Our recent publication, 50 for the Future, lists 50 things that we believe should happen in Scotland over the next 50 years to benefit both people and wildlife. In this week's 50 for the Future article, Dr David Genney from Scottish Natural Heritage, discusses the important balance between generating renewable energy via hydro-electric developments and protecting nationally important plants.

Number 9: Make sure ancient woodlands and ravines of high botanical interest are strictly off limits to hydro-electric and other development

Renewable energy generation can help us to mitigate the effects of climate change by reducing greenhouse gas emissions. However, we need to ensure that developments are sited where they can capitalise on Scotland’s landscape features but with as little as possible impact on our species and habitats. A strategic approach guiding renewable energy development towards the best locations is the best way to achieve this. 

Scotland’s ancient woodland and ravines support internationally important populations of lichens, and a wealth of flowering plants. However, the potential impact of hydro-electric development on our bryophytes has been the focus of particular interest recently. This has led Scottish Natural Heritage (SNH) to work with ecologists and the hydro-power development industry to develop an approach that encourages renewable energy generation whilst protecting our most important watercourse for bryophytes.

Bryophytes are a diverse group of plants comprising mosses, liverworts and hornworts. Globally there are estimated to be between 16,000 and 24,000 species. There are just over 1,000 species in Scotland, which accounts for 87% of the UK total, 60% of the European flora and as much as 5% of the world’s bryophyte species. These are astonishing figures given the country’s relatively small size.

This high diversity is due to Scotland’s damp oceanic climate. It is not, however, the absolute amount of rainfall that is crucial, but the absence of long periods of drought and relatively mild winters. Scotland also boasts a diverse geology, giving a mix of rock textures and chemistry, with much exposed rock in crags and screes and turbulent streams in deep ravines that maintain humidity. This type of climate and landscape is quintessentially Scottish and is found in very few other places in the world. The rocky terrain also means that tracts of woodland have been left relatively undisturbed, particularly in ravines, and these old woodlands support the heart of our oceanic bryophyte flora. The west Highlands of Scotland are particularly important for oceanic bryophytes and woodlands where they are part of a globally rare and restricted biome called Coastal Temperate Rainforest.

The group of bryophytes of particular relevance to hydro-electric development are those that are primarily, or entirely, restricted to sheltered, wooded oceanic ravines and have varying dependence on high humidity, splash and spray conditions. Most of these species are not aquatic but grow on rocks and trees close to watercourses.

Many of these oceanic ravine species have the majority of their European population in Scotland and are globally rare. With the increase in renewable-power generation, it became apparent that there was potential for overlap between watercourses suitable for small-scale hydro-power generation and internationally important bryophyte habitat. Reduced flows are expected to result in a reduced frequency of splash, spray and mist in habitats along and close to the stream, and a potential general lowering of humidity levels. A reduction in the frequency and intensity of intermediate spate events is also thought likely to result in an increase in colonisation of rocks by large common species. These effects could potentially lead to a reduction in the diversity of uncommon oceanic bryophytes.

SNH has, in collaboration with a team of expert bryologists, developed a novel method to quantify the relative importance of each watercourse in the west Highlands for oceanic bryophytes. This helps developers avoid the most important watercourse in Scotland, and provides a clear and consistent framework by which SNH and other environmental regulators can evaluate planning applications. Understanding the relative importance of watercourses allows a risk–based, but precautionary, approach; it takes a proportionate view and the risk of potential long-term negative impact on bryophytes is accepted for the majority of watercourses. A small subset of the very best habitat in Europe is, however, protected from development.

Scottish Natural Heritage will always work with developers to find ways for renewable schemes to go ahead if possible. However, by setting clear guidelines from the outset, and accepting that not all watercourses will be suitable for development, we will protect the rich botanical interest of our most important wooded ravines.

Let us know your thoughts by emailing thefuture@scottishwildlifetrust.org.uk or Tweet @ScotWildlife using #50fortheFuture.

Dr David Genney is a Policy Advisor on Bryphytes, Lichens and Fungi at Scottish Natural Heritage