Bringing together the disciplines of ecology, geography, economics, engineering and statistics, and funded by independent; philanthropists, Trinity’s FOREST project aims to objectively explore the challenges, opportunities, and trade-offs involved in delivering a socially just, environmentally sustainable and financially viable afforestation programme in Ireland. For my part, I am looking at some of the young native woodlands that have been planted over the past 20 years, with a view to understanding their ecological value and the ecosystem services they provide. With these new native woodlands being promoted as a critical tool to address the joint crises of climate change and biodiversity loss in one shot – Are they living up to the hype?
With a total forest cover of 11% in Ireland only 2% is considered to meet the criteria for classification as native woodland, the rest comprising mixed or non-native forests the majority of which are fast-growing sitka spruce ‘tree farms’, loved by many foresters but fiercely opposed by others. The legacy of past afforestation programmes have left us with these predominately single species forests, which provide benefits in terms of wood products and carbon sequestration. Dense monocultures however have little benefit for biodiversity, are frequently a significant pressure on waterbodies, often produce wood of lower quality, and while forestry practices have evolved in recent years, for many sites, the carbon balance sheet might not look so rosy if past land use, drainage, and planting methods were to get factored in. In this context, the planting of native woodlands for the multiple benefits they can provide, in addition to a longer term timber yield, has garnered increased attention.
As a starting point, I’ve spent the summer tramping around many of the sites planted with native trees under the Forest Services’ Native Woodland Scheme or similar planting approaches. Aside from some ad hoc studies, there is little information on how these young woodlands are doing. Aware of some stories of failed young ‘tree cemetery’ woodlands, the increasingly obvious effects of ash dieback, and tales of success achieved through natural regeneration rather than planting, I was apprehensive about what I would find.
It’s hard not to feel humbled when you’re in the presence of a mature tree, a wonder of nature driving up from the earth over years with such singular life force, however a woodland or forest is so much more than just the trees. Can these young native plantations, typically planted in fields used previously for some form of agriculture, get to a point where the flora and fauna that characterise woodlands firstly find a way in, and then start to interact to deliver a dynamic woodland ecosystem? The more sites I walked through I found myself feeling that, given the right start, the trees know what to do. The youngest sites, full of baby trees often almost overtopped by an aggressive neighbourhood of grasses, look worryingly vulnerable. Many of the owners and foresters I met talked sadly of losses during dry springs of recent years, a challenge that will no doubt increase with continued climate change. In many sites the failed trees were dutifully replaced though, and the new forests got a second chance.
Transformation starts after a few years as the trees develop. These 5-10 year old sites were thrumming with wildlife, the abundance of bird, mammal and insect life particularly notable, with the increased shelter and structure provided by the young trees clearly providing roosting, foraging, resting and nesting areas. They are not by any means a functioning woodland ecosystem, but their value for biodiversity is obvious.
After 10 years or so, depending on the site and trees planted, things generally start to look a lot more woodlandy. The oldest sites I visited were planted 15-20 years ago, with tree canopies closing in, the ferns, bluebells, wood sorrel and mosses start to emerge. I’m not sure whether these new arrivals were always there in the soil, biding their time, or find their way in, or a bit of both. The sensory load that a woodland delivers is also palpable in the damp musty aroma, crunchy twigs underfoot, soft mossy surfaces and dappled light. Decay, so crucial to a functioning woodland system, is clearly evident. The owners of these sites are always thrilled telling me ‘you wouldn’t have believed it when it was planted, they were only knee high’. I even found myself on one occasion not quite believing a site could have ever been a pasture field, and double-checking my information. That said, just how woodsy the woodland has become varies between sites, and this might come down to factors such as how intensive former agriculture use was, whether the sites were wooded in the past or how close they are to other wooded areas.
Though overall pleasantly surprised at many sites, there were also young woodlands clearly battling for their lives. Ash was planted in many native mixes before dieback hit. Certain landowners, usually those with a good forester advising or with knowledge of trees themselves, were quick off the mark and had it out and replaced quickly. In other sites, the owners have been watching the ash slowly die, frustrated and disheartened, but not quite sure what to do. With the loss of ash, the way the site was planted matters to the outcome for the wood as a whole. In a site where ash was put in rows with intervening oak, the effect of the dieback could be almost beneficial for the remaining oaks, like a managed thinning. Where large blocks of ash were planted however, the woodland ecosystem that was establishing is effectively lost.
Deer in Wicklow seem to find their way into woodlands, despite the best efforts of those involved, with nibbled trees, particularly oak, faring poorly. The cost of fencing and tree-guards, and the ongoing monitoring required to ensure they remain effective, is an onerous commitment for both the forester and landowner. You don’t need a research project to tell you that for these forests to survive in the longer-term, natural regeneration processes will need to be supported, and that won’t happen if deer aren’t controlled. In many sites, oak trees were also clearly being affected by a powdery mildew, which though it doesn’t kill them can limit their growth. In general, the oaks’ slower growth relative to other commonly planted species seems to stack the odds against it by just giving it more time in a vulnerable state for something to defeat it. A lot of oak has been planted under the native woodland scheme. It makes sense that that increasing the diversity of trees species planted wherever conditions allow would best buffer the future woodland against the risks of these multiple threats.
Then there is the question as to whether woodland is the ‘best’ habitat for the land in question at all, the issue being that ‘best’ may be subjective. A number of sites I visited where trees were faring well have equal potential to make nice grasslands if management were to be targeted at such. Then there were several areas that were particularly damp or particularly dry and which, with trees dead or stunted, would appear to be intent on reverting to their former wetland or dry grassland habitat.
So, who are planting these sites and why? It was a real highlight to get to meet and talk to the owners or foresters involved. There were a definite cohort of owners planting for the love of native trees, with a view to enhancing biodiversity and potentially leaving a legacy for their families and for nature. These owners often also had other areas of their land devoted to old woodlands, meadows, winter bird cover and natural regeneration, and usually had a walking trail through their woodland so they could savour it on demand. Some had sought out the native woodland scheme despite their foresters and farming neighbours strongly advising against ‘wasting their good field’ on it. Another broad grouping were the farmers who planted native woodland, often alongside other parcels of broadleaf or conifer plantations, on land that wasn’t of much benefit to them for farming anymore for one reason or another. They were pleased to see it growing, and happy with a payment for land which was sometimes their ‘bad field’ and a burden. They often admitted to not having step foot in their woodland for years. There were also a few sites where the contact person was a manager of a larger landholding, having little knowledge of the woodland or who planted it, and in once case not aware it existed.
The question gets asked whether planting should really have a role at all in the establishment of native woodlands. With nursery stock of varying quality, potentially harbouring pathogens, and the challenges of a changing climate, could our native woodland establishment approach fail in the long-term? Many argue that with patience, natural regeneration will deliver better and more resilient woodlands for us. Allowing woodland vegetation to regenerate naturally serves as a foundation for ‘rewilding’, a loosely defined concept, but one that at its core involves the restoration of food webs and the recovery of ecological processes. Of course, even such rewilded forests will need some level of ongoing intervention, as the diseases, deer and invasive plants that have found fertile ground in the remains of our crumbling natural ecosystem will otherwise scupper the best laid plans. As a farming nation we long ago lost the skills associated with a culture of having working woodlands within the farm setting, and so any broad scale woodland establishment within our farmed landscape is a hard sell even if the landuse policies shift to facilitate it, but this is particularly so for natural regeneration approaches given perceptions associating it with land abandonment.
A small but passionate group of foresters are strong advocates for the native woodland scheme. The management of planted native woodlands, particularly if close-to-nature practices are employed as they age, really draw on a foresters expertise and deep knowledge of trees and the environment. Ultimately native woodland scheme sites, when planted appropriately and with oversight of skilled foresters, do appear to provide a starting framework for a woodland which will, hopefully, also support natural regeneration as it ages to help sustain it in the long term.
It’s easy for the debate to get polarised, with proponents of rewilding often pitted against those in favour of a continued focus on non-native monocultures to support the timber industry. If we are to treat these climate and biodiversity crises with the urgency they deserve, we need all options available, as it seems our best chance of success lies with embracing diverse forests, both native and non-native, both planted and naturally regenerated, but all delivering multiple benefits for climate and biodiversity.
About the Author:
Kate is an Ecologist, nature-lover and PhD student based in the Dept of Botany, Trinity College. She is 1 year into her PhD research being completed as part of the FOREST project and supervised by Jane Stout and Fraser Mitchell.