Category Archives: Uncategorized

How an effective drought reshapes an urban bird community (a thesis seminar)

A few years ago we began what we hoped would be a long-term study of how urban water policy and water use by people affects the diversity and distribution of other species that share the city’s habitats with us. The “city” in question is the Fresno-Clovis metro area in California’s Central Valley, and the “we” in question refers to the multidisciplinary team I pulled together to successfully compete for one of the Urban Long-Term Research Area (ULTRA) – Exploratory Award grants given by National Science Foundation and US Forest Service. That grant was how my research directly benefited from President Obama’s stimulus package in his first term, and the relatively small two-year award came with a great deal of (eventually dashed) hope that there would be money to actually grow it into a real long-term research network.

We had a unique opportunity in Fresno-Clovis to study how human water use in cities influences biodiversity in a “found experiment” since the City of Fresno had just begun installing water meters in this quite large arid southwestern city. We were able to survey the city for birds, plants, and human perceptions of water before water metering went into effect in 2013, and stretch our NSF grant dollars to continue studying them in the years after. It has been fascinating to watch this urban ecosystem change over these years, and grapple with the challenge of tracking how people’s choices have changed and how biodiversity is changing in response to what people do in their yards and throughout the city. Our challenge became further complicated by another unplanned perturbation of water in this system: the onset and deepening of the drought over California in these recent years. The NSF grant funded a number of graduate thesis projects (and undergraduate students helping with the research) at Fresno State, and their work has opened up new questions for us to pursue, even as we look for other ways to fund the work for the long-term.

Today I am back in Fresno (having recently moved to North Carolina State University to join a new interdisciplinary faculty cluster for Leadership in Public Science, in case you missed that news) for the culmination of another Masters thesis from this project. My student Stephanie Slonka will defend her thesis today, where she has conducted the first detailed analysis of how bird species diversity and abundance have changed in Fresno-Clovis over recent years by comparing data from bird census (from the Fresno Bird Count) and habitat surveys from several years before water metering went into effect and more recent post-metering years. The increased cost of metered water combined with the drought (and calls from the California Governor) has caused people to reduce the amount of water they poured into their yards, creating a more “effective drought” with much less water available in the landscape. Meanwhile, the bird community in Fresno has also changed significantly, showing lower number of species and smaller overall population in recent post-meter/drought years compared to the pre-metering period. What does this mean? If you want an answer to that, you can come to the Fresno State campus today to hear Stephanie defend her thesis where she explores these dynamics.

post-metering-model

 

A thesis defense is a landmark event both for the student and the advisor, and I am proud to see another student achieve this today. Stephanie’s thesis exit seminar will happen at 4:30PM today, in Science II, room 110. Here is her seminar flyer with further details if you wish to attend.

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Winter song

I love these wintry days in the Central Valley when its dirty brown air has been washed out by the infrequent (but not this winter, gracias El Niño) rain and wrung out to dry with cottonball clouds hanging as if on invisible clotheslines across an impossibly blue sky. Days like this I can even see snow on the mountains of the Sierra Nevada from my office window, pulling my gaze away from the computer screen to wander off daydreaming…

View from my office window, drawing me away from my screen to the snow-frosted mountaintops of the Sierra Nevadas in the distance. This iPhone's camera doesn't do justice to what my eye sees...you may have to squint into the middle distance to glimpse the mountains underneath the floating clouds.

View from my office window, drawing me away from my screen to the snow-frosted mountaintops of the Sierra Nevadas in the distance. This iPhone’s camera doesn’t do justice to what my eye sees…you may have to squint into the middle distance to glimpse the mountains underneath the floating clouds.

Such days I imagine were the norm in this valley a century ago, before our vehicles and agricultural industry started filling up the air with so many of our effluents as to turn this beautiful air into some of the least breathable in the nation, a murky brown veil hiding the mountains on most days of the year. Yet the people keep coming to fill up this valley, remaking it in our own industrial image, flattening the topography and bending the natural and ancient rhythms of this land and atmosphere to our will. Days like this remind me of those rhythms, of what once was, what might have been, and what could be again in this beautiful place, even as the vision of those mountains seems to melt away the grimy sealed glass pane on my office window out of which I goggle at that impossibly blue sky like a goldfish trapped in a bowl.

Urban conifers against that impossibly blue winter sky. There be Great Horned Owls in some of these trees...

Urban conifers against that impossibly blue winter sky. There be Great Horned Owls in some of these trees…

That window glass is not thick enough to keep out the occasional soft hooting of the young Great Horned Owls hidden in the branches of those conifers, where they were raised a summer ago. And this morning, as I stepped out onto the external staircase, I was startled by the liquid burbling notes of a song that is common throughout the spring and summer around here, but shouldn’t be so loud so early in the year. A House Finch was sitting high up in one of the trees singing his heart out against a background humming with the urban noises of building atmospheric devices and traffic in the distance, and roaring with an occasional airplane flying over.

Looking out east from his high perch, I wonder if the House Finch noticed the snow on the mountains, or heard the chirping of the winter migrants in the trees nearby, but even if he did, these weren’t enough to dissuade him from following whatever internal hormonal clock was telling him it was time to start singing to attract a mate. Already, and it isn’t even the middle of January yet. Global warming, is it, or just the local warming effect from the urban heat island? No matter, this boy is already serenading the ladies about the bountiful spring to come.

Meanwhile, the chipping sounds you hear at the end of the sound clip above might well be the mild panic setting into the heart of the migrant Yellow-Rumped Warbler foraging in the branches nearby, perhaps wondering if it was time to leave its winter ground already even though the air felt cold and the clouds spoke of more rain to come.

Its been a topsy turvy winter (or a few) in California, and living in these disconnected urban landscapes beneath the gaze of those parched snow-covered mountains must be discombobulating even to the wild creatures trying to make this ever stranger land their home. I know the feeling well.

My Hit Single: Are Warblers Less Important Than Tigers?

Tigers Are Less Important Than Warblers

I had promised on this blog a long while ago that I would scan and make available online a copy of my article “Are Warblers Less Important Than Tigers?”. This article was published in the long-out-of-print (but update: still available via Amazon) book “In Danger” edited by Paola Manfredi (with photographs by Joanna van Gruisen who was the one who spotted my essay and solicited it for the book) for the Ranthambhore Foundation in India. To my continuing pleasant surprise and gratitude, this article continues to resonate with people in India (and elsewhere). It has been reprinted and anthologized several times. I keep getting requests (two in the past week) from people who want to reprint it, distribute it among students or citizens interested in conservation, and continue to share it widely. For what I was then told, as a Ph.D. student, to consider a rather frivolous bit of writing because it was not SERIOUS SCIENCE published in a PEER REVIEWED JOURNAL, this essay has probably had a much broader impact than many of my more serious science papers. Depending on how one measures such impact, of course, and something for my more serious scientist colleagues to consider as some of them keep looking down upon time spent writing for a broader audience outside of peer-reviewed journals.

Anyway, pardon me for being late in keeping my promise, but I have finally scanned the original article, and invite you to read and share it as you please. Do let me know what you think of it too, if so inclined.

Here it is, my Hit Single:

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A Fiery Skipper on an inflorescence of Lantana in downtown Fresno, some springs ago.

Pollen TSUNAMI!!!! Happy #PollinatorWeek!

A Fiery Skipper on an inflorescence of Lantana in downtown Fresno, some springs ago.

A Fiery Skipper on an inflorescence of Lantana in downtown Fresno, some springs ago.

It’s National Pollinator Week, a time to enjoy the deviant inter-species sexual dalliances of insects and flowering plants (also over 65 million years in the making, not unlike a certain monster movie currently sucking all the change out of your pockets at the box office). Also a time to curse the other plants which never bothered to enlist insects to be their highly targeted sexual couriers, but instead continued to merely spill their pollen into the air. To kill us all in what this year has become a POLLEN TSUNAMI!!

But, really, this IS the Worst Allergy Season ever:

Worst Allergy Season ever! (image via Comedy Central and Salon)

Worst Allergy Season ever! (image via Comedy Central and Salon)

How can that be, you ask, even as you stare at that rising graph? Watch the full Daily Show clip (below), which is a brilliant example of how to communicate science—in this case a statistically observed pattern—in a hilarious fashion that will nevertheless have you scratching your head and make you go “hmm…” (and perhaps sneeze).

As funny as Jon Stewart is in that report, he is also brilliantly accurate in demonstrating the statistically and biologically valid fact that each year of the past decade has, in fact, seen the WORST ALLERGY SEASON yet on record! That correlation showed by the spokesman for the Asthma and Allergy Foundation of America is a result of, you guessed it, Global Warming / Climate Change!

Well, more accurately, that correlation is a result of increased CO2 levels in the atmosphere, thanks to all the fossil fuel we’ve been burning up like there is no tomorrow. Experiments with plants grown in the controlled environments of greenhouses show that if you increase the amount or concentration of CO2 in the air, plants will increase the amount of pollen they produce, This is part of the broader growth response of plants to increased CO2 levels. More specifically, some plants (like the notorious ragweed which is one of the biggest allergen producers) make more (if smaller) flowers, and invest even more in producing pollen as CO2 levels increase. Now that we’ve turned the whole planet into a giant greenhouse with ever rising CO2 concentrations, this is what we can look forward to in terms of pollen production:

As CO2 rises, so does pollen production

As CO2 rises, so does pollen production. Full PDF of Ziska et al 2000 paper here.

This means, unless we start bringing CO2 levels in the atmosphere down (listen to the Pope, for god’s sake!) quickly, we will continue to face allergy seasons that get worse every year, along with the real danger that television news programs will run out of dire metaphors to describe the rising tide of pollen that will kill us all!!!

Meanwhile, let’s celebrate all the other plants which have enlisted the services of dedicated pollinators to carry out their mating rituals. Make the most of this high CO2: go plant some non-allergenic flowering plants which will attract some lovely pollinators to your yard and add a dash of beauty to your day.

Happy Pollinator Week!

Photo of a Green Leaf Warbler

Watching Jurassic Park in Ambasamudram

As excitement builds for tonight’s opening of the new Jurassic World, I (like many of you no doubt) am remembering the magical experience of our very first visit to see the dinosaurs of Jurassic Park, several decades ago

My experience of Jurassic Park, though, was somewhat unique, because I enjoyed it in two vastly different theaters on opposite sides of the world, and at opposite extremes of the cinema-viewing technology (and audience) spectrum.

I vividly remember the visceral experience of seeing it for the first time upon release, in one of the then brand new dolby surround sound equipped multiplexes in San Diego. I was a graduate student in the University of California, San Diego at the time, and on campus in between field seasons in southern India when the movie came out on this very date in June 1993. As a biologist (studying dinosaurs, very tiny ones, as it turns out), and a cinephile, of course I thoroughly enjoyed the experience of watching dinosaurs come to roaring life in crystal clarity on the big screen, in one of the newest theaters, stadium seating and all! I remember the sheer thrill of seeing this for the first time:

This must be everyone’s favorite scene from the movie, surely! What had Steven Spielberg unleashed upon the cinematic world?!

Thrilled as I was with every scene bringing dinosaurs back to vivid digital life, though, I was also left disappointed at the rather one-dimensional caricature almost every human character had been reduced to from the already limited dimensionality in the source material. Yeah, yeah, we scientists like to complain about how poorly we are represented on film, and I could rage at a long list of cinematic transgressions against science and scientists, not just in the Jurassic Park movies. Nevertheless, that scene when we first meet the dinosaurs grazing on the plains remains indelible in my cinematic memory – even without the help of YouTube. And for that we must all be grateful for the wizardry of Spielberg and his crew.

A year later, the film finally reached the distant backwaters of rural Tamil Nadu in Southern India where I was doing field research on these migratory Green Leaf Warblers (little dinosaurs, as we now know them to be, true) on Mundanthurai plateau:

Photo of a Green Leaf Warbler

A Green Leaf Warbler, on the ground, resting. And yes, this is the same little dinosaur I studied in a Tiger Reserve, and for whom I demanded respect vis a vis tigers.

My local field assistants invited me to join them on an 8 km bicycle ride out of the woods and down the hill into the nearest town, for an evening at the cinema that could not have been more different from the experience in San Diego.

Sankaran and Kumar with my daughter

The amazing Sankaran and Kumar who made many a Ph.D. possible. Seen here with our toddler daughter, and a Slender Loris they had just caught for Kaberi.

This “theater” in Ambasamudram, the only one for many miles around, was in fact a massive warehouse / barn building, with a cloth screen strung up at one end, flanked by big box speakers sitting on the floor, and no seats! Instead of seats, the enormous bare floor curiously had a rope running right through the middle, dividing it into two long halves facing the screen. The mystery of the rope was solved after we had rushed in with the throngs waiting in long lines outside: it was a barrier to keep the male and female members of the audience separate. Obviously, with no seats, the cinema owners could squeeze in (and I do mean that literally) as many viewers as was physically possible. The cacophonous crowd quieted down as soon as the projector was turned on, for this was an audience in perhaps the most cinema-crazy state in India, having elected multiple film stars as chief ministers of the state.

The audience reaction to what followed on screen left me even more astonished than the film itself.

For in that rustic “theater”, packed in like cattle, watching a film entirely in American with no subtitles or dubbing, this Tamil-speaking audience reacted almost identically to the one munching popcorn in the plush stadium seats in California. The gasps of awe at the dinosaurs were, of course, to be expected and relished, but what really surprised me were the reactions to the human characters speaking largely incomprehensible American. The naughty chaotician’s cheesy jokes were laughed at, the old grandpa admired and then critiqued, and the T. rex cheered enthusiastically – especially when it ate the lawyer! Even though lawyers were seldom as prominent or despicable in rural Tamil Nadu as they are in the States.

That is when the true cinematic genius of Speilberg hit me: for he had, in reducing the human characters to simple tropes, turned them into human universals that anyone could relate to (or revile) – something that would likely not have happened had he worried about satisfying the picky nerd audience like me instead. My hat was therefore off to Spielberg as, indeed, a truly great B-movie director.

As we cycled back in the night, high on the adrenalin rush from the movie – and from having battled the throngs in exiting that crazy cinema hall – Sankaran and Kumar could not stop talking and asking me about the movie, and about dinosaurs, and how they had made them come to life on screen. We talked about them for days afterwards, while catching warblers in mistnets, or just walking through Mundanthurai’s forests. Hard core committed local conservationists as these two were, their newfound love of dinosaurs turned into wishful thinking: “Wouldn’t it be great if we could actually release one of the monster dinosaurs into this forest, sir? That will take care of all the poachers killing wildlife here! That’ll show them!”

The film also spawned perhaps the cleverest bit of political art I have ever seen. At the Tirunelveli bus station some months later, I stood and marveled and laughed silently at a poster mocking the then Chief Minister (and ex movie superstar) Jayalalitha (Jaya-Amma for short): it mimicked the iconic film poster, the one with the profile of the T. rex with the words “Jurassic Park” across it:

Jurassic Park banner image

Except, the profile was that of Jaya-Amma, and the banner read “Jayassic Park“! To my eternal regret, I did not have a camera with me that day, nor did I think to peel the poster off the wall and steal it at the time. Jaya-Amma herself has had a remarkable political resurrection recently, having survived corruption scandals and jail time, only to come roaring back to devour Tamil Nadu politics again. Just as the dinosaurs are back on the big screen this weekend.

So hat’s off again, to Spielberg, and to the anonymous local artist who designed such iconic posters! And to Sankaran and Kumar, who will no doubt go to see the dinosaurs return to the theaters in Ambasamudram (I don’t know what they are like these days, but Google tells me that that little town has more than one theater now) soon. Perhaps with their children this time. And they may again wish for some dinosaurs in their backyards to keep their beloved forests intact.

Meanwhile I prepare to see it in California this weekend, with my 10-year-old self-proclaimed paleonerd daughter who is really excited about it because, she says, “It’s gonna be so stupid! They will get so many things wrong about the dinosaurs! It’ll be fun!!” That it certainly promises to be.

How to live with elephants, in the modern wired world

Coexistence is a journey… not a destination”

That useful reminder comes from the main human protagonist of this beautifully told story (see video below) of how elephants and people can coexist, even in places with a relatively high density of people sharing habitat with a small but resilient population of elephants.

Over the course of but a century and a half, less than two elephant lifetimes, a rainforest-clad mountain in southern India known as Anamalai, the Elephant Hills (in Tamil), has become a mosaic of tea plantations, coffee estates, and the settlements of people laboring in those “working landscapes”. The original rainforest habitat of thousands of native species now clings to the interstices of this mosaic, with a few big patches under protection, but many smaller ones facing the vagaries of “mixed use” by humans and non-humans alike.

In most places on Earth, I daresay, this would seem like an unlikely place for a population of elephants to persist. Especially when you consider how their kin in Africa have been slaughtered in recent years even in far less populated places, to slake distant markets for ivory. Yet, here in southern India, a different dynamic is at play, for the local people worship the elephants even as they work their habitats to satisfy other human needs. The elephants too have discovered that there is often more food to be found in the human plantations than in the diminished forests.

Conflict is inevitable when two dominant species compete to appropriate the primary productivity of any landscape. When one of the species is Homo sapiens, the inevitable outcome is seldom a good one for the other species. Yet a cultural reverence for the elephants has combined with the relatively low price placed on ordinary human lives in this part of the world to allow for a tenuous coexistence of sorts. With 39 human lives lost in the past two decades, the elephant god has extracted a bigger sacrifice than might be tolerated in places like the United States.

Now Ananda Kumar and colleagues from the Nature Conservation Foundation (an organization with which I am proud to be associated since its inception, through bonds of friendship and collaboration) tell the story of this coexistence between humans and elephants, and how they have worked to find ways to reduce that human toll and keep both elephants and humans out of harm’s (i.e., each others’) way. And this step forward in the journey of coexistence has been made possible by harnessing some of the very technology that so many of us nature-lovers love to deride as alienating us from nature: cable television and mobile phones!

Watch the story (filmed by my friend Saravanakumar) of how Ananda Kumar and colleagues found ingenious ways to use modern communication technologies to facilitate an ancient coexistence between two species who have long shared habitat in southern India:

Living in harmony with nature – that phrase evokes romantic notions of indigenous people living off the land in lives we imagine to be wonderful and harmonious and wise, but may in reality have been closer to “nasty, brutish, and short”. Nature lovers and conservations love to hate modern technology and blame it for many of our social-ecological ills. This project, and its success in saving human and elephant lives, shows us that we can, in fact, reconcile human development through technology, with the conservation of nature in the constant journey towards coexistence. It is a journey that requires sacrifice, and coexistence may have to be paid for in blood, but technology can soften the blow, even for the most vulnerable among us.

Science needs voices. All of them. Thank you @ehmee.

I can’t tell you how glad I am, as a father of daughters growing up in today’s world, that we have Emily Graslie’s voice, inspiring them every day in ways that I cannot, building their confidence so they too can add their voices to the conversation, as the discoverers and adventurers and explorers they are, without worrying about what anyone thinks of them.

Thank you, Emily, for this in particular today:

For more inspiration from this remarkable voice, this Chief Curiosity Correspondent for the Field Museum of Natural History, find her on tumblr, twitter, and of course the brainscoop channel.

The Conscience of an Asteroid

My new contribution to the series “The Moral Is” (hear my previous essays in their archives, or read them here) on Valley Public Radio was broadcast during Valley Edition a couple of weeks ago. Here’s my original, extended version of the essay, before it was pared down for broadcast. You can imagine me reading it in your head, or listen to the broadcast version recorded in my voice.

Artist's impression of asteroid slamming into tropical seas near Yucatan.

Painting by Donald E. Davis depicts an asteroid slamming into tropical, shallow seas of the sulfur-rich Yucatan Peninsula in what is today southeast Mexico. More info: http://www.jpl.nasa.gov/files/images/captions/p45062.txt

Sixty-five million years ago, an asteroid crashed into the earth near modern day Yucatan, setting off a chain of geological and climatic reactions that wiped out the dinosaurs. Nearly 70% of all species alive on that day disappeared forever.

This was the last known mass extinction event in Earth’s history. It was the fifth time that such a mass extinction has occurred on our planet. As far as we know.

The history of these extinctions is quite literally written in stone, in the fossils trapped in layers of rock. Like the pages of an ancient and incomplete book, these layers are inscribed with the story of the plants and animals and bacteria that have lived and died here since long before us.

The tools of paleontology help us decipher these stories written in stone. We can read of the long age of bacteria and other single-celled organisms; of the time when the air held no oxygen because no one had figured out how to make food from sunlight; of the first time that living organisms changed the global climate by releasing oxygen, likely triggering the first mass extinction of species who couldn’t breathe the air that sustains us now.

A later chapter tells of the age of carbon, when dense forests covered the land, before getting buried deep under it to be transformed into coal and oil. Now we burn the solar energy captured in carbon by those ancient forests to enrich our short lives. In doing so, we have transformed the earth’s climate yet again, dangerously.

The first stirrings of plants and animals on to land make for thrilling reading. We particularly love the tale of the plucky fish caught in tidal pools which began breathing the air and crawling around on land! How they eventually gave rise to the land mammals we call our own kin.

We discover pieces of our own story everyday, from humble origins as apes that stood up in Africa and spread out of that continent probably to escape a changing climate, and eventually occupied the entire planet.

Five times during the past billion years, this riveting story is interrupted by unspeakable horrors as some terrifying series of unfortunate events conspired to wipe out most species. Each time, the survivors got a fresh start to evolve on a mostly empty planet.

The Great Dying at the end of the Permian era 250 million years ago was the worst one yet, driving more than 90% of species extinct, including many among the otherwise hardy insects. But it cleared the way for reptiles and mammals. We don’t quite know what caused the Permian mass extinction, but massive, perhaps sudden climate change may have a played a big role.

The asteroid that took out the big dinosaurs at the end of the Cretaceous was a mere lump of rock drifting in orbit around the sun until it fell to Earth and wiped life’s slate almost clean for the fifth time. Driven by sheer gravity, that asteroid had no conscience or remorse about the horrors it would unleash. Nor any notion that humanity would eventually evolve in the absence of dinosaurs to become another force of mass extinction.

Now we find ourselves on yet another brink, where our own industrial civilization threatens a Sixth Great Dying. Within the past century, we have increased the pace of extinction, willfully or unwittingly, to a level last seen only in the wake of that asteroid. We have come so far, in building our diverse cultures and technologies, achieved so much worth celebrating given our humble origins. Yet our biggest legacy may end up as the epitaph for the sixth mass extinction on Earth, which will doom us just as surely.

We like to think of ourselves as creatures of conscience, infused with a morality and an intellect that allows us to understand and appreciate our kinship with other creatures. But as drivers of this sixth extinction, how different are we from that asteroid? Will our conscience give us pause and pull us back from the horrors we have unleashed? Or will we let our own chapter end abruptly, wiping the slate clean again, just like that remorseless asteroid?

chix.jpg

What do we do with the aliens among us?

Over at the excellent The Nature of Cities blog, editor David Maddox is hosting the site’s 8th Global Roundtable, this time focusing on the challenge of invasive and exotic species in cities. David recently invited me (as one of the regular contributors to the blog) to take part in this roundtable with a brief essay stating my perspective. My essay was posted to the roundtable earlier this week, along with about a dozen other perspectives from urban ecology practitioners around the world. Please visit the forum site to read all the different views, and share your own by commenting in the discussion – I really hope you will do so. All of the authors are reading comments and participating in the discussion actively over the next few weeks. So I hope to see you there. Meanwhile, as promised, here is a somewhat expanded (or more rambling) version of my essay:

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Aliens! Invasives! Species that don’t belong here and are taking over the ecological roles of native species. Those weeds choking the understory of native forests. The Starlings and House Sparrows pulled out of Shakespeare’s England that now so tragically dispossess native birds of their nest holes!

How can we tolerate these aliens among us? How fast can we get rid of them? Exterminate the aliens!

Pretty exotic flowers that make our suburban gardens so lovely. Grasses from halfway around the world that knit the dense mats of our lush lawns. Lovely succulent plants and delicately spined cactuses that dot our newly water-wise xeric landscapes and window ledges. Plants that flower and fruit out of their time and place, maybe year round.

Where can we get more of them so our gardens in Arizona look just like the ones in England or Singapore or Australia? So the corporate landscapes in Bangalore make the techs returning home from Silicon Valley feel like they never left California? Like the peacocks whose plaintive calls and stunning displays might make California feel more like Gujarat!

A Peacock in California

We humans sure do have a passionately ambivalent relationship with nature. Never more so than when it comes to the plants and animals we move around among our global habitats. The very words we use to describe them are so heavily laden with value judgment: invasive, alien, exotic. We move them around with us so we can evoke the landscapes of our childhoods halfway around the world, or recreate imagined ones from somewhere else entirely. We wage war on them when they refuse to stay in the gardens and pens where we put them, and start exploring new worlds on their own.

Humans are the most invasive species on Earth. Our cities, ecosystems we build and replicate around the world, are also focal points from which other species have invaded native habitats. Just as wanderlust defines our species, so does the biophilia which makes us take living elements of our habitats with us wherever we go. Carrying a suite of species as sources of food, comfort, companionship, and beauty, has always been part of our cultural and evolutionary baggage. Invasiveness is something evolution tends to reward, and our own evolutionary success springs from a certain restless invasiveness.

Ever since our ancestors realized they could control the lives of other plants and animals, so they could rely on them to feed the body and nurture the mind during lean times, humans have been moving species around the world. In scattering across the planet, we deliberately carried many such species to help fill our bellies, beautify our homes, and stave off homesickness in strange new lands. Meanwhile, other species latched on to our coattails, hitching rides around the world with this walking ape, this most efficient global form of transport and dispersal they had ever encountered! Wittingly and unwittingly, we set off evolutionary changes in species we want, species we tolerate, and species we hate, as they all became part of a human-ecosystem-complex we have set about replicating across the world. These places we call cities often serve as outposts from which many other species launch their invasions into surrounding native habitats. And so we end up with the dilemma of wanting to move some species with us to our new homes, but struggling to keep some of them from spreading out of our gardens and farms and taking over entire native ecosystems.

It is in the very nature of life to try to take control of its immediate environment, to transform resources to nurture itself, and to expand outwards to occupy and transform new places. Invasiveness, the ability to “invade” new habitats, is always favored by evolution. Natural selection rewards traits that allow species to grow rapidly, to outcompete other species vying for the same resources, or simply eat them as food. Moving to a completely new habitat, while quite risky, can also bring the benefits of escaping the co-evolved competitors and predators and parasites that might hold a species back in their native range.

So most species are always sending out their seeds and young ones into new habitats by whatever means available. Most often, these dispersals end in tragedy, but every once in a while, they open up vast unimagined new territory for the species, and new evolutionary opportunities to express and expand the range of their genetic potential. Humans, increasingly, provide some of the most perilous, exciting, and potentially high-risk/high-reward challenges to other species: if you can attach yourself to a human, and figure out how to survive in the strange new urban world, you stand a good chance of surviving in this Anthropocene, sometimes in places far from your evolutionary home.

We have spent millennia figuring out how to make some species grow where and when we want them. Meanwhile, other species have latched on to our coattails making the most of this new mode of hyper-efficient long-range dispersal: the hairless ape that travels the world, with baggage. Only recently have we realized the often devastating consequences of bringing exotic species into native habitats. Invasive species fuel some of the most intense debates among conservationists, often laden with hysterical rhetoric about alien, exotic, invaders who must be exterminated.

Invasiveness is in the nature of the most successful species. To know the truth of this, one need but look in the mirror. We are, after all, the most successful invasive species now occupying the planet! But our success has been the downfall of many other species, and we are only just now grappling with the consequences of our invasiveness. Yet the most passionate debates about what to do with invasive species, heavy with the metaphor of war and genocide and extermination, tends to somehow tiptoe around this elephant in the room: the fact that we humans are the ultimate invasive species on Earth, and are responsible for most other invasions that are destabilizing native ecosystems worldwide. Indeed, displaced species often form a big part of our own preferred global habitats.

Cities are where most humans now live, where we often first introduce new species, and whence some of these species launch invasions into new habitats. Indeed, cities themselves seem like invasive habitats proliferating in and destabilizing ecosystems around the world. Cities must therefore be central to our efforts to address the challenge of invasive species. Cities embody the contradiction between our desire to control nature, shaping entire ecosystems to suit our purposes, and our growing desire to conserve nature and biodiversity.

Urban gardens

How do we reconcile our innate desire to build habitats for our own biological and cultural needs with a growing awareness that perhaps we should leave nature alone? It must start with owning our central role in this ecological conundrum. It is time we accepted our responsibility, as the ultimate invasive species that has moved entire ecosystems around and built new ones. It requires us to transform our role beyond the dichotomy of active perpetrator / passive bystander in the drama of invasive species. We must embrace the role of more deliberate stewards of the lands we now dominate.

As more people recognize the problems of invasive species, many now seek ways to build native species friendly urban landscapes. Ecologists are good at understanding the effects of non-native species in native habitats, and in raising the alarm about invasive species. We haven’t done enough to actually transform the practices that contribute to the invasive species problem. Urban ecologists have been lax in engaging with one group who arguably wield the greatest influence on this challenge: gardeners, nurseries, and landscapers. The growing desire to make urban gardens native-friendly is constrained by lack of available species options in local nurseries, and of expertise in nurturing native species. Ecologists must fill this knowledge gap by developing better ways to support native species in urban habitats in partnership with the people who actively transform the landscape.

Forget “leave nature alone”; in cities we must become better ecosystem engineers, designing habitats more consciously to enhance native biodiversity while limiting opportunities for non-native species. We must also recognize that some non-native species have become naturalized to play important roles in their adoptive ecosystems, so simply eradicating them is not the ideal solution. People move and grow plants and animals to fulfill complex social, cultural, aesthetic, and emotional needs. We must develop a broader vision of biodiversity that includes both the ecological roles of species and their cultural resonance for people. Balancing these will be key to managing invasive species in and around urban landscapes.

Humans will continue to move species around, despite conservationists’ (and agriculturalists’) best efforts to limit the movement of exotic species into regions outside their native range. Some of these species can and do become invasive in their new habitats. As good gardeners in the city, we will therefore also have to keep a close eye on all the species in urban ecosystems to make sure they don’t escape and start threatening native habitats nearby. At the same time, it is also worth remembering the plight of the House Sparrow, that ultimate city slicker introduced around the world as part and parcel of the global urban template. Alarmingly, it has recently disappeared quite mysteriously from many of its native cities in Europe and Asia. If the species were to somehow go extinct in its native range, at least its emigre populations, like the House Sparrow diaspora in the Americas, may remain the only living populations of a threatened species! We therefore have to be careful even in our efforts to eradicate non-native species lest we destabilize ecosystems, or drive species to extinction in unexpected ways.

Leaving nature alone is not really a viable option in the social-ecological systems we call cities. Instead, our respect for nature, and our growing enthusiasm for enhancing native species diversity, must be tempered by Constant Vigilance (if I may borrow the wise Mad-Eye Moody’s words) when it comes to the interlopers from elsewhere.

Do exotic, invasive, aliens keep you up at night? Are they in your neighborhood?

Most of us live in cities now, which must seem like rather exotic, alien habitats to other denizens of our planet, full of strange creatures they’ve never encountered before. By which I mean not just us hairless apes, but many other species too, from distant corners of the Earth. For we also tend to fill our cities with plants and animals we like, even though they don’t come from the immediate neighborhood of the city.

Does this worry you, this proliferation of exotic species in urban landscapes? It should, especially when they become invasive. So what can we do about them? Over at The Nature of Cities (a wonderful blog to which I contribute from time to time) editor David Maddox is hosting a roundtable discussion on the topic of exotics in the city. I’m one of a dozen or so contributors to this particular roundtable, the 8th of a monthly series on the blog. We were all asked to submit short pieces (600 words) to address this month’s topic:

How much should we worry about exotic species in urban zones? How do we reduce damage from exotic invasives when management resources are limited?  Are there conflicts between management or eradication efforts and building general support for urban biodiversity?

So head on over there to read our brief essays, and then join the conversation by sharing your thoughts in the comments. All of the authors will be participating actively in the roundtable discussion over the next few weeks, addressing each other’s posts and responding to readers’ comments. So I hope to see you there!

In drafting my own essay response, my thoughts on invasive species wandered farther afield (there’s invasiveness for you!) than David’s questions, and I had to rein them in to stick to the roundtable’s format and word limit. So now I’ve got this whole other rambling post on invasive species, which I might as well share here. So watch out for that to land here too, shortly…