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Adonis Blue butterfly

Dr Alan Stewart on the area that will become chalky grassland once more

Don’t be fooled. The rolling green hills that surround the University of Sussex campus may look lush and healthy, but in ecological terms, they are a disaster.

In recent decades, farming practices that have created nutrient-rich pastures for grazing and crop-growing have also led to a serious decline in the biodiversity of the Downs.

Some of the UK’s rarest species of orchids and butterflies thrive best in the thinly layered, low-nutrient soils of natural chalky or ‘calcareous’ grassland. But more than 90 per cent of this ancient habitat across southern England and northern parts of Europe has now been lost, and what remains is fragmented.

Although it’s unlikely that these grasslands will be restored to their original levels, a project that’s just beginning at the University of Sussex will re-establish a two-hectare area on campus for scientific study.

Over the course of the summer, thousands of tonnes of chalk are being dug up and transferred from one side of the University of Sussex campus and deposited on a strip of ‘improved pasture’ on the other side.

And while the excavated site will soon see the replacement of student residences, the new white slope opposite will become a living lab for botanists and ecologists.

Dr Alan Stewart, Reader in Ecology at Sussex, who is overseeing the project, says: “What’s exciting is that, as a field experiment, this has never been done before on such a large scale.

“In terms of research, our students and scientists will have the opportunity to observe how plants grow and insects thrive in these environments, and hopefully we’ll be able to demonstrate to conservation and wildlife organisations best practice in terms of protecting them.”

The biodiversity of calcareous grassland is so great that up to 40 different flowering plant species can be found in one square metre. They include the round-headed rampion, also known as ‘pride of Sussex’, and much rarer flora such as spider and monkey orchids.

Among the fauna that inhabit these environments are rare bush crickets and several species of butterfly, such as the Adonis Blue and the Duke of Burgundy, while birds frequenting these areas for hunting and nesting include corn buntings and skylarks.

Alan hopes to use different parts of the site for different experiments. Some areas may be given a thin layer of topsoil and seeded with different combinations of species (through a collaboration with Wakehurst Place Seedbank). Other areas may be left “to see what gets blown in”.

Without fertilisers and herbicides, it’s unlikely that fast-growing and more dominant species will thrive in this environment and overshadow the more delicate, chalk-loving plants.

However, to maintain the nature of the grassland, it would still need to be kept short either through mowing – or by having “flying flocks” of livestock brought in for “mob grazing".

“We’re still working out some of the details,” says Alan. “But what we hope to be able to do is to demonstrate the importance of preserving these precious areas of grassland, not just for their natural beauty, but for the health of the countryside.”

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