Biodiversity in productive forests: Worth a further look?

BIODIVERSITY IN PRODUCTIVE FORESTS: WORTH A FURTHER LOOK? The crisis for woodland biodiversity in Scotland evolved over centuries with extensive forest removal and fragmentation, overgrazing, deteriorating climate, and loss of woodland culture. During the past 100 years or so, changes in policy and practice turned the tide of woodland loss and each UK nation has ambitious targets for further woodland creation and expansion. Nevertheless, there remains active debate over the character of woodland which will provide for future generations, responding to the climate and biodiversity crises and new societal demands. Much recent biodiversity response has focussed upon the protection, restoration, and creation of native woodlands and the use of native tree species. Attention is rightly given to the unique Atlantic Oakwoods and iconic Caledonian pine forest and ways of tackling significant threats to them from the shading of ground flora by invasive species such as Rhododendron ponticum, the browsing of regenerating seedlings by too many deer and sheep, or the spread of introduced pests and diseases through movement of infected plants or dispersal of spores on footwear and tyres. This focus can appear at odds with the woodlands created to provide fibre security, the resource for domestic industries, and the urgent need to sequester carbon. These have typically been extensive forests of fast-growing, often non-native tree species established on open ground, and sometimes replacing native woodlands. The collections of Scottish plant explorers in the 19th century were used to identify tree species most suited to the sites being afforested and with growth outperforming native tree species. A mark of success is the six-fold increase in timber production in Scotland over the past forty years. Such domestic production limits the biodiversity impacts of exploiting forests overseas, yet the UK still imports 80% of its forest products. The uniformity of approach to deliver a reliable resource for domestic markets can raise concerns around future resilience and opportunities to enhance biodiversity. Solutions to one crisis can then be seen as at odds with another – and increasingly binary positions (e.g. carbon sequestration versus biodiversity; native versus non-native) have surfaced. This challenges more holistic notions of sustainable forest management which suggest multiple ways in which biodiversity can be enhanced. One misconception is that forests of non-native tree species are ecological deserts. This is simply not the case. Many woodland generalists, and some woodland specialists, benefit from the habitat provided and different stages of the planted forest lifecycle provide different habitats. Whilst some criticise the choice of non-native species, others point out that the only non-native component are the trees themselves with many native species inhabiting woodland interiors regardless of tree origin. Some argue that nativeness is key whilst others consider it an arbitrary concept fixed at a point in time and challenged by the rate of climate change and the arrival of diseases such as Ash dieback. A common thread to many discussions is the inadequate evidence with which to inform choices. New research techniques such as environmental DNA or acoustic surveys, and new environments such as woodlands entering their second or third rotation merit further attention. Such new evidence could inform more nuanced positioning and debate over future forests and how to integrate them in landscapes of multiple functions. Delivering resilient solutions should involve exploring a wider range of forest structures, types, and management regimes at a range of scales and with a keen eye to future climates and must go beyond the either/or positioning currently prominent. Professor Chris Quine FRSE is Chief Scientist at Forest Research, and a Fellow of the Royal Society of Edinburgh. Knowledge in sound is an audio transcription of the Royal Society of Edinburgh's blog series. Featuring in-depth analysis and opinion pieces from some of Scotland's leading thinkers. The articles offer personal views on a variety of issues. These views are not those of the Royal Society of Edinburgh and are intended to provide different perspectives on a range of current issues.