Land managers vital to the success of rewilding in the Scottish uplands

upland

“We were interested in how changes in grazing might cascade through a system from the direct impacts of the grazers on the plants to indirect impacts on other parts of the system (invertebrates, birds and voles). The responses of individual plant species to the experiment took a minimum of 12 years and often 15 years to become apparent, with some species showing no detectable changes"

Rewilding in the Scottish uplands could take decades without the intervention of land managers, a new long-term grazing experiment at Glen Finglas has shown. The experiment, the first of its kind in Scotland, was set up in 2002 to explore how changes to Common Agricultural Policy, particularly decoupling of support from livestock numbers, might affect upland biodiversity.

The grazing experiment assessed the impact of intensification (tripling sheep numbers), abandonment (removal of sheep) and grazer diversification (partial replacement of sheep by cattle) on vegetation composition in a diverse area of grassland. It investigated how species respond to different grazing treatments and how responses at lower levels of the food chain affect those higher up.

Professor Robin Pakeman, of the James Hutton Institute, and part of the research team responsible for the experiment, explained: “We were interested in how changes in grazing might cascade through a system from the direct impacts of the grazers on the plants to indirect impacts on other parts of the system (invertebrates, birds and voles). The responses of individual plant species to the experiment took a minimum of 12 years and often 15 years to become apparent, with some species showing no detectable changes. In contrast, the meadow pipits responded within a year of the treatments being imposed.”

The research can be used to explore the concept of rewilding, which refers to the restoration of an ecosystem, where nature takes care of itself. Rewilding aims to encourage natural processes and, if required, introduce missing species, allowing them to shape the landscape naturally.

Robin said: “We were interested in the impacts of grazing on birds, so plots had to be big enough to have multiple territories of the most common breeding bird – the meadow pipits. We established the experiment on a mixture of uplands habitats: wet heath, wet and dry grassland and sedge mire.

Productive grasslands, such as those dominated by bents and fescues, which are the usual focus of grazing in these habitats contain few species capable of responding to reduced grazing, so the response to grazing removal was minimal. Tree invasion was also minimal apart from one no grazing plot near a wooded ravine. Some vegetation types responded quickly to the removal, for example wet heath and mat grass dominated grassland, indicating that these had species capable of adapting to change, such as heather.

The vegetation types that responded fasted to increased grazing were the moderately productive purple-moor grass and sedge mires, indicating a broadening of sheep foraging from their more preferred bent and fescue grassland. Partial replacement of sheep by cattle had little impact on the vegetation apart from suppression of bracken and blaeberry.”

The experiment suggests that without the direct involvement of land managers vegetation change in these relatively infertile grasslands is extremely slow. This makes forecasting any developments very challenging.

For more information, the complete paper can be found here.