Patrick Cook and his team share their experience investigating how moths respond to a landscape-scale woodland expansion project at Mar Lodge Estate in the Scottish Highlands.
Background
Upland landscapes in Scotland have a low cover of native woodland yet provides an excellent opportunity to expand woodland cover for biodiversity. For instance, native pinewood now covers less than 18,000 hectares in 84 small areas and an estimated 23 per cent of those are critically threatened. This has occurred due to historic tree felling, heavy browsing by deer, burning and climate change.
The Scottish Government has set ambitious targets to create 15,000 ha of new woodland a year from 2024/2025, of which a third will be native woodland. Much of this target is being achieved by tree planting but some projects are increasing woodland cover by reducing deer numbers to levels that allow native woodlands to naturally regenerate and expand. An example of such a project is the National Trust Mar Lodge Estate in Northern Scotland.
What did we study?
As deer numbers have been reduced on the northern half of the estate over the last 30 years the habitat response has been rapid and created a diverse landscape comprising (1) open heather moorland without trees which is representative of wider upland landscapes in Scotland to (2) moorland with predominately young Scot’s pine regeneration forming early successional woodland and (3) mature ancient woodland predominantly comprised of Pinebut with Birch components. In this study we investigated how moth species numbers, abundance and community composition differed across these three habitat types on the estate.
What did we find?
A total of 2977 adult moths of 115 species were recorded including some scarcer species such as Cousin German Protolampra sobrina. The highest number of species and abundance of moths were recorded in the remnant mature pinewood fragments, due to the diversity of habitat structure and foodplants for moths. We also found that moth abundance was higher in the early successional woodlands compared to open moorland showing the value of light tree cover in upland landscapes. The key conclusion from this section of the project was that to maximise number of species and abundance of moths in upland landscapes we need to protect remaining native woodland fragments as a priority but also seek to create early successional woodland.
The community composition results showed that each of the three habitats supported a slightly different community of moths. The community found in the early successional woodland was particularly diverse with open ground and tree associated moth species occurring side by side. Several species we think of as being moorland specialists also had high abundance in this habitat type. Importantly, we also found that the moorland supported some moth communities associated with open ground conditions not found in wooded habitat types. This shows the value of retaining some open areas of habitat in woodland restoration projects, particularly as such habitat types can benefit scarce day-flying moorland moth species. The key results from this section of the study were that we should promote early successional woodlands as they can diversify moth communities after 10-20 years of development, but that a landscape with a rich mosaic of habitat types is the best way to promote moth biodiversity in upland landscapes.
What does this mean for practitioners?
Our study shows that a mosaic of habitats is required to support moths in the uplands and that the protection and long-term expansion of native woodland should be a priority. We also show that early successional woodland, achieved by natural regeneration, increases the diversity of moth communities due to the high habitat heterogeneity and larval food plant opportunities. This latter habitat is largely absent from UK upland landscapes but with suitable herbivore control would quickly proliferate and deliver a boost to biodiversity in only 10-20 years in areas with a suitable seed source and ground conditions. Open areas of moorland should be retained in the wider landscape as woodland restoration projects progress, to maximise landscape heterogeneity and support moth communities that are distinct from those in woodland habitat. The results of this study show the effectiveness of landscape deer control for promoting habitat restoration and indicate the potential for positive changes to upland biodiversity if this management approach was adopted more widely.
Read the full article ‘Landscape-scale native woodland habitat restoration using natural tree regeneration provides a biodiversity boost for moths in the uplands’ in Ecological Solutions and Evidence.
