The great wood of Caledon brings stirring images of beautiful forests, rich in plant and animal diversity, filling the glens of the Highlands.

But this native forest has suffered dramatic losses over thousands of years, and our Caledonian pine forests now cover only one per cent of the land area. 

Human activity and climate have played their part in this decline: felling, burning and grazing have been ongoing for many thousands of years and about 4,000 years ago the climate became cooler and wetter, leading to faster peat growth in some areas that made it harder for pine trees to grow.

Our climate is changing again, so what of the future for our Caledonian pine forests – will Scotland still be suitable for this majestic tree into the future? 

Along with the changing climate there are increasing threats from tree pests and diseases spreading across the country (already exemplified by Dutch elm disease and ash dieback) – many of these pest species prefer warmer summers, so more outbreaks are expected under predicted climate change patterns.

Warmer temperatures may also speed up the life cycles of pests such as pine weevil, possibly increasing damage rates. 

In relation to pine, there is concern about a disease called Dothistroma needle blight, which is spreading across the UK and has already been found on some native pine trees.

The fungus that causes it is thought to be benefitting from the trend towards warmer springs, coupled with more summer rainfall, allowing more rapid spread.

Earlier this year, a report by the UK’s independent committee on climate change called for “urgent efforts” to reduce the vulnerability of our forests to pests and diseases. It is the combination of all of these pressures that gives the greatest concern for our Caledonian pine forests. 

Globally, Scots pine is the most widely distributed pine and is found throughout all Eurasia, growing across a diverse climatic range and from sea level to more than 8,500ft in altitude.

Its genetic diversity is known to be immense – and even within the few remaining pine forests in Scotland the genetic diversity is high. This should help pine to adapt to our changing climate but, given the speed of climate change and the tiny remaining area of this forest, can it adapt quickly enough?

Forests are dynamic systems that naturally shift around the landscape, but the isolation of many of our remaining Caledonian forest fragments hampers movement of species as well as genetic mixing and is likely to make adaptation to climate change much harder without active intervention. 

Couple this with the increasing threats from pests and diseases, along with ongoing pressures from grazing that can prevent young trees from establishing, and we have a problem. The grazing problem has been around for a long time and can easily be addressed given appropriate action.

But, to date, little work has been done to explore the potential within our native Scots pine genetic diversity to adapt to changing climatic conditions into the future. 

Climate change is, of course, also affecting all the other species associated with our Caledonian forests and research published by the James Hutton Institute shows changes in other plant species within these forests are already apparent. There is little doubt the composition of our forests will change, but the exact nature of these changes is hard to predict. 

So what are we doing to help increase the chance of our Caledonian pinewoods surviving into the future?

Across Europe there have been considerable efforts made to conserve the genetic diversity of tree species including pine (through a collaborative platform called EUFORGEN) to help protect these species into the future. There is also a move to create “native woodland networks” to help focus restoration and expansion and reconnect isolated forests, to help species move and adapt to rapid climate change. 

In Scotland, the James Hutton Institute, Forest Research, the Centre For Ecology And Hydrology and the National Trust for Scotland have also created a unique set of experimental sites where Scots pine trees have been grown from seed collected from all the remaining Caledonian pinewoods across Scotland, to cover the range of genetic diversity inherent in our native pine populations. 

This experiment was started in 2012 by the institute’s Professor Glenn Iason and the trees form part of a long-term experiment that will track them until they are fully grown to test how they respond to different climates and how they differ in their resilience to different pest and diseases.

The trees are growing at three sites: Glensaugh in Aberdeenshire, where the climate is cool and dry; Yair in the Borders, where the climate is dry but warmer; and Inverewe Gardens, Wester Ross, where the climate is warmer and wetter. 

By understanding the consequences of environmental and climate change and the potential for adaptation by our native populations of pine, we can help to promote resilience of our Caledonian pine forests into the future. 

Laboratory and greenhouse experiments are also being carried out on other trees grown from seeds from the same forests, to test the responses of different trees to specific climate-driven events such as summer drought and late frost. This will allow us to identify which provenances and tree characteristics are most suited to cope with a range of stresses.

This work will assess the challenges and prospects for our Caledonian pinewoods and provide crucial information for adaptive management policies to ensure these beautiful forests continue to thrive. 

Additional reporting by Dr Jenni Stockan, invertebrate ecologist 
at the James Hutton Institute.