Our latest Directors’ blog is by NatureScot’s Woodland Officer, Kate Holl, who has co-authored a best practice guide on how to establish common woodland plants in broadleaved woodlands. For more information on the recent publication, visit the NatureScot Press Release.
I think spring is my favourite season, and this year with us all having been locked away all winter, I am sure we are all watching with equally keen eyes for any sign that it is on the way. Today, though, it still seems a long way off with temperatures hovering around zero and unseasonal hailstorms leaving the ground coated in white. But when the sun comes through, the queen bumblebees are out investigating the early flowers. On my morning walk today I was admiring the bird cherry and gean blossom which has so recently exploded into a mass of frothy candyfloss across the countryside. These flowering trees are so important as a source of early nectar for pollinators; for there is not much else available yet in the way of flowers as a source of food for insects.
I keep a few bee hives, and in the past few years I have started to look at the countryside increasingly through the eyes of the bees. I have been dismayed at the lack flowers that are available for them through the year. Whether it is because the road verges are cut too early, or the hedges are cut too hard and too frequently, or the arable weeds are sprayed too often, or just that the fields and woods are grazed so much by livestock and deer; the end result is that there are just not very many flowers at all out there in our countryside.
As one of NatureScot’s woodland advisers for over 30 years, I have been lucky to visit many of the “jewels in Scotland’s crown” in terms of our best native woodlands. But if you were to take a stroll through any one of these woods, and if you were to look, you would see that there are not very many flowers. Before I really understood about herbivore impacts, I used to think that this was because flowers like sunny places and so don’t really thrive in the shade of a woodland canopy. But then I realised that much of our indigenous woodland is typically light and airy, and dominated by species such as birch, pine, willow and ash that don’t really cast a very heavy shade. So what is going on? Why are there not more flowering plants in our woods?
I have spent the past few years looking for answers to this question and have been on a bit of a learning journey. Working with fellow ecologists Helen Armstrong, Richard Thompson and Bob Black, we developed the Woodland Grazing Toolbox; an online guide to help woodland owners and managers work out how to sustainably manage their woodlands using livestock, for a variety of different objectives. On the way, we became aware of just how significant the impact of wild herbivores on woodlands is, and realised that the first thing you need to do when thinking of managing a woodland is to get your head around what the current level of wild herbivore impact is. There were no tools to help with this, and so we spent the next 10 years developing and refining one based on field observations of the impact that different herbivores have on different parts of a woodland at different times of year. The Woodland Herbivore Impact Assessment method is what we came up, with and it is a way of trying to understand and quantify this complex relationship. Just observing the signs of the impacts of herbivores on woodland ecosystems, has really opened my eyes and helped me to begin to understand what is going on.
Plants and plant-eaters (herbivores) are in constant “dialogue” with each other, through eating and being eaten, and scientists are only just beginning to understand how far the consequences of this complex and dynamic relationship extend. If you want to read more about this fascinating subject then I can highly recommend a book by Fred Provenza: Nourishment – What Animals can teach us about rediscovering our Nutritional Wisdom.
Many flowering plants are really palatable (tasty) to herbivores, which means that they eat them in preference to other things, and observations that we gathered while developing the Toolbox, suggest that it often seems to be the flowers or flower buds themselves that they prefer most. I have watched my own flock of native sheep, on being let into an un-grazed meadow, go through the field enthusiastically nipping off and eating all the flowers first, before they eat anything else.
Because of the historic and ongoing high level of pressure from herbivores on ecosystems here, there are now very few places in Scotland where it is possible to see how woodlands might look in the presence of low herbivore impacts.
I wanted to find out what a woodland that has had a long history of low herbivore impacts, and that has not been ecologically depleted by centuries of overgrazing, looks like. To be able do this meant finding some un-grazed woods in countries that could be compared to Scotland. As deer have expanded their range and increased dramatically in abundance worldwide in recent decades, this was quite a challenge! However, by targeting researchers and woodland managers in several countries, I eventually identified a number of places where herbivores were being managed at very low levels, and where I might find the kind of woods I was seeking. In 2017, with the help of a Churchill Fellowship, I visited a selection of these woods from south-west France, through the Isle of Wight, to south-west Norway, and Iceland. These are all places that are on the western Atlantic seaboard, and so, like Scotland, have woods that are wet and temperate with an oceanic climate, have similar landforms and have all been deforested in historical time through human land-use.
The best time to look at woodland flowers is in the spring when the trees are just coming into leaf, because later in the year when the woodland canopy has closed over, little light reaches the forest floor and there are few flowers to be seen. I wanted to be able to compare the woodland flowers in the four countries at the same stage of their seasonal development, and as spring comes earlier in France, I began my journey there and travelled northwards following the season.
During my six week long Fellowship I visited many woods in these four countries, across a range of latitude, topography and soil types, and all with a long history of very little or no browsing impacts from large herbivores (and if you want to see more you can read about all the woods I visited in my blog Where have all the flowers gone?). Compared to the Scottish woods that I am more familiar with, the woods I visited on my trip all had so many more flowers in the field layer, and often a well-developed understorey with fruit bearing shrubs such as dog rose, blaeberry, stone bramble and northern bilberry, honeysuckle and bramble. A selection of photos from some of the woods I visited will give you an idea of how full of flowers woods can be when they are not full of herbivores!
These woods also had abundant tree regeneration with little or no costly management intervention or fences, so as well as being rich in biodiversity, they also had the capacity to support human foraging and economic activity.
What I saw and learned on my travels confirmed to me that Scotland’s woods could, and should be more “flower-full”. Because of its historical management, most of our natural woodland completely lacks an understorey, a woodland’s “filling”, and because there are so few flowers, there are also very few woodland berries.
Furthermore, because flowers are preferentially browsed, few flowering woodland plants are now able to complete their reproductive cycle and actually produce seed. If they are able, many flowering plants will reproduce vegetatively through suckers or runners, but without seed, there will be no new genotypes emerging. If current genotypes are adapted to current conditions, then this lack of ability to produce new genotypes may limit plants’ adaptability to climatic changes and also, potentially, their resilience to pests and pathogens.
Healthy woodlands contain “filling”. Filling is the stuff that should be there between the ground and the tree canopy, which prevents you from being able to see through. It is comprised of young trees, climbing and creeping plants, dead wood, shrubs, ferns and flowering plants – like in the picture below:
This abundance of growth provides food and habitat for a huge range of insects, birds and mammals.
Take honeysuckle, a plant that can be found in most of our natural woodland. In order to flower it needs to reach the canopy which it does by climbing up through the understorey to get to the light; once there, it will produce a mass of scented flowers. Honeysuckle flowers support enormous numbers of pollinators, the berries are enjoyed by birds and mammals while the tangle of climbing shoots also provide places to nest.
As we have seen, most of our woodlands have had a long history of grazing and overgrazing so that they now totally lack their natural filling, like the wood in the picture below:
As a result, many dependent species (the creeping, crawling and flying ones) are simply missing from our woods because there is not enough food for them to eat, and few places for them to live.
Woodlands in Scotland have been depleted over hundreds of years by overgrazing. They have lost species and structural diversity, and consequently now have a low level of ecological productivity. This means that our natural capital is currently considerably less than it could be. Furthermore, pressure from herbivores means habitats that are dominated by grazing-sensitive or palatable species have been forced to “retreat” to places in the landscape where they can escape from grazing mouths, such as ravines, cliff ledges and islands. Some vegetation types like base-rich woodland and tall herb communities currently have a very restricted distribution in Scotland, limited to inaccessible places because of their sensitivity to grazing. However, under a lower level of grazing these habitats would be abler to come down off the cliffs and out of the ravines becoming much more extensive and evident in the landscape.
Interestingly, these communities are much more extensive in countries where herbivore numbers are much lower. It is exciting to see that where herbivores are now being controlled at the landscape scale in Scotland, such as Glen Feshie in the Cairngorms and Carrifran Glen in the Southern Uplands, these communities of flowering plants are starting to return where they have been absent for decades. The flowers and berries that follow allow a whole community of associated species to also return to the landscape.
As part of the government’s drive to address the climate and biodiversity crisis, new woodlands are being planted across the country. While this may help to address the climate emergency, it will take many decades, even under ideal conditions, before these plantations of trees become true woodlands, with all of the rich assemblages of associated biodiversity. Depending on where these new plantations are located and how they are managed, they may not ever acquire all of the flowering plants, climbers, shrubs and other dependent species.
When woodlands are planted on arable land and improved pasture, they often develop ground flora communities typical of disturbed land that lacks a woodland character, and end up being dominated by grass and agricultural weeds. These ruderal vegetation communities can be very persistent, and whilst the woods may acquire a few woodland species by natural colonisation, they generally fail to develop authentic woodland plant communities because the woodland plants are missing from adjacent habitats.
One means of addressing this ecological deficit in recently planted woods is through targeted conservation translocations of common woodland plants. With the right management these can then spread naturally within the wood over time, and help to create authentic woodland vegetation in time bringing woodland flowers into the woods. A handbook just published by NatureScot: Establishing Woodland Plants in Broadleaved Woods – Interim Best Practice Guidance for Conservation Translocations, provides loads of practical guidance on how you can establish small populations of common woodland plants in your woodland. Look out for the report on NatureScot’s website, and if you want to find out more, there will be a webinar later in the summer – a chance to get all your questions answered!
Part of the challenge of resolving any crisis is to first of all recognise that there is a crisis. With the passing of decades, as ecological baselines have shifted, we have grown accustomed to woods with no flowers, and no filling. I hope that after reading this blog you will look at your local wood with a more critical eye – are the deer having too great an impact? Could there be more flowers there??
As more and more people become aware of the crisis of overgrazing impacting upon Scotland’s natural heritage, there will be more and more voices being raised seeking a reduction in herbivore numbers for the sake not just of, but not least for, the flowers.
The Scottish government has recently published its response to the Deer Working Group recommendations in which the need for effective deer management is stressed. Only time will tell whether the measures outlined will be enough to allow the regeneration and re-flowering of Scotland’s woods!