I am Professor Carly Stevens, from Lancaster University.

When we look at a limestone pavement, what we see is a series of blocks of stone with cracks between them. The blocks are called clints, and the cracks are called grikes. The limestone that makes up limestone pavements was formed millions of years ago when this part of the world was under tropical seas. The planet changed and the limestone was buried under soil but then the glaciers came along and then scraped all that surface material away, revealing the pavements. Over time, the soil that was in the grikes eroded away, leaving us with what we see today. We are really lucky that in Cumbria and Lancashire, we have some of the best examples of limestone pavement in the UK.

Within the grikes, we get a unique plant community growing. There are often a mix of species that we would typically expect to find in woodland and those that we would typically expect to find in grasslands. That is because the grikes provide a sheltered and shaded habitat. Ferns are really characteristic of limestone pavements.
Limestone pavements are really important for conservation. They are a rare habitat, there are only a couple of thousand hectares of limestone pavement and Cumbria is one of the few areas where we can find them. They are a unique and interesting habitat, and that has value on its own, but they also support lots of rare species, both plants and insects, that don’t occur in other habitats or are found in very few places in England. Because the rock has taken millions of years to form, this habitat is irreplaceable. If the rock is removed for quarrying, then the whole habitat is lost forever so it is really important that we look after them.

Some of the rare species that are supported by limestone pavements in the region include rigid buckler fern, which is nationally scarce, holly fern, which is endangered and the dark red helleborine, an orchid which is critically endangered. Limestone pavements also support butterflies like the pearl-bordered fritillary and northern brown argus, which are species identified as in urgent need of conservation action.

I'm Ezra Tattersall, and I'm a PhD student at Lancaster University.

Limestone pavements can be undermanaged, for example, by undergrazing, and this can lead to scrub encroachment. This is the process by which trees colonise the grikes in open limestone pavements. Because there is less grazing pressure, trees are allowed to establish and can grow and eventually form a canopy - and this affects the conditions under the canopy, at the surface of the limestone pavement. For example, light levels within the grikes (where light is already limited) can become too low for plant species to survive. Leaf litter from the trees can also affect the physical structure of the limestone pavement by clogging up the grikes. There is also an increase in moss species, and sometimes you can get a thick bryophyte layer, which can inhibit plants from establishing in the pavement. Additionally, shading from the tree species can affect pollinators, as they tend to favour more open habitats with warmer microclimates. Some trees are beneficial, though, and can support different species; the issue is that as we lose more open limestone pavements, the landscape becomes more uniform and we lose the heterogeneity that supports more biodiversity. 

The scrub encroachment on limestone pavements can be managed by physically removing scrub, for example, by cutting saplings in open pavements to ensure that open areas stay open. We don't know if it's possible to restore limestone pavements once scrub becomes particularly dense. I'm working closely with Cumbria Wildlife Trust to set up an experiment to see whether this is an effective strategy and whether the plant communities of open limestone pavements recolonise after the trees are removed. This is particularly important to see how big a threat scrub encroachment is to limestone pavements, and whether it is possible for us to reestablish plant communities in open pavements.

My name is Scott Petrek, I'm the Reserves Officer looking after some of the amazing limestone pavement habitats here for Cumbria Wildlife Trust.

So our Hutton Roof Craggs nature reserve is essentially part of the big chunk of rock you can see from the motorway as you come up the M6 at junction 26. So the really big rocky outcrop is our neighbour's property Falton Knott, and then Hutton Roof is tucked away in the woodlands just to the south of that, so just off from the village of Burton in Kendal.

Hutton Roof is a national nature reserve, so part of the UK's big network of really important sites. It's got the amazing limestone pavement habitats, but it's also got a mixture of open pavements and wooded pavements, and some areas that are perhaps a little bit more scrubby, some areas of grassland, and it also has fantastic views right out across Morecambe Bay and up towards the North Lakes - it's a real fantastic place to visit.

So the open pavements we've got on Hutton Roof nature reserve are mainly managed at the moment through a mixture of volunteer activities, so we've got teams of amazing people joining us to help us look after these really special sites, and then we've also got some cattle grazing actually up on the pavements too that will venture out and help us keep on top of the scrub control a little bit.

Like many of our pavements, we're seeing that scrub is a real big issue, and it's increasing quite a lot in some places. That's partly through not managing perhaps enough, changes in management practices, where things have moved from perhaps sheep grazing to cattle grazing. Some scrub is actually beneficial to the pavements, it creates those little microclimates, but there is a tipping point where it gets too much. So scrub is definitely one of our biggest issues, but also so is long-term sustainability of things such as grazing - can we keep these things as sustainable and financially viable options for farmers to do? 

And then long-term, some of the issues that we face - definitely climate change. It's kind of a real unknown as to what is actually going to happen on these pavements. We're getting warmer, wetter winters, we're getting hotter, drier summers, some of those specialist plants - can they tolerate those changes? And then even things like all of the nitrogen that is being dropped by the atmosphere - we're getting a lot more nutrients put into these habitats that we don't have usually, and it's all a bit of a question mark to try and work out what we're going to be looking at in five, ten, fifty year's time.