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Trees will plant themselves, if we let them

Thursday 18 March 2021

When it comes to combatting global warming, people should step back more and let nature take the lead

The barn was long abandoned. The air inside was still and cold, my breath hanging in the air – great puffs of it dissipating behind me. I passed along a wide central aisle between what once were stalls where dairy cattle could be milked. Hundreds of them, maybe thousands of them, at once.

I was in Estonia, an hour or so inland from the coast, on the site of a former kolkhoz or collective farm dating from the Soviet era. During collectivisation in the mid 20th Century, traditional family-owned farms were gathered together to create huge monolithic enterprises with vast land estates and industrial scale farm buildings. Concrete super-barns like this were thrown up, with the functional, utilitarian architecture of aircraft hangers or warehouses. This one had a dusty haybarn in the eaves, a low ceiling in the milking parlour below, and all the atmosphere of an open-plan office. Pipes ran like arteries over the ceiling into a central hub where dusty valves and levers rust closed. 

Outside, a courtyard between this building and the next had become overgrown with whip-thin birches with leaves of green confetti and a fringe of dry weeds. And beyond that, across the road, what once was grazing land had taken on a strange, shaggy countenance – overgrown and uneven, neither meadow nor yet woodland. Slender sapling broadleaves huddling together in cliques. Brambles, sending out long limbs to search the earth, had tangled into impassable briars. Small conifers bristled from the ground. 

These scrappy, unbecoming old fields were the reason I had travelled to this region. Not for the views – the vegetation is dense enough that one can’t see for more than a hundred metres or so – but for this sense of landscape in transition, for this mongrel mix of species living in anarchy.

When the USSR disintegrated at the beginning of the 1990s, the collective farming system went with it, triggering one of the biggest revolutions in land use the world has ever seen. Since then, nearly a third of Soviet farmland – an estimated 63 million hectares, an area roughly the size of France – has been abandoned. Or, abandoned by humans. It has been reclaimed by other species.

First came the flowering weeds and long grasses. Later, shrubs and scrub – dog roses, brambles – then the first of the hopeful pioneer trees, trying it out for size: rowans and birches, skinny willows standing close together. The dry and spiny humpbacked junipers bowing their heads. A forest in the making, given time. And as the vegetation thickens, and the sproutlings mature, so carbon is absorbed from the air and into their bodies, their leaves, the lichens and the soil itself.

Tree cover in Estonia has rapidly increased in the years since the fall of the USSR, so that it has now become one of the most forested countries in Europe. Such has been the pattern in much of the former Soviet bloc: all in, this massive forest regrowth represents the biggest man-made carbon sink in history; an accumulation of carbon in the form of vegetation which lowers carbon dioxide levels in the atmosphere. Though notoriously difficult to quantify, one 2013 study estimated the carbon sink in Russian territory alone to be equivalent to around ten per cent of Russian emissions from fossil fuels. (If correct, these figures would mean that Russia had, technically, surpassed the terms of the Kyoto Protocol through the abandonment of farmland alone.)

So what can we learn from such a thing? Given the enthusiasm for tree-planting that has gripped politicians both here in the UK and elsewhere in recent years, I think it’s instructive to consider the wholesale transformation of former collective farms. This is regrowth and a rewilding of a kind, on what conservationists might describe as happening on “a landscape scale” – and with all its ecological and climatological significance.

Currently there are a number of major initiatives to get more trees into the ground, as a tool of carbon sequestration. The IUCN’s Bonn Challenge, for example, has brought the efforts of 74 governments, private companies and other bodies under one banner, which proposes to restore trees to over 210 million hectares across the world, while the World Economic Forum is spearheading international efforts to “grow, restore and conserve” one trillion trees in a project of the same name. These ambitions, though lofty, still lag behind the billion hectares of new forest that the Intergovernmental Panel on Climate Changes suggests to be necessary, if we are to limit global warming to 1.5ºC by 2050.

In the UK, it was announced in December that £40 million in funding – the first tranche of the Green Economic Recovery fund – would go towards, amongst other things, the planting of 800,000 trees, as part of the pledge to be planting 30,000 hectares of trees annually by 2025. Boris Johnson’s government has committed to significantly increasing woodland cover in the UK, largely through tree planting, from its current level of 13 per cent of land area up to 20 per cent. (Even then, we will be trailing behind much of Europe; in Germany, where there is a not-dissimilar population density, that figure is 33 per cent.)

As a tactic for the sequestration of carbon, it’s a solid one. Though not enough on its own to avert climate disaster, tree planting on a large scale has the potential to capture enormous quantities of carbon from the atmosphere – an opportunity to pay off a chunk of our vast, and still-growing, carbon debt. It too has other benefits – ecological, sociological – and is reassuringly low tech. As the geographer Susanna Hecht has noted, “trees have already been invented.” But tree planting comes with issues of its own. Past efforts at rapid afforestation have often brought unforeseen issues.  

In the UK, tree planting began in earnest after the First World War when tree cover was at its lowest ebb, around five per cent. Rates peaked in the 1970s and 80s at up to 40,000 hectares a year. But the huge plantations dating from this era have caused many issues in and of themselves. 

Sitka spruce, a hardy conifer native to Alaska, has become a notorious symbol of the industrial-scale monocultures of 20th-century forestry, those dense and unnatural forests that patchwork the landscape of Scotland, where I grew up. The trees, tall and tightly packed, block sunlight from the ground, and support little else in terms of biodiversity. And in the hurry to get trees in the ground, these plantations often sprung up in unsuitable locations, including peatland – which was often dug up and drained, releasing far greater quantities of carbon than the new trees could ever absorb.  

Much has been learned from the errors of planters past, and bodies like the Forestry Commission have changed their ways – designing plantations to be more organic in appearance, and making more use of native species. Nevertheless, to devote vast tracts of land, perhaps millions of hectares worldwide, to another form of manmade landscape feels unwise.

The drawbacks of tree planting on enormous scales start with logistics. To do it, we need industrial quantities of fertiliser, massive tree nurseries, seedlings produced on enormous scales. One recent study, published in February, warned that American nurseries would have to produce an extra 1.7 billion seedlings a year if current plans to plant 26 million hectares are to come to fruition – 2.3 times the current capacity. The total costs of such a project were likely to be in the region of $33 billion. 

Even if we produce enough seedlings, they are often frail – many die before they make it into the ground, or shortly after. Some dry out en route, or are shaken to death on the rough plantation tracks. Seedlings grown commercially have also been known to act as vectors of disease; ash dieback, caused by a type of fungus and expected to kill 80 per cent of all ash trees in the country, was almost certainly introduced to the UK by imported seedlings. 

Then there is the work of planting them: a labour intensive, back-breaking job requiring teams of skilled planters, and then years of follow-up work to monitor the baby trees for pests, diseases, windthrow and all such disasters to which young trees are prone.

Several start-ups have popped up offering to solve some of these issues through technological means: the Anglo-Australian company Dendra Systems, for example, uses drones to scan ground before “planting” up to 100,000 trees a day by firing seeds into the ground at intervals. An enviably quick and efficient approach to mass tree planting, if that’s what you value. (Perhaps this is why Glencore and Rio Tinto are listed as previous customers.)

But embracing tree planting as a cure-all, and rushing millions of trees into the ground whether through hand-planting or dropping by drone, has led to projects that backfire. In Chile, for example, financial incentives were offered to tree planters for nearly forty years as a major flagship conservation policy. But though total tree cover expanded over this period, researchers at Stanford University believe that the area of native forest actually declined. In some regions, existing natural woodland was cut back in favour of plantations of commercial trees. An own goal.

For all forests are not created equal. Sparse, artificial new “forests” are far less biodiverse and store far less carbon than natural woodland. Even scrubland, with its mix of bushes,rough grass and occasional tree, is better from an ecological point of view. Because you don’t just plant a few thousand trees and get a forest: a true forest is a complex, multi-generational ecosystem that builds up in layers, one species laying the groundwork for another, or filling in the gaps. Fungi, leaf litter, undercanopy, climbers – without them trees are forest in name alone. 

One alternative to plantation forestry is natural regeneration. Reforestation via natural processes of succession will take place of its own accord in areas left disused by humans, provided the ground is suitable for tree growth and they are protected from heavy grazing. 

Land owners can be hesitant to embrace natural regrowth. Partly, I think, because “doing nothing” feels counterintuitive and wrong. Partly too because progress feels slower; land in the process of regrowing, like the old fields of Estonia, can look unkempt, and unlike the forest that will, in time, take over. Land might become colonised by less desirable plants – offering sanctuary to invasive species, especially in the early days when the ground is still disturbed. But, given time, these naturally recovered forests are denser both with life and carbon, and made up of species better suited to the local conditions, and without need of nannying. 

Those who have witnessed the glorious fall colours of New England will know what forest regrowth can look like—the region, now 80 per cent forest, is largely secondary forest which has grown up in the decades since the farmers left the northeast of America for the “breadbasket” of the Midwest. The trees returned under their own steam, and with them came the moose, the beavers, the bears and the woodpeckers. All in, American forests expanded by around 360,000 hectares every year between 1910 and 1979. In the latter half of the 20th Century, huge tracts of China, South America and Europe have begun to follow suit. 

In Italy, for example, widespread farmland abandonment has led to rapid afforestation in many regions; since 2005, woodland in Molise, a region in southern Italy, has increased by 17 per cent, largely thanks to natural regeneration. In Sicily, that figure was 16 per cent, and in Basilicata 11 per cent. (Wild boar, roe deer and lynx have also boomed.)

Allowing abandoned land to regrow is clearly a cheaper and less labour-intensive model of reforestation on a grand scale. It also avoids many of the issues of plantation forestry, and the strange skin-deep habitats they create.

In all likelihood the way forward will involve both active planting and forest regrowth. Plantations of the fastest growing trees probably is the fastest route to carbon sequestration, even if they have knock-on environmental impacts. In degraded soils, stripped of seeds and nutrients, they jump-start growth. There will be a place for them. 

Also, people like to feel helpful, to look busy. They like an achievable task: a spade, a hole, a sapling tree is a simple way of expressing environmental enthusiasm. I know this pleasure, I’ve felt it myself. Patted myself on the back afterwards. 

Het up by news of impending disaster, we seek radical plans of action. Radical inaction can be harder. But in our hurry for satisfaction, for tangible results, we must not dismiss the potential of the slower, stepwise solution. Seeds blow in, are left in droppings, are buried by squirrels or jays. They germinate, take root. Given time and space, the trees will return of their own accord. 

“If we let them,” Rebecca Wrigley, Rewilding Britain’s chief executive, recently argued, “millions of trees would plant themselves across most of Britain.” The question is: will we let them?

Cal Flyn’s book Islands of Abandonment: Life in the Post-Human Landscape is out now