Wilderness housing boom challenges conservation

Houses in Keystone, CO, located in the Arapaho National Forest

The housing boom may be over in the United States, but things look very different when you take a step back. Since the 1940s, housing has grown at about 20 percent each decade. And while the current recession may have slowed things down, we’ll have to start building more houses eventually if we’re to house the 120 million more people by 2050. The decades-long housing boom magnifies in intensity when you start looking around national parks, wilderness areas, and national forests, as a recent paper in the Proceedings of the National Academy of Science did. While there were just 14.9 million housing units within 50 kilometers of a protected area in 1940, there were 61.9 million units in that same buffer by 2000. And not only have the raw numbers increased, so too has their share of all American housing.

It’s no surprise that people want to live near parks. Clean air, open space, and gorgeous scenery draw people in as tourists and bring them back as prospective property buyers. Retiring Baby Boomers, freed of their work commitments, have been particularly drawn to the borders of national parks, forests, and wilderness areas. Even working-age people—many willing to suffer through a long commute to live near natural beauty—have gravitated towards protected areas.

None of this would be a big problem if we didn’t mind clustering our houses together, limiting our impact on the land around us. But the reality is no one moves to the country to live in an apartment building. People buy a handful of acres, erect a house a good distance from the road, and string in a long driveway.

Though it’s tempting to think the environmental impacts of a house stop when grass gives way to trees, the reality is that houses cast a shadow far larger than their physical footprint. Roads, utility lines, and driveways dice up the landscape. This fragmentation reduces species’ ability to travel out of the now-noosed protected areas, trapping them in reserves that may not fulfill their needs. Houses also bring hordes of exotic plants and animals, including pets, which often prey on native fauna. All of these factors—and more—create disturbances that can affect protected areas, though they may be miles away.

The authors of the study cite a few examples of how wilderness housing has already changed the habitat in and around protected areas. In the east, the Great Smoky Mountains National Park is choked with pollution. In Colorado, the number of visitors to the Mount Evans Wilderness Area has increased so much that the Forest Service now requires permits. Wildfires in Cleveland National Forest near San Diego, most of which are set by humans, have skyrocketed in number, pushing out the native coastal sage scrub and ushering in exotic grasses. In Michigan, houses peppered within the boundaries of Huron-Manistee National Forest have led to the suppression of wildfires, which has depressed reproduction of the fire-dependent Jack Pine, which has hurt populations of the Jack Pine-dependent Kirtland’s warbler.

The surge in housing near protected areas seems poised to continue apace through at least 2030. The authors of the PNAS study forecast that 17 million additional housing units will be erected within 50 kilometers of protected areas. For those of us who love to live near wilderness—myself included—this news is bittersweet. The good part is that there will be plenty of places for me to live, if I choose to move there. The bad is that nature-lovers like myself run the risk of damaging that which we admire. But not all is lost. The paper’s authors offer a few suggestions as to how we can minimize our footprint. (Really, these are suggestions that we should all follow, whether we live in the city or the country.) Push for zoning laws that clump houses closer together, leaving more open space in tact. Site and build your house with your surroundings in mind. Landscape with native plants. Keep your pets from running rampant. Don’t fertilize too much. Turn off your outside lights, and keep the noise down. And one more (this one’s mine)—keep your lawn small.

Source:

Radeloff, V., Stewart, S., Hawbaker, T., Gimmi, U., Pidgeon, A., Flather, C., Hammer, R., & Helmers, D. (2009). Housing growth in and near United States protected areas limits their conservation value Proceedings of the National Academy of Sciences, 107 (2), 940-945 DOI: 10.1073/pnas.0911131107

Photo by Kara Allyson.

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This is your brain in the city

chaotic Times Square

For a kid who spent much of his childhood outdoors—alternately splitting time between the wooded park down the street, my friends’ backyards, and a patch of countryside my parent’s tended—I have been spending a lot of time in rather large cities as an adult. Ever since I left college, I’ve lived in cities that count their residents in hundreds of thousands and metro areas that count in the millions. It’s gotten me to wondering, what effect are these throngs of people having on my brain?

An answer to that question scrolled across my Twitter feed last week in the form of a paper published in Nature.City living and urban upbringing affect neural social stress processing in humans.” Boom. The title alone seemed to say it all. But question answered? Not quite.

The paper is the first of its kind, merely lifting the corner of a page in what is likely to be a huge tome of neuroscientific discoveries on how urban life affects the development of our brains and how we react to the populous world around us. The study’s sample size is somewhat limited, but the results are statistical home runs. And like many pioneering studies, it raises many more questions than it answers.

The Germany-based researchers started by administering a difficult math test to 34 college students. While the students were taking the test, the researchers harangued them about their substandard score or slow progress to stimulate social stress. All the while, functional magnetic resonance imaging machines (fMRI) scanned the students’ brains, recording their activity. After the test and scans were completed, the researchers weighed the students’ patterns of brain activity against their place of upbringing—big city, small town, or rural area. Subjects who were raised in the city exhibited higher levels of activity in their amygdala, a region of the brain which processes emotion, and cingulate cortex, an area which regulates the amygdala. The results were so powerful that the scientists conducted a follow up experiment to be doubly certain. That study confirmed the findings of the first.

When analyzing the data, the researchers also differentiated between students who were living in the city versus those who actually grew up in the city. Somewhat disconcertingly, subjects who grew up in a big city had poor communication between the amygdala and cingulate cortex, something seen in people genetically predisposed to psychiatric disorders.

Together, these results suggested that students who had grown up in the city were more sensitized to stress. This should come as no surprise to anyone who has spent time in a city. Compared to the country, cities are chaotic, mile-a-minute places, filled with stressors and aggravations. Indeed, cities have a documented and profound effect on our mental well being, with greater prevalence of general mood disorders and anxiety along with rates of schizophrenia twice that of elsewhere.

This being a pioneering study, it’s findings are peppered with caveats. The sample size is small. The subjects were all German. Only students were tested, not a random sample from the population. No change was found in subjects’ cortisol levels, a marker hormone for stress—a curious result that will certainly be investigated further. But despite these qualifications, the study offers a preliminary confirmation of what many of us have long suspected—city living can get inside your head.

The questions the study leaves unanswered are myriad. Do different cities affect your brain in different ways? Certainly growing up in Cincinnati and Mumbai are two different experiences. And what about access to green space? Andreas Meyer-Lindenberg, the study’s main author, points out in an interview with Wired Science that, “You can go between city and country very quickly” in Germany, allowing city dwellers easy opportunities for respite from the stresses of urban life. And I would be remiss not to raise the issue of population density. It is, after all, this blog’s raison d’être. Fortunately, I should have something to report in the coming years. Meyer-Lindenberg and his colleagues plan to investigate density’s role in future studies.

Sources:

Lederbogen, F., Kirsch, P., Haddad, L., Streit, F., Tost, H., Schuch, P., Wüst, S., Pruessner, J., Rietschel, M., Deuschle, M., & Meyer-Lindenberg, A. (2011). City living and urban upbringing affect neural social stress processing in humans Nature, 474 (7352), 498-501 DOI: 10.1038/nature10190

Photo by Werner Kunz.

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Backyard neighbors and the perils of retrofitting suburbia

Accessory dwelling unit

Sprawl, in many cases, is in the past tense. It’s already happened. Though it continues in plenty of places, it’s most problematic where it already exists. For booming regions, sprawlish suburban rings threaten to choke the central city with snarled traffic and lean tax rolls. Rather than throw their hands up in disgust and move on to a city that “gets” it, a group of planners and architects have focused on retrofitting diffuse neighborhoods and intensifying four lane boulevards. In the process, there are myriad problems to tackle, but I’d like to tackle one right now: What to do with suburban housing.

Density is suburbia’s saving grace and Achille’s heal. Who wouldn’t want to be ensconced in their own private garden? But that same dispersed living isolates people and causes many of the headaches of daily life. Sprawl retrofit really means higher density living, which also means more shops close at hand and less time behind the wheel. It’s no secret that many suburban lots would easily support another house. Slapping another behind the existing one is a simple way to double the density. It’s a common approach to sprawl retrofit, and one raised at the 19th Congress for the New Urbanism. But if erecting backyard residences solves one set of headaches, it risks inflicting more in the process.

Suburban homes were built with very specific ideals in mind. The front of the house is the public side, presenting its widest part to the street, shielding the backyard and creating a private area where people can relax in relative peace. While many early car-centric suburban houses reacted tepidly to the backyard—the best they offered were a few more windows and a back door—we soon became practiced in the art of suburbia. Large picture windows, sliding doors, four-season rooms, and covered porches quickly festooned the private side. The backyard became more than an outdoor amenity—it was a private garden to be enjoyed from the indoors, too.

Hacking a lot in two and adding a second residence could destroy one of the few things many suburban homes have going for them—a sense of privacy. The attractiveness of this feature should not be underestimated. Research suggests that open views are help ensure a feeling of privacy, even more so than actual proximity. The bad of suburbia—houses turning their backs on the street—was driven by a noble aspiration—homes embracing the yard. No one wants their view to embrace another home, no matter how beautifully designed.

And so a lynchpin of sprawl retrofit—boosting the number of houses—may be the most difficult to achieve. That’s not to say it cannot be done, but it will require careful consideration to do properly. Suburbia may be, in many ways, a consequence of bad planning, but it got one thing right—the yard. We crave green, open space, and suburban lots with suburban houses have it in spades. It may have given us too much, but we shouldn’t take it away in too much haste lest we compound the mistakes of the past.

Related post:

It’s not the yard that matters, it’s the view

Photo by faceless b.

16,422 people per square mile

cardboard box

Nostalgia is not something I avoid easily. It usually lies dormant until woken by some change, distinct or subdued. And when it does, it takes charge. Small details and insignificant landmarks shout out, begging me to remember everything about this place and this time, from the noteworthy to the not-so-historic. And something as momentous as a cross-country move hurtles me back even further as I sift through the scraps of paper that invariably define my life. A ticket stub from a tram in Germany. A Polaroid with an Elvis impersonator from college. A note my wife scribbled, explaining how to write her name in Chinese, and how its homonym is “Little Zero”.

And so every time I—now we—move, I am reminded of how this last place and the one before it and so on were good to me. Each time, I found friends, opportunities, and new perspectives. And each time, I am sad to leave.

The first time in my life I moved I was 16, and we were only moving three miles away on the same side of town. My school didn’t change and neither did my friends. But I was moving away from the only home I knew, and I was desperate to feel some attachment to our new house. I remember closing the linen closet door one night and noting how it made a whooshing sound. I thought, this is something I will remember. I belong here, because I will always remember how the linen closet makes a whooshing sound when you close it. It’s a silly detail, but I still notice it fourteen years later.

And so every time I move to a new place, I start cataloging those silly details. The first year is always the most difficult. With a sense of place like mine that is anchored in hundreds, even thousands of details on small, subtle scales, it can take a while. Necessities dominate at first—the path to the grocery store, a running route, a good place to get pizza—but the later details are what tell me I’m at home—the sound of the train, the smell after a rainstorm, the putterings of the neighbors.

And so here I sit, waxing nostalgic about my time in Chicago, and by extension the Midwest. The scraps of paper from Chicago and places previous are all safely tucked away in boxes, waiting to be shipped, again, across the country. 16,422 people per square mile. The population density of Cambridge, Massachusetts, our soon-to-be new home. It’s a statistic that’s very similar to our current Chicago neighborhood. But it’s only a number, and much as I’d like to think that I’ll quickly find my groove because the numbers align, deep down I know better. I know that it won’t feel like home until I know that number and the people and the trees and the streets and the sounds and the smells and more.

Photo by Justin Shearer.

U.S. not dense enough for high-speed rail? Think again

A comparison of population density and high-speed rail in the US and Europe

Low population densities are often cited as the reason why high-speed rail would never work in the United States. While it’s true that typical American metropolitan areas sprawl far and wide, many larger cities are still relatively dense, and a surprising number of our states are as dense as some European nations. California, for example, has just over 90 people per square kilometer (234 per square mile), while Spain has 88 people per square kilometer (231 per square mile). Given the success of Spain’s rail system, it stands to reason that California would be fertile ground for high-speed rail.

It’s probably not a bad argument to make, and one that sheds some light on why the Obama administration directed money toward certain states for rail upgrades. Ohio and Florida—both of which unfortunately rejected rail funding—are about as dense as France, a world leader in high-speed rail.¹ Illinois, Virginia, and North Carolina sit one density level down, but are on par with Spain and Austria, both of which host high-speed rail. As a state, Illinois may be a poor example since 75 percent of the state’s residents lives in the Chicago metro area. But if you look at the wider region—from Milwaukee to Detroit to Toledo, with Cleveland, Columbus, and Cincinnati not much farther away—you can see where the Midwest upgrades were headed.

Despite many regions with densities favorable to high-speed rail, only the Northeast Corridor hosts true high-speed rail, the Acela Express. It serves a relatively small fraction of the country. While the Northeast Corridor is most crowded in the U.S., many European nations have proven that high-speed rail can work at much lower densities—densities which are seen across the U.S.


  1. In fact, Florida’s population lives more densely than France’s.

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Raptors in the city

Red-tailed hawk in Chicago

Pip, the recently hatched red-tailed hawk featured in the New York Times “hawk cam,” was only the latest in a string of successful raptor hatchings in big cities. On the surface, raptors appear to have adapted to city living marvelously. Tall buildings present ideal perches and nesting sites, and lackadaisical pigeons provide easy meals. But as is often the case in ecology, the real story of urban raptors is far more complicated than can be shown with a simple web cam.

For all their visible successes, raptors still face myriad dangers in the city. Chief among them are windows. Anyone who has jumped at the sudden thud of a bird flying into a window—it happened to me yesterday in my office, so the sound is fresh in my mind—knows just how hard they hit. Nearly 25 percent of North American bird species are known to routinely smack into windows, and every building on the continent is thought to cause between one and ten deaths per year. Birds of prey are no exception. In fact, famed naturalist Thomas Nuttall recorded the first such strike in 1832, which involved a sharp-shinned hawk caroming into a window. A later study in Tucson, Arizona, reported that the majority of adult Cooper’s hawk fatalities were caused by collisions with windows.

But panes of glass are not the only dangers raptors face. Just making it out of the nest is an enormous milestone which, depending on the city, could be a 50-50 proposition. The Tucson survey reported that just less than half of all urban-born nestlings survived two weeks beyond their first flight, compared with over 95 percent in the surrounding countryside. Though their parents nested earlier and at higher densities and laid larger clutches than birds from the countryside, the nestlings devastatingly low survival rate meant fewer city hawks made it to adulthood. An overwhelming number fatalities were caused by a strain of the protozoan trichomoniasis, which is found in pigeons and doves and may be spread by tainted bird feed. Such birds constituted a large majority of urban Cooper’s hawks’ diet, but a small portion for country hawks.

The Tucson case isn’t unique, but neither is it universal. Other studies have investigated the trichomoniasis-urban hawk link and have come up empty handed, leading scientists to believe the problem is dependent on both the species and health of the doves on which the hawks feed. Still, it brings to light another concern that ecologists have about cities. For many birds—raptors included—cities may be “ecological traps.” Those environmental signals I mentioned above—preferable perches, natty nesting sites, and easy eats—may lure birds to cities, but environmental hazards such as windows, diseases, and vengeful humans can erode overall population numbers. Ecologists call this a population sink.

The solution isn’t easy or straightforward, especially for raptors. In the case of trichomoniasis, treating adults is possible in the early stages, but laborious. Nestlings can also be treated, but run the risk of reinfection when returned to the nest. Window strikes are even more troublesome—the usual window silhouettes do little to repel raptors, probably because they are modeled after those very same birds. Another option is to move bird feeders away from windows, since they attract prey species like doves, but that solution defeats the purpose of bird feeders for many people. Rather, limiting human impacts appears to be the real solution. Raptors are most successful is in areas of little human disturbance. While raptors do best in unspoiled native habitat, they can also thrive in low density residential areas. Chalk one up for small towns and suburbia.

Sources:

Boal, C., & Mannan, R. (1999). Comparative Breeding Ecology of Cooper’s Hawks in Urban and Exurban Areas of Southeastern Arizona The Journal of Wildlife Management, 63 (1) DOI: 10.2307/3802488

Chace, J., & Walsh, J. (2006). Urban effects on native avifauna: a review Landscape and Urban Planning, 74 (1), 46-69 DOI: 10.1016/j.landurbplan.2004.08.007

Dunn, Erica H. (1993). Bird Mortality from Striking Residential Windows in Winter Journal of Field Ornithology, 64 (3), 302-309

Klem, Jr., Daniel. (1989). Bird-Window Collisions The Wilson Bulletin, 101 (4), 606-620

Photo by Chicago Man.

Why the poor live in cities

Cabrini-Green, Chicago

If you ask any big city mayor what is one of the most pressing problems facing his or her city, I’m guessing poverty will be high on the list. Cities across the United States are filled with pockets of hardship, and while rural poverty is widespread, too, impoverishment within metropolitan areas tends to be strikingly concentrated near downtown. Did the rich flee or the poor converge? One study says transit provides the answer.

The article begins with pages of hypotheses, formulae, and tables, but the real history of the trend is buried at the end, just before the conclusion. The key to it all is the fact that public transportation is a distinctly modern invention, and before its advent, most people lived within walking distance of their jobs, regardless of income.

It is in the late 18th and early 19th centuries that we get a geographic glimpse, uninfluenced by modern public transit, at where the rich and poor lived. Proximity to employment dictated where people lived, and people, then as now, worked everywhere. Even the most successful hedge fund’s offices are cleaned by janitors who make little more than minimum wage, and this maxim held true back in the 18th and 19th centuries as well. The difference then was that the middle-class, the well-to-do, and even some of the wealthy walked to work. Only the fabulously wealthy had hansom cabs and carriages to take them about.

When mass transit started catching on, it was mostly enjoyed by those with money, like most new technologies. Affluent types began fleeing the city for “streetcar suburbs.” But as transit prices started dropping, a new technology burst onto the scene—the automobile. For the rich, cars were far better than cramped street cars. They could travel from home to work in relative privacy (though comfort was not a given due to the poor condition of most roads in those days). Plus, cars doubled as a status symbol.

Again, the poor were stuck in the city, and many remain stuck there today. The cost of owning and operating a car is simply beyond reach for a chunk of society. And given the limited reach or slow speed of many American mass transit systems, people without cars need to live closer to their jobs, which are typically in the city.

It’s a tidy narrative, and one that the study backs up with both anecdotal snapshots,¹ statistical models, and data-driven time points from the modern day. The modern observations paint a convincing picture, and one that backs up the narrative. In cities with extensive subway systems, the study found that incomes dip slightly within a one-mile ring of downtown—where land values drop but remain accessible by transit—and then rise and hold steady from three to seven miles out. Transit usage also rises after that first mile, peaking two miles out, where incomes begin to rise. This peak exists in those cities because rail systems—they move far more quickly—appeal to more than just the poor. Wealthier people are more willing to forsake their car for a train and a simpler commute. But in newer American cities without subway systems, buses rule. In those places, most people with sufficient means pay for the shorter commute by car.² The final piece of evidence lies in the geographic distribution of jobs. In “old” American cities with extensive transit, 55 percent of the jobs in the metro area are within five miles of downtown. In “new” cities, 81 percent of jobs are more than five miles out.

The evidence in this paper led me to a few conclusions of my own. First, since the poor are less likely to use roads and highways, government highway subsidies are regressive, that economic term that describes a policy that benefits the rich more than the poor. That makes transit subsidies progressive, but even that is an oversimplification. Transit gives the poor greater access to employment, which will hopefully make them not poor in the future. It also boosts property values in the near vicinity. Since the better-off can afford pricier houses, they clearly benefit, too. Still, some communities fail to understand transit’s merits, instead equating it with an influx of poverty. These rich communities³ will eventually need more viable transit options, though, because they employ poorer people to do the things they’d prefer not to do. And as gas prices rise, no one will want to pay through the nose for that privilege.


  1. “…in New York, 52 percent of workers earning less than $10 per week walked to work in 1907. Only 12 percent of workers earning $20 per day used that form of transportation, and instead used streetcars. Just as the car today favored the non-poor, the streetcar did in the past, and it helps to explain why the poor lived close to the city center 100 years ago.”
  2. This in turn gives the non-poor in those cities a negative opinion of transit. As in, “Only the poor take the bus.”
  3. Parts of Orange County, I’m looking at you.

Source:

Glaeser, E., Kahn, M., & Rappaport, J. (2008). Why do the poor live in cities The role of public transportation Journal of Urban Economics, 63 (1), 1-24 DOI: 10.1016/j.jue.2006.12.004

Photo by reallyboring.

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Atlantropa, or how to grow a continent

Atlantropa, dams at the Strait of Gibraltar

The 1920s were a time of great lows and tremendous highs. The specter of the Great War hung like a shadow over Europe, and financial ruin imposed by said war engulfed the belligerents (the United States being the lone exception). Adding to the calamity, Europe’s empires were wheezing under the weight of their colonies.

It is perhaps because of all that gloom that some people turned towards breathlessly optimistic ideas. After all, it was an age of wonder in many ways. Aeroplanes and dirigibles drifted and swooped from city to city and continent to continent. The Industrial Revolution had firmly cemented itself throughout the Western world, producing a surfeit of landmarks to human progress. Many big thinkers were dreaming up dams and skyscrapers and subways of unimaginable scale for the time. But one man was busy out-thinking the rest. Herman Sörgel had a plan so grand that it would have changed the face of the Earth.

Sörgel was a German architect living in Munich. A follower of the Bauhaus school, he did not produce any notable architectural works in his lifetime. Instead, he is remembered for devising an audacious plan to dam the Strait of Gibraltar and lower the Mediterranean Sea by 200 meters. Known as Atlantropa, the project would have generated enormous amounts of electricity, irrigated much of the Northern Africa (though how the water would be desalinated is unclear), flooded the heart of the African continent, and exposed over 250,000 square miles (660,000 square kilometers) of land in a bathtub ring around the Mediterranean.

Atlantropa had a solution for every European problem. Feeling crowded? The plan would add another France and Austria’s worth of land. Need more electricity? Various dams would have generated 365,000 megawatts of power by some estimates. Short on food? Just import it from the new African breadbasket, now a mere train shipment away.

There were, however, numerous problems that Sörgel overlooked. Workaday harbor towns would have been left high and dry. Dropping the Mediterranean Sea by 200 meters would have drastically altered its ecosystem, and the flooding of Africa would have inundated some world’s most diverse forests. Local climate regimes would have almost certainly changed in unpredictable ways. The plan also reflected the decidedly colonial and Euro-centric attitudes of the times. The proposed Saharan breadbasket may seem noble at first blush, but flooding central Africa in the process smacks of indifference. But perhaps Sörgel’s most glaring oversight was, how would they pay for it all? Europe was flat broke following World War I, and many countries would have had to work together to see it through. Such tight international cooperation is elusive even in today’s relatively peaceful times.

At its heart, the Atlantropa plan seems to be a reaction to the continent’s crowded landscape and thinning resources. Land was in short supply, mineral wealth was being mined at a rapid pace, and energy sources were hotly contested. The losers of the Great War—Germany among them—were in a deeper hole, having lost both territory on the continent and their colonies abroad. Sörgel hoped his massive project would change all that, ending resource shortages and bringing Europe and Africa together. Sörgel felt Europe could not compete with the land- and resource-rich continents of Asia and the Americas unless something drastic was done. His solution embodied a simple, if flawed, maxim: If you can’t import resources from faraway lands, bring the land needed to you. Sörgel’s fatal error, though, was the plan’s sheer scale. Securing resources for Europe’s future required spending a continent’s worth of resources today. Ultimately, Atlantropa was little better than a perpetual motion machine.

Sources and other links:

Edit Suisse Group. “Atlantropa.” Cabinet Magazine, Spring 2003.

Ptak, John F. 2011. “A Monumental and Fantastically Bad Idea: Draining the Mediterranean.” Ptak Science Books.

Jacobs, Frank. 2008. “Dam You, Mediterranean: The Atlantropa Project.” Big Think.

Morales, Michel. 2005. “Atlantropa: Der Traum vom neuen Kontinent.” TV documentary, German. (Parts 1, 2, 3, 4, 5, and 6 on YouTube.)

Green planet, clean water

Drinking water

In a world of finite resources, fresh water stands next in line to cause shortage, misery, and conflict. Only about 2.5 percent of the world’s water is fresh, and most of that is locked up in ice sheets and glaciers—much of which is melting into the salty ocean thanks to climate change. That tiny sliver that’s left has to support billions of people. And a small portion of that sliver—surface water in rivers, lakes and streams—supports at least half of the world’s population.

Keeping that water clean is paramount for public health. Ever since John Snow discovered the source of the Broad Street cholera outbreak in 1854, we’ve been hard at work keeping our water clean. But all that treatment costs money, and often the best way to ensure safe drinking water is to not sully it in the first place.

One of the best and most cost effective ways to ensure clean drinking water is to leave native vegetation within the watershed in tact. Each additional 10 percent of a watershed that remains forested reduces water treatment costs by 20 percent. In the United States, where two-thirds of the population gets its drinking water from surface sources, that ratio can save cities a lot of money. Seattle, Portland, and Boston have taken this to heart, conserving land specifically because it is cheaper than building new treatment plants or expanding old ones.

Fortunately for many U.S. cities, the typical American drinking water watershed is still nearly 80 percent vegetated. There is bad news, though: Not all watersheds are so fortunate—some have as little as 17 percent native vegetation—and half have only 3 percent of their area set aside for conservation. Threats to native vegetation are greatest in the populous Ohio River Valley and Southeastern states, and the amount of conserved land in much of that area is startlingly low, too. The median Ohio River Valley watershed has only 1.8 percent of its land set aside, while the median Southeast watershed has a mere 0.2 percent.

Plants do more than just keep water clean—they also make it more usable. Vegetation has a calming effect on water, slowing its progress down hillsides, allowing it to seep into the ground and emerge slowly and steadily into lakes and streams. Without plants to intervene, water surges into streams and rivers, quickly filling reservoirs to capacity and leaving dam operators with little choice but to open the sluice gates, wasting the water. (These impromptu floods can be beneficial to downstream riparian vegetation in some cases, but too much force can be torrentially detrimental.) Since people’s water use tends to be steady day-to-day, dams which capture water more slowly can make more efficient use of it.

The importance of vegetation in securing a clean and reliable supply of drinking water cannot be overstated. Safe drinking water is extremely difficult to come by in much of the world. Places like Ethiopia and Haiti have chronic shortages of safe drinking water. Not coincidentally, many of those same countries have lost nearly all of their forests. While the loss of native vegetation is not the only cause of these countries’ water woes, it plays an important role. Fresh water is an already scarce commodity. It’s important to keep it as potable as possible.

Sources:

Ernst, Caryn, Richard Gullick, and Kirk Nixon. 2004. Protecting the source: conserving forests to protect water. Opflow 30:1–7. (available online)

Wickham, J., Wade, T., & Riitters, K. (2011). An environmental assessment of United States drinking water watersheds Landscape Ecology DOI: 10.1007/s10980-011-9591-5

Photo by Cyron.

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Highfields, looking over the valley

Habitat loss can be like death by a thousand cuts for ecosystems. Each conversion to farmland, housing, or pasture, when taken on its own, may seem a small, inconsequential nick on the surface of a vast planet. But together, and over decades and centuries, these cuts add up, leaving only tiny remnants of the original scattered across the landscape. The result can be devastating for animals and plants which depend on the original ecosystem. Yet unlike the grisly metaphor drawn from an ancient Chinese torture, the wounds of habitat loss are not entirely fatal. Farms and subdivisions may not supplant virgin forest or grasslands, but they need not be inhospitable wastelands, either.

This post was chosen as an Editor's Selection for ResearchBlogging.orgThe field of ecology typically focuses on the leftovers of habitat conversion—the bits and pieces that somehow evaded plows and bulldozers. But just as no island is truly separated from the rest of the world, habitat remnants remain connected by the fields and yards that constitute the interstitial spaces. Known as “the matrix,” such spaces are important to the continued vitality of habitat fragments. In fact, according to new research out of Australia, the qualities of the matrix may matter more to the survival of native animal species than characteristics of the remnants themselves.

The matrix in the study are primarily cattle stations prevalent in the Toowoomba Regional Shire in southern Queensland. The area has been grazed heavily since the early 1900s, and pastoral uses are still the predominant land use, though urban development has been increasing in recent years. To quantify the amount of human influence within the matrix, the researchers measured a host of variables, mostly pertaining to roads and ranging from length to width to driving surface and even road kill statistics. They also closely studied the forest patches within the matrix and surveyed their resident mammal populations.

Many previous studies have focused on remnants’ size, shape, and geographic relationship to one another. This study did that, too, but also investigated the matrix itself. Of all possible landscape characteristics, the intensity of human development and number of tall trees within the matrix exerted more influence than any other.

To see how the matrix plays a role in this case, imagine you’re part of a group of people who are stranded on one of those islands, and your island doesn’t have everything you need to survive. Other islands do, though, so you’d need to set sail from time to time, just as the animals in the forest remnants may have to cross a pasture or pass through a neighborhood. The island metaphor is often used to describe how habitat remnants and their inhabitants interact with each other. Typically, people wax lyrical about the size, shape, and distance separating the islands. In this case, however, its not just the span of open water between the islands that matters, but the qualities of that water.

Neither the sea nor the matrix are absolute barriers, but they aren’t entirely hospitable, either.

Now let’s say you had a choice of islands on which to be stranded. Which would you pick? Quite obviously you’d prefer an island close to the mainland, but let’s say that’s out of the question. In lieu of that, you’d probably pick one that’s surrounded by calm seas so that exploring nearby islands would be infinitely easier. Some shallow waters between islands might be nice, too, to anchor your boat when you needed to take a rest. And if I were you, I’d also go for one with a bit of elevation to avoid high tides or tsunamis.

If those three wishes were granted, you’d probably have a good chance of living to a ripe old age. Conveniently, those wishes mirror what mammals in the Toowoomba study seemed to prefer, too. The researchers found fewer mammals traversing heavily developed areas—analogous to rough seas—and more where tall trees provided cover from predators—calm seas. The animals also favored a matrix with more nooks to roost or hide as they travelled—similar to shallow water for anchorage. Finally, the best remnants were those where human activities didn’t encroach too often—akin to higher elevation islands that guard against tides and tsunamis.

As a stranded soul, you wouldn’t have much influence over the ocean. But as stewards of the matrix, we decide its flora, its structure, and its ease of passage for animals. The biggest difference we can make is in reducing our developed footprint. The changes don’t have to be as drastic as ripping up subdivisions or farms. They could be as simple as carving roads only where they are most needed or avoiding areas where animals frequently tread. And failing that, plant trees.

Sources:

Brady, M., McAlpine, C., Miller, C., Possingham, H., & Baxter, G. (2009). Habitat attributes of landscape mosaics along a gradient of matrix development intensity: matrix management matters Landscape Ecology, 24 (7), 879-891 DOI: 10.1007/s10980-009-9372-6

Brady, M., McAlpine, C., Possingham, H., Miller, C., & Baxter, G. (2011). Matrix is important for mammals in landscapes with small amounts of native forest habitat Landscape Ecology DOI: 10.1007/s10980-011-9602-6

Photo by Shaun Johnston.

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City birds smarter than you might think

Pigeons in Krakow

Pigeons seem like particularly stupid birds. They alternate between frantic head bobbing and blank gazes, which are often interrupted with a lazy flutter of their oil-sheen plumage to avoid bone-crushing foot falls. But these flying rats may just be putting on a good show. Research published Wednesday shows that urban dwelling birds tend to have substantially larger brains than their country-bumpkin cousins.

A study of 82 passerine species in and around twelve continental European cities discovered that birds which are able to breed in the city center tend to have larger brains.¹ Pigeons occupy similar ecological niches to some of the surveyed species, despite the fact that they are not passerines and were not included in the study. So while the results don’t address the pigeon-stupidity issue directly, they do give us a clue about the potential intelligence lurking beneath that vacant exterior. In the study, researchers used the ratio of brain size-to-body mass as a proxy for intelligence.

The brain-body ratio, also known as Cuvier’s fraction, has been widely used as proxy for intelligence. It makes sense in many ways: the larger the proportion of the body devoted to intelligence, the better the chances the species will actually be intelligent. For example, look at porpoises and ostriches—both weigh approximately the same, but the cetacean is clearly smarter. In birds, such intelligence can aid adaptation to the “novel and harsh” urban environment, the researchers pointed out. The brain-body ratio isn’t perfect—there are small monkeys that have a larger ratio than humans, for instance—but it’s the best the researchers had given the dearth of bird brain studies.

Though this isn’t the first study to link avian intelligence to successful colonization, it is the first evidence of the trend applying in cities. That’s good news for the smart cookies, but could portend tough times for birds with smaller brain-body ratios in rapidly urbanizing areas.


  1. Here’s a sample of families that can successfully breed in Continental cities: Chickadees and tits (Paridae), nuthatches (Sittidae), kinglets or crests (Regulidae), starlings (Sturnidae), accentors (Prunellidae), and wrens (Troglodytidae). (There are many more species listed in the paper that have successfully adapted to the city—these are just the families where all of the surveyed species could breed in the city.)

Source:

Alexei A. Maklakov, Simone Immler, Alejandro Gonzalez-Voyer, Johanna Rönn, & Niclas Kolm (2011). Brains and the city: big-brained passerine birds succeed in urban environments Biology Letters : 10.1098/rsbl.2011.0341

Photo by Mr Thomas Piskortz.

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Plants rockin’ the suburbs, animals not so much

Tell me how much you drive, and I’ll tell you where you live

I-80 and M2

Travel can be revealing. In many cases, “where” can answer as much about a person as “who.” Much of who we are is tied up in what sorts of stores we frequent, where we work, and where we go for fun. While that sounds creepy—especially given the recent furor over smartphones storing location information—city-wide travel trends can help explain a lot about where we live.

A study comparing British and American travel habits discovered that trip distances in the United States predictably lengthen as the population thins out. In Great Britain, though, that relationship isn’t as strong, in part due to its greater population density. But when the researchers filtered out differences in income and density between Great Britain and the U.S., the British still traveled less.

The reason behind the travel discrepancy, the researchers suspect, lies in the strict separation of space for living, working, and shopping that is common in the U.S. To arrive at that conclusion, they had to use a bit of mathematical cleverness to make an apples-to-apples comparison. The model compared British and American cities of similar population and density, but shuffled the contents of the American ones until their general urban form resembled their ale-swilling counterparts. This meant that shops were now next to houses, grocery stores located just down the street, and pubs scattered about town. The results suggest that the jumbled urban land uses in England, Scotland, and Wales keep the lid on travel distances.

The British also get out from behind the wheel more often, using their feet for something other than operating gas and brake pedals. Whereas under 7 percent of trips in the U.S. are taken on foot, nearly one-third are in Great Britain. And while almost 90 percent of trips in the U.S. are made by car; only 58 percent are in Britain. More people in Britain take buses and trains, too. This modal flexibility could help explain why British of different incomes tend to take similar numbers of trips, unlike in the U.S. where wealthier people step out more often. In both countries, though, wealth is still tightly correlated with mobility, which is partially reflective of people’s ability to own, maintain, and fuel automobiles for such trips.

The one odd bit the researchers discovered was that people in smaller metropolitan areas—with populations between 250,000 to 500,000—traveled more frequently than larger ones. In theory, residents of large metro areas should have more available destinations and ways to get there, which left them stumped as to why big city people made fewer trips. My suspicion? Smaller metro areas may be a sweet spot in the spectrum, with just enough destinations and modes of transportation without the congestion present in big cities.

Source:

Giuliano, G., & Narayan, D. (2003). Another look at travel patterns and urban form: The US and Great Britain Urban Studies, 40 (11), 2295-2312 DOI: 10.1080/0042098032000123303

Photos by Minesweeper and Loganberry.

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Urbanites leave the car behind, but not as often as you might think

Urbanites leave the car behind, but not as often as you might think

Night traffic in New York City

It’s generally accepted as fact that people in big cities drive less. Things are closer together there, making it easier to walk to the store for a gallon of milk. For longer trips, mass transit is also an option. But boiling all that common sense down to a single number is difficult. And though our data-happy society can overdo it at times, numbers can reveal some surprising facts that simple observations otherwise wouldn’t—like the fact that increasing density reduces the amount people have to drive, but not by as much as you might suspect.

Determining precisely how far people drive—vehicle mile travelled (VMT) in the parlance of the field—is important for a number of reasons. With it, we can gauge greenhouse gas emissions from automobiles, allocate resources for road repairs or expansions, and refocus efforts to reduce car dependency. VMT is especially important in California, where the Global Warming Solution Act (also known as AB 32) calls on the state to reduce greenhouse gas emissions by 25 percent below 1990 levels by 2020. Cities and counties without a plan to reduce emissions within their jurisdictions risk losing transportation funding. With this in mind, two researchers from the University of California, Berkeley, set out to measure VMT per person in 370 urban areas around the United States and see how the built environment affects that number.

They discovered that people in more urbanized areas do drive less, but not that much less. Their lowest estimate for VMT was based on population density, but their more realistic result, which came from a model with more parameters, shows less of a reduction. Ironically, greater density is to blame for the lower than expected drop in VMT. As population density increases, VMT drops, but the densities of roads, shops, and services rise, all of which encourage automobile trips.

Urban areas need more roads because they have more traffic, which in turn tends to encourage more traffic. The researchers call it the “Los Angeles effect.” As Los Angeles filled the San Fernando Valley, it didn’t follow central travel corridors. Rather, it oozed out like a blob. This not only hindered mass transit in the city, it also required more roads to accommodate people’s varied travel patterns. The result is a “thicket of criss-crossing freeways and major arteries that form a dense road network,” the study’s authors write. Though Los Angeles is an extreme example of the road/population density relationship, other cities suffer from the malady, too.

The second curiosity that drives VMT in cities is the density of shops and services. It’s often easier to find a wider variety of goods and services closer to home in a city, which encourages people to leave home more often. So while people in cities still drive less, they don’t drive as little as they could.

Source:

Cervero, R., & Murakami, J. (2010). Effects of built environments on vehicle miles traveled: evidence from 370 US urbanized areas Environment and Planning A, 42 (2), 400-418 DOI: 10.1068/a4236

Photo by Josh Liba.

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Tell me how much you drive, and I’ll tell you where you live

The counterintuitive case of suicide and population density

Blueberry farm in winter

Suicide often raises one question more than any other: why? The answers are often varied, but that hasn’t stopped epidemiologists, psychiatrists, and other experts from trying to find some common threads. They may include anything from mental health to financial condition to gun ownership. Population density plays a role, too, though not the one you might suspect.

Sociologists in the 1930s speculated that the mayhem of the modern city drove people to take their own lives. On the surface, it sounds logical. Cities can be large, impersonal places. It’s easy to imagine a single person becoming lost in a swarm of millions with no safety net of friends or family to prevent him or her from falling into deep despair. Yet research seems to have proven that theory wrong. Many studies have discovered that people in rural areas—not cities—seem to have higher rates of suicide.

In Japan, a nation with a culture steeped in ritual suicide, suicide rates for men living in cities dropped between 1970 and 1990. Over roughly the same period, rates increased in rural areas. Suicide rates among Japan’s rural elderly are much higher than its urban elderly, too. Similar trends show up on the other side of the globe. In England and Wales, more people between the ages of 15 and 44 living in rural areas took their lives compared to those in cities. Many studies in the United States have discovered the same.

Suicide is also a significant problem in the Australian outback, where rates are two, even three times higher among men than their metropolitan analogs. At fault may be the consolidation of farms that took place in the latter half of the 20th century, leaving young men in the country with fewer employment opportunities. Combine that with easy access to firearms and pesticides (a very common method of suicide in agricultural areas around the world), and you have a recipe for disaster. Indeed, between 1964 and 1988, suicide rates for 15 to 19 year old boys living in the outback increased nearly fivefold, and the use of firearms in the act also increased fivefold.

Access to firearms is a recurring theme in the literature on suicide. Experts think easy access to firearms is partly behind the high rates observed in the countryside. Part of the problem is the lethal reliability of guns—an attempt with a gun is often more successful than other methods. Guns and suicidal tendencies are such a lethal combination that more people in the United States people kill themselves with guns than any other method.

Blaming guns would be a convenient way to wrap up this story, but the reality is that they are merely a means—albeit a very effective means—of committing suicide. Rather, there are deeper issues behind high rural suicides rates, most of which revolve around how mental health issues are handled. Mental health disorders are one of the main factors that lead people to suicide—as much as 70 percent of cases involve someone with a mental illness. Rural ideologies of self-reliance and hard work can lead to stigma against people with mental illness and discourage them from seeking help. Furthermore, the vastness of rural areas often means mental health services are few and far between. Even simple isolation is also a factor. Long distances mean fewer social bonds that could help pull someone back from the brink, especially for elderly people that have a hard time getting around.

That’s not to say the picture is hopeless. Education focused on reducing the stigma of mental illness can go a long way, especially considering that the majority of suicides occur among people with mental illness. Traveling counselors, crisis lines, and even educating clergy about risk factors can help. Though some of these proposed solutions are speculative—rural suicide is still greatly understudied—many are based on proven models from urban areas. The barrier, as always, is money. Providing services to rural areas is notoriously expensive, and in this age of budget cutting, social programs like these are often first in line for the axe.

Sources:

Dudley M, Waters B, Kelk N, & Howard J (1992). Youth suicide in New South Wales: urban-rural trends. The Medical journal of Australia, 156 (2), 83-8 PMID: 1736082

Hirsch, J. (2006). A Review of the Literature on Rural Suicide Crisis: The Journal of Crisis Intervention and Suicide Prevention, 27 (4), 189-199 DOI: 10.1027/0227-5910.27.4.189

Strong K., Trickett P., Titulaer I., & Bhatia K. (1998). Health in rural and remote Australia: the first report of the Australian Institute of Health and Welfare on rural health Report Other: 9780642247827

Photo by rkramer62.

Small farms in modern times

Two Indian farmers in a wheat field

Amartya Sen came from some not-so-humble beginnings. Born in to a well connected family and reportedly named by a Nobel Laureate in literature, Sen studied at Trinity College and received his first professorship at the tender age of 23. Expectations were high, and lucky for Sen, his career would live up to them, eventually winning him the Nobel Prize in economics in 1998 for his work in welfare economics and social choice theory. But Sen’s research has made another lasting impact, one that stemmed from a simple observation he published in 1962 in The Economic Weekly. Sen had noticed that larger farms in India produced less food per hectare.

It seems like a fairly simple and relatively banal observation, but it was one that had life or death implications. In 1962, the Green Revolution had yet to reach the Indian subcontinent, and the Bengali famine of 1943, which had a profound effect on Sen, had killed 3 million people. Food production per acre is key in crowded countries like India, and figuring out how to boost it can tip the balance from starvation to satiation.

The small farm advantage, Sen noted, was largely due to the extra attention each bit of earth received from its farmers. Large farms had to spread their effort over larger areas and often had to hire non-family help. Family members, as anyone who has helped move a relative knows, are cheap labor. Hiring outside the family is expensive, which leads to less labor per unit area compared to a farm that is worked exclusively by family members. Though Sen points out that these facts should surprise no one, it seems to have hit the economics literature like a bombshell.

Part of that was Sen’s near-perfect timing. His article landed just before the Green Revolution took root in India.  In fact, less than 20 years after Sen’s paper in The Economic Weekly, another study reported the advantage had been erased, that large farms with better access to credit for expensive seeds, machinery, and chemical fertilizers and pesticides were outproducing small farms hectare for hectare. But his work inspired coming generations to consider the plights of small farmers.

Despite the production booms of the Green Revolution, Indian farmers are still primarily small land holders. In fact, in many countries the proportion of small farms is increasing. These aren’t quaint 10 hectare farms, either. Average farm sizes continue to hover around one hectare, and has even shrunk in some places. Average farm size in the U.S., by contrast, is around 170 hectares (418 acres). With such small plots of land, it’s difficult for farmers in India to make a living, let alone a profit. A bit of consolidation would go a long way towards propping up incomes without turning Indian agriculture into a clone of Western factory farms.

Since 1962, the Green Revolution has saved many people from starvation. But our grasp on high crop yields is as tenuous now as ever. Modern farming is dependent on mechanization and chemical fertilizers and pesticides, both of which wouldn’t be possible without fossil fuels. As fossil fuel prices rise, productivity may again rely more on human labor, and large farms may find themselves at a disadvantage once more. In the end, farm sizes likely need to meet somewhere in the middle.  Exact acreage will depend on the crop and the region, but moderate sizes may prove to be both more profitable and sustainable.

Sources:

Eastwood, R., Lipton, M., & Newell, A. (2010). Farm Size Handbook of Agricultural Economics, 4, 3323-3397 DOI: 10.1016/S1574-0072(09)04065-1

Newell, A., Pandya, K., & Symons, J. (1997). Farm Size and the Intensity of Land Use In Gujarat Oxford Economic Papers, 49, 307-315

Sen, A. K. (1962). An Aspect of Indian Agriculture The Economic Weekly, 243-246

Photo from the World Bank Photo Collection.

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Can we feed the world and save its forests?

The rural-urban fringe, circa 1942

Sears House No. 115

It’s cliché to say, “Everything that’s old is new again,” but boy if it isn’t true sometimes. I recently unearthed a monograph from 1942 about the conflict between urban and rural land uses, and a number of sections read like they were written yesterday.

George Wehrwein, the author of the monograph and a well respected land economist in his time, speaks with a voice that sounds distinctly modern. He assails unguided development as “suburban slums.” He points out farmland’s unfortunate role in absorbing willy-nilly growth. He mentions the more than 2,000 cities that, even in 1942, were utterly dependent on automobiles—“these cities have no street cars or buses of any type.” Even in that austere time, the beginnings of the automobile’s coming golden age were evident.

While the automobile and the “modern highway” were accelerating the pace of suburbanization, they didn’t start the trend—streetcars and interurban lines were initially responsible. “Almost as soon as railways became established, industries began to ‘decentralize’ by seeking locations in the suburban areas,” Wehrwein writes. While both trains and automobiles drove decentralization, they invaded rural spaces in distinctly different ways. Trains left a pattern of hub-and-spoke development, drawing some industries far out of the metropolis while leaving closer yet less accessible land under the plow. Automobiles allowed this decentralization to diffuse across the landscape even further while also invading the interstitial spaces left by train-focused development. “As a result, cities have not merely expanded, they have ‘exploded,’ ” he wrote.

Cars and highways spread development more evenly across the landscape, but much of the growth came at the expense of valuable farmland, something that clearly rankled the economist. Large tracts of land weren’t developed immediately, leaving empty lots set amidst trafficless roads, both of which became financial burdens on the local government. In his paper, Wehrwein condemns speculators that drove such slapdash development and rails against weak rural governments that did little to check them. He wasn’t universally panning the suburbs, but he was dismayed at what he saw as a waste of land and resources.

If Wehrwein’s lamentations sound distinctly modern, then so too do his solutions. He calls for large scale regional planning in his paper and advocates granting counties the power to guide development in unincorporated areas. Thanks to his earlier efforts, that experiment had already begun on in a few places. Twenty-five of Wisconsin’s 72 counties had zoning laws, and the state of California granted local authorities power to do the same. But Wehrwein also realized that granting authority does not ensure a desired outcome. “Mere power does not carry with it the desire, courage, or the wisdom necessary to make for a well planned rural-urban region.”

Source:

Wehrwein, G. (1942). The Rural-Urban Fringe Economic Geography, 18 (3) DOI: 10.2307/141123

Image in the public domain.

The great (big) American lawn

A lawn being mowed

Spring is descending on the United States. Buds on trees and shrubs are swelling, and brittle brown grass is beginning to show green signs of life. As people put away their snow shovels and dust off their lawn mowers, it’s also a good time to take stock of the American lawn, which plays a starring role in the American dream. Backyard barbecues or weekend touch football games wouldn’t be the same without them, and there is something pleasing about a house perched amidst a nice green carpet. But grass is also a fussy plant, needing to be watered, fertilized, weeded, and, of course, mowed. For many, lawns are an American nightmare, yet we love them anyway.

Some Americans like to say they bleed red, white, and blue, but many should probably add green to that list, such is their devotion to their lawns. I myself am intimately acquainted with lawns and have been for many years. I started mowing my parents’ lawn as soon as I could safely see over the mower’s handle and took on a handful of my neighbors’ shortly thereafter. It didn’t take long until I was a lawn mowing connoisseur, changing the cutting pattern with every mow to give the yard a bit of golf course confidence. Even in college I couldn’t escape lawns. One of my summer jobs involved navigating a Toro Groundsmaster 322-D across school yards for eight hours a day. Even today, I still like the smell of freshly cut grass.

Our attachment to lawns means they have moved with us, even to climates where no lawn has any right to grow. Given how large they figure in the American subconscious, just how big is the collective American lawn? Nearly 50,000 square miles. That’s three times more than the area of irrigated corn in the U.S. And we grow a lot of corn. We’re still rolling out the green carpet, too. Between 1978 and 2001, we added between 170 and 355 square miles of lawn each year (depending on how you estimate it).

Much of that growth has come from the expanding suburbs. Lawns aren’t necessarily bigger than they used to be—in fact, median lot sizes have decreased while houses have continued to grow.¹ Part of the reason is that two story houses are more popular than before. Whereas only 23 percent of homes built in 1973 were had two stories, 53 percent do today.² So while houses have increased in size, lawns have kept pace, if only because they’ve reclaimed some of the built footprint.

More land under the seed-water-fertilize-mow regimen means more chemical applications, too. And given the intensity with which we dose our lawns, that should concern us. About 71 million pounds of active ingredients of herbicides, insecticides, fungicides, and other chemicals are dumped on U.S. lawns each year, or about 7 percent of all pesticides used in the U.S. Lawns may be attractive greenery, but they’re anything but green.

That’s not to say we should do away with lawns entirely. No way. But perhaps we could all do a little better by following two maxims my dad has for his lawn. First, he reasons that more fertilizer means more mowing. He applies it like a diabetic sugars his coffee—sparingly. It’s just enough to prevent our yard from becoming a neighborhood disgrace, but it’s a savvy approach. Some of our old neighbors fertilized religiously and therefore mowed religiously. The second mantra speaks to lawn size. “If the lawn takes longer than half an hour to mow, then it’s too big,” he says. While the half-hour rule was never entirely accurate—I paid close attention to how long I spent behind the mower—it’s the idea that matters. Our back yard was wreathed in butternut trees, general shrubbery, a small pond, and an honest-to-goodness prairie, all there, in part, to cut down on the amount of grass we had to maintain.  Some people might balk at giving up that much turf, but I can assure you, it was still enough for a weekend game of football with my friends.


  1. Average lot size—which is skewed by mammoth properties—has grown slightly since 1976.
  2. Fun fact: Split level homes which were all the rage in the 1970s and 1980s peaked at 12 percent of new homes in 1975 and 1976. Today, their numbers are little more than a statistical hiccup.

Sources:

Fishel, Frederick M. 2011. Pesticide Use Trends in the U. S. : Pesticides for Home and Garden Uses. PI-140. University of Florida Institute of Food and Agricultural Sciences Extension.

Grube, Arthur, David Donaldson, Timothy Kiely, and La Wu. 2011. Pesticides Industry Sales and Usage: 2006 and 2007 Market Estimates. U.S. Environmental Protection Agency.

Lindsey, Rebecca. 2005. Looking for lawns. NASA Earth Observatory.

Robbins, P. (2003). Turfgrass revolution: measuring the expansion of the American lawn Land Use Policy, 20 (2), 181-194 DOI: 10.1016/S0264-8377(03)00006-1

U.S. Census Bureau. 2010. Characteristics of New Housing.

Photo by seantoyer.

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It’s not the yard that matters, it’s the view

Plants rockin’ the suburbs, animals not so much

Tourism’s carrying capacity

Landing approach to Princess Juliana International Airport on Sint Maarten

Tourism can be a real boon to a local economy, propping up otherwise sleepy towns with an influx of cash. But as with many things, there’s a point where “just enough” becomes “too much.” Popular tourist towns with a few thousand residents can practically burst under the pressure of peak season. They’re like an experiment in population growth and decline repeated on an annual basis, and the strain can quickly become evident.

Perhaps nowhere has this experiment been more intensive than on the islands of the Caribbean. Between 1970 and 2010, the number of tourists soared from 4.6 million to 17.3 million, and that number doesn’t include the 18 million cruise passengers that traipsed around an island for an hour or three. It’s a staggering increase, and one that brings to mind the growth trends that populations exhibit as they near carrying capacity, the limits of their habitat.

Indeed, tourism for a particular region generally follows the same S-shaped—or logistic—curve. The initial number of visitors is a slow trickle, but once the place is “discovered,” the number of arrivals soars. Eventually, prices rise, the environment suffers, and crowding becomes an issue, all of which discourage further growth. Unless a new attraction is built or another natural wonder discovered, the annual number of tourists will either level off if appropriately managed or decline if not.

Carrying capacity for tourism is similar in some ways to ecological carrying capacity and different in others. Ultimately, physical resources limit both population and tourist levels. A dearth of land, shortage of food, or decline in water quality and availability will quickly put the brakes on both types of growth. But for tourism, cultural resources are also a concern.¹ Unique cultures that once attracted visitors can become spoiled or diluted, losing the draw they once had.

Some islands in the Caribbean may be in danger of soon reaching or exceeding their carrying capacities, according to a 2005 study. For example, Bermuda, St. Kitts, and Barbados, to name a few, had relatively high tourist densities and low increases in arrivals—the classic tapering off of the S-curve as the limit of carrying capacity approaches. The authors did discover a few anomalous islands that may show the way for the others. The Caymans, for example, have both high tourist densities and growing arrival rates, which the authors attribute to modern resorts and tourism development that limits environmental degradation.

Since that study, annual tourist arrivals for the entire Caribbean have been leveling off. While the number of cruise passengers shot up from 11 million to 17.3 million between 1996 and 2010, traditional arrivals only rose by about 600,000. While cruise ship passengers may substitute for other vacationers in some ways, they are not equal replacements. Their stays are shorter—typically only a few hours—meaning they spend less. And while cruise ships may require fewer local resources, they leave other environmental burdens, including sewage pollution from older ships and problems resulting from harbor dredging.

I never would have suspected that there could be a plausible link between limits on tourist capacity and ecological carrying capacity, but the comparison seems appropriate. Tourists’ demands are similar to those of their every day life, only ratcheted up a few notches. On vacation, service is expected where it otherwise wouldn’t be, and consumption is often higher (how many people wash their towels on a daily basis when at home?). Vacationers are experimental treatments of sorts, testing the limits of their destination’s infrastructure and environment.


  1. Though you could argue that a lack of culture could, in a way, lead to a decline in population growth as well.

Source:

Robert N. Thomas, Bruce Wm. Pigozzi, & Richard Alan Sambrook (2005). Tourist Carrying Capacity Measures: Crowding Syndrome in the Caribbean The Professional Geographer, 57 (1), 13-20

Photo by ToddonFlickr.

Proximity sans convenience: Houses near train tracks and freeways

Houses near train tracks

Train tracks and highways are wonderful things. They zip ourselves and our stuff around with unparalleled efficiency. Never has getting anywhere been so easy. They are true marvels of the modern age—unless you can’t use them. Train tracks without nearby stations or those that don’t serve passengers aren’t conveniences, they’re rumbling menaces. And highways without onramps close at hand are roaring headaches. No one wants to live next to them. When transit corridors are nuisances rather than amenities, home prices suffer.

There are a couple of ways to measure how big of a bite nearby-but-inaccessible transit corridors take out of housing prices. One of the simplest is to look at freight trains. Freight trains offer few tangible benefits to the general public, but they present a lot of downsides. Their diesel engines emit low growls, their whistles high pitched wails. Their burdened cars rumble through neighborhoods, shaking doors and windows as they pass. A study conducted in the late 1970s in London, Ontario, found that house prices started dropping off within 800 feet of the tracks. The closer the house, the greater the loss in value.

Another way is to look at freeways without nearby onramps. A study of the Interstate 90 corridor running east from downtown Seattle found that house prices near to the freeway but far from an onramp suffered. A second part of the study focused on the Mt. Baker neighborhood in Seattle, part of which overlies a tunnel for I-90. People who live in Mt. Baker do not have easy access to the freeway, but they also do not suffer from noise or air pollution because of the tunnel. Yet houses dropped in price anyway the closer they were to the tunnel, a fact the study’s authors attributed to stigma of living near a freeway. Houses situated on top of the tunnel were worth 20 percent less than those 300 feet away.

Then there’s the question of commuter or light rail. There are dozens of studies that show living close to a train station increases house prices, but there is such a thing as too close. Apartments in Haifa, Israel, that were within 50 to 100 meters (about 160 to 330 feet) of train tracks sold for 13 percent less than houses outside that buffer. Immediately outside that distance, prices shot up and then tapered off slowly, as those residences were conveniently close to the stations but far enough away from the noise.

One hundred meters is not the universally optimal distance from train tracks, though. Lines with less frequent service may not sufficiently offset the downsides of living next to tracks, and those that run at-grade (as opposed to underground) may drive prices south. For example, houses adjacent to tracks for CalTrain, which offers commuter service to the San Francisco Peninsula, sold for substantially less than houses next to tracks for BART, the light rail system for much of the rest of the Bay Area. The diesel CalTrain runs at-grade and offers less frequent service than the electric BART, large portions of which run underground.

Train tracks and freeways can be a nuisance, and each in their own way. Trains are generally quieter than freeways, but infrequent train passings and whistles at crossings can make them more noticeable. On the other hand, trains produce less pollution than freeways, which have proven negative effects on respiratory health. Living with neither set of problems would be ideal, but modern means of travel are not going away.

Sources:

Kilpatrick, John A., Throupe, Ronald L., Carruthers, John I., & Krause (2007). The Impact of Transit Corridors on Residential Property Values Journal of Real Estate Research, 29 (3), 303-320

Poon, L. (1978). Railway Externalities and Residential Property Prices Land Economics, 54 (2) DOI: 10.2307/3146235

Portnov, Boris A., Genkin, Bella, & Barzilay, Boaz (2009). Investigating the Effect of Train Proximity on Apartment Prices: Haifa, Israel as a Case Study Journal of Real Estate Research, 31 (4)

Photo by chrisjbarker.

Related posts:

Paying for proximity: The value of houses near train stations

Do people follow trains, or do trains follow people? London’s Underground solves a riddle

Keep your eyes to yourself

Crowded sidewalk in New York City

There’s an unwritten rule followed by nearly all city dwellers—never make eye contact. If you attempt to do so, your glance will be met with utter disregard. You do not exist, other than being an object to avoid. I learned this the hard way. Upon moving to San Francisco from Minnesota—the friendliest of all possible places—I would attempt to make eye contact with strangers on the street out of courtesy. In Minnesota, this is commonplace. There, my glances were often met with a polite smile or a courteous “hello.” In San Francisco—even on streets that were anything but crowded—they were ignored with complete indifference.

Imagine, then, my surprise when I learned of San Francisco’s reputation as a friendly city. If San Francisco is considered friendly, I thought, then I’m steering clear of New York. I mused that such indifference to others must be an artifact of city life. That’s not to say there aren’t friendly people there—it’s true that San Franciscans are a generally genial bunch once you get them off the sidewalk, as are the New Yorkers I’ve met and nearly every other person from a big city. But when I’m in a small town, things sure do feel different. Walking down the street is no longer a sterile affair. It’s no family reunion, but it is degrees warmer than in cities. Still, my own experiences weren’t enough to convince me that this could be a universal trend.

Luckily, my hunch was proved correct the other day by a study which compared the rates of eye contact among people in central Philadelphia, suburban Bryn Mawr, and rural Parkesburg. The study’s authors parked two college students—a guy and a girl—outside a post office and a store in each location for two hours. The students counted the number of people who made eye contact and if anyone said “hello,” “how are you,” or the like. Lo and behold, rural Parkesburg held true to the small town stereotype. Between 70 and 80 percent of passersby glanced at the stationary students in the Parkesburg, while just 10 to 20 percent did in Philadelphia. Bryn Mawr’s pedestrians fell predictably in the middle, with around 40 to 50 percent making eye contact.

The rural types were also much more likely to say something to the strangers. One quarter of people in Parkesburg opened their mouths in greeting, while just three percent did for Bryn Mawr and Philadelphia combined. (The city center was by far the least friendly—only one person said something to each person at both the post office and the store.) In addition, everyone who did say something did make eye contact.

The study’s authors contemplated a few possible explanations for why the city dwellers were so hesitant to make eye contact. They favored the sensory overload hypothesis—that people in big cities are surrounded by too many people, noises, and other distractions—though they also speculated that city folk may fear strangers more or that small town people may be more curious about strangers. They also touched on the idea that city people are more hurried than either suburban or small town people. This notion has been covered both before and since by a number of different researchers. In general, people in larger cities do tend to walk faster, so there may be some truth to this.

Whatever the reason, I admit I exhaled a slight sigh of relief when I discovered that science confirmed my suspicions. San Franciscans, New Yorkers, Londoners—no matter how friendly they are underneath, suffer the same aversion to eye contact as other big cities. Small towns do feel friendlier.

Sources:

Newman, J., & McCauley, C. (1977). Eye Contact with Strangers in City, Suburb, and Small Town Environment and Behavior, 9 (4), 547-558 DOI: 10.1177/001391657794006

Bornstein, M., & Bornstein, H. (1976). The pace of life Nature, 259 (5544), 557-559 DOI: 10.1038/259557a0

Bornstein, M. (1979). The Pace of Life: Revisited International Journal of Psychology, 14 (1), 83-90 DOI: 10.1080/00207597908246715

Wirtz, P., & Ries, G. (1992). The Pace of Life – Reanalysed: Why Does Walking Speed of Pedestrians Correlate With City Size? Behaviour, 123 (1), 77-83 DOI: 10.1163/156853992X00129

Photo by Susan NYC.