Author: Samantha Wallace

Biking the Distance… In 30 Minutes or Less: The Impact of Cost and Location on Urban Bike Share Systems

Citi Bike

Those of us who commute to the PLOS San Francisco office have noticed the emergence of bike share stations cropping up along the San Francisco Bay and on the city’s main drag. And we’re not alone here in San Francisco: the picture above is from the New York City Department of Transportation’s bike share. Around the world, bike share systems, which aim to make bicycles available on a short-term basis to anyone, have experienced massive growth as cities work to decrease gas emissions and encourage people to stay active. However, not everyone is ready to forgo the convenience of four wheels for two just yet. To understand why more people haven’t made the switch from cars to bike share systems, the author of a recently published PLOS ONE paper delved into possible factors affecting our willingness to don a helmet and cycle the distance.

Using publically available data from Washington DC and Boston, Dr. Jurdak, an Australian researcher, conducted a series of statistical analyses designed to examine the impact of bike share system pricing and neighborhood layout on potential bikers. It turns out cost is a major factor for commuters and tourists alike, but distance is not. Although analyses showed a bias towards shorter trips with a tendency towards a peak of 6 minutes—averaging 13 minutes per trip—a sharp drop off occurred in the likelihood of trips right around 30 minutes.

Why the decline at around 30 minutes? In both Boston and Washington DC, trips under 30 minutes incurred no additional cost in the bike share pricing system. Registered users of the bike share, typically commuters, must pay an initial registration fee but have a grace period for all trips completed in less than 30 minutes. Trips extending beyond 30 minutes, however, incur additional fees. In other words, public bicyclers are looking to maximize the distance biked and time spent without incurring any additional cost. Researchers have labeled this as ‘cost sensitivity.’

Statistical analyses also demonstrated the same cost sensitivity in casual users, or those who do not have a monthly or annual membership, and who likely use the bike share system for tourism. However, instead of noting a decline in the likelihood of trips around 30 minutes, Dr. Jurdak found a decline for casual users at around 60 minutes (another price point).

On the other hand, despite sensitivity to cost, bikers appeared less dissuaded from bike trips based on neighborhood layout. Although stations in Boston were on average much closer to other nearby stations than in Washington DC, in general, the trip distribution for both cities was remarkably similar. Perhaps not surprisingly, the most popular routes taken in both Boston and Washington DC were relatively flat.

To encourage more people to cut the car usage and grab a rental bike, Dr. Jurdak recommends that cities consider incentivizing their constituents with what they care about: cost. Modified prices for bike rental during peak hours may decrease car traffic on congested roads; an extension of grace periods for biking difficult topology, like up a steep San Francisco hill, might encourage us to bike even though the clock is ticking to 30 minutes and an incurred rise in price. As cities look to evolve public transportation systems and increase responsible urban mobility, and as city dwellers look for cost-effective ways to get around, bike share programs continue to offer healthy solutions for all, even at 30 minutes or less.

For more on the effects bike share systems are having around the world, check out another recent PLOS ONE paper and the researchers’ blog post on bike webs, visualizations of bike share schemes.


Jurdak R (2013) The Impact of Cost and Network Topology on Urban Mobility: A Study of Public Bicycle Usage in 2 U.S. Cities. PLoS ONE 8(11): e79396. doi:10.1371/journal.pone.0079396

Image 1: Citi Bike Launch by New York City Department of Transportation

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The Balancing Act in Borneo: Managing Deforestation, Sustainability, Biodiversity, Health, and the Value of Rainforests


Borneo: the third largest island in the world, one-third of which is home to 220,000 km2 of diverse and beautiful rainforest. Borneo is divided among three countries—Brunei, Indonesia, and Malaysia—and at approximately 130 million years old, the Borneo rainforests are some of the oldest in the world.

The landscape of Borneo, however, is rapidly changing. Natural forest resources provide significant income for both Malaysia and Indonesia, and oil palm plantations, which require the clearing of natural land cover, produced an annual revenue of US $40 billion for Indonesia and Malaysia in 2012. In contrast, Borneo rainforests present the only opportunity for large-scale conservation in Southeast Asia and are one of the few places still called home by large, endangered animals like orang-utans, elephants, bears and rhinos.

This summer, three different PLOS ONE studies addressed the complex issues surrounding deforestation. Separate groups of researchers mapped forest cover and logging roads, conducted statistical analyses on different uses of land, and investigated how Indonesian and Malaysian villagers of Borneo value and use these forests.

To better understand the troubling state of forests in Malaysian Borneo, researchers in one PLOS ONE study mapped forest coverage and conditions. Tracking the condition of big areas of land is no easy task. To accomplish the feat, scientists imaged forests areas using high-definition satellite imagery, charted logging roads, and did some serious number crunching.

Key to this assessment was the actual condition of the rainforests.  Are they intact, or have they been degraded—maybe severely so—by the effects of repeated logging? Critical damage is done to soil, waterways, and forest structure when forests are repeatedly logged without enough time to regenerate properly. To assess the condition of the residual forest, researchers distinguished between different types of coverage—bare, mangrove, plantation, and various levels of degradation, for example—and charted the number of logging roads created between 1990 and 2009. The image below depicts the forest cover and condition of Malaysian Borneo and Brunei in 2009.

Oct blog Type of Coverage

If one road was built in an area since 1990, the area was classified as degraded. If more than one road had been built in an area since 1990, that area was classified as severely degraded. Researchers charted enough roads built between 1990 and 2009 to circle Earth nine times if placed end-to-end. The image below depicts the new roads constructed in a forested region known as the ‘Heart of Borneo’ in purple.

Oct Blog Roads

Needless to say, a great deal of the forests in Malaysian Borneo was classified as severely degraded. Researchers found that rainforests covered only 22% of land area in Malaysian Borneo in 2009, and of that 22%, only 38% remained intact. What then is the future for these degraded rainforests?

The researchers of a second PLOS ONE study evaluated the role logged forests play in maintaining natural rainforests in Kalimantan, Indonesian Borneo, by conducting statistical analyses on areas designated as protected areas, areas designated for logging, and industrial plantations. Researchers concluded that, when logged responsibly, areas designated for logging, called timber concessions, maintained forest cover just as well as protected areas during 2000-2010. Protecting timber concessions would increase the amount of land dedicated to sustaining larger forest landscapes.

Oct blog 2 Transition

The alternative to returning these logged areas, often considered beyond the point of regeneration, to a state of natural regrowth is reclassification as industrial plantation. Palm oil plantations are economically viable options for Indonesia. However, to make the land viable for industrial planation use, workers must first strip larger trees, burn smaller trees and shrubs, and finally clear the remaining land. These researchers view responsible logging as a compromise in which forests continue to provide economic output to communities, but also are allowed to maintain the veracity of their biodiversity. Rather than being seen as wastelands and turned into industrial plantations, researchers consider timber concessions as valuable areas of tree coverage and biodiversity, which merit classification as IUCN Protected Areas.

However, as researchers from a third PLOS ONE paper state, “Striking a balance between economic development and maintenance of biodiversity is increasingly challenging in the face of climate change, rapid human production growth, and concomitant demand for natural resources.” To address the range of ways the forest is valuable, researchers assessed Indonesian and Malaysian Borneo’s peoples’ perceptions of the values and uses of forests, as well as the factors influencing these perceptions.

Of 1,837 people surveyed from 185 villages in Indonesian and Malaysian Borneo, 67% considered the forest to be important for maintaining their good health. The authors state that the forest was generally perceived as a provider of good health. Moreover, natural forest resources, even in those forests degraded by repeated logging, are important for local people. In their responses, participants frequently mentioned using forests for timber, rattan, fire wood, bushmeat and fish, traditional medicine, and forest gardens. Most people reported using forest resources even in areas severely degraded by logging, or where no canopy cover exists. Researchers therefore concluded that considering these areas “wastelands” or degraded beyond the point of use, with the result that these areas are converted into industrial plantations, is not warranted due to the value placed on resources obtained from forests, regardless of level of degradation.

Researchers also found that many believed small-scale deforestation benefitted welfare. 48% of respondents reported small scale clearing for purposes of farming as positive. Respondents were much less supportive of large-scale deforestation.

Initiatives to strike a balance between economic need and maintenance of these diverse rainforests in Borneo are ongoing. Researchers are divided about the most effective ways to conserve Borneo’s important natural forests; whereas the construction of palm oil plantations in place of forests is unquestionably destructive to conservation efforts, the place of logging in Borneo remains less defined. Conserving biodiversity, responsibly maintaining the economy, and valuing the input of local people must all be taken into account when devising compromises for the difficult issue of deforestation. In the meantime, research in Borneo continues to enable a better understanding of Borneo’s complex balancing act.


Bryan JE, Shearman PL, Asner GP, Knapp DE, Aoro G, et al. (2013) Extreme Differences in Forest Degradation in Borneo: Comparing Practices in Sarawak, Sabah, and Brunei. PLoS ONE 8(7): e69679. doi:10.1371/journal.pone.0069679

Gaveau DLA, Kshatriya M, Sheil D, Sloan S, Molidena E, et al. (2013) Reconciling Forest Conservation and Logging in Indonesian Borneo. PLoS ONE 8(8): e69887. doi:10.1371/journal.pone.0069887

Meijaard E, Abram NK, Wells JA, Pellier A-S, Ancrenaz M, et al. (2013) People’s Perceptions about the Importance of Forests on Borneo. PLoS ONE 8(9): e73008. doi:10.1371/journal.pone.0073008

Image 1: Flora and Fauna of the Borneo Rainforest by Rainforest Action Network

Image 2: Figure 2 journal.pone.0069679

Image 3: Figure 1 journal.pone.0069679

Image 4: Figure 2 journal.pone.0069887

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The Power of the Claw: Not Your Average “Soft” Material

Sep blog-tiger cropped

Earlier this month we gave you cuddling between affectionate lions. Lest we become overwhelmed by the desire to cuddle one of these (albeit adorable) feline predators ourselves, here is a look at exactly what one of their clawed paws could do to us, including to one of our toughest components: bone. In a PLOS ONE study published earlier this month, researchers tested the ability of claws to scratch the surface of bone. The effects of claw damage are often overlooked because claws are made of a material softer than bone. Contrary to expectations, however, these researchers found that claws produced recognizable bone damage.

The setup was simple: let a Kansas zoo tiger participating in their enrichment program spend an afternoon leisurely playing with carefully nested cow thigh bones, also called femora. To ensure that the cow femora were only accessible to tiger claws and not to tiger teeth, researchers bolted femora down into a log that was narrowly hollowed out—preventing the big cat from sticking his snout in.

Sep blog- cow femora

The result: impressively lacerated cow femora. Once tiger playtime was over, researchers removed the log, unbolted the femora, and microscopically examined the bone. Four scratches were clearly visible upon the bone’s surface. The scanning electron microscope (SEM) image below further highlights the depths of the tiger claw handiwork.

Sep blog-fomora scratches microscope

In this particular gouge, the main diagonal chasm in the image, the gulf made by the tiger’s claw penetrated the outer covering and subadjacent bone into the bony matrix. As we can see, tiger claws can do some damage.

Damage done to bone, however, is for the most part attributed to the effects of a predator’s teeth and not its claws, the reason being that measures of scratch resistance adhere to a so-called Mohs scale of mineral hardness. The Mohs scale is graded, with talc (1) as the softest material and diamond (10) as the hardest. On the scale, harder materials damage softer materials, but not vice versa. And in our case, bones are, in fact, harder than claws. Claws are made of the protein keratin—the same stuff is in hair, wool, nails, horns, and hooves—which scores a meager 2.5 on the Mohs scale. Bone, on the other hand, scores a much more formidable 5.0.

The current research, however, shows that we can expand our understanding of scratch resistance and mineral hardness to include the effects of softer materials striking harder materials, as long as we consider the kinetic energy involved, like the action of a tiger swatting or grabbing with its paw. In essence, more could be going on in the fossil record than previously thought.

Paleontologist and PLOS ONE Section Editor Andy Farke points out in the The Integrative Paleontologist that fossils inevitably resurface as imperfect objects, which is, in part, what makes them so interesting: These fossils bear the visible marks in postpartum decay of a long and varied history. When studying bone narratives, paleontologists encounter everything from water damage to the bore marks of little critters. Including big-critter claw marks in the repertoire of possible bone modifications broadens this narrative and evidences, as the researchers themselves so aptly put it, the power of the claw.

For more information from the paleontologist perspective, check out blog posts on this article in The Integrative Paleontologist  by Dr. Farke and National Geographic.


Rothschild BM, Bryant B, Hubbard C, Tuxhorn K, Kilgore GP, et al. (2013) The Power of the Claw. PLoS ONE 8(9): e73811. doi:10.1371/journal.pone.0073811

Image 1: Tiger by Dave Stokes

Image 2: doi:10.1371/journal.pone.0073811

Image 3: doi:10.1371/journal.pone.0073811

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Heating up the Science Behind PLOS’ New Climate Change Collection

Satellite images of penguin colonies in the southern Ross Sea

From penguin colonies in Antarctica, to California birds and North Carolina bugs, this month PLOS ONE focuses on the far-reaching aspects of climate change. In conjunction with the annual meeting of the Ecological Society of America (ESA), PLOS ONE and PLOS Biology unrolled a new collection of 16 research articles, curated by PLOS ONE Academic Editor, Ben Bond-Lamberty. The collection, “Ecological Impact of Climate Change”, features many articles that made a splash in the media. Here are some of the highlights:

Spring flowers are blooming earlier now than they did in the past. In a recent study, researchers compared the average flowering time for native species in Massachusetts and Wisconsin to data recorded by notable American naturalists Henry David Thoreau and Aldo Leopold. These native species have shown remarkable flowering shifts, especially during recent years: In 1865, Thoreau observed the highbush blueberry flowering in mid-May; in 2012, researchers observed this species flowering six weeks earlier in early April. For more about this study, visit National Geographic, NPR, and MSNBC.

Like spring flowers, corals also react to increasing temperatures, but to a much more ghostly effect. When pressured by unusually warm or polluted waters, corals shed the algae that enliven them with color, becoming white.

Tioman Island, Malaysia, Acropora colony

New research suggests that this phenomenon, known as coral bleaching and often fatal for coral colonies, may not be as devastating as expected: Coral colonies that survived previous coral bleaching were much more likely to rebound successfully the next time it occurred. An astounding 95% of Acropora, a coral species highly susceptible to bleaching, survived at a research site in Singapore in 2010. Read more about these tough coral taxa, in the New York Times blog.

Summer days are heating up in the city, too, and urban, tree-dwelling insects are thriving as a result. A recent PLOS ONE article reports that scale insects like Parthenolecanium quercifex are 13 times more numerous in the hottest parts of Raleigh, North Carolina, than in cooler, neighboring rural areas.

Scale Bugs CCBY Aug blog

And these scaly squatters don’t stop once they settle down. Researchers also found that urban scale insects were four times more abundant when placed in hot greenhouse conditions than rural scale insects in the same conditions. The Atlantic Cities and Discovery News have more on this and other urban insects studies.

As temperatures continue to rise, researchers in this PLOS ONE study integrated climate change threats with traditional conservation concerns by comparing the vulnerability of California’s birds in relation to the predicted effects of climate change over the coming years. Of the 29 threatened-bird taxa considered in the state of California, these researchers determined 21 of those 29 (72%) are considered vulnerable to climate change. Lucky for us and the birds who call those most vulnerable coastal environments home, the findings of this study can be used as an assessment tool to foster future conservation efforts. For more local and international coverage, check out KQED News and the Huffington Post.

Read Ben Bond-Lamberty’s overview of the Collection, learn how climate change may impact coffee plants, or more from the PLOS Blogs network. View the entire Collection here. For more news on PLOS ONE papers headlining in August, dive into our Media Tracking Project.


Ellwood ER, Temple SA, Primack RB, Bradley NL, Davis CC (2013) Record-Breaking Early Flowering in the Eastern United States. PLoS ONE 8(1): e53788. doi:10.1371/journal.pone.0053788

Guest JR, Baird AH, Maynard JA, Muttaqin E, Edwards AJ, et al. (2012) Contrasting Patterns of Coral Bleaching Susceptibility in 2010 Suggest an Adaptive Response to Thermal Stress. PLoS ONE 7(3): e33353. doi:10.1371/journal.pone.0033353

Meineke EK, Dunn RR, Sexton JO, Frank SD (2013) Urban Warming Drives Insect Pest Abundance on Street Trees. PLoS ONE 8(3): e59687. doi:10.1371/journal.pone.0059687

Gardali T, Seavy NE, DiGaudio RT, Comrack LA (2012) A Climate Change Vulnerability Assessment of California’s At-Risk Birds. PLoS ONE 7(3): e29507. doi:10.1371/journal.pone.0029507

Image 1: Satellite images of penguin colonies in the southern Ross Sea. doi:10.1371/journal.pone.0060568

Image 2: Tioman Island, Malaysia, Acropora colony. doi:10.1371/journal.pone.0033353

Image 3: Ants and sapsuckers by John Tann


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What Early Neolithic People Left Behind: Levantine Arrowheads Found in Saudi Arabia

Palaeodeserts Project Crassard et al PLoS ONE 2013 Thinking about spending the summer in the sun and sand? Early Neolithic humans may have thought so too, although with more survival-oriented goals in mind. A recent study published in PLOS ONE suggests that early humans, who set up camp in the Eastern Mediterranean (about 10,000 BCE), may have traveled as far as Saudi Arabia in search of game and water.

In this study, researchers unearthed several types of Neolithic arrowheads in the northern peninsula of Saudi Arabia at the site of Jebel Qattar, which suggests a link between Neolithic people of the Levant—modern-day Jordan, Lebanon, Syria, Israel, Palestine, and Cyprus—to areas as far south as Saudi Arabia. Arrowheads and other tools are, by and large, the main type of early human artifact observable today prior to the introduction of pottery (about 7000 BCE), and are integral to our understanding of the people who created and used them. Tools and arrowheads types, like the ones discovered at Jebel Qattar, provide researchers with evidence of early technology used for hunting.

Beyond the Levant Image

Helwan points found at Jebel Qattar

Accurately identifying early Neolithic artifacts is a tough job—these arrowheads are over 10,000 years old, after all—and requires researchers to carefully sift out other objects uncovered during surface collection and trench excavations. In fact, the researchers discovered a total of 887 stone tools at the site of Jebel Qattar, only ten of which have been identified as Levantine types, known more specifically to researchers as El-Khiam and Helwan points. Named for their places of origin in Israel and Egypt respectively, the El-Khiam and Helwan arrowhead types are common to Levantine sites throughout the Neolithic period. This study, however, represents the first time archaeologists have discovered them in the Nefud Desert of Saudi Arabia.

Levant Map

Current understanding of early people living during the Neolithic period is rooted in excavation sites in the Levant and the larger area of the Fertile Crescent—the area in green on the map above—a geographical region containing parts of Western Asia, including the Levant, as well as parts of the Nile Valley and Nile Delta of northeast Africa. The Fertile Crescent is home to several major innovations, including the domestication of animals and the development of cereal, and is often known as the ‘cradle of civilization’. The discovery of El-Khiam and Helwan arrowheads in Saudi Arabia alludes to this hotspot of innovation and technology and suggests possible interaction between these early Neolithic peoples.

However, because so little evidence from the Neolithic period survives intact today, our understanding of Neolithic peoples is a work-in-progress. Nevertheless, tracing Neolithic people from the Levant as far as Saudi Arabia suggests that we may want to study broader areas when considering their trajectory. Of course, there is further exploration to be done beyond the borders of the Levant.

Citation: Crassard R, Petraglia MD, Parker AG, Parton A, Roberts RG, Jacobs Z, Alsharekh A, Al-Omari A, Breeze P, Drake NA, Groucutt HS, Jennings R, Re´gagnon E, and Shipton C . (2013) Beyond the Levant: First Evidence of a Pre-Pottery Neolithic Incursion into the Nefud Desert, Saudi Arabia. PLOS ONE 8(7): e68061. doi: 10.1371/journal.pone.0068061

Images: doi: 10.1371/journal.pone.0068061

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