Tuesday, 28 February 2012

Scandinavian brown bears: hiders, not fighters

Humans are hardwired to find carnivores threatening, and negative attitudes toward these species can pose "a special challenge to managers" looking to conserve them. This has certainly been true in Scandinavia, where the beleaguered Scandinavian brown bear (Ursus arctos L.) is making a comeback from the brink of extinction. Although the brown bear population had dipped to a mere ~130 individuals by 1930, there are now thought to be about 3,500 living in Sweden and Norway, where the species is protected. Unfortunately, improvements in numbers have not been matched by improvements in habitat, and the bears are increasingly likely to bump into humans. Media coverage of recent injuries and fatalities has made the bears unpopular in Scandinavia, and particularly in Sweden, where the bulk of brown bears live.

(Scandinavian brown bear mother with cubs)

One group of Scandinavian scientists is interested in changing local attitudes to bears, and they hope to use education as their tool. In order to collect data on "normal" brown bear responses to unexpected meetings with humans, the researchers deliberately approached bears on 169 different occasions over a 3-year period. All approached bears had previously been fitted with radio collars, which not only allowed the scientists to locate the bears in order to perform each approach, but also to track the animals' movements before, during, and after the approach period. Walking and talking just like normal hikers would, the researchers passed upwind of the bears on trajectories aimed at taking them past the bears at a distance of 50 m. Many of the animals fled prior to this proximity, and the researchers made a note of the nearest approach that the animals tolerated. The scientists re-visited the sites several days later in order to collect information on habitat variables such as vegetation, the presence of bear daybeds, and the presence of carcasses--the last of which are often associated with more aggressive bear behavior. Habitat details were also evaluated for the areas to which bears relocated after being disturbed.

Although some bears stayed put and others moved away after encountering humans, in no case did any animals display aggressive behavior. Indeed, none of the "hikers" reported feeling threatened during the study. Despite the fact that the researchers knew the location of the bears prior to starting each approach, they only detected animals 15% of the time, whether by sight or sound or both. This suggests that humans may encounter bears--and experience no resulting catastrophes--much more than they realize. When bears were seen, it was not until an average distance of 18 m. In other words, the animals are good at remaining incognito, despite their large size.

(Frequency of brown bear observations in Sweden from 1998-2003)

In the majority (80%) of cases, bears immediately left their initial location and relocated elsewhere. Among those that stayed put, human proximity was tolerated to an average distance of 84 m, after which the bears finally ceded ground and fled. However, tolerance values ranged from 23-313 m, indicating that there is quite a lot of individual variation in bears' attitudes toward human proximity. Indeed, analyses indicated that older bears were more likely to remain in place than younger bears, suggesting that the animals may become more relaxed around humans as they gain more experience with them. Animal behaviors also varied as a result of their activity at the time of approach: "Passive" bears, or those that were sitting still when the approach began, were more likely to allow humans to come closer than were "active" bears, or those that were moving around. This may be related to differences in the bears' detection abilities during these behaviors. Bears were more likely to flee when they were approached by a larger group of hikers; they also appeared to be more easily disturbed during the berry season (summer and autumn), when they are bulking up prior to hibernation.

Using readings from the radio collars, the researchers were able to determine that bears moved an average of 1,173 m, but sometimes more than 6,000 m, after being disturbed. Additionally, the areas to which bears relocated were generally quite densely vegetated, enhancing their ability to hide. Cumulatively, all of these observations suggest that brown bears would really rather be left alone, and are more likely to achieve solitude by running away than by picking a fight with intruders. It is important to note that these results apply only to adult bears (>4 years old) and those without cubs or serious injuries. Juveniles, parents, and wounded animals may be less tolerant of humans; fortunately, however, encounters with such individuals are much less likely.

(A researcher collects data from anesthetized Scandinavian brown bears)

The authors hope that these findings can be incorporated into educational materials that can increase favorable attitudes to bears by reducing fear of the unknown. They particularly hope to reach hikers and berry-pickers, the groups most likely to encounter brown bears in the wild. As for the bears, the researchers hope to perform additional studies examining "unrecorded and unobserved" reactions to the approach of humans, such as increased heart rates and stress hormones. These can reduce health, survivorship, and breeding success--three very important factors in the conservation of threatened species like the Scandinavian brown bear.

For supplemental photos associated with this post, please visit the Anthrophysis pin board at Pinterest.

Moen, G.K., Stoen, O.-G., Sahlen, V., and Swenson, J.E. 2012. Behaviour of solitary adult Scandinavian brown bears (Ursos arctos) when approached by humans on foot. PLoS ONE 7(2):e31699.

Thanks to the following websites for providing the images used in this post:

Monday, 27 February 2012

Rethinking marine acoustic ecology research: is it time for a change?

Conservationists and managers are always looking to collect more and better data in order to verify that their policies are appropriate and biologically sound. This is particularly true when the policies are applied in environments undergoing rapid or constant change, and when those policies were originally based on relatively small amounts of data--two descriptions that reflect the situation in marine habitats exposed to anthropogenic noise.

(Sources of noise--both biotic and abiotic--in marine environments)

According to a team of bioacousticians writing in the most recent issue of Conservation Biology, most current marine regulations assume that the effects of noise are linked, in a dose-dependent manner, to the strength of the sound pressure level received by the animal. As a result, policies are developed using a "zones of influence concept," in which there are concentric rings centered on a sound source; animals positioned in the inner rings should suffer the most intense damage, while those in increasingly distant rings should suffer less damage. "Damage," in this case, is usually thought of as being predominantly physical, ranging from death and burst air bladders to permanent or temporary shifts in hearing thresholds (or, in other words, deafness).

But, the authors argue, studies in terrestrial environments have clearly shown that noise can have more subtle, but equally important, effects on wildlife. For instance, abundance and diversity may shift as animals flee from, or learn to avoid, particularly noisy areas; individuals may alter their behaviors in counterproductive or even dangerous ways; and noise may make important acoustic signals difficult to hear, even in the absence of actual deafness. In short, the researchers write, the current marine noise concept "ignores a diverse suite of environmental, biological, and operation factors" that can impact both perception of, and response to, anthropogenic noise. Thus, they argue, it is necessary to overhaul the system and "[incorporate] context into behavioral-response assessment."

 (Sources of anthropogenic sounds in marine environments)

In a previous study on behavioral responses of marine animals to noise, one of the authors of the current paper found that the "zones-of-influence approach did not reliably predict animal responses." Furthermore, we know from terrestrial studies that a variety of additional factors--an animal's past experience and conditioning, current behavioral state, acoustic environment, and type of exposure, to name a few--all affect the extent to which it will be impacted by noise pollution. Preliminary work in marine environments suggest these are also important factors for aquatic animals. A study on migrating gray whales (Eschrichtius robustus), for instance, found that the whales' orientations relative to the sound source were at least as important as actual noise level in determining their responses to acoustic stimuli.

One of the most fundamental pieces of information needed to gauge the impacts of noise pollution is the hearing sensitivity of each exposed animal, since, although loud noise can cause physical damage to any organism, it should result in behavioral adjustments only in those species that can hear it. A further consideration is the signal-to-noise ratio, or the amplitude of a sound relative to other background noises. It is also important to consider the fact that many animals are particularly attuned to some sounds or sound characteristics--those associated with particularly dangerous predators, for example, or with the mating calls of other individuals of its species. Animals are likely to be particularly susceptible to noise pollution that overlaps with these areas of sensitivity.

Studies of the effects of anthropogenic marine noise rely on the accurate measurement of noise disturbance events. There are a variety of ways in which to measure sound levels, and the authors caution researchers to choose wisely. In studies of "impulsive" sources of sound such as airguns, for instance, it would be inappropriate to use a methodology that attempts to obtain an average level of the signal. That may sound obvious for a short, "peaky" signal, and yet it's not an uncommon practice to use the root-mean-squared metric, which does just that, when investigating some impulsive noise events. Other characteristics, such as the signal's peak value, may be better predictors of animals' behavioral responses to noise pollution. Further, while many studies have assumed that sound transmission will be consistent during a single anthropogenic noise event, or from one event to the next, this is not always true--the presence of additional background sounds may vary for other reasons (stormy weather, for instance, or the delivery of noisy sexual advertisement calls by breeding fish), and changes to the physical structure of the habitat can also alter sound propagation.

(Hearing ranges of aquatic animals relative to sources of anthropogenic noise)

In order to incorporate all of these additional factors into both scientific studies and the management plans that are developed from them, the researchers suggest that it is important to measure animal responses to both absolute and relative levels of noise. This would enable simultaneous evaluation of physical effects, auditory masking, and behavioral annoyance. The authors argue that, at the high end of the absolute noise spectrum, animals should still respond to noise in a dose-dependent manner--for example, in terms of physical damage caused by noise. However, at more moderate levels of noise that are likely to elicit a behavioral response, they suggest it would be more appropriate to focus on relative noise levels and the context in which animals receive them. Because there "is no simple boundary" between the dose-response and context-dependent categories, they further advise use of a weighted combination of these two metrics.

The end product of this re-vamping of marine acoustics work would be a better understanding not just of the acute impacts of noise, but also of the effects of chronic exposure to underwater anthropogenic sound. Given how important the latter category has proven to be in terrestrial environments, additional work on this topic in aquatic environments should prove illuminating. The introduction of additional variables to measure may require more time and energy, but the researchers hope that it will lead to a reduction in uncertainty associated with "assessment, management, and mitigation."

Ellison, W.T., Southall, B.L., Clark, C.W., and Frankel, A.S. 2012. A new context-based approach to assess marine mammal behavioral responses to anthropogenic sounds. Conservation Biology, online advance publication.

Thanks to the following websites for providing the images used in this post:

Sunday, 26 February 2012

Protecting grassland-nesting birds from mowing activities

Among birds that have suffered declines as a result of anthropogenic activities, grassland species have been particularly hard hit. They have lost significant portions of their habitat as humans convert meadows to pastureland and agricultural fields. Although birds can still utilize these new types of grassland, they are often disturbed by early and frequent mowing regimes that disrupt their breeding season by destroying nests and killing or injuring both nestlings and incubating females.

(A whinchat, Saxicola rubetra)

One of several declining European grassland species is the whinchat (Saxicola rubetra), whose last healthy populations on the continent can be found in traditionally-managed cultivated fields in Alpine valleys. Unfortunately, mowing and harvesting activities are becoming increasingly more intense in these areas, putting the whinchats at serious risk. Researchers are currently looking for short-term measures, such as nest marking and delayed mowing, that will keep the whinchats safe until the Swiss government adopts policies giving this species official protection.

The efficacy of both of these techniques was recently investigated by scientists from the Swiss Ornithological Institute, working in the Inner-Alpine Engandine valley in Switzerland. Mowing practices have been recorded in this area since the late 1980's; researchers have noted increasingly early mowing dates (by 10-20 days) and larger size of mown patches. The government funds set-asides in a portion of the valley--mostly on the slopes--where whinchats can get a reprieve from mowing until at least the first of July. The authors considered these to be "delayed mown areas," contrasting with more intensely agricultural fields (or "early mown areas," mostly at the bottom of the valley) that are mown prior to July.

(Switzerland's beautiful Engandine Valley, where the current study was conducted)

In both types of meadow, the researchers performed territory mapping in order to identify the location of active nests. These were demarcated by two wooden stakes placed 10 m away from each nest, allowing farmers to preserve 10 x 10 m nesting patches during mowing efforts. To further help farmers identify protected breeding spots, the researchers also verbally informed them of all nest locations. Nests were revisited periodically so that nestling survival could be quantified throughout the nesting period; the last visit occurred once all remaining chicks had fledged. In addition to collecting data on basic life history characteristics such as laying date of first egg and clutch size, the researchers also used the census data to evaluate nest survival under each of four different management regimes: protected or not protected in either early-mown or late-mown fields.

Over the course of the 3-year study period, the researchers located 104 whinchat nests, of which 78 were early-mown and 26 were late-mown. Marking was performed for 31 nests in the former category, but only 6 in the latter. As hoped, nest survival was very high for marked nests. Nests in early-mown fields had the lowest survival probability, and, for obvious reasons, nest mortality was highest in the period when mowing was performed. Lest anyone suggest that nest failures resulted from non-mowing activities, the researchers documented the causes of each nest failure: Mowing was responsible for 71.4% of failures, predation for another 23.8%, and death of a parent for 4.8%. For this population of whinchats, then, mowing was the biggest threat to a successful nesting attempt.

(Whinchat nest, hidden in the grass)

Unsurprisingly, females at higher altitudes initiated their egg-laying activities later in the season, with a 0.7-day delay per every 100-m increase in altitude. This means that early and late mowing regimes will likely have altitude-dependent impacts on nesting whinchats. The researchers also observed that first clutches were larger than replacement clutches, indicating that breeders who lose their first nests to mowing activities will probably produce fewer total offspring per breeding season--assuming their second nest is not also destroyed by mowing. However, in early-mown areas, replacement broods had higher survival probabilities, indicating that the relationship between breeding and mowing activities can be relatively complex.

Based on their measurements of nest survivorship, the scientists calculated that late mowing and nest marking efforts could each nearly double the whinchat population growth rate; rates would be even higher if these management techniques also prevent female mortality. Because nest marking is labor-, time-, and cost-intensive, late mowing may be the more practical method of helping whinchats and other grassland-breeding bird species. However, the researchers suggest that it might be a good idea to employ both protection techniques just to be safe.

(Whinchat chicks dozing in their nest)

Two important issues not addressed in the current study are post-fledging chick survival and the potential impacts of mowing on overall habitat quality. Fledged chicks may respond to danger by crouching and remaining immobile in the grass--a tactic that is much more effective in higher grass than in areas mown short; thus, predation rates may be higher in intensively managed grasslands. Mowing also alters plant density and height, which could reduce the availability of food. The relevance of these two issues needs to be investigated with additional studies. However, it appears likely that, while nest protection and late mowing may have short-term benefits to breeding whinchats, long-term conservation plans should incorporate other techniques aimed at these problems, as well.

For additional photos associated with this blog, visit the Anthrophysis pin board on Pinterest.

Gruebler, M.U., Schuler, H., Horch, P., and Spaar, R. 2012. The effectiveness of conservation measures to enhance nest survival in a meadow bird suffering from anthropogenic nest loss. Biological Conservation 146:197-203.

Thanks to the following websites for providing the images used in this post:

Saturday, 25 February 2012

Reducing anthropogenic emissions has multiple benefits

When it comes to improving global air quality and reversing anthropogenic changes to the climate, we don't exactly have much room for error: Experimentation with ultimately unhelpful management techniques could waste precious time and resources, and might even do further damage. Luckily, climatologists and meteorologists have developed increasingly precise mathematical models that allow researchers to predict the impacts of one control measure or another, or even multiple measures performed simultaneously.

Case in point: recent work by a team of collaborators hailing from a staggering 13 institutions from around the globe. The researchers studied the efficacy of proposed techniques to reduce tropospheric ozone and black carbon (BC) emissions in the atmosphere. As discussed previously in another recent Anthrophysis post, stratospheric ozone helps protect us from the sun's harmful rays, but trophospheric ozone--levels of which are greatly increased by anthropogenic pollutants such as methane--can have negative impacts on the health of humans and agricultural crops. Black carbon, on the other hand, is pure carbon that results from incomplete combustion associated with vehicles, stoves, and kilns, to name but a few sources.

(Where ozone should be--the stratosphere--and where it is often found as a result of anthropogenic pollution--the troposphere).

A number of strategies have been proposed to reduce both ozone and BC pollution. In the first part of their study, the researchers sifted through approximately 400 management proposals in order to identify 14 (7 per pollutant) with the greatest benefits. This was achieved using computer models that utilized regional data on the success of already-implemented strategies to project the consequences of following these protocols over the long term. The models indicated that, in order to reduce ozone levels, managers should target methane emissions from coal mining, oil and gas production, long-distance gas transmission, management of both human and livestock waste, and rice paddies. BC emissions, on the other hand, could be minimized by regulating vehicles, stoves, kilns, waste-burning, and cooking/heating activities. Additional modeling revealed that policies that simultaneously target methane, BC, and carbon dioxide could limit global warming to <2 degrees Celsius over the next 60 years--a degree of success (no pun intended) not achieved by targeting any of those pollutants individually.

(Figure A is a microscope image of sulfates (the round particles) and black carbon (the chains identified by all the arrows). Figure B shows an enlarged view of black carbon, while figure C indicates "fly ash," a product of incomplete coal combustion that is often found in association with black coal.)

Next, the scientists shifted gears from a global perspective to a regional one, in order to model the potential climate impacts of the proposed management policies at national levels--an important step because this is the scale at which most regulations are selected and enforced. One of the most noticeable and widespread results of the measures was a reduction of albedo, or light reflection from the earth's surface. This would be especially noticeable over bright areas such as the Himalayas and the Arctic, and would reduce snow and ice melting. Another prominent pattern was a change in precipitation; this was predicted for southern Asia, western Africa, and Europe, where it would likely reduce the risk of drought. On average, these regulations could prevent approximately 0.5 degrees C of global warning by 2050. 

In the final portion of their study, the researchers estimated the economic benefits of ozone and BC regulation measures. Ozone-reducing policies aimed at reducing methane emissions could save $331 billion associated with climate impacts, $4.2 billion in crop impacts, and $148 in health impacts; BC policies could save $225 in climate impacts, $4 billion in crop impacts, and an impressive $5142 billion in health impacts--not to mention saving approximately 373,000 lives per year. The benefits of different emissions goals vary on a country-by-country basis. For instance, China stands to gain most from regulation of pollution associated with coal mining and municipal waste, while Central Africa, the Mid-East, and Russia would have the greatest results from regulation of oil and gas production. However, the benefit of avoided global warming was shared equally by all regions.

(The models in the current study indicate that the cryosphere would benefit most from BC regulations. Although the Himalayas and the Arctic were identified as areas where snow and ice melting would be particularly reduced as a result of decreases in albedo, many other countries have "cryospheric components" and thus would stand to gain from the stemming of BC emissions.)

Broadly speaking, ozone-reducing methane regulations achieve climate and agricultural improvements, while BC regulations are more helpful for climate, "cryosphere" maintenance (e.g., preservation of snow and ice), and human health; these patterns have consistently been predicted by multiple different models. Although ozone and BC policies are each useful individually, the authors stress that the greatest climate and economic benefits will derive from simultaneous implementation of both. Further, the scientists point out that these are "distinct from and complementary to carbon dioxide measures," and so a thorough emissions-reducing plan should target all three pollutants.

Shindell, D., Kuylenstierna, J.C.I., Vignati, E., van Dingenen, R., Amann, M., Klimont, Z., Anenberg, S.C., Muller, N., Janssens-Maenhout, G., Raes, F., Schwartz, J., Faluvegi, G., Pozzoli, L., Kupiainen, K., Hoglund-Isaksson, L., Emberson, L., Streets, D., Ramanathan, V., Hicks, K., Oanh, N.T.K., Milly, G., Williams, M., Demkine, V., and Fowler, D. 2012. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335: 183-189.

Thanks to the following webpages for providing the images used in this post:

Friday, 24 February 2012

Ambient noise may impact parent-offspring communication

To understand why anthropogenic noise has the potential to negatively impact animals--a topic visited often here on Anthrophysis--it’s helpful to know a bit about signal detection theory (SDT). First applied to animal behavior by bioacoustician extraordinaire Haven Wiley, SDT recognizes that it can be biologically costly either to miss an important signal or to respond to one that you shouldn’t. The presence of anthropogenic noise makes the former scenario more likely because it threatens to mask relevant sounds. Animals may react to this by “lowering their response threshold,” or responding more readily to any sound that seems remotely important—thus leading to the latter scenario. Both can have serious negative implications.

Such errors are particularly likely in juveniles learning the ropes of acoustic communication. Nestling birds, which use acoustic signals to determine when they should beg for food from their parents, may fail to respond to the adults' audible arrivals as often as 20% of the time, and may accidentally beg to a non-parental noise as much as 50% of the time. The first mistake could cost them a meal, and, if passing predators use the vocalizations to locate and prey on a nest, the second could cost their lives.

(Tree swallow, Tachycineta bicolor, peeking out of its nest box)

The likelihoods of these different scenarios were recently investigated by two biologists from Nova Scotia’s Dalhousie University. Using tree swallows (Tachycineta bicolor) as their focal species, the researchers quantified whether the presence of environmental noise increases the frequency of begging errors. To do this, they found 28 swallow nests with 4 chicks apiece; once the chicks reached 10-12 days of age, two individuals per nest were allocated to a noise treatment, while the other two were used as controls. For each trial, pairs of birds were removed from their home nest box and placed in an unoccupied "test" box. For one hour, chicks in the test box were either exposed to 65 dB of white noise (noise treatment) or left alone (control). During the next 20 minutes, while the original acoustic conditions continued, the birds were also exposed to 7 presentations of 3 audio recordings: a parent landing on a nest box and uttering a contact call to stimulate begging; a parent landing on a box but making no additional sounds; and a potential predator (common grackle, Quiscalis versicolor) landing on the nest box. Each trial was filmed, and the researchers later watched the resulting videos in order to observe the amount of begging the chicks performed in response to the different stimuli and ambient noise conditions.

As predicted, nestlings begged more often to the parent-with-call stimulus (96% of trials) than to the parent-without-call stimulus (54% of trials). Responses to both stimuli were significantly lower among birds in the noise treatment, indicating that the parental acoustic signals were being masked.  However, chick response levels to predator noises were similar (35%) in both the noise and control treatments. This suggests that noise-exposed birds had not lowered their response thresholds in response to the ambient noise conditions.

(Common grackle, Quiscalis versicolor)

Chicks that delay, or fail to perform, a begging display in response to a parent’s arrival risk being outcompeted by a more vociferous sibling; thus, it is important to respond both quickly and loudly once an adult lands at the nest box. Although there may be significant costs associated with failing to beg appropriately, it may be even worse to “jump the gun” and beg in response to noises that turn out to have been made by a non-parent. This may be why the tree swallows in this study failed to lower their response threshold despite the presence of noise pollution. However, the authors point out the possibility that there may be other mechanisms by which the negative impacts of noise are mitigated—for instance, the presence of “visual or tactile cues…[that] signal parental arrivals,” or the use of post-arrival parental vocalizations to stimulate begging.

In a previous study on nestling tree swallows, these same two researchers found that noise-exposed chicks did not suffer any decreases in feeding or growth rates. Thus, even if reductions in signal detection lead to missed feedings or redistribution of parental care among different siblings, this does not appear to have any long-term consequences chicks of this species. However, the scientists suggest that nestlings may owe their good health to their parents—who might compensate for noise-induced feeding problems by expending additional energy on chick care, spending less time looking after their own needs, or both; similar patterns have been reported for birds exposed to other types of anthropogenic disturbance.

(Tree swallow nestlings in their feather-lined nest box)

The many remaining questions associated with this topic reveal just how much there is to learn about anthropogenic noise and its effects on wildlife. For instance, it will be vital to evaluate whether younger chicks (who rely more on acoustic cues until their eyes open at ~day 5) are more susceptible to ambient noise, to quantify whether noise disturbance is particularly costly to adults attempting to rear broods, and to perform studies on additional breeding bird species.

Leonard, M.L. and Horn, A.G. 2012. Ambient noise increases missed detections in nestling birds. Biology Letters, online advance publication.

Thanks to the following websites for providing the images used in this post:

Wednesday, 22 February 2012

Ship noise causes stress in right whales

It’s not every day that serious scientific research revolves around the ability of a trained dog to sniff out whale poo floating on the ocean’s surface, but that is only one of several ways in which a recent study breaks new ground. The work, performed by collaborators from a variety of institutions from across the U.S., also took advantage of an international tragedy to provide data that might help prevent a natural tragedy, and provides some of the most unambiguous support to date for the hypothesis that anthropogenic noise is bad for wildlife because it increases their stress levels.

The international tragedy in question is the bombing of the World Trade Center on September 11, 2001. In the days that followed, ship traffic decreased markedly in (among other places) the Bay of Fundy, home to a right whale (Eubalaena glacialis) conservation area. During this period, researchers were already on site collecting both acoustic data and fecal samples—the latter of which were located using detection dogs whose sensitive noses guided the researchers close enough to use dipnets to scoop samples out of the water. 

(A right whale, Eubalaena glacialis, in the anthropogenically disturbed Bay of Fundy)

Although these data were intended for use in other studies, it occurred to the researchers that they could use this opportunity to test a long-standing but generally poorly-studied theory that the sound of boat traffic is stressful for acoustically sensitive marine species. To do this, the scientists re-visited the Bay during the next 4 years in order to collect additional fecal samples. By conducting their field work at the same time of year, they produced a dataset allowing them to compare seasonal variation in stress hormone levels both within a single year and among multiple years. Thus, they could examine whether any potential reductions in stress levels after 9/11 were simply a result of normal seasonal fluctuations, or were more likely a response to variation in ambient noise levels.

Noise levels in the Bay of Fundy were found to decrease by 6 dB in the wake of 9/11. There was a particularly noticeable drop-off in the amplitude of noises at low frequencies—in other words, the frequencies to which whales are particularly attuned. This was predominantly caused by a one-third reduction in ship traffic following the World Trade Center bombing. Fecal sample analyses revealed that, in “normal” years, whale stress hormones generally rise throughout the autumn; this corresponds to increasing courtship activity during this period. In 2001, however, there was a significant decrease in hormone levels just after 9/11, suggesting that the whales were “released” from the added stressor of anthropogenic noise.

(Whale poo--in this case, from a blue whale, Balaenoptera musculus. It floats because of its high nitrogen content.)

The researchers are quick to admit that “this is a retrospective analysis based on a non-repeatable event with all of the inherent limitations.” However, despite the unplanned nature of their study, and the lack of comparative acoustic recordings during the 2002-2005 portion of the research period, their work is still an improvement on previous studies of noise-related stress in marine animals. As the authors themselves state, the results “provide compelling evidence of a stress response in right whales exposed to…underwater noise from ship traffic”—an intriguing glimpse of the more subtle impacts of human activities on wildlife. In addition to conducting further research to verify the patterns reported here, it will also be important to determine the long-term and population-level consequences of stress responses to anthropogenic sound pollution.

Rolland, R.M., Parks, S.E., Hunt, K.E., Castellote, M., Corkeron, P.J., Nowacek, D.P., Wasser, S.K., and Kraus, S.D. 2012. Evidence that ship noise increases stress in right whales. Proceedings of the Royal Society B, online advance publication. 

Thanks to the following websites for providing the images used in this post:

Monday, 20 February 2012

Urban forests benefit your health and your wallet

These days it's common to hear about "ecosystem services," but what are they, really? According to G.C. Daily, who coined the phrase in 1997, ecosystem services are "the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life." Various authors have tweaked the definition over the years, sometimes to make it more accurate or specific to particular ecosystems. Recently, for instance, researchers amended the idea of ecosystem services to be more applicable to forests; their proposed definition referred to the "components of forests that are enjoyed, consumed, or used to produce specific measurable human benefits."

In cities, forest ecosystems provide a number of services ranging from giving urban residents a break from the concrete scenery to having beneficial impacts on the environment--for instance, by lowering temperatures, changing wind patterns, reducing energy, and improving air quality. This last service in particular was the focus of a recent study by collaborators from the Sapienza University of Rome and Portland State University. Although the researchers were already aware that Rome's extensive urban forests remove ozone from the city's atmosphere, they knew very little about how different tree species contribute to this process. In fact, the role of biodiversity in ecosystem function is not yet well understood in general, since previous studies on this issue have produced conflicting results.

 (Skyline of Rome, Italy)

The researchers predicted that different types of trees would work synergistically to accomplish ozone removal from Rome's air. This seems logical considering that different trees vary in their "ecophysiological and phenological traits," meaning that, among other things, they respire at different rates and respond differently to environmental conditions such as heat and humidity--high levels of which are found during the summer, when ozone levels usually peak. Although ozone is a beneficial chemical in Earth's stratosphere, where it helps protect us against the sun's rays, it can damage anthropogenic materials, harm crops, and have adverse health impacts on humans. Thus, understanding which tree assemblages are best at removing this chemical could significantly improve management plans.

Research for the current study was conducted in Rome, approximately 20% of which comprises public green space. Although there are a number of resident tree species, they can be broadly grouped into three categories--deciduous broadleaves (the most abundant, covering 3747 ha), evergreen broadleaves (covering 2121 ha), and conifers (the least abundant, covering 1605 ha). The ozone-removing properties of these three groups were investigated in 2003--a year that was both hotter and drier than urual--and 2004, which had more typical weather patterns. Weather stations automatically collected information on daily ozone and nitrogen oxide concentrations, temperature, and humidity; these data were entered into complex models that use known tree physiological information in order to estimate how much ozone each tree group could process given the current environmental conditions. In addition to assessing how much ozone was actually removed by the three types of tree throughout the year, the researchers also estimated how much would have been removed if the existing forests consisted of only one type of tree--in other words, if there were no biodiversity.

(Castelporziano, one of the greenest and most biodiverse areas in Rome)

Predictably, ozone levels fluctuated depending on temperature and, therefore, season; values were particularly high late in the summer and frequently reached levels thought to be harmful for human health. As the researchers hypothesized, their models indicated that the different groups of trees likely complemented each other in their ozone uptake activities. This was true both within a year and between years, and resulted from the fact that some trees increased their ozone capturing potential as temperatures rose, while others decreased or remained consistent--a pattern driven by, among other things, variations in the tree groups' photosynthetic activities, leaf transpiration rates, leaf areas, and flow of air and moisture through leaf pores known as stomata. Thus, while there may be ozone removal fluctuations at a local level--within small stands of similar trees--removal across the entire city remains fairly consistent over time because different groups of trees complement each other.

Overall, the total ozone uptake was estimated at just over 300 Mg in both years, with less than 2% variation between the two years of the study. Surprisingly, the reduced-biodiversity models indicated that a similar amount of ozone could be removed if all trees in the city belonged to the same functional group. This seems to suggest that biodiversity is not actually that beneficial to this particular ecosystem service. However, the variation from one year to the next was much higher under this scenario, indicating that the biggest advantage of having multiple species is consistency, rather than amount, of service performed.

(A holly oak (Quercus ilex), one of several species in Rome that, according to the authors, may perform an "ecosystem disservice"--by releasing volatile organic compounds into the air. More research is needed to understand the impacts of these compounds on air quality.)

In addition to providing some insights about the general importance of biodiversity, these findings may also be useful in an applied context. Models like these could help managers decide where to plant trees, what species they should choose, and how many they should install. Although this could be useful information in a variety of habitats, it is likely to be especially helpful in urban areas where ozone can be particularly problematic. These calculations could also shed light on the impacts of replacing native trees with exotics, either intentionally or via accidental introductions.

For those who aren't swayed by the biological aspects of the results, the authors also calculated the potential economic benefits of biodiversity. Previous researchers have estimated that ozone removal services are worth approximately $6750/Mg, which means that the city of Rome saves about $2 million each year thanks to its trees. Reducing ozone also minimizes the risks of ozone-related mortality, resulting in another $3 million or so in savings. Managers in several U.S. cities--including D.C., New York, Baltimore, Atlanta, and Chicago--already tout urban forests as a cost-effective method of reducing air pollution, and these results suggest that other cities would experience similar benefits. Given that over half the world's population currently lives in ever-expanding urban areas, this management practice could improve air quality for a significant number of people.

Manes, F., Incerti, G., Salvatori, E., Vitale, M., Ricotta, C., and Costanza, R. 2012. Urban ecosystem services: tree diversity and stability of tropospheric ozone removal. Ecological Applications 22(1): 349-360.

Thanks to the following websites for providing the images used in this post:


Saturday, 18 February 2012

Predictors of crop-raiding behavior in African elephants

There is not always much overlap in the research of conservationists and behavioral ecologists, but a study published in this week's issue of PLoS ONE shows why there should be. Collaborators from Duke University, the University of Notre Dame, and Kenya's Amboseli Trust for Elephants reported that both life history characteristics and social behavior influence crop-raiding behavior in African elephants--a finding that allowed the researchers to make improved recommendations for minimizing human-elephant conflict.

The results were produced by a study conducted in Amboseli National Park, which provides habitat for approximately 1,400 elephants--all of which are individually known and can be identified using physical traits. The park is in close proximity to several farming areas where maize, onions, tomatoes, and beans tempt passing elephants. Only males are known to raid crops, however, and these were the animals on which the researchers focused. Specifically, the scientists collected data allowing them to examine how well an individual's age, his companions, and his companions' ages, predicted the likelihood that he would raid crops. They suspected that a focal individual's would be important because it is associated with life history "milestones"--such as reaching the age of first reproduction (at 20-30 years) and reproductive peak (from 45 years onwards)--that require an individual to consume a large amount of food in order to meet energetic demands. However, an elephant's companions might also be important because these highly social animals can learn foraging tactics from each other, either directly (through teaching) or indirectly (through observation). If older males are more likely to raid crops, either because they need to meet energetic demands or because older individuals simply engage in more risky behaviors, then elephants associating with older companions might be more likely to pick up crop-raiding behaviors.

To investigate these possibilities, the scientists collected "association data" over a two-year period. Every time they sighted all-male groups, they noted which individuals were present and who/how old their companions were. Ages of all individuals were known with high accuracy because this population has been studied consistently for over 30 years. Ultimately, the researchers focused on a subset of 58 individuals that they had seen a minimum of 15 times, and whose frequent associates had also been seen at least 15 times. An "association index" was calculated for each male's companions in order to determine with whom the males were close "friends" and with whom they were merely "acquaintances" or even "strangers;" the influence of only the top 5 associates for each male were examined here. Of the 58 focal individuals, 21 were known to be raiders (from direct observations and also from genetic analyses conducted on fecal samples left at crop sites), and 37 were non-raiders. Statistical models were constructed to examine how well age and association data could predict each male's crop-raiding status.

As the scientists predicted, older males were more likely to be crop-raiders. Specifically, there was a "dramatic increase in the odds of being a raider" for males just beginning their reproductive period, and a "near doubling of these odds" for males reaching their reproductive prime. However, males' social interactions were also important predictors of crop-raiding behavior: Males were significantly more likely to visit agricultural fields when their closest associates were raiders. This was particularly true when either or both of their companions were raiders; behaviors of the third, fourth, and fifth associates, however, did not appear to be very important. The ages of these companions were also influential. In particular, males with older raiding associates were more likely to be raiders themselves, indicating that younger individuals were learning this behavior from their elders. Analysis of the elephants' social structure revealed that communities are close-knit but widely distributed. Thus, while elephants within a particular group are likely to learn from each other, sharing of information is unlikely to occur between groups.

Age and social structure are known to be important influences on learning and behavior in other animals, but they have rarely been studied simultaneously, and never in an elephant system. The current results indicate that elephants aren't born with an innate interest in eating farm food, but, rather, learn from more experienced individuals that this is a potential source of nutrition. Crop-raiding is a high-risk behavior, since animals that are caught may be injured or even killed by farmers; previous researchers have estimated that 65% of adult elephant deaths result from conflicts with humans. Presumably, then, those individuals that raid farms and live to tell the tale are particularly talented at this behavior and therefore pass on useful information to youngsters. Results from other studies suggest that feeding later at night, feeding during moonlit nights, and feeding in large groups are all techniques of minimizing the danger of farm visits.

According to the researchers, the current findings suggest that farmers who retaliate against crop theft by killing individual elephants may not actually be doing themselves any favors--particularly if they kill older males. Because this behavior is transmitted socially, and poached individuals have likely already passed on their bad habits to companions, farmers are probably only buying themselves a bit of time before other individuals show up for the next round of raiding. Additionally, older males are repositories of general "ecological knowledge," which means that they are familiar with the locations of natural sources of food; removing this knowledge from the population might drive younger males to visit agricultural fields simply because they don't know where else to look for resources.

Based on these results, the scientists suggest a two-pronged management approach whereby both older and younger elephants are simultaneously exposed to "aversive conditioning techniques" such as pepper spray canisters. Theoretically, this would keep older individuals out of fields--thus minimizing the exposure of youngsters to their bad habits--while also ensuring that current juveniles will avoid farms once they reach reproductive age and are looking for a quick and easy source of high-energy food. Future studies on the interplay of life history characteristics and social networking are likely to suggest additional management possibilities for this and other social-learning species that make pests of themselves in anthropogenic environments.

Chiyo, P.I., Moss, C.J., and Alberts, S.C. 2012. The influence of life history milestones and association networks on crop-raiding behavior in male African elephants. PLoS ONE 7(2):e31382.

Friday, 17 February 2012

Landscape factors impact urban pest control

Most people have had pests in their house at some point or another, and the problem may have been so extreme that it required treatment of some sort--a trap or two, or perhaps even some sort of chemical. These sorts of measures can be effective at removing target species, but they may also have an impact on other animals that find themselves in the wrong place at the wrong time. One well-known example of this is the massive die-offs of large bird species, particularly vultures, that have resulted from the birds' unwittingly feeding on carcasses of poisoned pest species. Because nuisance animals are often considered a more interesting research topic for exterminators than for scientists, many pest systems are not understood in the sort of detail that helps managers develop good treatment plans, or lawmakers to write bills protecting innocent animal bystanders caught in the crossfire.

(Norway rat, Rattus norvegicus)

Two collaborators from the Western Ecology Division of the U.S. Environmental Protection Agency recently published results of research aimed at rectifying this situation. Their study focused on the use of anticoagulant chemicals in two urban/suburban areas in California. Anticoagulants are commonly used on mammalian targets such as rats and mice, but they may also impact non-target species such as squirrels, rabbits and other small mammals, as well as the avian and terrestrial predators that eat them. Other at-risk species include those that are threatened, protected, or regulated for any number of other reasons, including foxes, bobcats, coyotes, and mountain lions.

The researchers suspected that use of chemicals might be associated with both landscape factors, such as the proximity of "natural" habitat and the type/age of the buildings in which treatments were used, as well as socioeconomic factors. In order to investigate this, they distributed questionnaires to residents in the two study sites--southwestern Bakersfield and a suburban area near the Santa Monica Mountains National Recreation Area (SAMO)--in order to collect information allowing them to better understand how chemical usage patterns are related to mortality rates, and also to investigate landscape variables associated with the use of these products. The study sites were chosen after local biologists conducted necropsies and home range analyses of dead wildlife there; these examinations revealed that the animals had died from poison distributed in and around Bakersfield and SAMO.

(House mouse, Mus musculus)

While rats and mice were the most common target species at both sites, residents in Bakersfield also used poison to control for kit foxes, while residents in SAMO treated for small mammals such as squirrels, gophers, and rabbits, as well as for larger animals such as bobcats, coyotes, and mountain lions. Although you might think that older homes would be more permeable to pest species, control and chemical use did not vary with building age in either study area. Likewise, residents in both locations were more likely to treat for nuisance animals if they lived in single-family dwellings rather than apartment complexes, and in lower-density developments. The main difference between Bakersfield and SAMO chemical usage patterns was related to distance to open space. In the former, only squirrel control efforts were associated with this variable (with more treatment occurring nearer open spaces), while in the latter, distance to open space influenced control of the two main target species, rats and mice (with more treatment occurring closer to open spaces). These differences probably stem from the fact that Bakersfield is, in general, less densely urbanized than SAMO, and located much farther from large tracts of natural habitats; both of these variables influence availability of resources and the movements of small mammals.

Both study sites had control and/or chemical "hotspots," where large numbers of residents reported taking measures, chemical or otherwise, to reduce the incidence of pests. The single Bakersfield control hotspot was located near both a golf course and a construction site, and was close to otherwise open habitat. The two SAMO control hotspots overlapped with three chemical hotspots; all were near densely-vegetated wash channels close to open space, and one was associated with development of a new residential subdivision. Thus, it appears that pest mammals are likely to become particularly problematic to humans who live near "natural" areas and those located in habitats under construction.

(Kit foxes, Vulpes macrotis)

Cumulatively, the results indicate that landscape patterns impact the distribution of nuisance species, which, in turn, impacts use of chemicals and other control measures. Predictably, the most human-commensal species, mice and rats, were targeted fairly uniformly across the habitats. However, other species were only controlled for in pockets. The researchers hypothesize that this is because the presence of these animals is strongly related to both the presence of land cover (acting as shelter and facilitating safe movement between habitat patches) and patterns of land use (e.g., for feeding, breeding, or hiding). Survey respondents frequently associated the presence of some pest species with exotic vegetation--particularly fruiting trees that provide an attractive source of food for many animals.  Future research will need to investigate the extent to which invasives influence habitat use by potential nuisance species--and to what extent this encourages nearby humans to use chemicals and other control measures.

Also intriguing is an apparent link between socioeconomic factors and the proximity of pests. Survey respondent income was linked to two variables (distance to open spaces, density of housing) that impacted chemical use. According to the authors, this suggests there is a "possible feedback loop of interacting ecological and social phenomena." Specifically, human habitat alteration creates appealing wildlife habitat, which draws animals in closer to humans; when these species become a nuisance, they are controlled for and, often, the damage they caused is repaired; because the original wildlife-attractive variables remain in place, more wildlife appear over time, and the cycle starts all over again. The researchers hope that the "hotspots" identified by their analyses can be used to pinpoint which urban areas are particularly at risk of entering this feedback loop. In these locations, landscapers and managers may need to get creative in order to find safe and effective ways to discourage pests from utilizing anthropogenic resources, while also ensuring that innocent bystanders don't get harmed in the process.

Morzillo, A.T., and Schwartz, M.D. 2012. Landscape characteristics affect animal control by urban residents. Ecosphere  2(11):1-16.

Thanks to the following websites for providing the images used in this post:

Monday, 13 February 2012

Effects of humans on plant biodiversity

It is easy to say that humans have influenced the world's biodiversity, but much harder to actually quantify our impacts. For one thing, we rarely (if ever) know the condition that ecosystems were in before we altered them; for another, biodiversity is impacted by a number of other factors besides humans, including latitude, climate, and topography.

However, using a relatively simple equation, collaborators from the University of Maryland and the Georg-August University of Gottingen have made a first stab at calculating anthropogenic species richness (ASR), or species richness patterns that results from human alteration of native habitats. ASR reflects native species richness minus all species lost (ASL) and all species introduced (ASI) as a result of anthropogenic influence. Local extinctions are usually a result of habitat loss and outcompetition by introduced species, while species gains generally reflect the presence of agricultural crops and ornamental species. In the current research, each of these components of ASR was calculated using previously-published models that, on the whole, are more likely to underestimate the influence of humans than overestimate it. Thus, ASR is only an estimate but one that probably gives us a decent best guess of the minimum effect that humans have probably had on vascular plant richness around the globe.

The researchers calculated ASR for each of 16,805 focal regions generated by dividing all of the Earth's ice-free land surface into equally-sized (7,800 square km) chunks. Although ASR was estimated separately for each region, the scientists could simultaneously evaluate patterns across all cells in order to investigate the effects of anthropogenic disturbance at a global scale. This revealed that species richness has been impacted by humans across a whopping 93% of the planet's ice-free land area.

Depending on the region being investigated, this pattern was a result of local extinctions, local introductions, or a combination of the two. Just over half of terrestrial landscapes have lost more than 5% of their native species, while over a quarter have lost more than 10%. At the same time, 89% of habitats have experienced invasion by exotic species; more than a quarter of the biosphere has in excess of 10% introduced species. So many plants have been introduced, in fact, that gains from invasives equal or outweigh losses of natives in many locations, with the result that overall species richness patterns are not drastically altered. To put that in numerical terms, while 93% of the planet has been impacted by human disturbance, only 61% has actually experienced a net change in richness.

(A 2005 map of biodiversity hotspots around the world. The authors of the current study examined 34 hotspots identified by Mittermeier et al. in 2004.)

Only rarely did the researchers find locations where richness was actually declining; when they did, it was a result of extremely high native losses that far outpaced "exotic gains." Habitats that were identified as particularly likely to suffer from richness depletions richness were grasslands, savannas, shrublands, and deserts. Over half of 32 "biodiversity hotspots" exceeded the global median for human-caused diversity fluctuations, indicating that "the most biodiverse regions on Earth also tend to be among the most challenged by anthropogenic transformation." Overall, the most anthropogenically altered hotspot was Japan, while the least impacted was the East Melanesian Islands (however, both of these results need to be interpreted with caution since island habitats are intrinsically different from their mainland counterparts when it comes to biodiversity levels and susceptibility to anthropogenic influences).

While some of the patterns reported here might be disheartening to some, the authors suggest that their results aren't all bad news. They are quick to point out that even in the most disturbed regions, many native plant species are thriving--despite the loss of some endemic species and the gain of many nonnatives. Further, it is likely that native species are quick to re-establish themselves in areas where humans once lived but can no longer be found. Thus, as many people abandon rural areas and flock to urban and urbanizing regions, the habitats they leave behind may be reclaimed by indigenous species.  Finally, the researchers suggest that we may be able to develop methods of "redirecting" ecological succession such that native plant species, rather than new exotics, can be encouraged to replace dying invasives.

Of course, that may require the development of new management techniques, plus it only addresses the problem of varying richness. Evenness and diversity--both in general, and in relation to phylogeny and function--are two other important characteristics of species assemblages, and future studies will be needed to see how these traits have been impacted by anthropogenic activities worldwide. It would also be useful to link these patterns to specific aspects of human existence--such as transportation networks, land use, and economics; those data could help explain particular biodiversity patterns and suggest potential methods of management. Should such analyses prove fruitful, one next step might be applying them to other groups of organisms as well, including animals, bacteria, and fungi.

Ellis, E.C., Antill, E.C., and Kreft, H. 2012. All is not loss: plant biodiversity in the Anthropocene. PLoS ONE 7(1):e30535.

Thanks to the following websites for providing the images used in this post:

Friday, 10 February 2012

Some landscaping techniques may reduce susceptibility to wildfires

Wildfires are known to occur on every continent except Antarctica, and both fossil and historical records indicate that these disasters have been a threat to human lives and shelters since our earliest days. Wildfires are particularly common in areas with long periods of hot and dry weather, but also with enough vegetative growth to provide fuel. Since global warming is predicted to increase temperatures and alter precipitation patterns, many worry that ever more human settlements will be threatened by wildfires in the future. Thus, it seems a good time to improve our understanding of the factors associated with wildfire damage, and to use this information to develop management techniques that reduce the risk of damage.

This was the aim of collaborators from Australia and the US who recently quantified which landscaping and management practices were associated with the loss of houses during a trio of Australian wildfires that occurred in 2009. They were interested in focusing on home loss not just because of the obvious value of homes, but, more importantly, because the majority of wildfire-related human deaths occur in domestic buildings--which residents often stay to defend, attempt to take shelter in, or evacuate from too late. In the Kilmore East, Murrindindi, and Churchill fires examined in the current study, for instance, 69% of the 170 documented fatalities occurred in homes.

Researchers already know that the behavior of wildfires is predominantly affected by three variables: terrain, weather, and fuel. Characteristics associated with each of these three categories were cataloged for a total of 499 houses--some of which escaped damage in the recent Australian wildfires, and others of which were not so lucky. Terrain was not found to have any effect on house damage, and the patterns associated with weather were highly predictable: more homes were lost when temperature and wind speed were high, and humidity was low. The real variable of interest was "fuel," since it is not only quite variable among homes, but is also often the easiest for humans to control.

The researchers found that houses were most at risk when they had buildings and vegetation--particularly native species, rather than exotics--within 40 m; when prescribed forest burning efforts had taken place at some distance, rather than nearby; and when houses had less private land separating them from public land, parks, or forests. These patterns are likely a result of the fact that most houses catch on fire after being exposed to embers and radiant heat generated by the burning of nearby fuel. Thus, it isn't surprising to find that modifying or removing potential fuel could "substantially reduce house loss." In this case, "substantial" could, in some cases, mean nearly halving the rate of destruction. Specifically, the scientists estimated that decreasing native vegetation within 40 m of houses could reduce house loss by 43%; removing all trees and shrubs within 100 m could reduce loss by 26%; and conducting prescribed burning efforts within 0.5 km of homes, instead of the current average of 8.5 km, could save 15% of properties.

On the whole, these results indicate that the most important goal is to increase "'defensible space,' or the area around houses in which suppression is most likely to be successful." While it's up to private property owners to follow up on many of these suggestions, government managers may also need to think about modifying their current prescribed burning techniques if they want them to benefit communities as well as wildlife. Specifically, one major finding of the current study was that the benefits of the burnings appear to be short-lived, indicating that they should be conducted more often, as well as closer to at-risk neighborhoods.

The authors caution that their results may not be applicable across all fire-prone regions; additional work should be done in order to investigate patterns in locations with different weather and floral communities. Furthermore, although the techniques reported here may be optimal for maximizing survival probabilities of homes exposed to wildfire, they may be costly or difficult to achieve--and they may have unintended negative side effects. Finally, the researchers suggest that it is worthwhile to investigate alternative management methods that could mitigate the important impact of weather; these include architectural solutions, creation of alternative shelters, and innovative suppression efforts.

Gibbons, P., van Bommel, L., Gill, A.M., Cary, G.J., Driscoll, D.A., Bradstock, R.A., Knight, Moritz, M.A., Stephens, S.L., and Lindenmayer, D.B. 2012. Land management practices associated with house loss in wildfires. PLoS ONE 7(1):e29212.

Thanks to the following websites for providing the images used in this post:

Thursday, 9 February 2012

Media coverage of ecological science: a rare occurrence

Before you started reading this sentence, when was the last time you read about ecology in the news? Probably not too recently, according to results of a new study published in the latest issue of the ecological journal Ecosphere. The study's authors, collaborators from Northern Kentucky University and Brigham Young University, noted that while the bulk of scientific studies escape the notice of journalists, ecological research in particular appears to be under-covered by the media. They set out to study this trend in more detail in order to develop recommendations for improving relationships between journalists and ecologists--with the ultimate goal of increasing public awareness of ecological studies.

The researchers were particularly interested in four main study questions: What proportion of ecological research makes its way from the academic literature into the mainstream media? Which types of media outlets are most likely to report ecological findings? When scientific research is discussed, which aspects of the studies are highlighted by journalists? Finally, are the studies that journalists find newsworthy also those that other scientists consider academically relevant?

In order to answer these questions, the researchers collected a sample of 1,513 focal studies published in the journal Ecology between 2000-2010. They then searched for instances of the journal name, authors' names, and authors' institutional affiliations in the news archive Nexis-Lexis, which collects news coverage found in newspapers, television and radio reports, newswires, newsletters, and online sources. They counted the number of times each focal study appeared in some type of mainstream media; they also noted which parts of the original academic write-up were discussed within that report--for instance, did journalists describe methodology and background content, or just the study's results? The scientists also performed searches in Web of Science, an academic database, in order to find out how many times other researchers had cited each focal study; the grand tally for each paper was considered its "impact factor" and indicated how highly it was regarded within the scientific community.

Only 26 papers--or a mere 1.7% of the total--were referenced in Lexis-Nexis; a total of 39 news stories were written on this research, indicating that some studies were covered multiple times. Interestingly, no one single topic was favored by the media; when ecological articles were covered by the mainstream press, they dealt with topics ranging from climate change to conservation to food webs. There was no consistent coverage pattern over the 10-year study period; no ecological studies were discussed in the media in 2000 or 2007, but 5.4% of papers received attention in 2003. Newspapers and newswires were most likely to feature references to ecology research, while radio and television reporters did not cover ecological science a single time over the study period. When ecology reports were covered by the media, journalists focused most often on content found in the discussion and results sections of the original academic paper; they were least likely to mention background scientific details or methodological descriptions. Impact factors were similar across all studies examined here, regardless of whether or not they were covered by the media.

These results left the authors wondering, "Why are ecological science findings so unlikely to reach the public through traditional media sources?" One reason, they suggest, is the fact that journalists do not feel attracted to ecological findings--perhaps because scientific literacy is lacking, and journalists feel uncomfortable interpreting the content of academic ecological papers. The dearth of ecology coverage may also reflect the fact that some media outlets do not maintain a dedicated science staff, and therefore do not have anyone on hand to interpret the sometimes complex analyses and relationships reported in the ecological literature. Another potential problem, according to the researchers, is the fact that journalists and ecologists often have competing interests; whereas the journalists want news that is exciting enough to attract the attention of fickle readers, scientists are more concerned with broadcasting topics that are scientifically important--those that "evaluate hypotheses and bring forth new understanding."

The remaining question, then, is how ecologists can increase the likelihood that their results will be covered by the press. The researchers suggest that a variety of changes need to be made, both by the scientists themselves and by the institutions that employ them. First of all, academics should work proactively with public information officers in order to generate press releases that are both appealing to journalists and scientifically accurate. Second, researchers should consider engaging directly with the media--whether this means making friends with a local reporter or using Internet resources such as blogs and Twitter feeds in order to advertise and promote findings. Even if these online methods don't attract the attention of news consumers, they may catch the eye of journalists and facilitate wider coverage. Third, scientists might produce their own media coverage and distribute it to news organizations directly--though of course this assumes that researchers have the time for this sort of activity in the midst of teaching, researching, writing grants, and publishing academic papers. Finally, and perhaps most importantly, the authors encourage an overhaul of the academic culture, such that public outreach is valued more highly at colleges and universities. Specifically, while interactions with, and coverage by, the media are now merely considered icing on the cake, in the future these might be used when assigning rank or making promotion decisions.

Baker, M.J., Williams, L.F., Lybbert, A.H., and Johnson, J.B. 2012. How ecological science is portrayed in mass media. Ecosphere 3(1):9.

Thanks to the following websites for providing the images used in this post:

Wednesday, 8 February 2012

Anthropogenic nitrogen sources are a major source of N pollution

Writing in the most recent issue of Frontiers in Ecology and the Environment, an international team of collaborators has described nitrogen (N) as "the largest pollution problem in coastal marine waters." Excessive amounts of N sometimes fuel blooms of algae that can outcompete or even poison other organisms, and evaporation of N into the atmosphere in the form of nitrous oxide can cause damage to our delicate ozone layer. Most of the nitrogen along our coasts is deposited there by rivers that pick up N-rich sewage, fertilizer runoff, and atmospheric deposits caused by the burning of fossil fuels; in other words, nitrogen is yet another form of anthropogenic pollution. While this has been known for a while, researchers have not always found consistent patterns relating human activity to nearby nitrogen levels. This likely stems from the variety of potential sources of anthropogenic N, and how they are influenced by climatic variables such as precipitation, temperature, and freshwater discharge. The complex interplay among these variables is exactly what the collaborators, from a variety of institutions in the US, France, Sweden, and UK, aimed to characterize in their recent study.

(Satellite image of the Black Sea showing algal blooms caused, at least partly, by nitrogen runoff)

Specifically, the researchers obtained data from a number of government, environmental, and academic resources in order to characterize nitrogen flow in 154 watersheds across the US and Europe. The scientists related riverine nitrogen flux, or the total amount of N deposited by rivers into coastal waters, to "net anthropogenic nitrogen inputs" (NANI). This variable is the sum of all human-related nitrogen in the system, and takes into account N contributions from synthetic fertilizer, fixation associated with agricultural crops, atmospheric deposition from fossil fuel consumption, and the movements of both human and animal food.

Across the watersheds examined in this study, the amount of N deposited into coastal areas was significantly related to NANI, indicating that human nitrogen use is the major driver of coastal N pollution. Rivers appear capable of exporting up to approximately 25% of NANI from the landscape to coastal areas; the rest is likely retained in soils and forest biomass, or is denitrifed. However, little is known about this stage of the process and the scientists encourage future research on this topic. 

In addition to investigating NANI as a single aggregate variable, the researchers also looked at the relative nitrogen contributions of each subcategory it comprises. In many watersheds, N levels were significantly related to individual anthropogenic sources of nitrogen. Fertilizer use, for instance, was highly correlated with coastal N deposition, as were agricultural fixation and atmospheric deposition. The influence of nitrogen from human and animal food was more complex. When these products were retained or introduced into a given watershed area, they were consumed by local animals and ultimately introduced into the water as a source of sewage and waste; this led to a positive relationship with coastal N deposition. However, when these products were removed in the form of crop exports, they were associated with fertilizer use and N fixation and therefore had a negative relationship with the amount of nitrogen delivered to the ocean.

(Estimated N deposition from global nitrogen emissions, as of 2008. Image courtesy of Science via Mongabay.com)

Perhaps unsurprisingly, NANI was found to be significantly impacted by all three climatic variables investigated here. However, despite the statistical significance of both temperature and precipitation, neither was that useful in accurately predicting NANI levels. On the other hand, freshwater discharge, or movement of nitrogen from the landscape via local water systems, was an important predictor of NANI exportation. 

However, despite the relevance of this climatic variable, the amount of N deposited into oceans seems to be more heavily influenced by anthropogenic activities. This is a valuable insight for water-quality managers, who, the researchers suggest, should focus their efforts on "field-scale agricultural practices" in locations where NANI is dominated by N fertilizer, but on waste treatments in areas where movements of human and animal foods are most important. Where data are available, it would be beneficial for managers and researchers to consider not just NANI, but also the simultaneous impacts of NANI and freshwater discharge, as the resulting "dual" models allow more precise estimates of coastal nitrogen pollution. This will be particularly important as the climate continues to change, since some regions will become wetter while others become drier. By impacting local rates of N discharge, this will alter the number of nitrogen sinks in the landscape and, ultimately, the percentage of NANI that winds up in coastal waters.

Howarth, R., Swaney, D., Billen, G., Garnier, J., Hong, B., Humborg, C., Johnes, P., Mörth, C.-M., and Marino, R. 2012. Nitrogen fluxes from the landscape are controlled by net anthropogenic nitrogen inputs and by climate. Frontiers in Ecology and Environment 10(1):37-43.

Thanks to the following websites for providing the images used in this post: