Thursday, March 29, 2012

Whales, trees wish you would shut up already

Image Credit: Thing Three.

The noisiest place I ever lived was an apartment at the corner of Sixth Avenue and 15th Street in Manhattan. It was the nexus of several bustling neighborhoods and a hub of public transportation, with subway stops mere blocks in each cardinal direction and even a New Jersey PATH train station within easy walking distance. New York City’s endless stream of vehicles gushed down the avenue day and night, and an array of 24-hour fast food establishments and markets ensured a steady flow of both gregarious revelers and ranting vagrants. On weekends, street festivals awoke us with their blaring music and electric generators. On rainy nights, the din of hydroplaning taxis made watching a DVD with the windows open impossible. It was effing loud.

As a species, humans excel at making noise. Not content to stick with the howling and growling of other animals, we’ve created machines to augment our collective clamor. And, thanks to our ever-increasing transformation of the planet’s landscape, we’re sharing that noise with other organisms. Everywhere we go, we bring sirens and jets and jackhammers. How is the rest of nature faring with this parade of sound? Sometimes not too well. And a pair of recent studies, each published in the Proceedings of the Royal Society B, highlights how the effects of our auditory intrusions are not limited to land-dwelling animals, or even animals.

Right place, right time
In the weeks following the September 11th, 2001 World Trade Center attacks, many New Yorkers were on edge. They jumped at the sound of car alarms, fretted over riding the subway, and had anxiety dreams filled with airplanes. Meanwhile, North Atlantic right whales (Eubalaena glacialis) were finally able to relax a bit. Why? Because for once they could hear each other without yelling. Ship traffic in the Bay of Fundy, Canada, where whale studies were underway, dropped following the attacks, and with it so did underwater noise levels. Ships produce low frequency sounds that interfere with right whales’ communication vocalizations. So while life on land was newly terrifying and chaotic, underwater an invisible wave of tranquility was sweeping through.

As you can imagine, the exact course of the research wasn’t planned. In the weeks prior September 11th, scientists were plodding along measuring underwater noise levels and also collecting samples of whale crap, unaware of the tragedy-borne opportunity lurking on the horizon. The audio data were collected from August to September of 2001, but the fecal sample study would continue through 2005, from the months of late July to early October (the whales aren’t in town year round).*

Consistent with the scientists’ empirical observations, underwater recordings made after September 11th showed a decrease in noise. But perhaps most interestingly, analysis of the fecal samples found that the post-911 poo had lower levels of glucocorticoid metabolites. Glucocorticoids are secreted in response to various kinds of stress, so the lower levels suggest that quieter waters resulted in calmer whales. Depressingly this might also indicate that, under normal, non-catastrophic circumstances, whales in the region are chronically stressed.

Soothing sounds of the forest
While I myself have never attended a grade school science fair (my childhood was sparse on extracurricular activities) I’m told that a popular experiment for such things is testing whether plants grow better in the presence of soothing classical music versus abrasive rock ’n’ roll. If you’ve read this far hoping to learn about laboratory scientists subjecting potted ferns to daily doses of death metal, I’m sorry to disappoint you. The study at hand dealt with the indirect effects of noise on plant pollination and seed dispersal. Both of these services are sometimes provided by animals, so while the plants themselves may be indifferent to manmade noise, animal reactions to it can influence the plants’ reproductive success.

The authors conducted their research in New Mexico in the Bureau of Land Management's Rattlesnake Canyon Wildlife Area, which houses not just wildlife, but also natural gas wells and the noise-making compressors used for extraction and transportation of the resource. This provided an ideal setting for the study, as the location had both quiet control areas (without compressors) and loud experimental areas (with compressors) and yet none of the confounding variables typically found in noisy spots (i.e., the various urban indignities discussed back in the opening paragraph).

To examine the effect of noise on seed dispersal, the scientists focused on the piƱon pine (Pinus edulis), tracking the volume of seeds taken by different animals from both the loud and quiet spots. While some animals seemed to prefer snatching seeds in the noisy areas, the one most likely to help the seeds take root, the western scrub-jay (Aphelocoma californica), carried away more seeds in quieter locales. † This suggests that pines residing in noise-polluted districts may have less luck producing offspring.

Yet the effects of increased noise weren’t always negative. The pollination experiment looked at the auditory preferences of the black-chinned hummingbird (Archilochus alexandri). Unlike the scrub-jays, these birds visited flowers in the noisy sites more often, potentially conferring a reproductive advantage to hummingbird-pollinated plants in loud regions. However, the authors note that the cause of this was probably not the hummingbirds’ fondness for generator sounds, but their aversion to predators that stake out the quieter areas. Like humans choosing an inferior restaurant because it’s easier to get a table, hummingbirds likely hang out in less desirable neighborhoods to avoid the hassles of more popular ones.

So while the exact effect may be difficult to predict, noise pollution – like other more publicized forms of pollution – does have an impact on both flora and fauna, on land and in water. Repercussions of the increasing cacophony of daily life on our own species might also merit examination. Anecdotally, I can tell you that I felt less stressed out after vacating the Manhattan apartment. Though perhaps the toxic fumes emitted by the Cheesesteak Factory (yes, such an establishment exists) were the bigger problem.

* If you’re wondering how one goes about finding whale droppings, as with drugs and bombs, it’s done with the help of trained dogs.

† The scrub-jay stores some of the seeds it swipes, and not all these are eaten later. Thus the unconsumed seeds have a shot at becoming new trees.

Sunday, March 11, 2012

Paint it White: How New York City is getting cooler

New York vista by Tim Pearce.

It’s official: white roofs are cool. The declaration comes from the tastemakers at NASA, and, as always, New York City is at the vanguard of the new trend. In fact, the city’s recently brightened rooftops were found to be over 40 degrees Fahrenheit cooler than traditional dark roofs at the height of summer heat waves.

If you’ve weathered a NYC summer and were lucky enough to escape to the country for a weekend, you probably noticed that it feels several degrees cooler once outside the city – and consequently several degrees insufferably hotter upon reluctant reentry. Having myself spent over a decade in the city, I’d assumed this temperature gradient was caused by the fact the New York summers were literally Hell and the months of July and August a period of non-eternal damnation, but it turns out there’s a simpler explanation.

New York City is crowded, not just with people, but with buildings. Lots of buildings, built close together and typically topped with dark roofs that excel at absorbing the sun’s rays. Outside of the city, manmade structures are interspersed with these things called trees. The green of suburban and rural foliage reflects back some of that solar radiation, resulting in cooler ground temperatures. Meanwhile cities bake in their black asphalt casing. The phenomenon is called the “urban heat island” effect, and, scientifically speaking, it thoroughly and unequivocally sucks.

Higher temperatures not only make city dwellers miserable and irritable, they also result in greater energy usage and higher greenhouse gas emissions, which ultimately makes things even hotter. Hoping to reign in this unfortunate positive feedback loop, city planners have been working to replace traditional dark roofs – made of conveniently waterproof and durable asphalt and tar – with new fangled white materials (household staples like ethylene–propylene–diene monomer (EPDM) and a thermoplastic polyolefin (TPO)). Since not every building owner is willing and/or able to replace an otherwise functional black roof, the NYC CoolRoofs program is also promoting a less involved option – “retrofitting” existing dark roofs with old-fashioned white paint.

So is it working? A multi-year study recently published online in the journal Environmental Research Letters examined how the high-tech versus DIY brightened roofs fared against each other and as well as compared to standard dark roofs. Initially, both the two professionally-installed membranes and the civilian-applied white paint performed admirably – with white surfaces measuring an average of 43 degrees Fahrenheit cooler on hot summer days than dark samples. (Those asphalt rooftops can reach a disheartening 170 degrees Fahrenheit.) However, while the fancy whites were resistant to the ravages of time, the humble white paint lost some of its luster (and, more measurably, its reflectance) by the second year… not unlike the interior paintjobs in Manhattan apartments. Still, even the two-year old paint was an improvement over the dark roofs, and you can’t beat the price (about 50 cents per square foot, whereas the pro roofs ran between $15 to $28 per square foot).

So that’s all pretty impressive, but I seem to recall that New York has not just one but two problem seasons, in terms of both human suffering and energy usage. What about winter? Is white after Labor Day as gauche on rooftops as it is in ensembles?* The EPA, whose standards for roof reflectivity these white materials are striving to meet, acknowledges that brightening roofs in colder climates may come with a “winter heat penalty”. That is, in reducing unwanted summer heat, the more welcome heat that would have been generated by sunlight-absorbing dark roofs in winter is also forfeited, and gas or electric heaters must work harder to make up the deficit. However, since fewer hours of sunlight are available during the coldest months, it’s not a major loss (relative to the improved efficiency in summer) unless you’re dealing with frigid locations where heaters run 9 months out of the year. †

Additionally, the authors of the current study found that at least one of their measured materials (our friend EPDM) seemed to avoid the winter heat penalty entirely. They attribute this to the material’s emissivity level. Here’s the deal (in as much detail as I’m willing to tackle), white roof initiatives are looking only at a material’s reflectivity. This is the amount of sunlight reflected back instead of absorbed. To qualify for the EPA’s “energy star” rating, a material must have a solar reflectance of 0.65 or greater upon initial installation, and 0.50 or greater after three years. (It’s a zero to one scale, with 0.0 absorbing all light, and 1.0 reflecting all light.)

But materials also have an emissivity factor. Emissivity is the amount of heat something emits after absorbing solar radiation. Since close to half of that sunlight is being absorbed by the white surfaces (still far better than black, which is typically around 0.05 in reflectivity) how much of it they emit will also affect a building’s surface temperature. The white materials tested were assumed to have a high emissivity in addition to their high reflectivity (i.e., whatever sunlight got in would quickly be booted back out), but the EPDM seemed to cling a bit harder to its absorbed heat, thus keeping its surface toastier in the winter.

The authors therefore suggest that materials with high reflectivity but middling emissivity may be the best fit for colder climates. Got all that? Don’t worry, I’m not sure I understand it either. Emissivity is a tricky concept to get a handle on. Apparently even the folks manufacturing the EPDM couldn’t figure out how much heat their product would emit.‡

In any event, it’s nice to see that New York City is getting its environmental act together. When I left the place in July of 2008, it was a sweltering cesspool with insufficient bike lanes and a surfeit of Sex in the City-spawned shopping zombies. Less than four years later and, well, at least two out of those three problems are being addressed. While the world could do without some East Coast fads (I had to endure a second round of Brooklyn’s ironic mustaches when I moved to Austin), one can only hope that the trend of going green by way of white will soon fan out to other cities. Especially those in the south, where I currently reside. It's totally uncool here.

* Yes, I’m aware that no white after Labor Day is an outmoded fashion rule. Austin isn’t that behind the curve.

† And if you’re living somewhere truly freezing, isn’t your roof covered with snow most of the time anyway? Now if we could just get it to snow in summer instead of winter, then all our problems would be solved.

‡ The product was rated as having an emissivity of 0.90 (high), but the authors estimated it to be closer to 0.48 (not so high).

Tuesday, March 6, 2012

America's grossest invasive species

As if 12-foot pythons and lizards capable of biting off limbs weren’t enough for Americans (especially Floridians) to worry about, now comes a nonnative species that is not only harmful to indigenous flora and fauna, but also thoroughly disgusting. Meet the European earthworm (species of the genus Lumbricus) a grotesquely-long squirming squishy blob of an animal that is responsible for the decline in populations of the completely non-revolting ovenbird (Seiurus aurocapilla). It’s a bit backward sounding, I know, as birds typically eat worms, but the problem is more complex than ordinary predation or resource competition.

Happy, earthworm-free woods. Image: Duane Burdick.
The worms aren’t attacking the birds (they’re not that big) or even nosing in on their food supply. You see, the issue is that ovenbirds – a migratory species that nests in North America and flies south during the colder months – build their nests on the ground, and they do so in what was previously earthworm-free hardwood forest, which normally has a thick layer of understory plants. The abundance of low plants helps conceal ovenbird nests from predators, but now these nauseating euro-worms are ruining the delicate environmental balance.

Personally, I feel a titch misled. Being none too keen on earthworms from day one, I’d been told many times that we must appreciate (or at least tolerate) the slimy bastards because of all the good they do for plants. You’ve surely heard the same spiel. Worms’ subterranean writhing tills the soil, distributes nutrients, and makes gardens flourish. But such pro-worm propaganda, while true, is only part of the story. And what’s good for the garden isn’t necessarily good for the forest. That important understory foliage grows from the slow decomposition of leaf litter on the forest floor. Earthworms, which happily eat all sorts of rotting vegetation, feed on this litter and hasten the decomposition process. As a result, there is less fertilizer for the understory plants and subsequently less protective cover for ovenbird nests.

How did these clammy wriggling beasts from abroad worm their way into American soil? Like pretty much every other invasive species, they were delivered here courtesy of human sloppiness and/or cluelessness. European earthworms have been in the country as long as European humans, (you know, pilgrims and founding fathers and the like), brought in accidently by boat or deliberately by ambitious gardeners. More recent activities, logging and the dumping of fishing bait, delivered the pests into hardwood forests, where they’re currently running amuck. Yuck.

I don’t claim that earthworms have no place on our planet, or even in North America. Nor would I profess that any one animal was superior to another. I can only present to you the facts as I have uncovered them....

Images: U.S. Fish and Wildlife Service (L) and Michael Linnenbach (R)
I rest my case.