Chalkhill blue butterfly in a chalk grassland

Chalk grasslands are home to many important species of invertebrates, such as the chalkhill blue butterfly © gailhampshire/Wikimedia Commons

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Brilliant Butterflies project launched to restore rare grasslands

Patches of chalk grassland in south Croydon will be restored to help conserve nationally rare plants and insects, including many species of butterfly.

The Museum has partnered with the London Wildlife Trust (LWT) and Butterfly ­­Conservation on the Brilliant Butterflies project, which is funded by a £1-million Dream Fund Award from the People's Postcode Lottery. It will improve the health of existing patches of grassland in south London and restore other sites to help reduce habitat fragmentation.

Katy Potts is the Museum's Biodiversity Officer working on the Brilliant Butterflies project.

'The Museum's role in this project will be to undertake the invertebrate monitoring using traditional survey techniques and environmental DNA (eDNA) surveys. We will also develop a training programme to teach the volunteers that the LWT will recruit on how to identify and survey the chalk grassland invertebrates that we survey,' says Katy.

Chalk grassland in southern England

Chalk grasslands are mainly found in northwest Europe, with a large proportion of the habitat found in southern England © Clem Rutter/Wikimedia Commons

'The LWT will be taking over all of the habitat management on the sites and running a public engagement programme, while Butterfly Conservation is surveying the butterflies.'

In addition to this, the Museum will restore its own patch of chalk grassland in South Kensington as part of The Urban Nature Project

Declining grasslands

Chalk grassland is a habitat only found in northwest Europe, and a large proportion of it is  in England.

It was once widespread, but following the Second World War and the intensification of agriculture, chalk grasslands are thought to have declined by around 80%. Their habitat is now generally limited to chalk valleys and plateaus of southern counties such as Kent, Sussex, Surrey and the Isle of Wight, as well as across portions of the Chilterns.

The grasslands are characterised as lime-rich but nutrient-poor, with thin soils that struggle to hold moisture. This might not sound like a particularly productive landscape, but the more challenging conditions mean that prolific plant species such as many dominant grasses find it difficult to take hold.

Duke of Burgundy butterfly

Butterflies, such as the Duke of Burgundy, can be found in chalk grasslands © Sharp Photography/Wikimedia Commons

This allows for the development of more distinctive community of herbs, flowers and grasses, including many species rarely found across the rest of the country.

In fact, the species diversity on chalk grasslands is impressively high, with up to 40 species per square metre. It is this high diversity that leads to a great variety of insect species on chalk grasslands. 

'There are a lot of unusual wildflowers and orchids that will persist on these chalk soils, and in turn there are an array of rare insects that are associated the wildflowers,' says Katy.

'So this habitat supports these interesting and rare invertebrates that you don't really get elsewhere.'

These include species such as the wart-biter bush-cricket, the roman snail, scares snipefly and an array of butterflies including the grizzled skipper, Duke of Burgundy and chalkhill blue.

Wart-biter bush-cricket on a hand

The grasslands are not just good for butterflies, but also many other species of invertebrate such as wart-biter bush-crickets © xulescu/Wikimedia Commons

Butterfly highways

It might come as a surprise to find that south Croydon is home to a handful of beautiful chalk grassland habitats that are mature and well developed. These patches still support a range of protected species of plants and invertebrates, such as the yellow rattle and small blue butterfly.

With habitat fragmentation and a decline in grazing, there is a risk that the grasslands will succumb to natural succession and that the butterflies and insects that rely on them will be unable to disperse.

'There are already some core chalk grasslands sites in the project, but the aim is to make butterfly banks between these areas around south Croydon to create a wildlife corridor to allow better dispersal of the invertebrates between these core habitats,' says Katy.

'In road verges, school playgrounds and housing estates, we are going to try and recreate some of these chalk grassland sites to link the bigger sites and create more little habitats.'

Brillant Butterlies launch event

The Brilliant Butterflies project was launched in south Croydon as a partnership between the Museum, the London Wildlife Trust and Butterfly Conservation

The Museum will be training local volunteers on how to survey invertebrates and identify what they find. The teams will also be sampling eDNA from the sites which will feed into the Museum's work on creating a barcode library of all invertebrate species that live in the UK.

The data gained from this will then help organisations such as the LWT and Butterfly Conservation to better manage the sites and help protect the rare species found in these habitats.  

Mathew Frith, Director of Conservation at London Wildlife Trust, says, 'Brilliant Butterflies provides us with an unrivalled opportunity to reverse the declines of the amazing diversity of London's chalk grassland wildlife.

'Not only will we be able to create new havens for butterflies, beetles and bees within our nature reserves, but we can bring nature closer to the communities that live nearby by transforming green spaces into colourful wildflower spaces.'

Launching this week, the Brilliant Butterflies project will kick into action next year when volunteers will be trained to identify the insects and butterflies that they may find on the chalk grasslands.

To find out more and register your interest as a volunteer, visit the London Wildlife Trust's website.