Alissa MacMillan
Q: I planted Sitka spruce many years ago and it will be ready for harvesting soon. I sometimes feel regret about it and wondered what the most environmental next step might be for the land.
A: While many of us might look at our Sitka spruce plantations and think, in retrospect, we’ve made a mistake for the health of the environment, it’s not as clear-cut as that. As you note, there are complex decisions to be made about what to do with your land, especially as you weigh economic and environmental concerns.
Dr. Markus Eichhorn, senior lecturer in forest ecology at UCC, wants to “challenge the assumption that planting Sitka spruce is automatically a bad thing to do.” Indeed, he says, “it has lower biodiversity value than the native woodland, but it’s not really a fair comparison because they are doing entirely different things.”
As Eichhorn explains, Sitka spruce is a crop, and “we need crops, we need timber, we should be using timber to replace concrete and steel.” Of the many materials we do use, “it is renewable, natural, and sustainable, and while we may not appreciate having Sitka in our backyard, forestry has to be part of our plans for land use for our country,” especially forestry that grows fast and meets our need.
For those who argue that it’s a non-native species, so shouldn’t be here, Eichhorn notes that this isn’t applied to, say, potatoes. Both are “crops grown for a specific purpose.” As with all these things, non-native species are usually a lot more productive than native, he says, and there isn’t a native species in Ireland that will support economically viable forestry. It’s not impossible, with, for example, birch, and might work on a small scale, but oak is productive in about a hundred years, making it “not a viable proposition from an economic standpoint.”
DECOMPOSITION
As for your spruce plantation, after the felling, the land might look like “a war zone,” but it’s far from it. “When you see harvested plantations, people get very upset,” Eichhorn says, seeing lines of brash, the twigs and branches. But it’s all a positive thing.
“Leave it in rows on the land. It protects the soil, it stops the soil being washed away, and it provides habitat for lots of birds, animals that will nest in it, wood is broken down by decomposing things like fungi, and it provides shelter for the next generation of trees.”
The waste after felling decomposes in five or six years, he says, and you can usually wait a few years for things to recover.
“The soil will recover very quickly,” and your new planting can happen amid the decomposing matter. “If you plant into that, it will come,” he adds.
Eichhorn points out that, apart from growing rotation forests, “there is a spectrum of things you can do,” like continuous cover forestry, where instead of a clear felling and replanting, you remove a portion over time to create more complex forestry, still producing large trees. “You can move to growing broadleaf trees,” which grow slower and require more management, but sometimes produce higher quality wood.
At the far end, you can restore native woodland, “and that’s great,” he says. “We need people to do that.” But, he reminds us, growing native species for forestry is not a replacement for strong native woodlands, even if it’s a bit better for biodiversity.
And if you let your Sitka grow?
“They are gorgeous when left but the downside is they are going to produce seed and spread, turning into an invasive species, as is happening in Scotland.” And if the felled land is left, new Sitka likely won’t grow but bushes and other trees will show up.
‘THE PERFECT FOREST DOESN’T EXIST’
Even while the Sitka spruce is growing, the land is not dead, Eichhorn points out. “There is less in a Sitka plantation than a native oak woodland, but that’s not what it’s for.” Also, as 30% of any planting must be native species, oak bordering a plot is helpful, offering “spillover benefits,” like more biodiversity. In practice, it very much depends on how it’s implemented, consideration needed for things like protection from deer, planting species that are appropriate to the site, and, as oft happens, choosing seed that’s easily available, like alder, simply to meet requirements, instead of choosing what’s best for biodiversity.
In his view, “the conversation we need to have is about landscapes and how there isn’t one forest type that will solve all our problems at once.” We need some sites for timber, some for nature restoration, and some for ecological services, and we need to balance those collectively. “The perfect forest doesn’t exist.”
He adds, “If making a decision, you need to make a balance with economic returns and natural returns; you can’t do both with a single forest.”
Deciding on priorities and accepting that there are trade-offs, he adds, it’s helpful to recognise that “neither the forestry sector nor the agriculture sector is evil when, fundamentally, society depends on them.” The global demand for timber is growing, statistics from the UK showing that the average person uses one cubic metre of wood a year, which is “a big block of wood per person per year.”
“If it’s not coming from forestry, it’s coming from a native forest somewhere else, so forestry is one of the ways to protect native forests somewhere else,” he notes.
“Establishing forests is an active decision,” Eichhorn adds. Ireland has a lower native woodland cover than almost anywhere else in Europe, and, “collectively, I think people would like to see more forests in Ireland,” this is happening thanks to restoration projects and NGOs like HomeTree, but more difficult for agencies like Coillte which need to make a profit.
“Even if we care deeply about restoration, we need a healthy, viable forestry sector to make restoration possible, we need seed stock, planters, and managers, that still need to make money.”
It’s also “a valuable service for the world,” he adds. “We talk about high quality timber, but we also need low quality timber that’s just good enough,” he says, which is what Ireland produces. “Slovenia produces timber for cellos and violins,” and Ireland doesn’t. “Ireland is producing a resource that the country and the global economy needs and we shouldn’t be embarrassed about that.”
While Sitka spruce is mainly what’s planted, Eichhorn notes that we need to diversify and plant other tree species and explore what different types grow well here. But, he reminds us, planting for a crop is planting for a crop. If you want biodiversity, you need to plant for biodiversity, like restoring native woodlands. It’s a different aim, both beneficial in their ways.
