Unnatural Histories
Contents
1. Genetically Modified Organisms
2. The Hitchhikers Guide
3. Dazzling Urbanites
4. Distress and Despair
5. Pick Up the Pieces
6. Do Not Disturb
7. The Bountiful Harvest
8. Captivated
Genetically Modified Organisms
Welcome to the blog series Unnatural Histories!
The world’s a stage. So too in the natural sciences, George Evelyn Hutchinson talked of an evolutionary play being acted out in the ecological theatre. In the modern era, humanity has constructed a theatre unlike anything seen before. Crumbling walls, a leaking roof, the building is in a state of disrepair, collapse is imminent. With over a million species presently threatened with extinction, most of the contemporary performances in this ailing venue are tragedies.
Yet hope springs eternal.
Rewilding is an attempt to restore the theatre to its former grandeur. Some have argued this to be pure folly - we lack the resources and the vision to pull off such an ambitious rebuild. Besides, nature does not stand still. The world as it was before is confined to the annals of history. The world as it will be resides solely in the haze of future possibilities. In this series we will describe the architecture of the modern ecological theatre, explore how this new environment has influenced the evolutionary stories of its actors, and speculate on the catalogue of dramas that await us. Curtain up!
The Hitchhikers Guide
Don’t Panic
~ Douglas Adams
The concept of ‘survival of the fittest’ inevitably draws the same astute question: why is there so much diversity? This is an excellent question that, for the most part, baffles scientists. Explaining patterns of diversity is a major branch of the biological sciences, and answers to date are largely underwhelming in their explanatory power and often mind-bogglingly complex. Critics have a much easier time of it. If what you say about Darwinian evolution is true, the doubters assert, why does not one species dominate all others to the point of exclusion? Why isn’t there just one type of frog, the fittest, most well-adapted frog that drives all others to extinction?
In the modern era, the questions surrounding biodiversity and species coexistence are not as hypothetical as one would hope. A mass homogenization is taking place; a global experiment with potentially disastrous consequences. Animals and plants are being moved around the world both accidentally and purposefully. The end result is the same; something somewhere it’s not supposed to be. Instantly, the landscape changes - species that were once kings of their respective domains suddenly face a new challenger. They must fight tooth and claw to remain ‘the fittest’, but nothing in their evolutionary history to date has prepared them for this novel threat. Native species are completely naive to the alien’s tricks and tactics; powerless to prevent the newcomer from taking root, and defenceless against their rapid spread. Never underestimate the element of surprise. For the locals, the situation can only be described as dire. As we speak, invasive species are driving extinctions, reducing biodiversity, and in certain extreme cases, leading to entire collapse of ecosystems.
Ecosystems are intricate, interwoven fabrics, such that you cannot alter one aspect without having knock-on effects that percolate throughout the biota. Herein lies the destructive power of invasive species. Their impacts are often so far-reaching they are near-impossible to predict, and have only begun to be quantified. The most straightforward impact of invasive species is direct competition with residents that occupy the same niche. Indeed, a loose ‘one in, one out’ policy was elegantly described in the 1960s by researchers studying colonisation and extinction dynamics on islands. This delicate balancing act however, assumes that the system in question exists in a serene, idyllic state of equilibrium. Invasive species are, by definition, a severe disruption to the equilibrium, and tend to exert a much more damaging influence on local fauna. The result then, is typically more of a ‘one in, many out’ state of affairs. We have only scratched the surface when it comes to documenting the cascading, unpredictable impacts of non-natives. However, despite only the tip of the iceberg in view, we can readily surmise that if we do not divert our course, this thing is big enough to sink us.
Like a Duck to Water
May 3rd, 1890 - a transatlantic steamer pulls in sight of Ellis Island. The Statue of Liberty, dedicated only four years prior, is perhaps the only recognizable feature of the Manhattan skyline. It towers above the Hudson Bay, glistening water meets glistening steel. Passengers disembark, their necks craning upward to take in the spectacle. A mixture of awe and wonder strikes all that come to these shores. A new land, full of promise. But for some, the change of scenery is too drastic. Many long for the simple pleasures of home; we all yearn for the familiar.
A plan has been formed. A newly established amateaur dramatics society is keen to bring a piece of the old world to the new. Even small things, they contend, can alleviate the homesickness they and their families have developed over the preceding years. They proudly march with cages to their local green space, central park, and select a suitable spot. Eighty birds, representing a dozen or so of each species mentioned in the works of Shakespeare, are released, set loose in New York City to take root and multiply.
And they do take root. They do multiply. Now when little-Englanders reach the land of opportunity and take in their surroundings, the avifauna will no longer be entirely alien. Whenever one of the huddled masses feels lost or isolated, a glimpse toward the heavens will provide them with comfort and cherished memories. By any standards it was a veritable success. But in true Shakesperian fashion, a tale with innocuous beginnings will come to end in tragedy.
By the mid-20th century, one of these transplanted birds, the European starling, had consumed the continent. The starlings have out-competed native bird species for resources, including nesting sites and food. The locals never stood a chance. In response, some species have conceded defeat by way of rapidly evolving shorter bills and smaller body sizes such that their diet and habitat requirements no longer overlap with the European invader. Despite this flexibility, many native bird populations in North America have suffered precipitous declines.
Part of their success in North America stems from their ability to thrive in urban areas. Even in the densest concrete jungle, starlings can achieve flocks that are over a million birds strong. And they shit on everything. Those unfortunate enough to leave their car parked on the street under a roost tree wake up to a mountain of guano with not even a single inch of bodywork visible. Shooting and trapping, as well as the reintroduction of peregrine falcons and Cooper’s hawks, have had little to no effect. As we stand, scenes in Manhattan now resemble less Shakespeare, and more Alfred Hitchcock or one of the plagues of Egypt.
Citizen Cane
August 9th, 1935 - a cargo ship docks in Cairns harbour. The 102 toads on board are documented by customs and promptly transported to the arable region of Queensland. The toads are to serve as a biological control agent against a voracious beetle pest that is decimating Australia’s sugar production. The beetle itself is a non-native, hailing originally from Europe. The hope is that these South American toads can suppress the beetle invasion; fight fire with fire.
As it turned out, the toads ate everything but the beetles. With no native predators and an abundant source of naive prey sources, the toads proliferated. And they spread. Within ten years the toads had reached the Northern Territory, within twenty years they had colonised the western half of the continent. With sugar cane beetle populations largely unaffected, the Australian government now has two disastrous invasions to deal with.
Human-mediated colonizations have myriad consequences. Indeed the distinction between an invasive species and merely an introduced species is their perceived impact. Once an alien species reaches foreign shores, the outcome is not certain, but there is no going back - the walls have been breached. Cane toads are most certainly invasive. They are considered one of the most destructive non-native species on the planet. Each year, millions of dollars are spent on culling, trapping, and toad-proof fencing to mitigate their impacts. But the integrity of native ecosystems has already been compromised, at this stage damage-limitation is the best we can hope for.
Much of the cane toad’s detrimental impact derives from its acute toxicity. Anything that tries to eat them, mistaking it for something edible, suffers fatal or sub-lethal poisoning. For many predators the consequences are disastrous. Again, some local species have attempted to move out of the way of the steamroller by way of rapid adaptation. Evolution thrives under pressure. Black snakes, for instance, although certainly reduced in numbers as a result of cane toad poisoning, are over the worst and likely to recover. Their solution to the problem? Smaller heads. Snakes with small heads are not capable of stretching their jaws wide enough to consume a toad large enough to kill them. Natural selection at breakneck pace - snakes with big heads die, snakes with small heads survive; future generations of snakes all have small heads.
Several other species are maintaining the same head size and instead developing resistance to the toad toxins, and some have learned to stop viewing toads as prey items. Encouragingly, both of these novel adaptations can be induced through cleverly designed conservation measures; scientists are presently deploying food laced with small amounts of toxins in the hope that resistance is more speedily acquired. We are learning - that is perhaps the only positive one can take from this episode. We have learnt a tremendous amount about the physical process of invasion, the ecological and evolutionary responses of native fauna, and evaluating mitigation strategies. The hope then, is that we have learnt enough from our mistakes to prevent this from happening again. Or at the very least be more prepared when it does.
Scorched Earth
June 20th, 1938 - a cargo ship docks in the port of Mobile, Alabama. On board are thousands of ornamental plants, set to adorn gardens and windowsills across the nation. With such a profusion of goods, it is rather unsurprising that the colony of small, red ants taking temporary residence at the base of a potted Hibiscus went unnoticed by customs. Once ashore, the colony found a suitable patch of earth to set up camp, largely unaware of how far they had travelled, and, as ants do, began to forage. From humble beginnings, as they say.
Fiercely aggressive, and forming huge super colonies, the red imported fire ant quickly outcompeted and displaced native ant species. And they spread. Within twenty years the ants had reached Texas, Louisiana, Mississippi, and Georgia. Despite their early flourish, there remained a cautious optimism that the ants would not spread much beyond the southern states on account of the harsher winters experienced in the rest of the continent. However, a few decades later it became apparent that the ants were evolving a higher tolerance to cooler temperatures, facilitating their northward march.
Although we often focus on the detrimental impacts and evolutionary responses of native species to introductions, the invaders are subjected to perhaps an even greater pressure, that of being thrown into a completely alien environment. Again, evolution thrives under pressure. Within fifty years the distribution of fire ants in North America was transcontinental. In a matter of a few generations, fire ants evolved to be more aggressive than in their native range, an extremely useful trait when attempting to dislodge native incumbents. At the same time, the ants perfected a novel reproductive strategy to expedite their expansion; “budding”, a process in which a group of workers and a queen leave the main colony to establish new ones nearby, allowed the ants to spread into unoccupied territory at a much faster rate.
Eating virtually anything and everything, as well as damaging the roots of several important cash crops, the accidental introduction of fire ants to North America has become an invasion of colossal proportions. Since the Mobile ‘landing’, human trade routes have brought fire ants to the shores of Asia and Australasia, and the same unfortunate drama is playing out again and again. Fire ants are spreading across China, Taiwan, Australia, and New Zealand. The invasion is now a global one, with no end in sight.
Coda - Bullfrog Moan
Have you ever woke up with them bullfrogs on your mind?
I got the bullfrog blues and I can’t be satisfied,
Mexico got ‘em,
Japan got ‘em,
Cuba got ‘em,
Jamaica got ‘em too,
I got the bullfrog blues and I can’t be satisfied,
Italy got ‘em,
France got ‘em,
Brazil got ‘em,
the Netherlands got ‘em too
I got the bullfrog blues and I can’t be satisfied,
Canada got ‘em,
China got ‘em,
Brazil got ‘em,
And Columbia got ‘em too,
I got the bullfrog blues and I can’t be satisfied,
Uruguay got ‘em,
Venezuela got ‘em,
Argentina got ‘em,
And South Korea got ‘em too.
Dazzling Urbanites
The rats have all got rickets
They spit through broken teeth
~ John Cooper Clarke
As a rule, urbanisation is bad for wildlife. Rather intuitively, the conversion of natural habitat to a mosaic of concrete, metal, and tarmac leads to population declines of many species and an overall loss of biodiversity. Green spaces become few and far between; animals struggle to survive in the remnant fragments. Their behaviour and reproductive cycles are severely disrupted by the incessant noise and fast pace of modern human societies. For many, it is nigh on impossible to keep up.
A small minority of species however, thrive in the big city. Some creatures have successfully adapted to the urban lifestyle and taken advantage of the new, formidable landscape that others have been driven out of. After all, it is not strictly the loss of habitat that results from urbanisation, but more so a dramatic shift in habitat. Survival of the fittest plays out in concrete jungles like any other. Darwinian selection applies to Accra just as much as it applies to Amazonia. The rules of the game have not changed, merely the theatre. And in such a novel setting, the strategies for success are often quite different from those that emerge in forests or prairies. Squirrels, pigeons, mosquitos. These are the new superstars that tower over the competition. All have found a way to not only scrape by, but to dominate.
Bright Lights, Big City
For the first 25 years of my life I lived in a city. First London, the Big Smoke. A small garrison on the outskirts of the Roman Empire, Londinium has become one of the largest urban centres in the world. A place of kings and playwrights, football fans and fishmongers. As a budding biologist, the natural history museum in south Kensington held particular appeal, with its breathtaking Victorian architecture and mesmerising collection of curiosos. At 18 I left London for Sheffield, the former steel capital of the world, the current home of snooker. Built on seven hills, steep cobbled streets wind their way through row upon row of terraced houses. Quintessential Yorkshire. Good beer abounds. Yes I do like cities. They have character, they have goings on. There is magic in the hot, noisy air.
But I yearned for something different. As a young man I decided to emigrate to southwest Virginia, in the heart of the Appalachian mountains of North America, to pursue my doctorate degree. I was to study salamanders, a charismatic group of amphibians that includes newts, axolotls and hellbenders. My choice of study location was simple - the Eastern US has more salamanders than anywhere in the world. The university resided in a small, isolated town, several hours from the nearest metropolis. In every direction, a veritable paradise of cool mountain streams, moss-draped boulders, and humid forests that stretch for thousands of miles. So much to see, and so much different from whence I’d come.
Of all the new sights and surroundings, the one that stood out, the one that seemed most unfamiliar, was the darkness. At night it gets dark. Properly dark. A darkness I had never experienced before. To a lifelong city-dweller it was unsettling. Without any contrast, I had taken the night lights of cities for granted. I had become accustomed to 24-hour illumination - neon signs, street lamps, blue-tinged, starless skies. These collective phenomena have been jocularly dubbed ALAN by urban biologists studying their effects - ALAN stands for Artificial Lights At Night.
ALAN is a form of pollution that has been found to have detrimental effects on many species including humans. Exposure to ALAN has been linked to increased risk of obesity, diabetes, and cardiovascular disease, and even some types of cancer. More intuitively ALAN also disrupts circadian rhythms and alters the behaviour of animals. Much can be drawn from the contrasting proclivities of human beings in urban and rural settings. Wildlife is similarly more nocturnal in cities; birds can still be heard singing at midnight, leaving them exhausted and confused. Flowers open at odd times of day because they do not receive the appropriate environmental cues; if pollinators do not respond in kind, the plant’s reproductive success is put in serious jeopardy.
On beaches around the world, sea turtle hatchlings emerge from their nests in the wee hours. They are timing their emergence to avoid the myriad avian predators that are active during daylight hours. Hatchlings have learnt to follow the light of the moon reflecting off the ocean surface to reach the safety of the ocean. However, on developed coastlines, the ALAN emitted from raucous bars and late-night shops completely swamps out anything the moon can muster. Disorientated, the hatchlings march toward the town. Even if they manage to avoid being run over by traffic or falling down storm drains, they will eventually succumb to dehydration.
Geckos are now a ubiquitous feature of cities in tropical climates. Their adhesive toe pads allow them to navigate walls and windows without trouble. The vertical surfaces that dominate urban landscapes offer no challenge, and the heat-absorbing property of concrete provides cold-blooded reptiles with enough warmth to remain active almost indefinitely. Moreover, geckos are one of the few species to benefit from ALAN. Artificial lights attract moths, their primary prey item, from far and wide. At dusk, every security light and shop sign turns into a banquet. These small, unassuming lizards have never had it better. With the increased availability of food, and the ease with which it can be obtained, gecko populations in urban areas have resources to spare. Females lay twice as many eggs as their counterparts in forested habitats, and numbers have skyrocketed.
Skyscrapers
Pigeons, above all other avian species, have made cities their home. The pigeon has a long and fascinating history, dating back over 5,000 years. The wild ancestor of the domestic pigeon is the rock dove, native to Europe, North Africa, and parts of Asia. The ancient Egyptians were the first to domesticate pigeons, using them for food and as messengers. The Greeks and Romans did the same. Genghis Khan used them. Right up until the First World War, carrier pigeons were used to transmit military messages across battlefields during conflict. With the advent of the telegraph and later, the telephone, the use of pigeon post declined.
Today, domestic pigeons can be found throughout the world and are still used for racing and as pets. Feral populations of domestic pigeons can be found in virtually every major city. Their long historical association with humans has predisposed them to urban life. They quite content using buildings, bridges, and statues as roosting and nesting sites. They will eat virtually anything that humans drop or leave unguarded. Urban pigeons have larger brains than their rural counterparts, possibly due to the cognitive demands of navigating such a complex, highly dynamic landscape. They are so successful, train stations and office buildings will spend considerable money covering every possible perching spot with rows of spikes as a deterrent. But such attempts are largely futile.
Pigeons are not the only birds to conquer the concrete jungle. Crows, house sparrows, and European starlings have all successfully adapted to urban environments. The key to success in all these cases appears to be an indiscriminate nature. All of these species have a cosmopolitan diet; they will eat most things and are not above scavenging from trash piles and dumpsters. And all of these species will build a nest anywhere they can. This generalist, flexible life-style has allowed a handful of birds to achieve extraordinary population sizes and exist at very high densities. Apart from chickens, house sparrows are the most common bird in the world. Starlings are next. For those that can hack it in the hustle and bustle of cities, the rewards are great.
Peregrine falcons, once an endangered species, almost driven to extinction in the mid-half of the 20th century, have recovered. And they have cities to thank. From New York to New Delhi, they gleefully take advantage of the hyper-inflated populations of their prey. They nest on some of the tallest buildings in the world. Being so isolated, their growing chicks enjoy an unprecedented level of safety. The multistory buildings that now dominate city skylines also provide the perfect vantage point from which to swoop down and snatch an unsuspecting pigeon in flight. For Peregrines, cities are sanctuaries, a refuge from the threats that drove their historical declines - pesticide poisoning, shooting, and egg poaching. Perhaps more a savage indictment of our impact on wild areas than a testament of the welcoming nature of urbanity.
Any Port in a Storm
Not all cities are the same. The aforementioned Sheffield, for instance, proudly claims to be the greenest city in Europe. Parks, gardens, and remnant forest dot the industrial landscape. Such a mosaic of semi-natural areas can lessen the harsh realities of urban living, providing food, water, and refuge for native wildlife. Myriad species benefit from Sheffield’s gardens. Back yards often contain a tremendous diversity of plants and habitats. Indeed in recent years, conservationists in Britain have successfully shifted public opinion to move away from manicured lawns toward more ‘wildlife friendly’ gardens. Planting native flowers attracts bees and butterflies. In turn, the insects will attract birds and bats. It doesn’t take much to create an ecosystem; once you set the ball rolling, nature is good at building from the ground up. Some homeowners go so far as to construct habitat features in their gardens to support particularly affable species - nesting boxes for hedgehogs, ponds for frogs and newts, and rock piles for lizards and snakes.
However, ornamental plants, non-native species from around the world that are cultivated for their aesthetic value, remain a staple of the English green space. And this foreign window dressing can completely negate any of the benefits that an urban garden might confer. Many ornamentals are chosen for their hardiness, as well as their beauty, and this trait becomes a source of all problems. Case in point, Japanese knotweed. Put it in the ground and you have a pretty bush that lives for years and requires little to no care. But you plant it at your peril. Japanese knotweed has reached infamy around the globe as an extremely destructive invasive Once it becomes established, all hope is lost. Knotweed is so pervasive it can alter soil chemistry and disrupt nutrient cycling. It develops such a monopoly on water and mineral resources, that many native species are driven out. The presence of knotweed in your garden has the power to reduce property value. Knotweed is a particularly extreme case; hydrangeas from Asia - an easy to maintain bush that yields voluptuous florets of violet and pink - offer a more typical example. They have been linked to the decline and loss of native plants in parts of the United States where they festoon front lawns. Moreover, these ornamentals are not attractive to native pollinators or wildlife. They take up space, but provide nothing for the local fauna. Ornamental gardens can be as inhospitable as an unadorned square of asphalt.
Distress and Despair
coming soon!
Pick Up the Pieces
coming soon!
Do Not Disturb
coming soon!
The Bountiful Harvest
coming soon!
Captivated
coming soon!