Book Summary: The Treeline by Ben Rawlence

My Personal Summary

This book is about global warming, viewed through the lens of the “treeline” – the latitude above which there are no trees – which has been steadily shifting north as the temperatures near the arctic circle are becoming warmer and able to support the growth of trees.

It turns out that there are six main trees that make up this treeline:

  • Scots pine in Scotland
  • Birch in Scandinavia
  • Larch in Siberia
  • Spruce in Alaska
  • Poplar in Canada
  • Rowan in Greenland

The author of this book visits each of these regions firsthand to talk with both locals and scientists about the changes in the treeline that they’ve observed in recent years.

There are two huge concerns for forests that are associated with a warming planet:

(1) As they warm, forests lose their ability to absorb and store carbon dioxide. While the boreal is the greatest planetary source of oxygen, more trees there does not necessarily mean more carbon sequestered from the atmosphere.

(2) As trees invade frozen tundra they hasten the melting of permafrost, frozen soils that contain enough greenhouse gases to accelerate global warming beyond anything scientists have modeled.

Both of these effects are extremely concerning and most global warming models don’t even take them into account.

Book Notes

  • Ever since the Pliocene epoch, three million years ago, when the explosion of plants cooled the atmosphere to its modern equilibrium, ice ages have marked our planet in 100,000 – year pulses. The pulse is because the earth does not spin evenly but wobbles like a top. The wobble is called the Milankovitch cycle. It tilts the planet a fraction away from the sun every 100,000 years, chilling it ever so slightly and causing the ice at the poles to expand and retreat in a millennial version of our annual seasons.
  • The northern hemisphere meanwhile has been forested and deforested over and over. Time – lapse photography of geological time on planet earth would show a sheet of ice descending and retreating in a rhythmic pattern, and a green mass of forest rising toward the North Pole then falling again, like breath. But now the planet is hyperventilating. This bright green halo is moving unnaturally fast, crowning the planet with a laurel of needles and leaves, turning the white Arctic green. The migration of the treeline north is no longer a matter of inches per century ; instead it is hundreds of feet every year. The trees are on the move. They shouldn’t be. And this sinister fact has enormous consequences for all life on earth.
  • More than the Amazon rain forest, the boreal is truly the lung of the world. Covering one fifth of the globe, and containing one third of all the trees on earth, the boreal is the second largest biome, or living system, after the ocean. Planetary systems — cycles of water and oxygen, atmospheric circulation, the albedo effect, ocean currents and polar winds — are shaped and directed by the position of the treeline and the functioning of the forest.
  • As they warm, forests are losing their ability to absorb and store carbon dioxide. While the boreal is the greatest planetary source of oxygen, more trees there does not necessarily mean more carbon sequestered from the atmosphere. As trees invade frozen tundra they hasten the melting of permafrost, frozen soils that contain enough greenhouse gases to accelerate global warming beyond anything scientists have modeled. Many contradictory things are happening at the same time.
  • It was only when I discovered that a tiny handful of tree species make up the treeline that I began to see that an attempt at description might be possible. An elite club, the six featured here are the familiar markers of the northern territories: three conifers and three broadleaves evolved to survive the cold. Moreover, remarkably, each of these tree species has made a section of the treeline its own, outcompeting other species and anchoring unique ecosystems: Scots pine in Scotland, birch in Scandinavia, larch in Siberia, spruce in Alaska and, to a lesser extent, poplar in Canada and rowan in Greenland.
  • The natural lifespan of a Scots pine is up to six hundred or seven hundred years within the healthy network of a forest. Scotland’s surviving granny pines are mostly under four hundred. Major dips in the pollen record suggest this is because of the massive extraction of trees from 1690 to 1812.
  • The boulder is a miniature showcase of the treeline at work : a future hummock. An exposed rock will first be colonized by crustose lichen mining its minerals, growing at a rate of 0.1 millimeters a year. To obtain the minerals, the lichens secrete an acid which breaks down the rock. Other foliose lichens, with more leafy structures, take advantage of this broken layer as do mosses which then trap further organic material in their fronds and accelerate the process of soil accumulation. When this top layer eventually overcomes a tree stump or boulder and joins up with the surface soil, it will form a hummock.
  • Hummocks in regular sizes close together are often remnants of ancient woodland where soil has accumulated over tree stumps. Their formation can take decades, if not hundreds of years.
  • The “treeline” is the latitude above which there are no trees, which is roughly the arctic circle. It turns out that there are six main types of trees in this treeline, which the author explains in detail in the book.
  • Deer are woodland creatures essential to the healthy functioning of a pine wood — opening up ground through grazing, fertilizing the forest floor with their dung — but if they stay too long or become too many, they can wreak havoc. Deer will eat almost any tree as high as they can reach, and they will attack seedlings with their antlers to scratch them, breaking young stems in half. The Scottish nature writer Jim Crumley calls the wolf the “ painter of mountains ” because it keeps deer populations in check.
  • Studies have shown that birds lay stronger, larger eggs in older forests.
  • This is the signature characteristic of wildwood — dead trees are allowed to rest where they fall. Dead trees support far more life than living ones, hence the density of bird life. Some species like tree pipits and redstarts associate only with old – growth forests because of the volume and species of insects. The greater spotted woodpecker nests only in dead Scots pines. Even more niche, the pine hoverfly breeds exclusively in wet hollows of dead Scots pines.
  • In any carbon cycle, death is the engine of life. When a tree dies, wood – boring beetles enter the sapwood and begin the process of decay. Then fungi enter the spaces along with wasps, spiders and other insects, and invite other fungi. And in the final stages, the humification phase, soil organisms convert the last of the wood molecule lignin to soil. The cycle is complete. Because of its high resin content, a mature Scots pine takes forty years to decay, releasing nitrogen slowly into the soil, feeding the grubs and bacteria that are the bottom of the food chain for insects and birds.
  • In an effort to bring back the growth of forests in northern Scotland, there has been a program put in place to kill vast amounts of deer to bring their population down so that they can’t graze unchecked on all small plants and tiny trees.
  • Planting trees without regard for the essential symbiotic “ other half ” of the forest belowground may be far less effective than allowing the ground to evolve into woodland at its own pace. Oliver Rackham describes a planted oak wood in Essex that even after 750 years still does not possess the orchids, plants and mushrooms that you would expect of a natural wood. 12
  • Britain is desperately trying to increase the size of its woodlands. At 13 percent forest cover, the UK is far behind the European average of 37 percent and the global average of 30 percent. Moreover, much of that 13 percent is plantation — a single crop grown for timber — with very little diversity of species living among the trees or beneath them. Indeed, plantations are not really forests at all. Sweden and Finland account for a third of the forests in the European Union with 68 and 71 percent of their territories wooded respectively.
  • Peat moss loves carbon dioxide. With the increase in CO2 in recent years, peat moss has been thriving in forest floors. However, too much of it can choke out room for other plants to grow.
  • Scots pine is currently able to grow from Scotland all the way to Southern Europe. But with rising global temperatures, pine needles turn brown earlier in the year and crumble. It’s predicted that in less than 100 years, Scots pine will no longer be able to grow in southern Europe.
  • Various species of birch trees are the only trees that grow in Scandinavian countries. Humans are dependent on these trees for houses, tools, food, fuel and medicine.
  • In Finland, reindeer herding supports the livelihood of many people as reindeer meet is considered a delicacy and can be sold all over the world. However, reindeer depend on their ability to feed on carbohydrate and sugar-rich lichens underneath the snow. In recent years, temperatures have become so warm in the winter that snow begins to melt and when temperatures dip lower again the snow freezes, making it impossible for the reindeer to break through the frozen snow to reach the lichen. This results in massive reindeer deaths.
  • If it is not cold enough to leave the autumn grazing and move to winter pastures, the herd will not go but will risk overgrazing a single area or range beyond its normal territory. And if there is too much moisture, meaning the ground locks, or the food supply is bad, a female reindeer can even consciously abort her unborn young, a trait shared with a few other mammals such as mice, monkeys and killer whales.
  • The downy birch loves the warmer weather. It used to be confined to the dips and gullies on the plateau, out of the icy winds, but, unleashed by the warmth, it is storming over the top and out into the open, moving upslope at the rate of 130 feet a year. An enormous amount of territory is being transformed from tundra into woodland at a lightning pace. On the face of it, more trees might sound like a good thing. Except that the greening of the tundra is closely linked to more warming as the birch improves the soil and warms it further with microbial activity, melting the permafrost and releasing methane — a greenhouse gas eighty – five times more powerful than carbon dioxide in its warming effects over a shorter timeframe.
  • In Norway aggressive tree growth is now creating havoc. The birch is racing over the tundra faster than the pines can keep up. This is bad news for the reindeer and the humans that rely on them. Upright birch forests don’t develop a canopy, they are more like thickets. Without a canopy, they trap more snow, their branches bending and cracking with the weight and their mass forming a windbreak for drifts too deep for the reindeer to walk or dig through. Their roots warm the ground below, causing ice and melt around them.
  • The change in color of the tundra has serious consequences. Reindeer are the only mammals that can see ultraviolet light — invisible to humans. In the low light of the polar night, when the sun doesn’t rise, this ability is crucial to their survival. Lichen absorbs UV and so appears black against the snow. There is also emerging evidence that lichen fluoresce in different colors and so might be visible to reindeer through the snow.
  • Their eye has a special strip called a tapetum lucidum, common to nocturnal animals and insects, a “ bright tapestry ” that absorbs light and reflects it back into the retina to improve their vision in low light. Unique to reindeer, in summer the tapetum is golden and in winter it turns deep blue to absorb the UV. In unbroken snow the reindeer are calm and usually stay in one place, digging the snow to reach their food. But a speckled black and white is tempting and confusing, raising the possibility that more easily accessible food might be on offer. They avoid digging and instead nibble the grass and lichen uncovered at the base of trees, moving over much greater distances and causing a headache for the herder, who must keep an eye on them and keep them together, to avoid straying onto the territory of a neighboring siida or, worse, mixing with another. Separating ten thousand reindeer can take two weeks.
  • In cold conditions the tracks of an errant animal are easily visible on the snow, and a snowmobile can fly over open tundra, frozen lakes and rivers in a twenty – mile circuit. An unfrozen landscape pocked with shrubs is much harder to negotiate. Without sufficient snow for a snowmobile, and without ice, a herder on a quad bike must go around lakes, rivers and trees, sometimes up to forty or fifty miles further. It takes a whole day, burning a lot of fuel and crushing a lot of lichen that takes hundreds of years to return.
  • A reindeer herder can make about $1,400 per reindeer, so losing even one is a big deal.
  • There is also bread made with dried reindeer blood, reindeer brains and flour from ground pine bark. This is an important source of vitamin C and other minerals that meant the Sámi never suffered from scurvy despite shortages of vegetables during the long winters. This is one of the reasons the pine, called bèahci by the Sámi, is sacred — it is necessary for life.
  • Of all the forests in the world, the Russian taiga is the greatest. It covers over half of the land mass of Russia, stretching for more than three million square miles across two continents and ten time zones. It is a green carpet of trees atop permafrost and makes up well over half of the boreal’s planetary engine, regulating patterns of wind, rainfall, climate and ocean circulation in the northern hemisphere. The boreal is largely made up of the Russian taiga, and the taiga is predominantly larch.
  • More than one third of the taiga (37 percent) is larch, it is the keystone species. Like pine in Scotland, the larch has mastered its environment better than any other tree and therefore dominates the ecosystem, shaping the life cycles and evolutionary paths of other plants and animals. Its leaf litter is the basis of the soil, its cycles of seed production regulate the populations of birds and rodents, its demand for light sets the limits for what can grow in the understory, and its resistance to fire as well as its appetite for colonizing burned ground mean it has shaped the very architecture of the taiga forest in Siberia as we know it.
  • Interesting: Scotland has historically struggled from deforestation while Norway is now struggling with afforestation (the conversion of land into forest) at too rapid of a pace.
  • In the high taiga at the treeline, in Ary Mas for example in the north of the district, fire was always a rare visitor, usually the result of lightning. There the interval between fires is long, up to three hundred years, but frequency and intensity increase as you go south. In the lower latitudes the fire interval was previously 5 – 30 years depending on rainfall. Now in some places fires are an annual event. As temperatures have increased and the soil has grown drier, fires are hotter, longer and more frequent, consuming more of the soil and making it harder for larch to reestablish afterward.
  • Repeated burning makes terrain almost impossible for trees to root in. Instead plants that like very marginal soils have taken their place. This means shrubs like willow crowding out the larch and building up dense clusters of wood that in turn burn hotter next time. Over time, the burn cycles open the door to grasses from the steppe, which prevent trees from germinating and smother everything else.
  • Since different species have different plumbing, their contribution to the atmosphere and climate is varied and unique. Of the carbon dioxide that the taiga sequesters, larch is responsible for soaking up 55 percent even though it only accounts for just under 40 percent of the trees. This single species is the greatest arboreal source of oxygen on earth. Because larch is deciduous, it transpires a lot more water than evergreens, taking in 20 percent more carbon dioxide than pine, and the soils beneath larch, covered as they are with half – decomposed larch needles, emit a quarter less carbon dioxide than those under pine. Moreover, a warming forest is less efficient at cycling and sequestering carbon as trees lack water to photosynthesize, stop growing or lose their leaves earlier.
  • Unlicensed logging to fuel China’s construction boom means there is much flammable waste. In addition, a warmer, more humid atmosphere means double the amount of lightning and double the number of ignitions.
  • Prior to 2018 the average volume of wildfire emissions was 2 megatons of carbon dioxide per year. In 2019 it was 5 megatons. Later in 2020, after I visited her, fires in Siberia would break records, emitting 16 megatons in the month of June alone. Forest fires on this scale had not been predicted until 2060.
  • Daisies, swallows and dragonflies have started appearing in the tundra, and last summer people swam in the sea for two weeks. Usually summer only lasts a few days. The berries are getting larger, and the sea ice in the bay in Syndassko is taking longer to freeze in winter. And the shore by the meteorological station is collapsing into the sea ! Anna says they’ve been noticing other things too : ravens have started appearing, and cranes. Both birds that they never used to see, whose normal breeding grounds are much further south.
  • Frozen tundra soils are one of the largest stores of organic carbon on the planet — living matter, plants and animals that have not totally rotted away or are rotting so slowly that they have been preserved or fossilized intact. That is why Kolya and Kolya spend every summer digging for mammoth tusks in the tundra of Taimyr ; melting permafrost is turning the search for prehistoric ivory into a kind of gold rush. As the temperatures warm up and the permafrost begins to thaw, anaerobic decomposition releases methane. These days bubbles of methane have started appearing in the tundra ponds and in the sea ice out in the estuary.
  • The Siberian Shelf, which forms the seabed off the coast of Taimyr, means the ocean toward the North Pole is shallow. At the end of the last ice age, this was tundra. When the glaciers melted they inundated the land, trapping all the half – decomposed soil and vegetation beneath a cold sea that remained frozen for most of the year, resulting in methane hydrates, ice structures holding the gas. But now that the reflective blanket of sea ice has nearly gone, the dark sea floor absorbs up to 80 percent more radiation from the sun, and the shallow water heats up fast and stays warm throughout the year.
  • Sentinel, an EU satellite, can measure methane concentrations in the atmosphere, but figuring out where it is coming from is difficult. Some studies have suggested that an unstable seabed could release a methane “ burp ” of five hundred to five thousand gigatons, equivalent to decades of greenhouse gas emissions, contributing to an abrupt jump in temperature that humans will be powerless to arrest.
  • There is twice as much greenhouse gas — carbon dioxide, methane and nitrous oxide — stored in the permafrost as currently is in the atmosphere, enough to accelerate global warming exponentially and effectively end life on earth as we know it if it were all released at once. Yet most climate models discount permafrost because of the lack of data even though 40 percent of permafrost is projected to be gone by the end of the century.
  • This is why larch makes such good firewood in winter, and why they can survive in these temperatures at all : they have evolved a mechanism for avoiding the fatal formation of ice crystals inside the living cells of the tree.
  • It is this ability to manage moisture in the form of water and ice that allows the larch to thrive in the comparative desert of Siberia. In the winter their roots may be frozen solid, but even a short day of winter light on the tips of their branches can activate the roots, drawing moisture up into the branches and needles from the iron – hard ground. At low temperatures moisture is scarce, but ice — in the form of permafrost — is abundant. Dahurian larch likes the cold so much that researchers believe it coevolved with the spread of permafrost. It is no surprise that this cryolithic forest, the frozen forest of the northern taiga, should be dominated by the species that has learned to love the ice the best.
  • In northern Siberia, ornithologists have been seeing birds they’ve never seen before in recent years because the climate has never been so warm.
  • After a couple of feet or so of solid ground, the soil underneath was slush, just as he predicted : the permafrost was melting from below as well as from above. Almost everyone had assumed that the permafrost would gradually melt from above, as a result of warmer air temperatures deepening the active layer of unfrozen soil on top. But Sergei’s finding pointed to a different future : rapid permafrost collapse. It meant any frozen ecosystem based on permafrost was in urgent trouble, not to mention the unquantifiable emissions of methane and carbon.
  • With larch on top of it, the permafrost is much more vulnerable to warming because larch traps snow.
  • “That five – degree warming of the soil is caused by snow,” Nikita explains. The winter cold does not penetrate into the soil because of snow cover.
  • So, in 1988 he acquired sixty – two square miles of scrubby forest – tundra treeline from the Russian government to establish Pleistocene Park, an experimental safari park just outside Cherskiy. The park is stocked with six species of large herbivore ( horses, moose, reindeer, musk ox, elk and bison ) to replicate the grazing activities of Pleistocene savannah herds and to demonstrate that converting the taiga back to tundra – steppe is the best way of slowing permafrost thaw, thus buying humanity a little more time to avert catastrophic global warming. As expected, the animals crushed shrubs, moss and seedlings and encouraged more grass, and data showed that the soil of the park was indeed up to two degrees colder than the forest. And two degrees can make all the difference.
  • Alaska has two keystone species that northeastern Siberia does not: spruce and beavers.
  • Spruce are hardy conifers with tough waxy needles, tall spires with short lateral branches and shallow root systems that can extract moisture from the most meager terrain or endure boggy waterlogged conditions and are among the planet’s great survivors.
  • Beavers, it turns out, have more impact on surface water in Alaska than climate. They could control up to 66 percent of surface water on the tundra, paving the way for trees.
  • Beavers don’t need a full forest to flourish ; the enhanced shrub growth on the tundra of the last thirty to forty years and the dwarf willows and alder are enough for them to build dams and make ponds. Water conducts heat better than land, so when you create more water and make it deeper, you are making the environment warmer, and you are carrying the warmth closer to the soil, to the permafrost. Beaver ponds create a foothold for more trees and for other species that rely on them : amphibians, insects, fish and birds. They are geo – engineers of the first order. So the forest – tundra ecotone in Alaska has a new keystone species, Castor canadensis.
  • Spruce has a strong reliance on mycorrhizal networks and on lichen to supply it with nitrogen and minerals, as most plants do. Over 90 percent of plant species rely on fungi to survive. One end of a fungal fiber embeds itself in or around a tree root. The other end of the fungus, a thread called a hypha, can be fifty times finer than the thinnest roots and hundreds of times longer. This effectively extends the reach of the tree’s root. Globally, these threads of mycorrhizal fungi make up between a third and a half of the living mass of soils. 5 Soil is in fact a huge, fragile tangle of tiny connected threads.
  • Warmer air holds more water vapor, increasing the vapor pressure deficit, the mechanism which encourages plants to transpire and release water vapor into the atmosphere. Essentially, warmer air sucks more moisture out of leaves. In order to avoid losing moisture in warmer temperatures, trees are closing up their stomata and stopping photosynthesis. Even if there is plenty of water in the ground, if the rate at which they are losing water exceeds the rate at which they can take it up then a tree will do the sensible thing and shut down growth, limiting its ability to build leaves and to sequester carbon.
  • At the same time, this acceleration in the water cycle means there is more transpiration from all vegetation, which increases the convective energy in the system. This leads to more storms, more thunder and lightning, which means more ignitions and more fires, the doubling of burned area and exponential increases in emissions nearly every year. In 2019, Brendan says, Alaskan forest fires emitted seventy terragrams of carbon dioxide, the same as human activity in the state of Florida.
  • Spruce don’t need to be dead to burn well. Black spruce is called “gasoline on a stick” by firefighters because of its flammable gum. The leaf litter of spruce contains camphor — used in pyrotechnics. This is because black spruce only regenerates after fire : its sticky black serotinous cones lie dormant until the gum is melted, releasing the seeds. But with larger and larger areas burning every year, as in Russia, traditional patterns of succession are becoming disrupted, and black spruce are not regenerating.
  • Each tree is a tiny independent rain – making factory. Trees take up and transpire far more water than they use for photosynthesis; up to 90 percent of the water they take in is not used. Why do they do it? As the scientific journalist Fred Pearce puts it, “ Trees release moisture to make a world fit for more trees, ” and us.
  • Fifty percent of the rain falling on land originates from evapotranspiration in trees. And since trees continue to take up and emit water, recycling the rain that they make, contiguous stretches of forest seem to be important highways for rain and wind, as rain that falls on forest is transpired and then falls as rain again across continents, like a kind of pump that has been called “ flying rivers. ” 15 Other research has called this phenomenon “ teleconnections ” between forests on different continents, such as the link between the Amazon rain forest and the west African monsoon. The spruce forests of Alaska and northern Canada seem to have a direct relationship with the rainfall in America’s bread basket, the great plains of the American Midwest.
  • The temperatures between spruce branches and beneath the trees can be considerably higher than the air beyond, as the tree re – radiates energy absorbed from light downward to the snowpack. This is why human inhabitants of the northern forests often camp beneath spruce trees and hold large specimens sacred as places of shelter.
  • In the deep cold, heat is more critical to human survival than food. A well stacked wood store is a sign of prestige.
  • Between twenty – one and twenty – five medicinal biochemicals are found in the spruce. They are concentrated in the growing tips of the tree and in the resinous gum that forms a protective sheath over the emerging leaves. This gum is a cardiotonic that helps with the oxygenation of the blood, reduces blood pressure and helps regulate arrhythmia in the heart. The dispersing agents that fire these biochemicals into the atmosphere have antibiotic and antiseptic properties — the same chemicals that do the work when you use pine disinfectant in your home. In their billions, the meristems of the spruce trees of the north are actually sterilizing the air we breathe.
  • In a surprising symbiosis, the spruce multiplies this antibiotic function by encouraging the lichens that live among its branches to do the same. The needles of the spruce release an alkaloid called ethanolamine which circles the crown of the tree and triggers the manufacture of antibiotics by lichen. These then hitch a ride on the other aerosols of the spruce and sweep down, carried by the winds pumped by the forest, to disinfect the airways of the northern hemisphere.
  • Among the cocktail of aerosols released is a sticking compound called betaphellandrene, which acts like a glue. The antibiotics released by the tree have their own adhesive which sticks to exposed skin from where they are absorbed into the bloodstream. All this is carried in the fragrance of the tree. No wonder Japanese forest bathing in coniferous forests has been shown to have positive effects on health and respiration.
  • At Churchill three ecosystems converge — the sea, the tundra and the trees. This three – sided ecotone has led to the town’s reputation as the polar bear capital of the world. Bears leave the rotting sea ice in the summer to forage on land and to den on the tundra and in the forest, giving birth in the autumn before returning to the ice when it freezes.
  • Half of Canada is forest. Most of the other half used to be, but the southern sweep of the boreal band bordered hundreds of miles to the north by Hudson Bay has been progressively gobbled up by agriculture, industry and the cities and suburbs of eastern Canada. The current rate is 1 percent deforestation a year.
  • Warmer temperatures lead to more evaporation, which leads to more precipitation, but the rain does not stay on the ground. The heat accelerates the cycle of evaporation and condensation, with more of the water converted to atmospheric water vapor.
  • This is why warming is so dangerous. Not that it will kill humans by making the planet too hot for human habitation today, but the acceleration of the water cycle will cause drought and excessive soil moisture that will stress the forests and trees and the root systems of all the plants needed to oxygenate the atmosphere.
  • Trees cycle about half the oxygen in the atmosphere ; photosynthesizing algae in the ocean maintain the other half. Both are projected to function less well as the planet warms.
  • One consequence of its adaptability is the poplar’s ability to reproduce itself vegetatively. Both male and female trees can send out tuberous roots laterally underground, often a good distance, which then sprout into new trees that are somatic clones of the original. The poplar can create a forest all by itself, linked by a network of roots underground that store nutrients and transport messages, food and carbon among all the trees in a constant exchange that research is beginning to reveal looks an awful lot like mass computation. What appear to be young trees are often just sprigs of a much larger and older creature — especially if they are present in numbers.
  • The oldest living organism yet discovered is a stand of aspen trees in Utah, all connected over eighty acres, each clone bearing the same DNA of one ancestor, dating to the Pleistocene ice sheet melt, 1.6 million years ago.
  • The base of the ocean food web is huge columns of tiny unicellular creatures called phytoplankton ; the growth of these organisms depends on the presence in the water of nutrients and minerals such as phosphorus, nitrates, and iron in a form which they can utilize. Matsunaga’s research led to the unexpected conclusion that the bioavailability of one of these molecules, iron, is promoted by the natural decay of trees in the forest. How does this happen ? Iron is a catalyst in many biochemical reactions used by all cells to make proteins to grow and reproduce.
  • For plants and phytoplankton, iron is also an essential catalyst of the all – important process of photosynthesis. In photosynthesis, light from the sun is captured by pigments such as chlorophyll. By a complex sequence of reactions, the photons are converted into energy stores which drive the fixation of carbon dioxide into sugars. Captured light is also used to convert water into both electrons and hydrogen, which are used in energy production, and oxygen.
  • Phytoplankton can only efficiently access the key resource of iron, which is normally present in water in trace amounts, if it is first bound and concentrated by a large carrier molecule such as humic acid. This is made in the forests by decaying deciduous leaves, and the humic acid and bound iron are washed into the oceans by the rivers.
  • When protein is available, phytoplankton use iron to reproduce and divide. Zooplankton eat the phytoplankton. Crustaceans, minnows, molluscs and mites eat the zooplankton. Fish eat them, and bigger fish … and so on. Iron made available by trees is the foundation of the food web in the ocean.
  • It turns out there is something behind the old Japanese proverb, “ If you want to catch a fish, plant a tree. ”
  • One seventh of Canada’s boreal has been clear – cut since 1990, a shocking proportion going as pulp for toilet paper. We are actually wiping our behinds with the last remaining trees that stand between life and death for humans on planet earth.
  • The forest is drier. The fires burn hotter and for longer. More of the peat and organic soil is burning, and the species that take advantage of the severely burned areas — the fireweed and willows — are thicker and more aggressive than the delicate understory of berries and tea. The jack pine has been hit by budworm and the poplars dominate. It is the young jack pine that the hares love most of all. Poplar has trace minerals that it uses to make the leaves of very young trees taste bad to hares. What will the hares eat? And what will the carnivores eat? And …
  • And that is why the warming of the boreal is so dangerous : it is not just the faltering ability of the forest to continue to sequester carbon that we should fear but the release of all the carbon previously sequestered by prehistoric forests as well.
  • If Nadezhda in Russia is right and the tipping point has already passed when emissions from melting permafrost will now drive more warming regardless of what humans do, then we should be very worried indeed.
  • There are two main ice sheets on the planet, Antarctica and Greenland, and Greenland is much easier and cheaper to get to. It is also melting much faster than Antarctica.
  • But the reason there are no trees in Greenland is not because it has been too cold. It is because there has been no seed. Vegetative changes take thousands of years. This is what ecologists call disequilibrium dynamics, an ecosystem or a biome that is in the process of working out its equilibrium. Rather like the changes under way with our current global heating, there is a time lag as species and ecosystems catch up with changed temperatures or currents — in some cases thousands of years. Greenland is still playing catch – up from the last ice age.

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