The speed of a tree: how plants migrate to outpace climate change

One afternoon in April 2020, I took an old bamboo rod out of my shed and cut it to a length of 115cm. Stood on the ground, it came about halfway up my chest. I laid it on a scrubby patch of our garden on the island of Aegina, in Greece: one end next to a tough-looking dandelion, the other pointed northwards. Then I dug up the dandelion with a trowel and replanted it at the other end of the stick. A small step for humans, but quite the leap for the dandelion.

This 115cm corresponds to a particular measurement. It is the present average velocity of climate change — how fast the effects of global heating are moving across the surface of the planet — and thus represents the speed we need to move in order for the conditions around us to stay the same. It also implies a direction: the bubble habitats where different forms of life can survive and thrive are moving uphill, and towards the poles.

Local differences in velocity are determined by the shape of the land and of the Earth itself: climate change moves fastest in flooded grasslands, mangrove swamps and deserts; and is slower in mountain uplands and boreal forests. The impact is uneven too: if you live in a desert, you might have a lot of room to move, and a long way to go before you run into obstacles. If you’re already halfway up a mountain, you might soon have nowhere to go.

Scientists in California took averages of the change in global temperature over the past century, and those from forecasts of the next, and came up with a figure of 420 metres per year — or 115cm per day, the length of my bamboo rod. That’s the distance the dandelion has to move — every single day — just to live in the same conditions.

We know that climate change is occurring but, for a long time, it has felt like an abstraction. While numbers in reports and rising lines on graphs stirred unease, the effects weren’t always visible in our local environment. In recent years, of course, these effects have started to become clearer, wherever we live: hotter summers, fiercer storms, more severe wildfires, to name a few. But in the global north at least it’s still more of a feeling than a tangible event: something in the air, rather than on the ground.

Author James Bridle: ‘Plants move, and they are on the move: our whole worldview might begin to shift if we were to understand and internalise this realisation’ © Navine G Khan-Dossos

Worse, it seems like there is little to nothing we can do as individuals in response to this feeling, other than fearing its impacts: impacts that are already wiping out thousands of species and threaten the survival of our own. Climate change is no longer something we can reverse, but something we have to adapt to, cope with and mitigate as much as possible.

Such actions will not be possible without international-level state action, but combating the existential dread that accompanies the realisation of these changes is necessary too, and changing our relationship to and understanding of plants is one route to doing so.

In 2018, the artists Chris Woebken and Sascha Pohflepp created a small garden, just 25 sq m in size, on the island of São Miguel in the Azores. The Azores, far out in the Atlantic, are wet and cool in the winters. But Woebken and Pohflepp planted the garden with a dozen or so species of plant — including dandelions and fruit trees — native to the hotter, drier climates of the Mediterranean and north Africa. These plants were selected because in 100 years, that is the climate the Azores will have too: that’s where the velocity of climate change will have taken us.

The assisted migration garden created by Chris Woebken and Sascha Pohflepp in the Azores
The assisted migration garden created by Chris Woebken and Sascha Pohflepp in the Azores

The kind of work that Woebken and Pohflepp undertook, that I partook in too, in shifting that dandelion, is known as “assisted migration”. It can be highly controversial among botanists, not least because, in Britain, the arrival of new plants is associated with “invasive” species, such as Japanese knotweed and floating pennywort, prolific pests that were originally imported by gardeners but that threaten endemic species.

But in order to survive changing conditions, plants, like humans, need to move. And moving they are, it turns out, in ways far greater and grander than humans usually imagine. A vast migration is already under way, which challenges not only our idea of what plants are and what they are capable of, but perhaps some of our ideas about the world and our place in it.

What does plant migration actually look like? In part, it is a steady, local effort: creeping roots and floating seeds establishing the next generation in favourable areas along a population’s leading edge, leaving a dwindling trail of less successful plantations in the rear. At other times, it is accomplished in great strides, as seeds are flung into the atmosphere and carried by the winds to establish new and distant colonies, dispersed outlier populations that rapidly expand when conditions become favourable.

The bamboo rod used in James Bridle’s experiment with dandelions in his garden
The bamboo rod used in James Bridle’s garden experiment to see how far a dandelion would need to travel to remain in the same environmental conditions

Across the eastern US, populations of trees have been migrating for at least the past 30 years, probably much more. Researchers who examined Forest Service data from 1980 to 2015 found that three-quarters of species in the eastern US were shifting north and westwards, at an average rate of 10km-15km per decade.

Speed and direction is different for different types of trees: the conifers are mostly heading north, while broad-leafed and flowering trees, such as oaks and birches, move west. The fastest moving are white spruce, which clock up more than 100km each decade, almost unswervingly northwards.

By contrast, American sweetgums and balsam poplars have barely moved at all, registering shifts of just a couple of kilometres in the same period. This means that the white spruce is keeping well ahead of climatic change for now — but starting as it is from higher latitudes, across the top of the US, it won’t have as far to run as the sweetgums of Alabama and Georgia when things get tough.

In Scandinavia, which is experiencing warming that far exceeds the global average, fast-growing birch saplings are racing up mountainsides they had previously shunned, gaining as much as 500m elevation in just a couple of decades. Swedish pines, spruce and willow are now growing at higher altitudes than ever before. A comparison of photos taken by oil surveys in Alaska in the 1940s with the same locations today shows alder, willow and dwarf birch flooding into once-sparse valleys and pushing up once-bare hills.

River Flowing Through a Valley in Boreal Forest, Alaska
Populations of trees have been migrating in recent years; in Alaska alder, willow and dwarf birch have moved into once-sparse valleys © Ami Parikh/Alamy

Trees are adapting to climate change faster than we are, and as a result have more chance of adapting successfully. In fact, climate change is probably only one of several factors they’re responding to. Other human activities, such as construction and pesticide use, are also likely to be playing a part. Whatever the combination of factors, however, mass plant movements are in process, and not for the first time.

The last great tree migration occurred at the end of the last Ice Age, around 10,000 years ago. Following the retreat of the ice, trees started to return to the higher latitudes they’d earlier been frozen out of. They did so surprisingly quickly.

The Victorian geologist and palaeobotanist Clement Reid, writing in 1899, noted that oaks had already reached the far north of Scotland two millennia earlier, as shown by acorns turning up in archaeological excavations of Roman-age sites. He concluded that “to gain its present most northerly position in North Britain after being driven out by the cold”, the oak “probably had to travel fully six hundred miles, and this without external aid would take something like a million years”.

In fact, fossil pollen records show that some of the oaks travelled, at times, at nearly a kilometre a year, a rate confirmed by more recent, climate-based studies. It also seems likely that this recovery was abetted by the existence of a few, scattered refugia: ice-bound sanctuaries where small groups of trees survived in temperate pockets to seed the ground after the thaw.

As the planet warmed, the forests re­conquered the land. In North America, beech trees leapt over the Great Lakes as the glaciers retreated. Norwegian spruces circumnavigated the North and Baltic seas before modern humans did.


100km


Distance that white spruce trees in the eastern US have been moving each decade over the past 30 years

These processes are grand and magnificent; they inspire awe and wonder — but still mostly in the abstract. I can comprehend the mathematics of species dissemination, read accounts of fossil pollen counts, trace the lines of movement through decades of database records — but what does it mean to experience it? Living at human speed, at animal speed, it’s almost impossible to get my head around the vegetal unfolding of plant migration, an endeavour taking place at spatial and temporal scales beyond my natural understanding.

And this is our problem. We humans live in such a narrow slice of time and space that we are incapable of thinking of, or thinking at, the pace and scale of the world, the changes we have wrought in it, and the changes we will have to make to survive them. Our given minds are insufficient to the task — but we do have tools to hand.

Another recent hobby of mine, when not acting as a Fluchthelfer for dandelions, is time-lapse photography. For this purpose I acquired a small, weatherproof camera designed for documenting construction projects: a few inches high, it can sit undisturbed in a corner, observing the world for weeks, powered only by a couple of AA batteries.


For months, I shuffled this little device around my apartment, spending days at a time with each of the potted denizens of the living room. When I review the footage, the apparently inert ferns and ficus burst into life; philodendron curls its fingers around the lampshades; monstera bobs and waves its leaves; lilies open and close, turning to follow the sun as it moves across the walls.

Latterly, I’ve turned the camera on my little garden, to the same effect (see video above): vegetables burst from the soil, just as the weeds rush across the earth to meet them. Each creature has its own pace, its own rhythm, but all move together, flexing, turning, bending, stretching. What appears to me from my desk as perfect stillness is in reality a frenzy of activity in another register. Nothing could persuade me better that, in the words of the botanist Jack Schultz, “plants are just very slow animals”.

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Plants move, and they are on the move: our whole worldview might begin to shift if we were to understand and internalise this realisation. We’re so used to the idea that plants are rooted in place that such a revelation might shock us out of our complacency: about plant migration, about wider patterns of climate-induced animal and human migration, and about the devastating effects of climate change itself. It’s hard to see at first, but we have the tools to do so: we need to match them with our hope and will.

Experiments such as these were undertaken at the same time as I was working on a new book, Ways of Being, which explores the myriad ways in which animals, plants, ecosystems — and new forms of artificial intelligence — challenge the idea of human superiority through their own abilities and agency. Understanding that plants and all the other beings that we share the planet with are intelligent, communicative and full of their own knowledges about the world is crucial to building new relationships with them, so we may survive an uncertain future together.

While these changes are happening at a global scale, they are occurring in our homes and gardens too, and the first, and most significant, step we can take is to start paying attention to them.

Ways of Being” is published this month in the UK by Allen Lane; in June in the US by Farrar, Straus and Giroux

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