Transcript

INTERVIEWEE

Chalk is an amazing rock. It was formed back in the Cretaceous period about 100 million years ago. And how it's formed is by lots and lots of tiny shells of marine algae. And when I say lots, I mean absolutely billions and billions, all crushed down together. And it's actually now a really internationally rare rock, but we've got to everywhere.

KADY LEE-PRESTON

About 6,000 years ago, all of this was forest, which was cleared by Neolithic farmers. They grazed their animals here, and change it to grassland. But this left the area exposed to the elements.

INTERVIEWEE

A lot of the topsoil has been washed off over the years. And it's created a really nutrient-poor surface, nutrient-poor soil.

KADY LEE-PRESTON

It may seem strange, but low fertility soil actually encourages the rarer species. If this soil were rich, it would be overgrown by the boring, old common species you get everywhere. But because it's poor, it gives the uncommon plants a chance. And that's what makes it so rare and so precious.

[MUSIC PLAYING]

And so Western Heights of Dover are home to an enormous number of chalk-loving species. As we can demonstrate with a wooden square, which biologists call a quadrant.

BIOLOGIST

So if we go over here somewhere and just throw the quadrant randomly, we can see the different species that are here. This is rock rose. This one's salad burnet with its cucumberly smelling leaves. This is milkwort. And this is horseshoe vetch, very important for the butterflies. And this is [INAUDIBLE] weed with its lovely little fluffy ear-like leaves. And just in this quadrant alone, there's 40 or 50 different species of chalk [INAUDIBLE] plants.