Habitat connectivity: evaluating potential

Roy McGhie – Conservation Project Assistant

Over the last month or so I’ve been investigating habitat connectivity in a new target area – near Boltby on the western fringe of the North York Moors.

Landscape from top of escarpment, near Boltby - copyright Roy McGhie, NYMNPA.

This particular area has a fantastic variety of habitats, from the arable plain on top of the escarpment, down the slope through Boltby Forest and across to the pasture fields in the west. Our overarching objective for this area is to strengthen the mosaic of habitats, with special reference to improving networks for butterflies and bats.

After my initial desk-based research I proceeded to ground truth the area to establish how much of our mapping and existing information was still accurate and to build up a current picture of the area. With so many public rights of way in the National Park exploring is usually pretty straightforward, but for closer examination of any particular area we would always ensure we have the land manager’s permission.

Felled veteran tree with dead wood left in situ (good for invertebrates, fungii and lichens) - copyright Roy McGhie, NYMNPA.

It’s important to establish what levels of connectivity already exist. Above the escarpment most of the arable fields are in Environmental Stewardship agreements, which suggests positive environmental land management is already in place and making use of national agri-environment schemes is something we would always encourage where appropriate for the environment and the land manager.

The Forestry Commission own a large forest within the area – Boltby Forest – and their Forest Design Plan sets out their long-term vision. This includes increasing the ratio of broadleaved trees to conifers and maintaining areas of open space. The open space is very useful in terms of meeting our original objectives for the area because open spaces in woodland create edge habitat which attracts bats.

Within Boltby Forest - copyright Roy McGhie, NYMNPA.

Another valuable habitat found within this area is unimproved and semi improved grassland, both acidic and calcareous in terms of soil pH because it’s where the farmland of the Vale of Mowbray meets the western edge of the moorland. Some of these grassland sites appear to be in a good condition and have an appropriate level of grazing to maintain this, whereas others seem more precarious.

Heath bedstraw and tormentil, indicative of an acidic grassland site - copyright Roy McGhie, NYMNPA.

Lots of wild thyme, commonly found on calcareous sites - copyright Roy McGhie, NYMNPA.The biggest threat to most of the grassland appears to be a lack of effective grazing. On several sites rank grass are beginning to dominate, resulting in wildflowers being outcompeted. On other sites scrub encroachment means that the grassland interest will diminish.

Rank grass and ash trees taking over a grassland site - copyright Roy McGhie, NYMNPA.

In a site where grazing is happening, there is occasional poaching (heavy ground trampling) by cattle alongside the small watercourse. This happens when stock congregate along particular parts of the bank to drink, or cross over.

Poached land beside a small beck - copyright Roy McGhie, NYMNPA.

Bracken is another issue in the target area. Bracken isn’t necessarily a bad thing – it can provide excellent cover for ground flora and butterflies such as the rare Pearl-bordered fritillary, but its tendency to spread means that it can very quickly outcompete and overcome other vegetation.

Bracken alongside a public footpath - copyright Roy McGhie, NYMNPA.

There are plenty of positive biodiversity hot spots in this area, including patches of habitat that are excellent for butterflies. There are also a number of established hedgerows acting as wildlife corridors for bats to navigate by.

Common blue butterfly - copyright Roy McGhie, NYMNPA.Small copper butterfly - copyright Roy McGhie, NYMNPA.

So once I’d assessed the area and its connectivity potential, I discussed ideas and options for how best to deliver the original objective with input from Rona, our Ecologist, and Mark, our Woodland Officer.

One of the key ideas coming out of these discussions is to provide long term replacements for the many mature in-field and boundary trees. These trees provide multiple benefits such as shelter for stock as well as a habitat for birds, invertebrates and insects. I recorded a standing veteran tree during my on-site survey and ideally we would like to see this tree fenced off as the stock in the field are causing considerable erosion around the base which may be weakening it.

To reduce the poaching alongside the watercourse we could help repair the fencing and investigate the use of a field trough so the cattle wouldn’t need to drink out of the beck.

Another idea is to fence off a particular area of mature ash trees to allow natural regeneration. This is because some ash trees show genetic resistance to the ash dieback pathogen, so whilst planting new ash trees is currently not encouraged assisting natural regeneration by older trees might mean that potentially disease resistant stocks are bolstered.

For the various grassland sites in the area, different management options are proposed. On the sites with bracken encroachment we could suggest organising volunteer tasks to help keep the bracken under control. On other sites we will need to discuss with the land manager their aims for their land and see if there is scope to manage levels of grazing to ensure the wildflower interest remains and potentially expands. Land manager engagement is a crucial part of the habitat connectivity development process – our management proposals on private land can’t happen without their permission and goodwill. Negotiations are the next step in the habitat connectivity process.

Overall I think this target area near Boltby is in a pretty well connected condition. There is already a mosaic of habitats suitable for bats and butterflies, and it forms part of a much more extensive network along the western fringe of the North York Moors. Our involvement will probably be relatively minimal, working where we can with local land managers to conserve the valuable grasslands and to sustain the important tree population into the future.

Landscape near Boltby - copyright Roy McGhie, NYMNPA.

 

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