during summer and wild orchids have appeared in several locations – no sowing required.

You can support things where you are in Amersham. Help these groups by becoming a member; signing local petitions, joining their work parties in reserves; or collect data for surveys. At home, try not to fertilise or mow all or part of your lawn in spring and summer and see what emerges. Seeds can lay dormant for years; some Amersham residents have had orchids appear, but you will find many other interesting species. If you do introduce plug plants or seed, make sure they are native chalkland flora. Support the Council in its attempts to not mow verges so often, and resist mowing verges yourself; perhaps you might team up with neighbours to ‘rewild’ a verge or other public space; the Rough Around the Edges project of BBOWT can provide support and advice.

But most of all, enjoy this natural abundance and get to know you patch: the harder you look, the more flowers you will find. Apps such as PlantNet, ObsIdentify, PictureThis and Seek will help you with ID. And if you would like to experience what local meadows were – and could be – like again, visit one of the chalk grassland reserves in the area, eg Aldbury Nowers near Tring; Grangelands near Princes Risborough, Aston Rowant National Nature Reserve near Watlington, Hartslock near Goring-on-Thames, and closer to home, Frogmore Meadows near Chenies, Yoesden near High Wycombe and Prestwood Nature Reserve.

Old Amersham is surrounded by an ancient landscape, a unique heritage that is worth getting to know and protecting. Yet there are no chalkland meadow reserves, large or small, in Amersham. Given its key role in preserving Amersham’s built and oral heritage, and the importance of our chalkland habitat, particularly at a time of immense biodiversity loss, might there be a new role for the Amersham Society in preserving this very special natural and cultural heritage? It is worth a thought – and, quite possibly, action.

Marieke Bosman
With thanks to Karen van Oostrum, Dominic Turner and Edward Copisarow. Information for this article was gleaned from online publications of the Wildlife Trusts, the National Trust, Plantlife, the Field Studies Council, the Chilterns AONB, the Sussex and Kent Wildlife Trusts, Magnificent Meadows, Wikipedia and the South Downs National Park.

January 2022 Newsletter