Tuesday, 30 August 2011

Menus differ for city foxes and their country cousins

The old saying, "One man's trash is another man's treasure" may need to be rewritten for Bakersfield, California, where it turns out that "Everyone's trash is the foxes' treasure." This was discovered in a recent study seeking to quantify the extent to which urban-living San Joaquin kit foxes (Vulpes macrotis mutica) utilize anthropogenic food items.

(What looks like trash to us seems like a buffet to scavengers and opportunistic feeders such as raccoons, opossums, gulls--and foxes.)

In order to investigate diets of Bakersfield foxes and conspecifics living in nearby nature areas, a two-pronged approach was taken by collaborators from the University of Wyoming, the Geophysical Laboratory of the Carnegie Institution of Washington, the National Zoological Park of the Smithsonian Conservation Biology Institute, and California State University--Stanislaus.

First, scat was collected from foxes living in urban areas within Bakersfield--where they prefer open habitats such as golf courses, drainage sumps, vacant lots, and school campuses--and from foxes living outside the town in the nearby Lokern Natural Area. By dissecting the scat, the researchers could look for tell-tale "signatures" of particular food items, such as chitinous exoskeletons of grasshoppers and beetles, hair and teeth from small rodents, bird feathers, and bits of wrapper from human food items.

(A map of the San Joaquin Valley, at the southern end of which lies Bakersfield. The current study focused on the southwestern quadrant of the Bakersfield Metropolitan Area.)

Second, they conducted stable isotope analysis on hairs and whiskers collected from urban and natural foxes (this time including animals not only from Lokern, but also from Kern National Wildlife Refuge). This allowed the researchers to look at the ratios of different types of carbon and nitrogen atoms found in the animals' bodies; since isotope values differ over time and space, the scientists could compare values from foxes in the two locations to see how much their diets overlapped. Human hair--collected from barber shops and salons within Bakersfield--was also included in the analysis, as were samples from major fox prey species. Values from these samples were used to create a more complete picture of the total "isotope environment" in the urban and natural areas.

(Adult and juvenile San Joaquin kit fox, Vulpes macrotis mutica)

Results from scat analyses indicated that both urban and natural foxes depend primarily on small vertebrates and insects. Kangaroo rats (Dipodomys spp.) appeared to be particularly common food items for natural foxes, and their most common insect prey was grasshoppers. Urban foxes, on the other hand, appeared to eat a mixture of squirrels, gophers, and birds, and their most common insect prey was beetles. No signs of human food were found in natural fox scat, but 12.5% of urban fox scat contained food packaging material.

The isotope analyses revealed even bigger differences in the consumption patterns of the two types of fox. Both carbon and nitrogen isotope values were significantly different in samples from urban and natural foxes, with the latter animals showing higher variation in nitrogen values than either foxes or humans from urban areas. This is related to living in a more variable environment where availability of particular food items is heavily impacted by variations in rainfall. Urban humans and foxes also had considerable overlap in their carbon isotope values, indicating high similarity in their diets. There were no significant differences between male and female foxes within each type of location, indicating that both sexes ate similar diets.

(Adult San Joaquin kit fox)

These results suggest that San Joaquin kit foxes, like other scavengers and "opportunistic generalist carnivores," are doing quite well in urban areas by expanding their menu; they join the ranks of animals such as raccoons, opossums, crows, gulls, and coyotes. Surprisingly, studies so far have not shown any negative impact of this shift in the foxes' diet (as has been observed in, for instance, birds eating large amounts of fried food out of dumpsters). The urban kit fox population is more stable than natural populations; they live in higher densities and have smaller home ranges, likely because of the consistent and abundant availability of anthropogenic foods. The urban animals have higher, steadier reproductive rates, and despite findings that they have higher cholesterol, city foxes have higher survival rates and better fecundity. It appears that the urban foxes have more to fear from vehicle collisions and toxins than they do from eating unhealthy human fare. This is good news for this apparently thriving population of a species that is, on the whole, classified as endangered.

The authors of the study emphasize how important it is to couple scat and isotope analyses, since the latter can uncover dietary patterns associated with foods that do not leave much of a physical trace after digestion. Further, isotope analysis allows researchers to generate urban-to-rural gradients so they can investigate the impacts of human food items on the diets of wild animals. This provides another way to gauge the effects of anthropogenic disturbance on wildlife populations, as well as to explore food web dynamics in urban ecosystems.

Newsome, S.D., Ralls, K., Van Horn Job, C., Fogel, M.L., and Cypher, B.L. 2010. Stable isotopes evaluate exploitation of anthropogenic foods by the endangered San Joaquin kit fox (Vulpes macrotis mutica). Journal of Mammalogy 91(6):1313-1321.

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

Monday, 29 August 2011

Anthropogenic habitat modifications don't scare off marsh harriers

Over the past several decades, a growing number of studies have linked declines in biodiversity and abundance--especially of birds--with intensification of agricultural practices. Replacement of uncultivated areas with farm fields, use of pesticides, increases in monocultures, and earlier harvesting dates have all been associated with reductions in the quality of hunting/nesting habitats, reproductive failure, mortality of individual birds, and increased heterogeneity of bird communities.

However, as has been discussed in previous posts, not all animals respond to anthropogenic disturbance in the same way. Thus, it is likely that some species might not be negatively impacted by agricultural practices--in fact, they might benefit from them. For instance, species that depend on wetlands might thrive in agricultural areas where the use of irrigation has created artificial ponds and wetlands that either generate new habitats or replace those that were previously lost to agricultural expansion.

(Hunting marsh harrier, Circus aeruginosus)

This appears to be the case among marsh harriers (Circus aeruginosus) in the Catalan Ebro basin, an agricultural area in the Iberian Peninsula. The harriers declined in Europe between 1960 and 1980 because of pesticide contamination, hunting, and heavy drainage of the wetlands where they breed. Harrier populations have been recovering in recent decades, to the point where they are actually increasing their geographic range in some locations. These improvements appear to be linked with the birds' use of artificial ponds/reservoirs created by local farmers.

(Map outlining the Ebro Basin area of the Iberian Peninsula. Traditionally, agriculture here included extensive cultivation of cereal crops separated by field margins; fallow grounds were allowed to rest for one or more years, during which time they were used for grazing of livestock. During the 20th century, however, farming practices changed: A variety of alternative crops became popular, irrigation systems were established, and both the fallow system and field margins were eliminated. Currently, the region is an "agricultural mosaic" composed of arable, non-irrigated cereal crops, irrigated fields, dry fruit trees, and irrigated fruit trees.)

To investigate this hypothesis, researchers from the Universitat de Barcelona, the Estación Biológica de Doñana, and the Universidad Pablo de Olavide monitored breeding marsh harriers from 1997-2008 and measured habitat variables within and around wetlands where the birds were found nesting. Parameters of interest included type of habitat (e.g., artificial pond vs. reservoir vs. river, etc.), amount of vegetation in the wetland, shape of the wetland, amount of open water, type of agriculture associated with the wetland, and proximity to anthropogenic structures such as villages and roads.

Of the 617 total wetlands in the study area, only 51 had the minimum requirements that made them suitable for marsh harrier breeding. Of these, 68% were artificial water bodies associated with agricultural irrigation. Approximately 69% of these wetlands were occupied at least once during the study.

(Marsh harrier in flight)

Features of both the immediate (within-wetland) and extended (within a 3-km radius of the wetland) environment were associated with chosen breeding territories: Marsh harriers seemed to strongly prefer habitats with higher areas of aquatic vegetation; they were also drawn to wetlands near agricultural fields with highly irrigated herbaceous crops. The importance of these two levels of habitat features--both near to, and far from, the nesting site--suggests that the birds are satisfied not only with the apparent safety of the breeding ground, but also with the likelihood that they will find sufficient prey in the nearby fields. The fact that they are particularly drawn towards heavily managed cropland indicates that the birds are not being scared off by anthropogenic activities. Even better, the researchers did not find any relationship between habitat attributes and productivity. In other words, harriers in agricultural areas are not suffering reduced breeding success because of their fondness for artificial wetlands.

The scientists suggest that one of the reasons harriers may thrive in anthropogenic areas is the constant wetness due to influx of water from irrigation; in natural environments, wetlands often dry out during spring and summer because they are not continually supplied with fresh water. The authors also point out how the current results support previous findings suggesting that marsh harriers are able to find an abundance of prey in "agriculturally intense" habitats. However, neither study was able to document specifics related to harrier hunting practices, so more data will need to be collected--how far the birds fly, which areas of the habitat they use, what species they are eating--in order to explain the mechanisms behind their apparent success in anthropogenic areas.

Raptors such as the marsh harrier are often used as bioindicators--species whose population trends reflect the health of an ecosystem--because they are at the top of the food chain. This study shows that at least some raptors can adapt to the presence of humans; thus, this group of animals may not uniformly be good at providing early warnings of habitat degradation. However, the researchers point out that "finer cues" such as individual health and survival might indicate forms of ecosystem degradation that were not studied here--including water pollution and pesticide use. This is another possibility that will require attention in future studies.

Cardador, L., Carrete, M., and Mañosa, S. 2011. Can intensive agricultural landscapes favor some raptor species? The marsh harrier in north-eastern Spain. Animal Conservation 14:382-390.

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

Sunday, 28 August 2011

Road noise reduces avian richness and abundance in a Costa Rican park

Without roads, we would be unable to visit some of the world's natural marvels. We would be less able to support parks and reserves with funding from ecotourism, inspire hearts and minds with nature, or easily conduct scientific studies in far-flung locations. Unfortunately, without roads, we also wouldn't be adding chemical and noise pollution to habitats, fragmenting pristine areas of land, generating unpleasant and sometimes unhealthy vibrations through the ground, or causing collisions that injure or even kill animals.

Time and again, these and other negative impacts of roads have been documented by scientific research in a variety of habitats. One of the most recent of these studies--and one of the first to examine the impacts of roads in tropical habitats--quantified the impact of traffic noise on the richness and abundance of bird species in Costa Rica's Carara National Park, the western side of which is bordered by one of the biggest and busiest roads in Costa Rica. There, the average distance between the road and the forest edge is 5 m, causing noise levels in the nearby forest to approach a very unpleasant 100 dB.

(Map of the Carara National Forest in Costa Rica)

In order to quantify the impact of road noise on avifauna, scientists from The School for Field Studies (Alajuela, Costa Rica) conducted surveys at 16 permanent sample points--8 along trails near the road, and another 8 along trails farther away. During 10-minute sampling efforts conducted twice a day during both the wet and dry seasons, they counted all birds seen or heard within a 30-meter radius; they also conducted mist-netting at 6 nets within the "near" and "far" habitats. In addition to measuring ambient noise at each of the bird count locations, the researchers tallied passing vehicles at different times of day and classified the vehicles as either "heavy" (e.g., trucks) or "light" (e.g., cars and motorcycles).

(Some of the lush habitat in Carara National Forest, Costa Rica)

As anticipated, sampling points closer to the road had significantly higher noise levels than those farther away. Eight fewer bird species were detected in the louder areas than in the quieter ones (89 vs. 97, with a total of 129 unique species counted throughout the entire study). Although this difference in avian richness was not significant, there was a significant difference in relative bird abundance: an average of only 6 birds in the loud sites, compared to 8 birds in the quiet sites.

(Red-capped manakin, Pipra mentalis)
Noise from the road was found to attenuate more during the wet season than during the dry season, reflecting the sound-dampening effects of the leaves. However, traffic levels were also found to fluctuate with season: More vehicles (particularly those classified as "light") used the road during the dry season.

Because the road is an important conduit for traffic moving along the coast, it can't be shut for the sake of the birds. So what can be done to prevent the highway from making the neighboring habitat less suitable for bird use? The authors' first suggestion is to implement speed limits, which not only would diminish noise levels, but might also reduce the number of collisions between animals and passing cars. They also discuss the installation of barriers along the road--an expensive, large-scale project, but one that would have the added benefit of making trail use more pleasant for the 33,000 human visitors who visit the park annually and who, presumably, do not want to hear traffic noise any more than the birds do. Given the fact that "heavy" vehicles were consistently found to be louder than "light" vehicles, it might also be a good idea to limit truck access to the coastal highway--especially during the dry season when there are fewer leaves in the forest to buffer the birds from road noise.

The broader implications of the study are clear: In tropical environments as well as more temperate areas, noise from roads can have negative impacts on local bird communities. Where possible, managers should try to alter the roads and/or their traffic patterns in order to protect wildlife. In places where roads have not yet been built but have been suggested, hopefully planners can find a way to avoid sensitive habitats or include features that dampen sound transmission. In some places, voters may have the opportunity to prevent construction of proposed roadways, either by voting on initiatives themselves or by pressuring their lawmakers. Hopefully everyone will see the advantage of driving a few extra miles around important bird habitat, rather than taking a noisy shortcut that takes them too close to sensitive species.

Arévalo, J.E. and Newhard, K. 2011. Traffic noise affects forest bird species in a protected tropical forest. Rev. Biol. Trop. 59(2):969-980.

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

Saturday, 27 August 2011

Saturday stuff: Hyperbolic Crochet Coral Reef

Recently I found out about a unique and fascinating project called the Hyperbolic Crochet Coral Reef, currently on display at the Art Center College for Design in Pasadena, California, but originating at Institute for Figuring in Los Angeles. The Institute was founded by sisters Margaret and Christine Wertheim, who began the coral reef project in their L.A. living room in 2005. Hailing from Australia, they wanted to produce something to pay homage to their motherland's Great Barrier Reef and also to draw attention to the ecological struggle faced by reefs worldwide.

(Part of the hyperbolic reef, features starfish, anemones, and corals, among other things. Photograph taken by the Institute for Figuring.)

On their website for the project, the describe the Hyperbolic Crochet Coral Reef as "a woolly celebration of the intersection of higher geometry and feminine handicraft, and a testimony to the disappearing wonders of the marine world." The exhibit has traveled around the world, but if it isn't coming to a venue near you, you can take a tour of the show online. Also, the Wertheims encourage needleworkers to begin their own satellite reefs; their website provides information on coordinating with the larger effort and techniques for producing your own hyperbolic yarn creatures.

If you are interested in finding out more about the reef, check out some of these many resources:

1. The main Hyperbolic Crochet Coral Reef website
2. Video of Margaret Wertheim discussing the reef project at the TED conference
3. A blog about the reef and the attention it has been getting in the press
4. Facebook site for The Institute for Figuring
5. Information on satellite reefs that may be closer to you than the original
6. A field guide featuring the creatures that can be made using hyperbolic crochet techniques

Thursday, 25 August 2011

Helping smallholder farmers join the sustainable biofuel industry

Renewable energy sources have been getting increasing attention over the past several years, since these alternatives to petroleum are supposed to allow us to develop more Earth-friendly, sustainable practices of energy use. Options such as solar, wind, geothermal, and biofuel energy are expected to increase in popularity from 5% of the market in 2010 to 18% by 2030; in that time, production of biofuel is projected to rocket from 1.8 to 6.7 million barrels a day.

Biofuel in particular is a bit of a sticky issue because, while it does provide an alternative to gasoline, growth of biofuel crops has been related to deforestation, excessive use of freshwater resources, greenhouse gas emissions, and overuse of fertilizer. Despite these drawbacks, governments at many levels have passed initiatives to increase biofuel use and set goals for reduction of greenhouse gas emissions.
In many of the developing countries where these policies are particularly common, there is not enough domestic production capacity to generate the raw materials needed to create biofuels. As a result, growth and production are outsourced to developing countries, where other environmental and social concerns become a problem. One particular issue is the need for farmers and manufacturers to obtain certification proving that their biofuels are sustainably produced. Unfortunately, current standards and schemes are biased toward large-scale production, forcing small-scale farmers either to turn their backs on the potentially lucrative biofuel market, or sacrifice their freedom by seeking partnerships with larger organizations.
In a new article published in Biological Conservation, collaborators from Switzerland's Universitätstrasse, Sweden's Umeå University, and Indonesia's Center for International Forestry Research consider the hurdles that must be jumped by smallholders looking to join the biofuel revolution. Further, they suggest a 6-point plan for balancing the conflicts that are inherent in the current system:

1. Rather than being required to adopt sustainable practices overnight, farmers should be allowed to incorporate these standards on a step-by-step basis at a pace suited to local conditions. This would prevent farmers from being penalized for environmental, educational, social, and economic variations among regions.

2. Small-scale farmers should receive rewards and compensations to ensure that their prolonged involvement in biofuel production is worthwhile. This is particularly important in poorer communities, where asking farmers to trade off short-term benefits in the interests of long-term environmental goals can sometimes be equivalent to suggesting that they skip dinners this week so they can eat better next year.

3. Instead of setting a single goal that all individuals can strive for, use a continuous system of improvement. By looking forward to incentives at each stage of improvement, farmers would be encouraged to steadily improve rather than reaching a plateau. Perhaps more importantly, those already at the top of their game would be encouraged to innovate further instead of maintaining the status quo.

4. Governments should be encouraged to provide assistance to smallholders within their boundaries. For instance, they can improve infrastructure and develop financial incentives. In addition to helping individual farmers, these schemes would also likely have broader positive impacts on the economy at the local, regional, and national levels.

5. Those who are already in the biofuel industry should make it easier for smallholders to develop biofuel businesses. For example, existing biofuel institutions could share the financial burdens of sustainability certification schemes. Rather than being altruistic, this tactic would benefit existing entities by increasing the number of providers available to contribute raw products, thus growing the sector as a whole and allowing it to become an increasingly important player in the renewable energy industry.

6. Develop innovations along the way in order to continually improve the industry. For instance, find ways to link sustainability and developmental benefits such as health and education services, or employ extension officers who can provide education and training for farmers looking to make the transition into the biofuel industry.

The length of the list may seem daunting, but the authors emphasize that it merely reflects the real-world complexities inherent in a system where large-scale industrial entities and small-scale farmers must work together to achieve a common goal.

In many places, consumers may also have a say in how things are done; after all, we vote for the officials who draft biofuel and sustainability laws, and we buy the biofuels that are produced at the end of the day. We should educate ourselves about which companies and countries are making the fairest and most biologically sound decisions. That way, the next time we're in a position to make a choice--at the polls or at checkout--we can choose wisely.
Lee, J.S.H., Rist, L., Obidzinski, K., Ghazoul, J., and Koh, L.P. 2011. No farmer left behind in sustainable biofuel production. Biological Conservation 144:2512-2516.

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

Wednesday, 24 August 2011

Water pollution affects both aquatic and terrestrial organisms

Most people are familiar with the devastating environmental impacts of industrial waste, one of the major effects of which is to pollute water and cause harm to, or even the death of, aquatic wildlife. Previous studies of these processes have tended to focus on species that spend their entire lives in the water--fish, for example. However, there are some aquatic organisms that only dwell in the water for a portion of their life cycle. Many invertebrates, for example, spend their larval stage in streams and rivers, but, once they emerge, move onto land or the air just above it. There, they are an important source of food for species such as birds, bats, and other arthropods--including spiders.

Recent work by collaborators from the University of Sheffield has investigated the possibility that, by diminishing numbers of aquatic insects available for consumption, aquatic pollution can negatively impact predatory spiders. Although this possibility has been investigated in short-term experiments performed in a laboratory setting, the current study is the first to look at the effects of long-term pollution on entire populations of these animals.

(Map of some of the British coalfields, including the Yorkshire coalfield where the current study was carried out.)

The researchers performed their study in England's Yorkshire coalfield region, where many streams are polluted by iron-rich runoff that discharges from abandoned coal mines. The iron forms compounds with other elements in the water, yielding a sludge known as ochre; this smothers the stream bed and reduces both the abundance and productivity of the aquatic insects that make up a vital component of riparian spiders' diets.

The scientists focused on 15 polluted streams that had received coalfield runoff for at least 10 years and were anywhere from 100-1000 m long. Each of these polluted aquatic sites was paired with a nearby "healthy" partner located in similar habitat. Within each of these pairs, the researchers compared the density and biomass of aquatic insect larvae, emerged aquatic insects, other terrestrial invertebrates that might be an alternative food source for spiders, and the spiders themselves. They also measured a variety of habitat variables just to make sure that their results weren't impacted by habitat-specific differences in things like canopy cover and dominant plant species.

(Aquatic pollution caused by coal mining.)
On average, aquatic insect larvae were 88% less abundant, and had 80% less biomass, in polluted streams. Unsurprisingly, the abundance and biomass of emerged adult aquatic insects were similarly impacted. As a result, there were significantly fewer web-building spiders in the terrestrial habitat bordering the polluted streams. Of all the spiders surveyed, 99% fell into one of two families: the Tetragnathidae, or long-jawed orb weavers, and the Linyphiidae, or the sheet web weavers. The abundance and biomass of both groups were significantly reduced at polluted sites. Absolute numbers of Tetragnathidae were lower than those of Linyphiidae, likely because the orb weavers have stronger preferences for aquatic insects.

(Top: a Tetragnathidae spider; bottom: a Linyphiidae spider)

Interestingly, there were no significant differences between the polluted and non-polluted sites in abundance and biomass of alternative terrestrial prey organisms. In other words, there was no sign that spiders at the polluted sites had shifted their eating preferences to focus on more readily available prey--a behavioral response that might have allowed the arachnids to maintain higher population densities. Rather, the spiders' smaller population numbers likely reflect their consistent and maintained preference for emerged aquatic insects.

The authors found some minor impacts of habitat variables on spider densities, but these had nowhere near the effect of pollution. The one piece of good news for the spiders is that the coalfield pollution does not appear to be causing bioaccumulation of associated toxins such as iron, aluminum, manganese, and zinc.

Organisms that depend on an influx of food into their habitat from somewhere else--such as the riparian spiders studied here--are known as "recipient consumers;" the prey items that enter their habitat are called "spatial subsidies." Recently, it has been conjectured that alterations in spatial subsidies will affect recipient consumers differently depending on where in the food web the consumers are located; this is related to the amount of food that needs to be eaten by organisms at different locations in the web in order to consume adequate amounts of energy. While the current study shows that spiders are impacted by pollution-mitigated reductions in aquatic insect numbers, one unanswered question is how reductions in spider numbers might go on to affect other organisms in the terrestrial food web--including birds and small mammals. Thus, it appears that a good next step would be to census populations of these small predators in riparian habitats along polluted streams and explore their dietary preferences. It probably wouldn't be a bad idea to try to clean up the streams and stop the runoff, as well.

Paetzold, A., Smith, M., Warren, P.H., and Maltby, L. 2011. Environmental impact propagated by cross-stream subsidy: Chronic stream pollution controls riparian spider populations. Ecology 92(9): 1711-1716.

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

Tuesday, 23 August 2011

Balancing environmental and economic value: The case study of fertilizer use among farmers

Those of you who follow the Anthrophysis Facebook site may remember this recent link to a newspaper article on lethal algae at French beaches. In yet another topical confluence, a new paper from collaborators at the University of Alberta discusses the driving force behind these problematic algal blooms, (not to mention water quality issues in general and global warming): excess nitrogen use.

Or, rather, nitrogen imbalance, since some areas of the world have too much nitrogen as a result of over-fertilization, while other areas could benefit from the addition of nitrogen-based fertilizers that would improve crop yield. Nitrogen is the key limiting nutrient for most crops and is a vital part of growth processes in both terrestrial and aquatic ecosystems. Unfortunately, when nitrogen is added in the wrong form, the wrong amount, or at the wrong time of year, it may just end up leaching out of the soil and polluting water--causing algal blooms like those observed in France--and contributing to greenhouse gas emissions.

One method of rectifying the nitrogen imbalance is to reduce nitrogen overuse, but this is not always practical or possible. For one thing, as mentioned above, not all countries or regions are guilty of using too much nitrogen-based fertilizer. For another thing, there is already a high demand for nitrogen-thirsty agricultural crops such as cereals, and this demand is only likely to increase with rising population numbers and dietary shifts. If we can't reduce nitrogen use across the board, then we need to become smarter and more efficient with our agricultural practices.

This was recognized decades ago in many developing countries. In the European Union, for instance, there was a 56% decrease in excessive fertilizer use between 1987 and 2007, leading to reductions in ammonia emissions and nitrate levels in drinking water. Because so many farmers had been over-fertilizing, halving fertilizer use did not necessarily diminish agricultural output; rather, it saved farmers money that they would have spent on unnecessary nitrogen treatments, and it saved everyone the cost of cleaning excess microbes and chemicals from their drinking water.

At the opposite end of the spectrum is China, where the government has encouraged farmers to increase fertilizer use in order to improve crop growth. It is thought that current yields could be maintained even after a 30-50% reduction in fertilizer use--leading to a savings of $11.3 billion per year, as well as helping the environment.

Of course, what works in one area may not work everywhere because of variations in soil quality, weather, preferred crop, and farming techniques (among other things). In sub-Saharan Africa, for instance, soil quality can be fairly poor, and many farmers would benefit from increased use of nitrogen fertilizer. Because of these sorts of regional differences, farming practices should be tailored to specific ecosystems. Farmers can manipulate tillage type, rate, timing of fertilizer application, source of nitrogen, type of crop, and the use of bioinoculants (which can improve plants' nitrogen-fixing abilities). This type of multidimensional approach would be well worth not only the current savings generated by reduced spending on unnecessary fertilizer, but also the future savings associated with having a cleaner environment. The researchers calculated that savings of $19.8 billion and $56 billion per year could be obtained by 2020 and 2030, respectively, even if the only thing farmers did was reduce their nitrogen budgets to match the regional fertilizer recommendations made by agricultural scientists. If growers manipulated other factors, as well, the savings would likely increase.

Overall, the authors recommend a 4-step plan to improve fertilization practices in a way that benefits both the economy and the environment. First, we need to reassess fertilizer use requirements in all agricultural systems, using criteria that consider both economic and environmental concerns and find a balance between the two. Second, these reassessments need to be translated into "user-friendly" models that are easily understood by everyone involved--not just farmers, but also policy-makers, economists, and conservationists. Third, we need to make sure that producers are not penalized when they volunteer to use less fertilizer or employ alternative agricultural techniques. Currently, some crop insurance policies will not cover farmers unless they use predetermined (and sometimes outdated) fertilization practices. Finally, researchers need to think outside the box when developing ideas for making reduced fertilizer use not only possible, but practical and even desirable. In Austria and Finland, for instance, "green taxes" are levied on farmers when they purchase fertilizer.

Some conservationists may feel uncomfortable with the idea of attaching a price tag to clean water and reductions in global warming. The authors of the current paper began their essay by quoting the American ecologist Garrett Hardin, who, in 1968, wrote "The Tragedy of the Commons." In that seminal work, he stated that individuals will sacrifice others' interests for the sake of their own--for instance, polluting water and air in the process of growing crops that put food on the table and money in the back. Because of this, it will sometimes be necessary to look at the environment from an economic perspective and show how conservation--or, at the very least, preservation--can also be lucrative. What matter if some people measure the benefit in coin while others measure it in peace of mind and spirit? As long as we all have the same goals in the long run, everyone wins.

Good, A.G. and Beatty, P.H. 2011. Fertilizing nature: a tragedy of excess in the commons. PLoS ONE 9(8): e1001124.

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

Monday, 22 August 2011

Cryptic poaching severely constrains growth of a Scandinavian wolf population

Trends often emerge in biological research, with several papers on a similar topic being released over short periods of time. This seems to be the case for poaching, which I wrote about last week. That post covered the development of new survey techniques that more accurately estimate poaching rates among groups of potential hunters—in that case, South African farmers. Just a couple days later, a new study was published in which collaborators from the Swedish University of Agricultural Sciences, Hedmark University College, the Norwegian Institute for Nature Research, and Colorado State University reported on their use of mathematical modeling to explore the concept of “cryptic poaching” and measure its potential impacts on conservation efforts among Scandinavian wolves 
(Canis lupus).

From 1999-2009, the authors radio-tracked 104 wolves—approximately 10-15% of the total population—in order to quantify breeding attempts and population growth, and later determine the causes of the wolves’ deaths. Of the 26 verified mortalities during the study, 5 were known to be caused by poaching (a necropsy revealed a deliberately caused death outside of a legal hunt, or someone was later convicted of the death in question), while another 18 were thought to result from “cryptic poaching.” This category comprised all sudden, unexpected losses of radio transmitter signal, where individuals could not be located with aerial searches, snow-tracking efforts, or DNA sampling of scat, and/or where circumstances strongly indicated that poaching was likely (for instance, there were police reports documenting an attempted poaching attempt).
In addition to collecting empirical data, the researchers also used mathematical modeling to estimate probable mortality rates associated with non-poaching, verified poaching, and suspected poaching, so that they could compare these with the rates actually observed in the wild.

Over the course of the 10-year study, poaching accounted for 51% of total mortality; 69% of these deaths could be attributed to cryptic poaching. Rates of cryptic poaching observed in the field were very similar to those calculated with the mathematical model, suggesting that this possible source of death was, in fact, very probable.

While the original study population included only 74 individuals, it eventually grew to 263. Although this sounds like a success story for this endangered species, growth would have been almost 4 times this (yielding 990 individuals) had there been no poaching. Even if only cryptic poaching had been absent, the population could have grown to 676 wolves.

The authors of the study are quick to point out that they cannot prove that what they have measured—in the field and with computer models—is actual poaching. However, their data clearly show that there is an additional source of wolf loss outside of natural death and known poaching. Since the wolf population on the Scandinavian population is very remote from the Finnish/Russian population and migration between these two groups is known to be extremely rare, it seems that cryptic poaching is the most likely cause of wolf loss in this area.

This has kept the annual growth rate to a mere 13.5%, despite the fact that it could theoretically be as high as 29.5%. Because of these slow growth rates, officials refuse to distribute permits for legally killing problem individuals. This, in turn, has increased wolf-human conflicts, meaning that, in effect, the poachers are undermining their own cause. Of course, they are also undermining the wolves’ cause, in more ways than one: The lack of genetic variation among the slowly-growing population has shrunk the gene pool to a dangerously small size, further constraining the animals’ ability to rebound from centuries of persecution.
Scandinavian wolves are not the only animals thought to suffer from cryptic poaching, rates of which have been estimated at anywhere from 32-74% among timber wolves, lynx (Lynx lynx), wolverines (Gulo gulo), and Amur tigers (Panthera tigris). In populations of these and other affected species, cryptic poaching can have a huge influence on conservation work. Thus, the authors of the current study suggest that researchers need to make an effort to better understand the role of this factor, and the uncertainty it causes in datasets; to this end, they advocate the development of more and improved methods of calculating this complex and influential variable.

Liberg, O., Chapron, G., Wabakke, P., Pedersen, H.C., Hobbs, N.T., and Sand, H. 2011. Shoot, shovel, and shut up: cryptic poaching slows restoration of a large carnivore in Europe. Proceedings of the Royal Society B, online advance publication.

Thanks to http://environment.no/Topics/Biological-diversity/Large-carnivores/Wolf/ for providing the images used in this post.

Sunday, 21 August 2011

Sunday Stuff: E. O. Wilson

Originally I had thought to profile some of my favorite "anthrophysic" books today, but when I realized how many of them were by the same author, I decided to focus on him, instead. That author, E. O. Wilson, has been a rather controversial figure in modern biology, and a huge influence on my own scientific career.

Wilson's career as an author began in 1967 when he collaborated with Robert MacArthur on The Theory of Island Biogeography, which sought to explain species richness (or lack thereof) on ocean islands. By and large, this theory has stood the test of time quite well, with the idea of "island biogeography" being used to explain population and community dynamics in any fragmented habitat--including anthropogenic areas where large roads and stretches of buildings separate patches of habitat that are suitable homes for wildlife. To this day, I still routinely read anthropogenic disturbance paper that cite Wilson and MacArthur's seminal work.

In 1971, Wilson published a second book entitled The Insect Societies, in which he examined the life history characteristics that cause social insects to behave as they do, and described the fascinating interactions that can be observed among individuals of these species. Wilson's main love--and the focus of his academic research--was ants, which not only inspired The Insect Societies, but also his Pulitzer Prize-winning The Ants, co-authored by Bert Holldobler; Journey to the Ants: A Scientific Exploration, also co-authored by Holldobler; Anthill: A Novel, Wilson's first foray into fiction; and his most recent work, The Leafcutter Ants: Civilization by Instinct, again co-authored by--you guessed it--Bert Holldobler.

Undoubtedly, Wilson's most controversial work was his 1975 book Sociobiology: The New Synthesis. In this volume, Wilson states that humans behave as they do--not only at the individual level, but also at various societal levels--as a result of evolution. I once asked my undergraduate sociology professor what he thought of the theory of sociobiology; he was so disgusted at the mention of the word that he would not answer except to say--emphatically--that it was rubbish. Actually, I think his precise word may have been "bullshit." Another opponent of sociobiological thinking was Wilson's colleague Stephen Jay Gould, with whom Wilson had an incredibly public feud over the issue. Siding with Gould were heavyweights such as Richard Lewontin and John Maynard Smith; advocates of Wilson's point of view include Steven Pinker and Richard Dawkins--and, for what it's worth, me.

Wilson's next book was the first that won him a Pulitzer Prize: On Human Nature. This book explores sociobiological concepts in a format that is accessible for a lay audience. Wilson reminds readers that humans are just a species of animal, and, like other animals (and, indeed, all other living creatures), we are subject to evolutionary processes at all levels of our existence. A corollary of this tenet is that biology is intimately linked with psychology, religion, sociology, politics, and pretty much any other field you can think of. While some readers may find these ideas threatening, I personally find them liberating, comforting, and--once you think about them--just plain obvious.

The theme of "interrelatedness" is expanded upon in Consilience, in which Wilson explores how different scientific fields have been unified over the years. He suggests that a similar process of unification among other fields of research--including such diverse areas as economics, the arts, the sciences, and politics--would advance our thought processes and lead to new innovations.

In the 1990's, Wilson increasingly began to focus on conservation and biodiversity. In 1992, he published The Diversity of Life, followed by The Biophilia Hypothesis, In Search of Nature (illustrated by Laura Southworth), The Future of Life, and The Creation: An Appeal to Save Life on Earth. The aforementioned Anthill also falls into this category, though it stands as the lone piece of fiction amidst this group of nonfiction volumes. Despite the fact that each of these books has been shaped around a plea to notice, value, and preserve the abundant beauty of our planet, they are all different enough that it is worthwhile to read each of them individually. Wilson has traveled widely during his life and has seen amazing things first-hand; his descriptions make you feel as though you are there with him, sharing his excitement at discovering and experiencing the amazing things that our planet has to offer.

The book in which this is most true is also my favorite, and the one book I can definitively say has changed my life: Naturalist, Wilson's 1994 autobiography. I was 13 when my dad gave me a copy of the book that he'd received as a press release. I had no idea who Wilson was or what he'd done, but I was mildly intrigued by the strange dust jacket picture of the distinguished-looking author peering at an ant specimen. One night, with nothing else to read, I found myself captured by the book's beautiful illustrations, and suddenly I was hooked--as were judges from the Los Angeles Times, who awarded the book the 1995 book prize for science and technology publication. It is, essentially, a romance: between boy and nature, young man and ant, adult scientist and discovery of knowledge. I have never read anything that so clearly drives home the message that you should always follow your heart and do the things you love; when you do, not only will you feel fulfilled yourself, but you can help others become so, too.

When I had to write an essay as part of my college applications, I discussed the importance of Naturalist in helping me decide that I wanted to become a biologist--and for inspiring me to pursue a career not only in science, but also in science communication, so that I, too, might help someone have an epiphany of his/her own one day. Imagine my surprise when the author himself arrived on my campus during my freshman year in order to speak at the dedication ceremony of our new integrated science center; imagine my excitement at meeting him, having him autograph my copy of Consilience, and getting the chance to tell him that he'd changed my life (I probably made a fool of myself, but I was so nervous at the time that I've almost completely blanked it from my memory now; at least I don't have to look back in embarrassment).

Many people agree that Wilson is probably a bit full of himself these days. When you've won over two dozen honors and recognitions for your work--work that includes generating and/or describing entirely new concepts never before articulated by any man--I suppose that's bound to happen. It's always a bit disappointing to find out that someone you admire is not 100% admirable, but I'm not perfect either. What really matters is that Wilson's writing is engaging and informative, with descriptions that are both accurate and exciting--because nature is an adventure, and even the most minute organisms and characteristics are full of meaning and importance.

That's one major reason why Wilson suggests that conservation is worth the effort. Another is that humans are just another species in the vast bio-catalog that is Earth. While we tend to think of ourselves as the most important creature, every other organism would say the same thing about itself, if it could. Wilson does an excellent job showing that we're all worthy in our own different ways; in some cases, that "worth" is actually literal--an economic, psychological, or ecological value.

Speaking of worth, if you're in the market for a little bio reading, it's worth a shot to try one of Wilson's two dozen or so books; with that many to choose from, you're bound to find something to keep you occupied. You might be infuriated, you might be fascinated, you might get depressed, you may find yourself uplifted...but you will definitely not be bored.

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

Friday, 19 August 2011

Changes in climate are associated with shifts in species' ranges

Those of you who routinely spend time outdoors may have noticed some disturbing trends over the last several years: Wildlife cannot always be found in the same place, or at the same time, as in the past. Studies have shown that, in many cases, this is because species are altering the timing of their life cycles and the placement of their home ranges. There is fairly conclusive evidence that changes in the timing of behaviors, such as migration and breeding, are closely related to variations in temperature. Specifically, because climate change has turned up the thermostat, "minimum appropriate temperatures" are reached earlier in the spring and later in the fall, causing a shift in when animals engage in certain behaviors. However, little work has been done to definitively link similar variations in geographic distribution with temperature change--until now.

Collaborators from the University of York, the Academia Sinica, Durham University, and the Centre for Ecology and Hydrology have just published a "meta-analysis" investigating this issue. Meta-analysis is a technique whereby researchers look for broad patterns in the results of multiple different studies that investigated related hypotheses. In this case, the authors looked at research documenting latitudinal and elevational range shifts (or lack thereof) for a variety of wildlife. The original field work was conducted in Europe, North America, Chile, Malaysia, and Marion Island, and covered as many as 1367 species in 31 different taxonomic groups.

The scientists calculated the average range shift across all species of a taxonomic group within a single region. In other words, they produced a single value for all birds in England, or all fish in the US, etc. The resulting analysis indicated that, on average, taxonomic groups have moved away from the Equator at a rate of 16.9 kilometers per decade, and have moved to higher elevations at a rate of 11.0 m uphill/decade. These values are significantly higher than those calculated by a meta-analysis from 2003 in which shifts were investigated at the species level. These differences may partly be due to the new data collected in the 8 years since the previous study, with which different species and habitats have been analyzed, and from which more extreme shifts may have been reported.

When the authors of the current study compared geographical range shifts with variations in local temperature, they found that changes in both latitude and elevation were significantly greater where temperatures had increased. The scientists also calculated the distances that individual species would need to move in order to consistently place themselves in habitats at the same temperature. These distances strongly correlated with shifts actually observed in the wild, indicating that species were "tracking" temperature changes and adjusting their behaviors accordingly.

Interestingly, both of these patterns were stronger for latitude than for elevation, despite the fact that less physical distance is required to achieve elevation-related temperature shifts. This may reflect the fact that temperature-appropriate elevations may be difficult to reach (for instance, require traveling between two mountain peaks separated by a valley), or the fact that elevation is associated with more complex variations in topography and microclimate (for example, cooler locations may be on different-facing slopes, as well as at higher elevations).

(Click on the map to see a bigger version where the font is easier to read.)

The researchers found that different groups of animals varied in how much, and in what way, they responded to increasing temperatures. For instance, while birds responded least in terms of elevation, they responded most in terms of latitude. Further, nearly a quarter of species shifted in the opposite direction as expected. This variation reflects a broader pattern of greater differences among species within a taxonomic group than among taxonomic groups, likely caused by time delays in responses (for instance, among immobile species or those that are not good at colonizing new locations), species-specific physiological constraints (including different sensitivities to temperatures), and alternative or interacting influences on habitat choice (for example, the need to coexist with a particular prey item).

In order to better understand which species are likely to shift their ranges, and why, it will be important to collect additional, finer-grained information on physiological, topographic, climatic, geological, and ecological constraints. These details should allow researchers to predict the consequences of habitat alterations and, potentially, develop plans to help species in need.

Chen, I.-C., Hill, J.K., Ohlemuller, R., Roy, D.B., Thomas, C.D. 2011. Rapid range shifts of species associated with high levels of climate warming. Science 333:1024-1026.

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

Thursday, 18 August 2011

Birds alter nest site preferences after exposure to human disturbance

Even the most well-meaning field researchers are often guilty of disturbing their study species, since visits to natural habitats involve activity and noise to which the animals would not otherwise be exposed. With a bit of caution, though, the negative impacts of these disturbances can be minimized. In some places, they can even be studied in order to elucidate the long-term impacts of such events.

This was the case at a field site in the Gahai Wetland, China, where collaborators from Lanzhou University were studying black redstarts (Phoenicurus ochruros). These birds nest in clay cavities originally dug into the earth by Tibetan ground tits (Pseudopodoces humilis). Although the original excavations include a small nesting chamber at the end of a long tunnel, the redstarts position their nests somewhere along the tunnel. The distance between the mouth of the tunnel and the nest can be used as an indicator of how worried the redstarts are about predation: If the adults feel that they are in danger, they should put nests closer to the exit in order to hear predators, and effect an escape, sooner; if they fear for their young, they should locate the nests further down the tunnel in order to make it difficult for predators to gain access to the chicks.
(Gahai Lake, China)
The scientists took advantage of these variations in order to investigate whether nesting redstarts responded to the presence of researchers as they would to predators—by shifting the placement of their nests between breeding attempts. This worked because the redstarts have high site fidelity, which means that they return to breed in the same areas in successive years. Thus, the researchers recorded the locations of nests during years when the birds had not been exposed to people during the nesting-building period; if the redstarts found the disturbance from the research project threatening, then when the birds returned to breed during subsequent seasons, they should have positioned their nests differently within the ground tit chambers.
(Black redstart, Phoenicurus ochruros)
Indeed, the proportion of nests at shallow locations (<20.0 cm from the mouth of the tunnel) decreased considerably after the introduction of researcher disturbance. Similarly, the average absolute value of nest depth increased between undisturbed and disturbed years, from approximately 20 cm to almost 40 cm.
The researchers were able to follow six individual females across multiple time points. Each bird responded similarly to exposure to humans: She built her nest at a greater depth the following year. Both of the failed nests recorded during the four-year study were caused by predation, indicating that attacks are a very real threat in this habitat (usually by common ravens, Corvus corax; red-billed choughs, Pyrrhocorax pyrrhocorax; and little owls, Athene noctua). These failures occurred at shallow depths, highlighting the benefit of shifting nests deeper in the chamber in response to nest-threatening disturbance.
(Black redstart nest. The birds will occupy any secondary "cavity"--including those that aren't fully enclosed and are made of anthropogenic materials.)
Prior to disturbance, mid-depth nests were dominant, which suggests that, in general, adults attempt to balance their safety needs with those of their young. The fact that they move their nests deeper in the cavities in response to anthropogenic activities suggests that redstarts view humans as a threat to their young, rather than to themselves. This response to “nonlethal predation” by humans shows that redstarts, like many other species of bird, are impacted even by innocuous human behaviors. It also indicates that at least some birds use previous experience with people to guide decision-making—in this case, at least a year later. Further work will be needed to determine just how long-term avian memory can be, and whether other species’ behaviors are also guided by recollections of unpleasant anthropogenic encounters.

Chen, J.-N., Liu, N.-F., Yan, C., and An, B. 2011. Plasticity in nest site selection of black redstart (Phoenicurus ochruros): a response to human disturbance. Journal of Ornithology 152:603-608.
Thanks to the following websites for providing the images used in this post: