Inheritors of the Earth

by Chris D. Thomas

  We have been changing the planet for too long to go back. The escalating impacts of Homo have been taking place for some 2 million years in Africa12 and a million in Asia. Around 46,000 years ago, Australian aboriginals eradicated two-tonne Diprotodon marsupials and their kin, as well as half-tonne birds and seven-metre reptiles,13 heralding a global slaughter. Cave paintings represent our encounters with giant beasts, some now extinct, some alive. The first known animal painting is a pig, whose 35,000-year-old image survives in a cave at Maros in Sulawesi. Wild pigs still survive in Sulawesi, but the 30,000-year-old Ardèche hyenas represented at the Pont d’Arc cave in southern France were not so lucky. Our ancestors who sheltered in that limestone gorge must have wiped them out–or extinguished the animals they preyed upon. Today, we think of hyenas as exclusively African, but this used not to be the case. European rhinoceros went the same way, and they are no longer around to repopulate Chernobyl. Waves of human invasion continued to exterminate large animals across Asia, and then in North and South America. By ten thousand years ago, we had killed off most of the world’s largest land animals, long before we built our first city, or started to write.

  The timing of events meant that the largest animals were near enough gone, or at least on their way out, by the time the climate warmed at the end of the last ice age. When the climate did warm, the world’s forests, grasslands, deserts and tundras migrated across the planet’s surface, but without these megabeasts in tow. Modern-day elephants can transform the vegetation, and extinct animals would have done the same. They would have altered the structure of the world’s forests, savannas, grasslands, marshes and tundras, and hence influenced the types of plants and other animals that thrived in them. The new vegetation that developed after the last ice age is not the same as it would have been in a human-free world. Nor is it the same as any vegetation that went before. Virtually all ecosystems on the land surface have been fundamentally altered by humans for over ten thousand years.14 The great acceleration of human innovation and impacts in the last few centuries has, in reality, been transforming a world that our ancestors had transformed many millennia earlier. For the two groups of animals for which the best–albeit still crude–historical reconstructions are available, namely mammals and birds, at least twice as many species died out before 1700 as have disappeared since. We should not imagine that recent events are taking place in a previously pristine world. The world has been transformed so thoroughly it is no longer feasible to identify the parts of ecosystems that have been uniquely altered by humans.

  The ubiquity of human-influenced change15 for such a long period means that biological gains associated with our existence are as universal as losses. Yet the gain side of the world’s loss–gain equation is often seen as a problem, rather than as a triumph of nature to adjust to altered conditions. Many ecologists and environmentalists, and particularly a special cadre of ‘invasive species biologists’, are prone to regard changes to the locations where species live as evidence that we are moving towards a less desirable world.16 They regret how the world is turning out. It is as if there is an ‘ought to be’ state of the world, with each species having its own ‘correct’ location. Except that ‘ought to’ never existed. Nature just happens, and the distributions of species change–no slice of time has any more or less merit than any other. Like it or not, these biological gains will not go away, and more changes will take place in the future. Regarding these changes as unnatural and undesirable is a myopic view of the world.

  We need to encourage, not resist, dynamism if we are concerned about enabling nature to accommodate to the human world. That is how our planet’s species have survived past change. Too often, we act as if nature is an old master, a great painting that must be kept just as it is. When we perceive nature to be blemished, we attempt to ‘restore’ it to some past state, just as we might try to repair a damaged masterpiece. To do so requires us to weed out those plants and animals that we think are in the wrong place. We kill successful species to protect unsuccessful ones. It is sometimes possible to do this, but the larger the area we consider and the longer the time period we encompass in our thinking, the more certain it is that we will eventually fail to keep things as they are. But nature itself will not lose. We will simply lose our human fight to return the Earth to one particular romanticized vision of what it might once have been. Like so many Canutes, we have taken on an unrealistic challenge.17 The tide did not stop for King Canute, and biological change is not about to stop for us.

  We can think of the Anthropocene epoch as a fresh start for life on Earth and not only as a passing of the old guard. This is liberating. ‘No change’ is not an option when we contemplate the future: our choices are all about the direction and speed of future change. We can look forward to future changes with an element of excitement and interest, not just with foreboding. This does not let us off the hook, however. It is entirely within our capacity to turn the Earth into a place that is far worse for humans and also far worse for most (but not all) other forms of life. We need to be vigilant. But simply regretting that things are no longer as they were and venting our frustration at the unnatural state of the world is not the way forward. Let’s make the best choices that are possible, accepting that humans are part of the new natural world order.

  11

  Noah’s Earth

  Who is to notice the stench of sea lions when enjoying the culinary delights of Fisherman’s Wharf: slurping warm chowder, swallowing abalone and savouring seafood stew, accompanied by a bottle of Napa Valley’s best? It was a warm end to a chilly day exploring 1073 Lighthouse Avenue, the most peculiar of places, a small park perched above the town of Monterey. Hemmed in by million-dollar homes and retirement pads for the inhabitants of San Francisco, the park contains a remnant of Monterey pine forest. Yet some of these pine trees looked distinctly odd, apparently bearing orange leaves. A new art installation, perhaps? It is California, after all. The billowing crowns of the pines mixed with the long leaves of Australia’s gracious gift to the world, the Eucalyptus, or gum tree, which also appeared to be covered in orange leaves. Then, as the morning sun rose over the horizon, the leaves opened, revealing the brilliant orange and black of a thousand or more monarchs,1 America’s most iconic butterfly, a few fluttering to the ground to form a golden carpet.

  Visitors beware: ‘Molesting a butterfly in any way’ can result in a $1,000 fine, according to a 1939 city ordinance. Take care where you tread, lest stepping on one constitutes molestation. Famous for spending the winter clinging to branches in the fir forests of central Mexico in their millions, monarchs to the west of the Rockies mainly head for the coastline of California instead. Monarch Grove Sanctuary, at 1073 Lighthouse Avenue, is one such place. There the butterflies sit out the winter in the not too hot (because they will burn up their fat supplies unnecessarily during the winter if they get too hot), not too cold (so as to avoid being damaged by freezing weather), and not too dry (to avoid becoming desiccated) conditions that are provided by these groves of trees. The oceanic currents that speed past Monterey Bay alternately cool them when it is too hot inland and warm them when it is freezing inland. Having completed their winter snooze beside the sea, the butterflies will then head back up the Cascades and across the Sierras and Great Basin, seeking milkweeds for their caterpillars to eat during the warm summer months, before their great-great-great-offspring (or however many generations it is) return to spend the following winter back in California.

  This mild climate, which attracts both monarchs and humans to the Californian coast, is also ideal for Monterey pines, although the pines are even fussier in their requirements than the butterflies. They do need some moisture, but it has to be dry enough for occasional fires to spread through the forest canopy. Fires can kill the mature trees but at the same time they release seeds from the tree’s resin-sealed cones to start the next generation. Without heat, the seeds are entombed, and there would be no new seedlings. Fire is therefore an essential part of the
ecological system that allows Monterey pines to survive from one generation to the next. The local homeowners in suburban Monterey are less than enthusiastic about reducing their properties to piles of ash, so converting the forest into a bonfire meets with a certain level of resistance. The seeds require an alternative means of escape. This is where the local authorities have stepped in: rather than torch the neighbourhood, they collect the cones, extract the seeds and deliberately plant them to establish the next generation of forest trees.

  While occasional fires are essential, the Monterey pine does not like it to be too dry because then the fires become too frequent. If the trees burn to the ground while they are still too young to produce new seed capsules, the generations will be interrupted. The trees disappear without replacement. Their not too hot, not too cold (and not too wet, not too dry) lifestyle makes the West Coast’s Goldilocks tree one of America’s rarest. It survives on a handful of coastal Californian hills, and on the Mexican islands of Guadalupe and Cedros, off the coast of Baja California. Already threatened by urbanization, fire suppression and pine pitch canker, a fungal disease that has been imported from the south-eastern United States, human-caused climatic changes could now push this tree over the edge. The twenty-second century could mark the Monterey pine’s final hurrah.

  Monarch butterflies overwintering in California: resting and sunning themselves while sitting on leaves of Australian-origin Eucalyptus,

  and flying among shiny-barked Eucalyptus trees.

  The Goldilocks tree has been sensitive to the climate throughout the last million years of ice ages and intermittent warmer periods. Over this period, pollen blown out to sea and material washed down California’s Santa Clara River has sunk to the bottom of the Santa Barbara Basin, where it has become incarcerated in layers of marine deposits. There it waited patiently until geologists and ecologists hired a boat and set sail across the basin, drilled holes into the deposits, pulled up the cores, then counted the pollen grains in each layer, allowing scientists to track changes to the tree’s abundance as the region’s temperatures waxed and waned. In the words of Connie Millar of the US Forest Service: the Monterey pine ‘was least abundant during full interglacials [relatively warm periods like today], when oaks dominated coastal habitats, and was also uncommon during the cold periods of the glacials [full ice-age conditions], when junipers dominated’.2 The problem today is that we are already in a too warm interglacial period, when the trees are at their rarest, and it is getting warmer still, which means that the climate is becoming even less suitable for the Monterey pine. Under attack from concrete, canker and now climate change, the Goldilocks tree could disappear completely.

  Fortunately, some inspired–or perhaps just lucky–foresters have been on the case. The Monterey pine, whose scientific name is Pinus radiata, was included in a trial of tree species that was carried out in Canterbury, on the South Island of New Zealand, in the 1850s.3 It seemed as though the tree had been yearning for antipodean weather all along. New Zealand’s moderate climate, bathed by the waters of the south Pacific, was ideal for the sensitive tree. Growing about seven times faster than back home in California, radiata, as it is now known, has become the mainstay of New Zealand forestry, covering some 18,000 square kilometres of plantations. This amounts to nearly 90 per cent of New Zealand’s forestry and represents about 4 per cent of the entire country’s economy.

  And it didn’t stop there. Radiata now generates around 95 per cent of Chile’s timber production and forms the largest part of Australia’s plantation wood. It is grown in Argentina, Kenya, Uruguay and South Africa, where the climate is so ideal that the tree has gone wild, colonizing grasslands, parts of the native fynbos vegetation and forest clearings in the mountains. Thanks to foresters, the Goldilocks tree has discovered that there are plenty of other places on planet Earth where it can grow. A species perched on a few coastal cliffs in California has become a global colonist–an endangered species converted into an heir to the world. In Australia and New Zealand, it has even been joined by the monarch butterflies, which have been introduced there, too, along with the milkweeds their caterpillars eat. Although there are justifiable fears about the survival of some of the overwintering sites for North American monarchs, the butterfly itself is one of the most successful in the world. It lives in the Americas, and now, thanks to us, it has become widely established in Southeast Asia, on many Pacific, Atlantic and Indian Ocean islands, and in southern Europe, as well as in Australasia.

  Meanwhile, back in Monterey, blue gum trees, Eucalyptus globulus, have made the journey in reverse. Originally confined to the island of Tasmania and to the southernmost parts of Australia’s Victoria state, they pose a particularly tricky Anthropocene conservation challenge for those who live around Monarch Grove. According to the California Invasive Plant Council, they are actively regenerating along the coast, represent a fire danger and oust native plants. Are they foreigners that should be evicted, or attractive trees that are well suited to California’s coastal climate? The paradox is heightened because the larger leaves of the blue gums–compared to pine needles–form just the right conditions for the Monarch butterflies to settle down for the winter.4 Planting more gum trees may be one of the best ways to help protect North America’s most iconic butterfly.

  This is the antithesis of traditional conservation thinking. Australia’s blue gums are thriving in California, Hawaii, Ethiopia, southern Africa, Morocco, Spain, Portugal, Cyprus and elsewhere in southern Europe, right across to the Caucasus in Georgia. Giant wombats, Tasmanian wolves and disease-sensitive frogs that evolved in isolation in Australia have generally succumbed when they have faced up to the virulent inhabitants of Europe and Africa. Not so the blue gum, which today thrives on all the world’s major landmasses, save Antarctica.

  Monterey pine and blue gum were both confined to small areas of the world’s land surface until humans evolved and transported them elsewhere. They illustrate the current importance of some formerly rare species to humans, and we might presume that some presently rare species will be valuable to us in future–although we do not yet know which. Both trees could have been threatened by human-wrought changes to the vegetation and climate.5 And yet they have become widespread, to such an extent that there is no risk that either of these species will be extinguished for the foreseeable future. Gum trees seem destined not only to survive the human era but potentially to become a globally important (rather than just Australasian) type of tree for tens, if not hundreds, of millions of years to come. Forests of the new natural world will never be the same again. Environmentalists may dislike them for their new-found success,6 but there is no doubting they represent previously rare species made good.

  Monterey pine, Pinus radiata, clings to cliff edges to the south of Monterey, in California, where it is a rare and potentially endangered native species of tree.

  It also grows as serried ranks in plantations in New Zealand. Radiata, as it has become known, has been plucked from obscurity to become one of the world’s most important commercial trees, with a wide variety of uses, from pulp for paper-making to timber for house-building.

  Rare species becoming common and common species rare is not a human-created phenomenon that has been invented in the last few centuries. It has happened repeatedly over the last 2 million years as the Earth’s climate has zigzagged back and forth between glacial and warmer climes. The alpine chough is a perky yellow-billed and glistening-black relative of the crows that today wheels in a dancing flight over meadows at high altitudes in the European Alps and Pyrenees, but it used to be a more frequent denizen of the lowlands during the depths of the last ice age. We know this because our cave-dwelling ancestors, who hunted over treeless ice-age landscapes, did not put their rubbish out, leaving chough bones to be discovered by archaeologists who carefully sifted through their twenty-thousand-year-old trash.7 And this is likely to be true of many other mountain plants and animals that are adapted to colder conditions, and which were much commoner
during the ice ages than they are today–as was the case with the British dung beetles that Russell Coope studied, one species of which now survives only in the Pyrenees, and another in Tibet.

  While alpine choughs and many others were thriving under the colder and drier climate of twenty thousand years ago, oak, lime, beech and hornbeam trees were banished from the European prairie–the frigid, open steppes of Asia extended right into Europe at that time. These trees survived in sheltered valleys and on sunny slopes, mainly in the Balkan states, and in the Italian and Iberian peninsulas of southern Europe. They were quite localized plants, just as the Monterey pine was rare until humans came along and redistributed it across the southern hemisphere. Yet these European forest trees survived and, when the Earth heated up, a little over eleven thousand years ago,8 they spread out and colonized the land. Once-rare trees sprang up across the continent and became the dominant vegetation: the foundations for the new forest that grew around Lake Maggiore, spread to France and the British Isles in the west, reached Chernobyl and even further east, and gained a footing in Scandinavia in the north. The summer-green forests of oaks and limes and hornbeams that would clothe most of Europe (if humans had not cut most of them down again) did not come into existence until at least thirty thousand years after modern humans colonized Europe.

  Similar stories can be told for most of the other extensive forests of the northern hemisphere. The conifers that form Canada’s great boreal forest, for example, moved in only once the ice retreated at the end of the last great glacial period. When foresters and conservationists refer to primeval forests that were inhabited by European bison and aurochs and boar, and by woodpeckers and dormice, they are talking about places that used to be grassy steppes where our ancestors hunted. These forests are primeval only in the sense that the cultural knowledge of our steppe-dwelling ancestors has been lost, making them seem ancient and enduring to recent generations of humans. Those ancestors may well have been rather irritated by the arrival of trees. The trees inherited this warmer land from the grassland and (now) mountain plants that went before.