A pristine stretch of Amazon rainforest–teeming with malaria-transmitting mosquitoes? Photo by Phil P. Harris

Most people consider saving the Amazon rainforest a noble goal, but nothing comes without a cost. Cut down a rainforest, and the planet looses untold biodiversity along with ecosystem services like carbon dioxide absorption. Conserve that tract of forest, however, and risk facilitating malaria outbreaks in local communities, a recent study finds.

Nearly half of malaria deaths in the Americas occur in Brazil, and of those nearly all originate from the Amazon. Yet few conservationists consider the forest’s role in spreading that disease. Those researchers who do take malaria into account disagree on what role forest cover plays in its transmission.

Some think that living near a cleared patch of forest–which may be pockmarked with ditches that mosquitoes love to breed in–increase malaria incidence. Others find the opposite–that living near an intact forest fringe brings the highest risk for malaria. Still more find that close proximity to forests decrease malaria risk because the mosquitoes that carry the disease are kept in check through competition with mosquitoes that don’t carry the disease. Most of the studies conducted in the past only focused on small patches of land, however.

To get to the bottom of how rainforests contribute to malaria risk, two Duke University researchers collected 1.3 million positive malaria tests from a period of four-and-a-half years, and ranging over an area of 4.5 million square kilometers in Brazil. Using satellite imagery, they added information about the local environment where each of the cases occurred and also took rainfall into account, because precipitation affects mosquitoes’ breeding cycles. Using statistical models, they analyzed how malaria incidences, the environment and deforestation interacted.

Their results starkly point towards the rainforest as the main culprit for malaria outbreaks. “We find overwhelming evidence that areas with higher forest cover tend to be associated with higher malaria incidence whereas no clear pattern could be found for deforestation rates,” the authors write in the journal PLoS One. People living near forest cover had a 25-fold greater chance of catching malaria than those living near recently cleared land. Men tended to catch malaria more often the women, implying that forest related jobs and activities–traditionally carried out by men–are to blame by putting people at greater risk for catching the disease. Finally, the authors found that people living next to protected areas suffered the highest malaria incidence of all.

Extrapolating these results, the authors calculated that, if the Brazilian government avoids just 10 percent of projected deforestation in the coming years, citizens living near those spared forests will contend with a 2-fold increase in malaria by 2050. “We note that our finding directly contradicts the growing body of literature that suggests that forest conservation can decrease disease burden,” they write.

The authors of the malaria study do not propose, however, that we should mow down the Amazon in order to obliterate malaria. “One possible interpretation of our findings is that we are promoting deforestation,” they write. “This is not the case.” Instead, they argue that conservation plans should include malaria mitigation strategies. This could include building more malaria detection and treatment facilities, handing out bed nets and spraying for mosquitoes.

This interaction between deforestation and disease outbreakis just one example of the way efforts to protect the environment can cause nature and humans to come into conflict. Around the world, other researchers have discovered that conservation efforts sometimes produce negative effects for local communities. Lyme disease–once all but obliterated–reemerged with a vengeance (pdf) in the northeastern U.S. when abandoned farmland was allowed to turn back into forest. Human-wildlife conflict–including elephants tearing up crops, tigers attacking livestock, and wolves wandering into people’s backyards–often comes to a head when a once-declining or locally extinct species makes a comeback due to conservation efforts.

“We believe there are undoubtedly numerous ecosystem services from pristine environments,” the PLoS One authors conclude. “However, ecosystem disservices also exist and need to be acknowledged.”

A potato affected by P. infestans, the pathogen responsible for the Irish Potato Famine. The exact strain involved in the 1840s famine has now been identified for the first time. Image via USDA

For nearly 150 years, starting in the late 17th century, millions of people living in Ireland subsisted largely off one crop: the potato. Then, in 1845, farmers noticed that their potato plants’ leaves were covered in mysterious dark splotches. When they pulled potatoes from the ground, most were shrunken, mushy and inedible. The blight spread alarmingly quickly, cutting yields from that year’s harvest in half. By 1846, harvest from potato farms had dropped to one quarter of its original size.

The disease—along with a political system that required Ireland to export large amounts of corn, dairy and meat to England—led to widespread famine, and nearly all of the few potatoes available were eaten, causing shortages of seed potatoes that ensured starvation would continue for nearly a decade. Ultimately, over one million people died, and another million emigrated to escape the disaster, causing Ireland’s population to fall by roughly 25 percent; the island has still not reached its pre-famine population levels today.

At the time, the science behind the blight was poorly understood, and most believed it was caused by a fungus. During the twentieth century, scientists determined that it was caused by an oomycete (a fungus-like eukaryote) called Phytophthora infestans. However, without access to the 1840s-era specimens, they couldn’t identify exactly which strain of the organism was responsible.

Now, an international group of scientists has gone back and sampled the DNA of Irish potato leaves preserved in the collections of London’s Kew Gardens since 1847. In doing so, they discovered that a unique, previously unknown strain of P. infestans that they call HERB-1 caused the blight.

Irish potato leaves from 1847, the height of the famine, used as part of the study. Image via eLife/Kew Gardens

The researchers, from the Sainsbury Laboratory in the UK and the Max Planck Institutes in Germany, came to the finding as part of a project sequencing DNA from 11 different preserved historial samples and 15 modern ones to track the evolution of the pathogen over time, published today in the journal eLife [PDF].

Currently, P. infestans is distributed worldwide, with the vast majority comprised of the destructive strain US-1. Most of the other strains of P. infestans occur only in Mexico’s Toluca Valley, where wild potato varieties are indigenous, so scientists long believed that US-1 had been responsible for the 1840s famine.

But when the researchers extracted small pieces of intact DNA from the old dried-out potato leaves, originally collected from from Ireland, Great Britain, Europe and North America, and compared them with present-day P. infestans specimens, they found that the strain responsible for the famine differed slightly from today’s US-1.

Based on their analysis of the genetic variation between the two strains and the other historical samples, they suggest that sometime in 1842 or 1843, the ancestor of the HERB-1 strain of P. infestans made it out of Mexico to North America and then to Europe, perhaps contained within the potatoes that ships carried as food for their passengers. Soon, it spread across the world, triggering famine in Ireland, and persisting until the 1970s, when it died out and was largely replaced by the US-1 strain. The two strains likely split apart sometime soon after their common ancestor made it out of Mexico.

The study is the first time that the genetics of a plant pathogen have been analyzed by extracting DNA from dried plant samples, opening up the possibility that researchers can study other plant diseases based on the historical collections of botanical gardens and herbaria around the world. Better understanding the evolution of plant diseases over time, the team says, could be instrumental in figuring out ways to breed more robust plant varieties that are resistant to the pathogens that infect plants today.

The invasive Spanish slug, one of the worst alien pests in Europe, is naturally repelled by ecosystems if soils house a healthy population of earthworms, new research suggests. Photo by Xauxa Håkan Svensson

They creep through a garden, lubricated by their own secretions, leaving a trail of mucus behind. In their wake is destruction–their rapacious appetites can require them to consume several times their own body weight each day, chomping roots and leaves with guillotine-like jaws and thousands of backward-pointing teeth. Hermaphroditic as adults, they lay tiny pearls of eggs easily mistaken for fertilizer beads in potting soil, allowing them to rampantly proliferate in gardens and nurseries.

They’re slugs, and their fleshy, squishy bodies are basically one huge stomach on a foot, driven by one overarching goal: to consume. Although some native slugs help decompose dead organic matter, returning nitrogen and other nutrients to the soil, the voracious hunger of several invasive species can destroy gardens and farms in the damp regions of the globe that slugs prefer to roam. Slugs are known to devour ornamentals, leafy shrubs and–because they enjoy slithering underground–bulbs, tubers and plant roots. If you see large, irregular holes in your hostas, you know who to thank.

New research, however, suggests that there might be simple ways to ward off slug damage. A study published this week in the journal BMC Ecology by scientists at the University of Natural Resources and Life Sciences Vienna shows that earthworms burrowing in the soil can protect plants overhead from being a slug’s next meal. Further, higher plant diversity also decreases the destruction slugs can wreak on individual plants.

To come to these findings, the researchers used large incubators to create mini grassland ecosystems in a laboratory setting. Different incubators contained different levels of plant diversity–between three to 12 species of either grasses, forbs, or legumes. After four weeks of plant growth, researchers introduced to the soil of some of the incubators a healthy amount earthworms (about 333 per square meter) who were free to burrow, convert organic matter into richer and more fertile soil, aerate soil, excrete nutrients in a more accessible form for plants and do the myriad of other things that earthworms do.

Five weeks later, two Spanish slugs (Arion vulgaris)–a critter in the top 100 worst alien species of Europe according to projects funded by the European Commission–were added to select micro-ecosystems and left there for one week. Throughout this week, plants were monitored periodically for slug damage.

If you’re hoping for an epic battle between slugs and earthworms, think again. Instead, the mere presence of earthworms reduced the number of leaves damaged due to slugs by 60 percent. Additionally, the researchers found that slugs ate 40 percent less in bins with high plant diversity than in those with low.

“Our results suggest that two processes might be going on,” explained lead author Johann Zaller in a statement. “Firstly, earthworms improved the plant’s ability to protect itself against slugs perhaps through the build-up of nitrogen-containing toxic compounds. Secondly, even though these slugs are generalists, they prefer widely available food.” As a result, in highly diverse ecosystems “slugs eat less in total because they have to switch their diets more often since plants of the same species are less available,” he added.

Earthworms may play a crucial role in helping plants defend themselves from being devoured by slugs. Photo by Flickr user goosmurf

Gardeners are familiar with the idea that varying up their plant beds helps preserve the plants most tasty to invasive slugs. But the tenacity of these slugs and their insatiable appetites cause many horticulturalists hover over their plants like helicopter parents, employing all sorts of methods to curb slug infestation.

Approaches vary in their effectiveness and efficiency. For example, those with the time and inclination to coddle their plants can tent cardboard overnight on the ground around prize plants to create a moist shelter for the nocturnal gastropods. Removing the newspaper in the morning often yields a writhing clutch of slugs, which can then be removed and killed. Quicker methods can be found with slug bait, but many can increase the toxicity of surrounding soil and can be harmful to wildlife and pets if ingested. Salting slugs–death by dessication–also can be harmful to nearby plants, as salt can interfere with the plant’s ability to uptake water.

Some gardeners place copper strips around the perimeter of flower beds–the copper supposedly reacts with slug slime to produce a kind of electric shock, repelling the creatures. Others use cans of stale beer, buried around a garden, as traps–the slugs, lured by beer’s fermented smell, get caught in the can, can’t escape and then drown. But the new results suggest that earthworms–already the gardener’s best friend because of their ability to improve soil fertility–may be even more effective than all these methods, highlighting the idea that organisms in soil can affect the health of organisms above ground.

Such interactions are largely ignored in ecological research, according to Zaller. “What we know from other studies is that earthworms change the nutrition of plants, thus enabling them to better respond to herbivores,” he told Surprising Science in an email. “As a response against herbivores, plants usually change their chemistry and they build up (costly) secondary chemicals in their leaves. If the nutrition of the plant is improved by the activity of earthworms, more of these defense compounds can be build up and the plant is better protected against herbivores.”

Of course, “one has always be very cautious in translating results from a specific experiment into the natural world,” Zaller continued. “In ecology many results are context specific, species-specific etc. Whether our results can be applied to other invasive slug species (or herbivores in general) would of course demand specific experiments. However, I would guess the mechanisms we suggest happening in our setting should be similar in settings involving different species.”

Periodical cicadas, like the one pictured above, have missed a lot of news about insects since they last appeared. Photo via Wikimedia Commons

After 17 years underground, billions of cicadas are ready to emerge and see sunlight for the first time. They will blanket the East Coast until around mid-June, buzzing like jackhammers in harmony as they search for a mate. Since 1996, the periodical insects, which belong to a group called Brood II, have lived as nymphs two feet deep in the soil, feeding on nothing but the liquid they suck out of tree roots. Once they crawl up to the surface, they molt, mate, lay eggs and die within a month.

Scientists are still trying to determine how periodical cicadas know when to emerge. But in the last 17 years, researchers have made some other important discoveries about other insects, some of whom also enjoy swarming the United States. Here are 17 news items about the bugs’ brethren since 1996.

1. British researchers figured out how insects fly. In 1996, scientists at the University of Cambridge solved the mystery of how many winged insects can produce more lift than can be explained by aerodynamic properties. The team unleashed hawkmoths into a wind tunnel with smoke and then took high-speed photos of the insects in flight. By studying how the smoke moved around the moths’ wings, researchers were able to determine that flying insects create whirling spirals of air above the front edges of their wings, providing more lift.

2. Cuba claimed that the United States brought an insect infestation to the island. In 1997, Cuban authorities accused the U.S. of staging a biological attack the previous year by using a crop-duster to spread insects over the island. But what really happened? An American commercial airliner had flown over the country and released smoke to signal its location, an event that coincided with bug infestations on Cuba’s potato plantations.

3. A plague of crickets ravaged the Midwest. In 2001, hordes of crickets descended upon Utah, infesting more than 1.5 million acres in 18 of the state’s 29 counties. The damaged wreaked on the ironically named Beehive State’s crops totaled nearly $25 million. Michael O. Leavitt, Utah’s governor at the time, declared the infestation an emergency and sought help from the U.S. Department of Agriculture in combating the little critters.

4. Scientists uncovered an entire new order of insects. In 2002, entomologists discovered a group of inch-long wingless creatures that comprised a new order, a taxonomic rank used in the classification of organisms. The first to be identified in 88 years at that time, the order, dubbed Mantophasmatodea, consists of insects with features similar to praying mantises. The finding became the 31st known insect order.

5. A swarm of butterflies, thought to be one single species, turned out to be 10 of them. In 2004, researchers used DNA barcoding technology to study the Astraptes fulgerator butterfly, whose habitat ranges from Texas to northern Argentina. What they found was remarkable: an insect that was thought to be one species was actually 10 different species. The species’ habitats overlapped, but the butterflies never bred with its doppelganger neighbors.

6. Researchers pinpointed the world’s oldest known insect fossil. Until 2004, a 400 million-year-old set of tiny insect jaws—originally found in a block of chert along with a well-preserved and well-studied fossil springtail—lay untouched for almost a century in a drawer at the Natural History Museum in London. The rediscovery and subsequent study of the specimen meant that true insects appeared 10 million to 20 million years earlier than once thought. The researchers believe these ancient insects were capable of flight, which would mean the tiny creatures took to the skies 170 millions years ago, before flying dinosaurs.

7. Brood X invaded the East Coast. In 2004, another group of cicadas known as Brood X emerged after 17 years underground. The bugs’ motto? Strength in numbers. This class is the largest of the periodical insects, including three different species of cicada.

8. America’s bee population started to plummet. By spring of 2007, more than a quarter of the country’s 2.4 million honeybee colonies had mysteriously vanished. Something prevented the bees from returning to their hives, and scientists weren’t sure why, but they gave it a name: colony-collapse disorder. According to a recent report by the U.S. Department of Agriculture, the phenomenon continues to plague apiaries across the country, and no cause has been determined.

9. Gypsy moths destroyed thousands of trees in New Jersey. In 2007, gypsy moths ravaged more than 320,000 acres of forest in the Garden State. One of North America’s most devastating forest pests, the insect feeds on the leaves of trees, stripping branches bare. Agricultural officials said the infestation was the worst of its kind since 1990.

10. Scientists figured out how to extract DNA from preserved insect specimens. In 2009, researchers removed a barrier from the study of early insects, a practice that often left ancient specimens destroyed. In the past, too much tinkering around with tiny specimens meant that the samples often became contaminated or eventually deteriorated. The scientists soaked nearly 200-year-old preserved beetles in a special solution for 16 hours, a process that allowed them to then carefully extract DNA from the bugs without damaging them.

11. Hundreds of ancient insect species were found lodged in one chunk of amber. In 2010, a team of international researchers discovered 700 new species of prehistoric insects inside a block of 50-million-year-old amber in India. The finding signaled to scientists that the area was much more biologically diverse than previously thought.

12. The first truly amphibious insects were discovered. In 2011, a study reported that 11 species of caterpillar with the ability to live underwater indefinitely were found in freshwater streams in Hawaii. The twist? The same insects studied were land-dwellers too.

13. Scientists discovered a cockroach with more than just a spring in its step. In 2011, a new species of cockroach, for whom jumping and hopping accounts for 71 percent of movement, was found in South Africa. Saltoblattella montistabularis can cover a distance 50 times its body length with each hop. Dubbed the leaproach, the insect relies on its powerful hind legs, which are twice the length of its other limbs and make up 10 percent of its body weight, to propel it forward in high-speed bursts.

14. Japanese scientists documented radiation-induced mutations in butterflies. When a massive earthquake and tsunami severely damaged the Fukushima nuclear power plant in 2011, dangerous radioactive materials were spewed into the air and waterways. The following year, Japanese researchers said they observed dented eyes and stunted wings in local butterflies, mutations they believe were a result of radiation exposure.

15. The East Coast suffered a stink bug epidemic. In the summer of 2011, growing numbers of stink bugs prompted the Environmental Protection Agency to issue an emergency ruling that would allow farmers to use lethal insecticides. The insects had invaded crops of apples, cherries, pears and peaches from Virginia to New Jersey.

16. The world’s largest insect was discovered in New Zealand. Scientist Mark Moffett, known as Doctor Bugs, discovered the world’s largest insect, a surprisingly friendly female Weta bug, while traveling in New Zealand in 2011. The massive creature has a wingspan of seven inches and weighs three times as much as a mouse. Here’s a video of the bug eating a carrot out of Moffett’s hand.

17. A fly found in Thailand was determined to be the smallest in the world. Discovered in 2012, the fly, named Euryplatea nanaknihali, is 15 times smaller than a house fly and tinier than a grain of salt. But don’t let the miniature bugs fool you: they feed on tiny ants by burrowing into the larger insects’ head casings, eventually decapitating them.

Helpless babe or capable professional navigator? Photo by Samuel Blanc

With their big, glossy black eyes and downy fluff, baby Weddell seal pups are some of the most adorable newborns in the animal kingdom. But these cute infants are far from helpless bundles of joy. New research published in the journal Marine Mammal Science reveals that Weddell seal pups likely possess the most adult-like brain of any mammal at birth.

The seal pups’ brains, compared to adult seals’ brain proportions, are the largest known for any mammal to date. The researchers write that this is “remarkable” considering that the pups are quite small at birth compared to many other newborn mammals.

To arrive at these findings, a team of researchers from the Smithsonian Environmental Research Center and the National Museum of Natural History traveled to Antarctica to collect fresh pups specimens. They took advantage of the fact that many pups never make it to adulthood due to stillbirths, abandonment and accidental death, such as being crushed by an adult. The researchers collected 10 dead seal pups (which quickly freeze in the Antarctic temperatures), conducted a few measurements and then decapitated and shipped the frozen heads back to the Smithsonian. They also tossed in a couple adult Weddell seal heads into the mix, one of which had died from acute toxemia–possibly from its gut being punctured by a fish spine–and the other whose cause of death could not be determined.

Back in the U.S., the researchers partially thawed the skulls in a lab and–like a well picked-over Thanksgiving turkey–manually peeled the tissue off of the baby seal faces. Then, they drilled into the skulls to extract the intact brains. Finally, they put the bones into a tank full of flesh-eating beetles to remove any remaining scraps of meat. Clean skulls and brains in hand, they went about taking measurements, and they also drew upon measurements of some older Weddell Seal skull specimens from the museum’s collection.

Remarkably, baby Weddell seal brains are already 70 percent developed at birth, the team found. Compare this to human infants, whose brains are a mere 25 percent of their eventual adult mass. As a Smithsonian statement explains, baby animals born with proportionally larger brains usually live in challenging environments in which they need to act quickly in order to survive. Other animals that share this trait include most marine mammals, zebras and wildebeest.

For Weddell seal pups, large brains likely help with diving under ice sheets and orienting themselves under water at less than three weeks old–an extremely dangerous task for any mammal, newborn or not. The pups must acclimate quickly since Weddell seal mothers abandon their young at about 6 weeks old, meaning they need to be able to completely fend for themselves when that day arrives.

In nature, however, everything comes with a price. The Weddell seal pups may have the biggest, best developed brains on the block when compared to what they will be as adults, but this metabolically taxing organ requires excessive energy to maintain. A pup weighing just 65 pounds needs between 30 to 50 grams of glucose per day in order to survive, and the team estimates that the energetically hungry brain may account for a full 28 grams of that demand. 

Luckily for the seal pups, their mothers’ milk is almost exactly matched to the babies’ caloric needs. Weddell seal milk supplies about 39 grams of sugar per day. Females seals, however, lose significant weight while tending to their young, which jeopardizes their own survival. At their mother’s cost, the babies’ brains are allowed to thrive. That is, until their mother decides she’s had enough with the nurturing and leaves her pups to survive on their own.   

How many unborn brothers and sisters did this sand tiger shark devour to be here today? Photo by Amada44

Baby animals may seem irresistibly adorable, but in reality many of them are calculating killers. Hyena, wolf or even dog litter runts are pushed aside by their larger siblings and left to go hungry; fuzzy white egret chicks will kick their weaker clutch mates out of the nest to certain doom; and  baby golden eagles sometimes go so far as to snack on their smaller brothers and sisters while their mother looks on.

Perhaps most disturbing of all, however, is the case of the baby sand tiger shark. While sharks may not be the most snuggly animals to begin with, the sand tiger shark sets a new precedent for fratricide. This species practices a form of sibling-killing called intrauterine cannibalization. Yes, “intrauterine” refers to embryos in the uterus. Sand tiger sharks eat their brothers and sisters while still in the womb.

Even by nature’s cruel standards, scientists admit that this is an unusual mode of survival. When sand tiger sharks develop in their mother’s uteri (females have both a left and right uterus), some–usually the embryo that hatched first from its encapsulated, fertilized egg–inevitably grow faster and larger than others. Once the largest embryos cross a certain size threshold, the hungry babies turn to their smaller siblings as convenient meals. “The approximately 100 mm hatchling proceeds to attack, kill and eventually consume all of its younger siblings, achieving exponential growth over this period,” a team of researchers who investigated the phenomenon wrote this week in Biology Letters.  

Size differential between a recent hatchling (H) and an older embryo (E) from the same uterus in a typical litter the researchers samples. Photo by Chapman et al., Biology Letters

From what began as two uteri full of a dozen embryos results in just two dominating baby sand tiger sharks coming full term. What’s more, once the unborn babies consume all of the living embryos, they turn to their mother’s unfertilized eggs next, in a phenomenon called oophagy, or egg-eating. By the time those two surviving babies are finally ready to be introduced into the big, bright world, all of the pre-birth inner feasting has paid off. They emerge from their mother measuring in at about 95 to 125 centimeters long, or a bit longer than a baseball bat, meaning fewer predators can pick them off than if they had shared food with siblings and were smaller.   

This peculiar situation has implications for the genetic makeup of the species. Female sand tiger sharks, like many animals, mate with multiple males. Oftentimes in nature, females determine which males will sire the next generation by selectively choosing to mate with the most impressive bachelor (or bachelors) around. If mating with multiple males at any given time–as sharks, insects, dogs, cats and many other animals sometimes do–the babies that the female eventually produces share the same womb with siblings that may have different fathers. 

In this case, however, there are two modes of selection at work. Females may choose mates, but that does not guarantee those males’ genes will make the cut. The embryos the males sire will also have to survive the subsequent frenzy of cannibalism going on inside the female’s body. 

To find out whether some males are mating but missing out on actually producing offspring, the authors of this new study undertook microsatellite DNA profiling of 15 sand tiger shark mothers and their offspring. The researchers collected the sharks from accidental mortality events near protected beaches in South Africa between 2007 to 2012. By comparing the embryo genetics, the researchers could determine how many fathers were involved in fertilizing the eggs.

Nine of the females, or 60 percent, had mated with more than one male, the researchers found. When it came to which embryos hatched and grew large first (and thus would have survived if their mothers hadn’t have been killed), 60 percent shared the same father. This means that even if a female mates with more than one male, there is no guarantee that the male has been successful in passing on his genes. Rather, he could have just provided a convenient entree for another male’s offspring.

This also explains some male sand tiger shark behavior and physiology. Male sand tiger sharks often guard their mates against other males just after copulation. Males of this species also produce a conspicuously large amount of sperm compared to other sharks. Both of these characteristics increase the likelihood that the embryo fertilized by that male will successfully implant in the female’s uterus earlier, giving it a significant head start for developing more quickly than its siblings, which makes it more likely that the recent mate’s offspring will eat the others that may come along.

As for the females sand tiger sharks, some researchers think they actually may not have much of a choice when it comes to mating with multiple males.  It could be that females just give in to some amorous partners because the energetic cost of resisting those advances outweighs the cost of just conceding to the act–a behavior biologists call the convenience polyandry hypothesis. In this case, however, females may still get the final laugh since the males they first mated with and most likely preferred will have the greater chance of actually triumphing as the father of their children. “[Embryonic cannibalism] may allow female sand tigers to engage in convenience polyandry after mating with preferred males without actually investing in embryos from these superfluous copulations,” the researchers speculate.

While the females did invest in initially developing those doomed embryos, those investments are much smaller than what would be required to bring multiple embryos to full term. Those smaller embryos also represent resources allocated to the stronger, dominate embryonic winners, which thus have a better chance of surviving and passing on their mother’s genes than if she had spent the energy to instead birth multiple, weakling babies. In a way, the mother shark is providing nourishment for her strongest babies by producing multiple embryos that the most robust can eat. 

“This system highlights that competition and sexual selection can still occur after fertilization,” the authors write. For example, the first embryo to implant may not end up being the the one that survives the gladiator arena of the sharks uterus. While this new research still needs to delve into the details of the competition that takes place within the uterus, a picture is emerging based upon these initial findings: Females may chose which males to mate with or may be coerced into reluctantly mating, but male sperm fitness and the quality of the embryos they produce could also carry significant weight in which animals ultimately wind up as winners in this system. 

“This competition can play an important and probably under-appreciated role in determining male fitness,” the authors conclude. 

A baby cao vit gibbon learns to search for food. Photo: Zhao Chao 赵超, Fauna and Flora International

You probably haven’t heard of the world’s second rarest ape, the cao vit gibbon. Scientists know of only one place the species still lives in the wild. In the 1960s, things got so bad for the cao vit gibbon that the species was declared extinct. But in 2002, to the surprise and elation of conservationists, the animals—whose shaggy coats can be a fiery orange or jet black—turned up along Vietnam’s remote northern border. Several years later, a few gibbons were found in China, too.

Also known as the eastern black-crested gibbon, the cao vit gibbons once covered an expanse of forest spanning from southern China and northern Vietnam just east of the Red River, but today only about 110 individuals survive. This gibbon is highly inclined to stick to the trees—in a previous study, during more than 2,000 hours spent observing gibbons in the field, researchers saw only once and very briefly one young male cao vit gibbon come down from the canopy and walk on a rock for a few seconds. Population surveys based on watching the animals in the branches reveal that the gibbons live in 18 groups scattered throughout the area. That makes it the second least populous species of ape, just after the Hainan gibbon, another type of extremely rare gibbon living in the same area of Asia.

In 2007 and 2009, Vietnam and then China hustled to establish special protected areas dedicated to preventing the cao vit gibbon’s extinction. Much of the area surrounding the remaining populations of gibbons is quickly being converted to agricultural fields and pasturesor cut down to make charcoal to sell and use at home, a common practice in the area. Hunting—though illegal—is also an issue, as exotic wild meat dinners are popular with locals in the region.

For an endangered species to recover rather than just survive, it needs to grow in numbers. But any given patch of land can only support so many animals given the amount of food and space that’s available. If populations exceed this threshold—called a carrying capacity—then animals will either starve, get picked off by predators or have to move somewhere else. 

Researchers from Dali University in Yunnan, the Chinese Academy of Sciences in Kunming and the Chinese Research Academy of Environmental Sciences in Beijing wanted to find out how much of the protected forest the cao vit gibbons had expanded into, and also how many animals that pocket of land could eventually support. To answer this question, they turned to high-resolution satellite images, describing their results in the journal Biological Conservation.

Once they acquired aerial images of the gibbons’ habitat, they classified it into forest, scrub, shrub land and developed areas. This was important because gibbons can only live high in forest canopies, meaning the latter three categories were out of bounds for potentially supporting the animals. Overall, the area could be divided into five different zones that were split apart by either roads or rivers. From there, the researchers plugged the data into computer models that ranked possible gibbon habitat from high to low quality.

Habitat quality over the five zones the researchers identified. Stars mark sites where gibbons currently live. Image from Fan et al., Biological Conservation

Their results revealed several bits of news, some good and some bad. First, from the models it seems that 20 groups of gibbons could eventually live in the protected forest areas before the population reaches its carrying capacity threshold. However, as human development creeps closer and closer, that disturbance could lower that figure. As things stand, the gibbons will likely reach their carrying capacity in the current habitat in 15 years, which doesn’t bode well for building up the species’ numbers.

There are a couple options. The protected area isn’t all great habitat, it turns out. Some of it is just mediocre for gibbons. If that span of forest could be improved, it could eventually support up to 26 groups of animals. The researchers also identified two other potential areas where gibbons could live if they could somehow manage to travel there (no gibbon has ever been known to cross a river or a road). But these patches of welcoming forest, located in Vietnam, are not protected, so they likely will not remain forests for long. If the government decided to protect those areas, the researchers write, they could serve as places for cao vit gibbons to live in the future, especially if narrow corridors of trees connecting the two areas were protected and restored as well.

If these patches of forest were protected, gibbons would not be the only species to benefit. Numerous other species of primates and monkeys, civets, pangolins, porcupines, birds, bats and many more depend upon those last remaining jungle habitats for survival. “In summary, the last remaining population of cao vit gibbon is nearing its carrying capacity in the current remaining forest patch,” the authors write. “Forest protection and active forest restoration using important food tree plantings to increase habitat quality and connectivity should be the most critical part of the ongoing conservation management strategy.”

Emperor penguins swimming. Photo by Polar Cruises

Penguins seem a bit out of place on land, with their stand-out black jackets and clumsy waddling. But once you see their grace in the water, you know that’s where they’re meant to be–they are well-adapted to life in the ocean.

April 25 of each year is World Penguin Day, and to celebrate here are 14 facts about these charismatic seabirds.

1. Depending on which scientist you ask, there are 17–20 species of penguins alive today, all of which live in the southern half of the globe. The most northerly penguins are Galapagos penguins (Spheniscus mendiculus), which occasionally poke their heads north of the equator.

2. While they can’t fly through the air with their flippers, many penguin species take to the air when they leap from the water onto the ice. Just before taking flight, they release air bubbles from their feathers. This cuts the drag on their bodies, allowing them to double or triple their swimming speed quickly and launch into the air.

3. Most penguins swim underwater at around four to seven miles per hour (mph), but the fastest penguin—the gentoo (Pygoscelis papua)—can reach top speeds of 22 mph!

Gentoo penguins “porpoise” by jumping out of the water. They can move faster through air than water, so will often porpoise to escape from a predator. Photo: Gilad Rom (Flickr)

4. Penguins don’t wear tuxedos to make a fashion statement: it helps them be camouflaged while swimming. From above, their black backs blend into the dark ocean water and, from below, their white bellies match the bright surface lit by sunlight. This helps them avoid predators, such as leopard seals, and hunt for fish unseen.

5. The earliest known penguin fossil was found in 61.6 million-year old Antarctic rock, about 4-5 million years after the mass extinction that killed the dinosaurs. Waimanu manneringi stood upright and waddled like modern day penguins, but was likely more awkward in the water. Some fossil penguins were much larger than any penguin living today, reaching 4.5 feet tall!

6. Like other birds, penguins don’t have teeth. Instead, they have backward-facing fleshy spines that line the inside of their mouths. These help them guide their fishy meals down their throat.

An endangered African penguin brays with its mouth open, showing off the bristly inside of its mouth. Photo by Dimi P (Flickr), with permission

7. Penguins are carnivores: they feed on fish, squid, crabs, krill and other seafood they catch while swimming. During the summer, an active, medium-sized penguin will eat about 2 pounds of food each day, but in the winter they’ll eat just a third of that.

8. Eating so much seafood means drinking a lot of saltwater, but penguins have a way to remove it. The supraorbital gland, located just above their eye, filters salt from their bloodstream, which is then excreted through the bill—or by sneezing! But this doesn’t mean they chug seawater to quench their thirst: penguins drink meltwater from pools and streams and eat snow for their hydration fix.

9. Another adaptive gland—the oil (also called preen) gland—produces waterproofing oil. Penguins spread this across their feathers to insulate their bodies and reduce friction when they glide through the water.

10. Once a year, penguins experience a catastrophic molt. (Yes, that’s the official term.) Most birds molt (lose feathers and regrow them) a few at a time throughout the year, but penguins lose them all at once. They can’t swim and fish without feathers, so they fatten themselves up beforehand to survive the 2–3 weeks it takes to replace them.

An emperor penguin loses its old feathers (the fluffy ones) as new ones grow in underneath. Photo by Carlie Reum, National Science Foundation

11. Feathers are quite important to penguins living around Antarctica during the winter. Emperor penguins (Aptenodytes forsteri) have the highest feather density of any bird, at 100 feathers per square inch. In fact, the surface feathers can get even colder than the surrounding air, helping to keep the penguin’s body stays warm.

12. All but two penguin species breed in large colonies for protection, ranging from 200 to hundreds of thousands of birds. (There’s safety in numbers!) But living in such tight living quarters leads to an abundance of penguin poop—so much that it stains the ice! The upside is that scientists can locate colonies from space just by looking for dark ice patches.

13. Climate change will likely affect different penguin species differently—but in the Antarctic, it appears that the loss of krill, a primary food source, is the main problem. In some areas with sea ice melt, krill density has decreased 80 percent since the 1970s, indirectly harming penguin populations. However, some colonies of Adelie penguins (Pygoscelis adeliae) have grown as the melting ice exposes more rocky nesting areas.

14. Of the 17 penguin species, the most endangered is New Zealand’s yellow-eyed penguin (Megadyptes antipodes): only around 4,000 birds survive in the wild today. But other species are in trouble, including the erect-crested penguin (Eudyptes sclateri) of New Zealand, which has lost approximately 70 percent of its population over the past 20 years, and the Galapagos penguin, which has lost more than 50 percent since the 1970s.

  Learn more about the ocean from the Smithsonian’s Ocean Portal.

Hikers ascend through the smog of  Los Angeles, one of six cities where researchers studied the effects of air pollution on the heart. By Flickr User Jason Morrison

One morning a couple of years ago, I decided to take a jog around the perimeter of my hotel in Delhi, India. A little bit of exercise might mitigate the crushing jetlag after my 24-hour flight from California, I thought. Within a minute or two of sucking in the city’s soot-filled air, my lungs and eyes were scorched. While I knew that Delhi’s air quality was bad, I had no idea it’s the 12th worst in the world—nor was I aware of precisely how damaging air pollution can be to the body.

As we’ve written about recently, researchers have discovered that smog can cause lung cancer and that nano-particles in the air burrow through cell membranes, possibly damaging the lungs and the circulatory system. But a new study published today in the journal PLOS Medicine shows that exposure to fine particulate matter in the air may be linked to a faster hardening of the arteries in otherwise healthy people, which can lead to increases in stroke and heart attack.

The study, conducted by researchers from University of Michigan and University of Washington, followed nearly 5,500 people—all heart-disease-free—from six American metro areas (Baltimore; Chicago; Los Angeles; New York City; Winston Salem, North Carolina and St. Paul, Minnesota). Scientists began the study by conducting ultrasound tests to measure the thickness of each participant’s right common carotid artery, which supplies blood to the head, neck, and brain.

Residents of New York City participated in a study that linked air pollution to increased risk of heart attack and stroke. By Flickr user JRGCastro

The participants’ home addresses were then recorded, and the researchers tapped the Environmental Protection Agency’s Air Quality System, a database of air quality levels gathered by monitors throughout the country, to gauge the amount of fine particulate matter in their neighborhoods. The scientists were able to factor in variables including proximity to major streets and highways, which allowed for a great deal of precision–air pollution concentrations varied, as it turned out, even within specific neighborhoods. Within the next five years, the thickness of each participant’s artery was tested once more. The scientists estimated their exposure to fine particulate matter during the period between the exams.

What they found was that exposure to higher concentrations of fine particulate air pollution correlated with an accelerated thickening of the arteries. Conversely, reductions in air pollution were linked with a slower progression of arterial thickening. Such a thickening or hardening of the arteries can eventually block the flow of blood to the head, resulting in stroke, or to the heart, causing heart attack.

“Linking these findings with other results from the same population suggests that persons living in a more polluted part of town may have a 2 percent higher risk of stroke as compared to people in a less polluted part of the same metropolitan area,” study author Sara Adar said in a statement.

The findings may also help shed light on previous studies that have linked chronic air pollution exposure and death, and may encourage lawmakers to support clean air standards. “Our findings furthermore bolster recent reports that falling pollution levels in the United States after the adoption of the Clean Air Act are associated with reduced mortality and increased life expectancy,” the study authors wrote.

Air quality in the United States is far superior to that in many parts of the world. But where is air quality the worst? The World Health Organization’s database of global air pollution statistics reveals that low- and middle-income regions of the Eastern Mediterranean have the worst air quality overall. Among cities, Ahwaz in Iran is the world’s most polluted. Mongolia’s Ulan Bataar ranks second in air pollution and Delhi comes in 12th.

The W.H.O. rankings are based on the number of parts per million of particles smaller than 10 micrometers (PM10) floating around in the air. Even the filthiest air in the U.S., in California’s San Joaquin Valley, pales in comparison to these other cities. Ahwaz has 372 PM10, while Delhi has 198. Bakersfield, the most polluted city in the U.S., has 38.

The best cities in the U.S. for keeping your arteries free and clear? Santa Fe, New Mexico and Clearlake, California–each with a PM10 of just six. Much healthier choices for a jog the next time around.

This chimp may look innocent, but he may harbor any of dozens of diseases that infect humans. Photo by AfrikaForce

Anyone who has read a Richard Preston book, such as The Hot Zone or Panic in Level 4, knows the danger of tampering with wildlife. The story usually goes something like this: Intrepid explorers venture into a dark, bat infested cave in the heart of East Africa, only to encounter something unseen and living, which takes up residence in their bodies. Unknowingly infected, the happy travelers jump on a plane back to Europe or the States, spreading their deadly pathogen willy-nilly to every human they encounter upon the way. Those people, in turn, bring the novel virus or bacterium back home to strangers and loved ones alike. Before the world knows it, a pandemic has arrived.

This scenario may sound like fiction, but it’s exactly what infectious disease experts fear most. Most emerging infectious diseases in humans have indeed arisen from animals–think swine and bird flu (poultry and wild birds), SARS (unknown animals in Chinese markets), Ebola (probably bats) and HIV (non-human primates). Therefore, experts prioritize the task of figuring out which animals in which regions of the world are most prone to delivering the latest novel pathogen to hapless humanity.

With this in mind, researchers at Harvard University, the University of Granada and the University of Valencia set out to develop a new strategy for predicting the risk and rise of new diseases transmitted from animals before they happen, describing their efforts in the journal Proceedings of the National Academy of Sciences.

To narrow the hypothetical disease search down, the team chose to focus on non-human primates. Because monkeys and great apes are so closely related to us, their potential for developing and transmitting a pathogen suited to the human body is greater than the equivalent risk from animals such as birds or pigs. As a general rule, the more related species are, the greater the chances they can share a disease. The researchers gathered data from 140 species of primates. They overlaid that information with more than 6,000 infection records from those various primate species, representing 300 different pathogens, including viruses, bacteria, parasitic worms, protozoa, insects and fungus. This way, they could visualize which pathogens infect which species and where.

Like mapping links between who-knows-who in a social network, primates that shared pathogens were connected. This meant that the more pathogens an animal shared with other species, the more centrally located it was on the tangled web of the disease diagram.    

A diagram depicting shared parasites among primate species. Each bubble represents one species, with lines connecting species by shared pathogens. The larger the bubble, the more emerging infectious diseases that species harbors. The dark blue bubbles represent the top 10 primates that share the most emerging infectious diseases with humans. Photo by Gomez et al., via PNAS

From studying these charts, a few commonalities emerged. Animals at the center of the diagram tended to be those that lived in dense social groups and also covered a wide geographic range (yes, similar to humans). These species also tended to harbor parasites that are known to infect humans, including more pathogens identified as emerging infectious diseases. In other words, those species that occurred in the center of the diagram are the best positioned to kick off the next pandemic or horrific infectious disease, and thus should be the ones that experts should keep the closest watch on.

Such animals could qualify as “superspreaders,” or those that receive and transmit pathogens very often to other species.”The identification of species that behave as superspreaders is crucial for developing surveillance protocols and interventions aimed at preventing future disease emergence in human populations,” the authors write.

Apes appeared in the heart of the disease diagram and are among the species we should be most worried about, which is not surprising considering that diseases such as malaria and HIV first emerged from these animals. On the other hand, some non-ape primates, including baboons and vervet monkeys, also popped up in the center of the diagram and turn out to harbor many human emerging disease parasites. 

Currently, our ability to predict where, when and how new emerging infectious diseases might arise is “remarkably weak,” they continue, but if we can identify those sources before they become a problem we could prevent a potential health disaster on a regional or even global scale. This new approach for identifying animal risks, the authors write, could also be applied to other wildlife groups, such as rodents, bats, livestock and carnivores. “Our findings suggest that centrality may help to detect risks that might otherwise go unnoticed, and thus to predict disease emergence in advance of outbreaks—an important goal for stemming future zoonotic disease risks,” they conclude. 

By combining genes from different bacteria species, scientists created E. coli that can produce diesel fuel from fat. Image via Marian Littlejohn/PNAS

Over the past few decades, researchers have developed biofuels derived from an remarkable variety of organisms—soybeans, corn, algae, rice and even fungi. Whether synthesized into ethanol or biodiesel, though, all of these fuels suffer from the same limitation: They have to be refined and blended with heavy amounts of conventional, petroleum-based fuels to run in existing engines.

Though this is far from the only current problem with biofuels, a new approach by researchers from the University of Exeter in the UK appears to solve at least this particular issue with one fell swoop. As they write today in an article in Proceedings of the National Academy of Sciences, the team has genetically engineered E. coli bacteria to produce molecules that are interchangeable to the ones in diesel fuels already sold commercially. The products of this bacteria, if generated on a large-scale, could theoretically go directly into the millions of car and truck engines currently running on diesel worldwide—without the need to be blended with petroleum-based diesel.

The group, led by John Love, accomplished the feat by mixing and matching genes from several different bacteria species and inserting them into the E. coli used in the experiment. These genes each code for particular enzymes, so when the genes are inserted into the E. coli, the bacteria gains the ability to synthesize these enzymes. As a result, it also gains the ability to perform the same metabolic reactions that those enzymes perform in each of the donor bacteria species.

By carefully selecting and combining metabolic reactions, the researchers built an artificial chemical pathway piece-by-piece. Through this pathway, the genetically modified E. coli growing and reproducing in a petri dish filled with a high-fat broth were able to absorb fat molecules, convert them into hydrocarbons and excrete them as a waste product.

Hydrocarbons are the basis for all petroleum-based fuels, and the particular molecules they engineered the E. coli to produce are the same ones present in commercial diesel fuels. So far, they’ve only produced tiny quantities of this bacterial biodiesel, but if they were able to grow these bacteria on a massive scale and extract their hydrocarbon products, they’d have a ready-made diesel fuel. Of course, it remains to be seen whether fuel produced in this way will be able to compete in terms of cost with conventional diesel.

Additionally, energy never comes from thin air—and the energy contained within this bacterial fuel mostly originates in the broth of fatty acids that the bacteria are grown on. As a result, depending on the source of these fatty acids, this new fuel could be subject to some of the same criticisms leveled at biofuels currently in production.

For one, there’s the argument that converting food (whether corn, soybeans or other crops) into fuel causes ripple effects in global food market, increasing the volatility of food prices, as a UN study from last year found. Additionally, if the goal of developing new fuels is to fight climate change, many biofuels fall dramatically short, despite their environmentally-friendly image. Using ethanol made from corn (the most widely used biofuel in the U.S.), for example, is likely no better than burning conventional gasoline in terms of carbon emissions, and maybe actually be worse, due to all the energy that goes into growing the crop and processing it info fuel.

Whether this new bacteria-derived diesel suffers from these same problems largely depends upon what sort of fatty acid source is eventually used to grow the bacteria on a commercial scale—whether it would by synthesized from a potential food crop (say, corn or soy oil), or whether it could come from a presently-overlooked energy source. But the new approach already has one major advantage: Just the steps needed to refine other biofuels so they can be used in engines use energy and generate carbon emissions. By skipping these steps, the new bacterial biodiesel could be an energy efficient fuel choice from the start.

Image via NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Last year, to celebrate the 42nd Earth Day, we took a look at 10 of the most surprising, disheartening, and exciting things we’d learned about our home planet in the previous year—a list that included discoveries about the role pesticides play in bee colony collapses, the various environmental stresses faced by the world’s oceans and the millions of unknown species are still out in the environment, waiting to be found.

This year, in time for Earth Day on Monday, we’ve done it again, putting together another list of 10 notable discoveries made by scientists since Earth Day 2012—a list that ranges from specific topics (a species of plant, a group of catfish) to broad (the core of planet Earth), and from the alarming (the consequences of climate change) to the awe-inspiring (Earth’s place in the universe).

Even the supposedly pristine Antarctic landscape is marred by trash heaps. Image via Germany Federal Environment Agency Report (PDF)

1. Trash is accumulating everywhere, even in Antarctica. As we’ve explored the most remote stretches of the planet, we’ve consistently left behind a trail of one supply in particular: garbage. Even in Antarctica, a February study found (PDF), abandoned field huts and piles of trash are mounting. Meanwhile, in the fall, a new research expedition went to study the Great Pacific Garbage Patch, counting nearly 70,000 pieces of garbage over the course of a month at sea.

2. Climate change could erode the ozone layer. Until recently, atmospheric scientists viewed climate change and the disintegration of the ozone layer as entirely distinct problems. Then, in July, Harvard researcher Jim Anderson (who won a Smithsonian Ingenuity Award for his work) led a team that published the troubling finding that the two might be linked. Some warm summer storms, they discovered, can pull moisture up into the stratosphere, an atmospheric layer 6 miles up. Through a chain of chemical reactions, this moisture can lead to the disintegration of ozone, which is crucial for protecting us from ultraviolet (UV) radiation. Climate change, unfortunately,  is projected to cause more of these sorts of storms.

3. This flower lives on exactly two cliffs in Spain. In September, Spanish scientists told us about one of the most astounding survival stories in the plant kingdom: Borderea chouardii, an extremely rare flowering plant that is found on only two adjacent cliffs in the Pyrenees. The species is believed to be a relic of the Tertiary Period, which ended more than 2 million years ago, and relies on several different local ant species to spread pollen between its two local populations.

4. Some catfish have learned to kill pigeons. In December, a group of French scientists revealed a phenomenon they’d carefully been observing over the previous year: a group of catfish in Southwestern France had learned how to leap onto shore, briefly strand themselves, and swim back into the water to consume their prey. With more than 2,000,000 Youtube views so far, this is clearly one of the year’s most widely enjoyed scientific discoveries.

5. Fracking for natural gas can trigger moderate earthquakes. Scientists have known for a while that whenever oil and gas are extracted from the ground at a large scale, seismic activity can be induced. Over the past few years, evidence has mounted that injecting water, sand and chemicals into bedrock to cause gas and oil to flow upward—a practice commonly known as fracking—can cause earthquakes by lubricating pre-existing faults in the ground. Initially, scientists found correlations between fracking sites and the number of small earthquakes in particular areas. Then, in March, other researchers found evidence that a medium-sized 2011 earthquake in Oklahoma(which registered a 5.7 on the moment magnitude scale) was likely caused by injecting wastewater into wells to extract oil.

6. Our planet’s inner core is more complicated than we thought. Despite decades of research, new data on the iron and nickel ball 3,100 miles beneath our feet continue to upset our assumptions about just how the earth’s core operates. A paper published last May showed that iron in the outer parts of the inner core is losing heat much more quickly than previously estimated, suggesting that it might hold more radioactive energy than we’d assumed, or that novel and unknown chemical interactions are occurring. Ideas for directly probing the core are widely regarded as pipe dreams, so our only options remains studying it from afar, largely by monitoring seismic waves.

The berries of Pollia condensata were found to produce the most intense color in the natural world. Image via PNAS

7. The world’s most intense natural color comes from an African fruit. When a team of researchers looked closely at the blue berries of Pollia condensata, a wild plant that grows in East Africa, they found something unexpected: it uses an uncommon structural coloration method to produce the most intense natural color ever measured. Instead of pigments, the fruit’s brilliant blue results from nanoscale-size cellulose strands layered in twisting shapes, which which interact with each other to scatter light in all directions.

8. Climate change will let ships cruise across the North Pole. Climate change is sure to create countless problems for many people around the world, but one specific group is likely to see a significant benefit from it: international shipping companies. A study published last month found that rising temperatures make it probable that during summertime, reinforced ice-breaking ships will be able to sail directly across the North Pole—an area currently covered by up to 65 feet of ice—by the year 2040. This dramatic shift will shorten shipping routes from North America and Europe to Asia.

9. One bacteria species conducts electricity. In October, a group of Danish researchers revealed that the seafloor mud of Aarhus’ harbor was coursing with electricity due to an unlikely source: mutlicellular bacteria that behave like tiny electrical cables. The organisms, the team found, built structures that traveled several centimeters down into the sediment and conduct measurable levels of electricity. The researchers speculate that this seemingly strange behavior is a byproduct of the way of the bacteria harvests energy from the nutrients buried in the soil.

Kepler 62f, discovered yesterday, is the most promising exoplanet candidate yet in terms of its potential to harbor life. Image via NASA/Ames/JPL-Caltech

10. Our Earth isn’t alone. Okay, this one might not technically be a discovery about Earth, but over the past year we have learned a tremendous amount about what our Earth isn’t: the only habitable planet in the visible universe. The pace of exoplanet detection has accelerated rapidly, with a total of 866 planets in other solar systems discovered so far. As our methods have become more refined, we’ve been able to detect smaller and smaller planets, and just yesterday, scientists finally discovered a pair of distant planets in the habitable zone of their stars that are relatively close in size to Earth, making it more likely than ever that we might have spied an alien planet that actually supports life.

Drought and an increased demand for water have stressed the Colorado River, which flows nearly 1,500 miles through seven states and Mexico. Photo by Flickr user Alex E. Proimos

When Alexandra Cousteau, granddaughter of Jacques, recently went to Mexico to explore the southern terminus of the Colorado River, she found mud, sand and dust where water once raged. The expedition was videotaped for a short film (viewable below) produced in conjunction with Cousteau’s nonprofit, Blue Legacy, which raises awareness about water issues. The video was called Death of a River: The Colorado River Delta.

That title, it turns out, is an apt one: Today, the conservation organization American Rivers released its annual ranking of America’s most endangered rivers, and the Colorado topped the list.

The group cites outdated water management as the main malady attacking the Colorado’s health. “A century of water management policies and practices that have promoted wasteful water use have put the river at a critical crossroads,” a statement (PDF) released by the organization reads. “Demand on the river’s water now exceeds its supply, leaving the river so over-tapped that it no longer flows to the sea.”

At one time, the river emptied into the Gulf of California, between mainland Mexico and the Baja Peninsula. In fact, this river mouth can still be found on maps, including Google’s, because it’s supposed to be there. But a recent study (PDF) conducted by the Bureau of Reclamation (a division of the U.S. Department of Interior) determined that the entire river and its tributaries are siphoned off to meet the drinking, bathing and toilet-flushing needs of 40 million Americans throughout seven states, including Arizona, California, Colorado, New Mexico, Nevada, Utah, and Wyoming. It also irrigates 5.5 million acres of land and helps meet the electrical-power appetite of much of the West through hydro-power facilities. Nearly two dozen Native American tribes depend on it, and it’s the centerpiece of 11 national parks, most famously the Grand Canyon.

“Growing demands on the Colorado River system, coupled with the potential for reduced supplies due to climate change may put water users and resources relying on the river at risk of prolonged water shortages in the future,” the study authors write. “Ultimately,” they add, “the Study [sic] is a call to action.”

Low water levels at the Colorado River’s Hoover Dam, on the Arizona-Nevada border. Photo by Flickr user Remon Rijper

But what action is needed? Water conservation, water reuse and water augmentation–replacing water drawn from wells–the authors say. Specifically, landowners and municipalities must boost their agricultural, municipal and industrial water conservation agendas, as well as improve their energy water-use efficiency. Solutions for the most challenging regions include finding ways to import water, reuse waste water and desalinize ocean and brackish water.

Scientists acknowledge some solutions they’ve looked into are easier said than done and that not all are viable in every region. For instance, options like importing water to Southern California via submarine pipelines, water bags and icebergs (PDF), along with watershed management techniques like weather modification (aka cloud-seeding) are a bit pie-in-the-sky.

The Colorado isn’t the only endangered river, by far. Georgia’s Flint River, the San Saba River in Texas, Wisconsin’s Little Plover River, the Catawba River in the Carolinas and Minnesota’s Boundary Waters were all also red-flagged by American Rivers this year.

The challenge for all of these rivers, including the Colorado, only grows in the future. Climate-change-induced drought is working against them. American Rivers notes (PDF) that changes to climate are expected to reduce the Colorado River’s flow by as much as 10 to 30 percent by the year 2050. It could leave yet more sand and mud behind, making parts of the American West and Southwest even more parched.

Scientists believe the absence of seed-dispersing birds is thinning the forests on the island of Guam. Photo by Isaac Chellman

Visitors to Guam’s forests find them quiet–eerily so: No chirping of birds can be heard overhead. But slithering in the shadows on the ground are snakes, each some six feet long. Brown tree snakes made their debut on Guam, the southernmost island in the Mariana Archipelago, when islanders were rebuilding after World War II. Most likely, they were stowaways in lumber shipments heading north through the Pacific Ocean from New Guinea. They quickly began feasting on the birds and small lizards they discovered in Guam’s dense forests, and–free to slither through the mountainous terrain without predators of their own–they completed an invasion of the island at a pace of one mile per year. By the late 1940s, the forests had largely fallen silent, and now, all of Guam’s native bird species are history.

Last fall, scientists from Rice University and the University of Guam published one of the first studies of the island’s extinct forest birds, which include species such as the Mariana fruit dove, Guam flycatcher and Rufous fantail. They focused on how the absence of birds has caused a spike in the spider population, which is 40 times greater on Guam than nearby islands.

Now, the researchers are turning their attention to the issue of Guam’s thinning forests—a consequence, they also believe, of the bird deficit. This summer they’ll launch a four-year study of 16 tree species, looking at how the loss of birds, which scatter seeds, is affecting tree distribution.

The brown tree snake has obliterated nearly all of Guam’s bird species since it was introduced during World War II. Photo by Isaac Chellman

The study has its roots in an a-ha moment that lead scientist Haldre Rogers recently had while conducting another seed-dispersal study in Guam’s forests. “I noticed that there seemed to be a lot of gaps [in the trees] and that the pioneer tree species–such as papaya and sumak–were difficult to find on Guam, compared to nearby islands,” she explained to Surprising Science. She discovered that there were in fact twice as many such gaps on Guam per unit area of forest. 

Pioneer trees, which are the first to appear after a disruption to the ecosystem and thrive in the full sunlight of open spaces in the forest, have small seeds that are consumed by small birds. “Without birds to move their seeds to these sunny spots in the forest, these quick-growing trees may be less likely to germinate or grow to their full size,” Rogers hypothesized.

The problem with such thinning is that it could change the structure of Guam’s forests. “There’s a concern that [they] may become filled with open areas and start to look more like Swiss cheese than a closed canopy forest,” Rogers said. In other words, what were once cool, dark forests could transform into hot, open sunny ones.

There are other possible explanations for the tree-thinning: An undiscovered forest disease could be targeting pioneer species, or mammals like pigs and deer might have a strong taste for the trees. But according to Rogers, there isn’t strong evidence to support either of these scenarios. The upcoming study will attempt to determine the cause definitively.

The Mariana fruit dove was driven to extinction by the brown tree snake on Guam and is highly endangered on other islands in the Mariana Archipelago. Photo by Isaac Chellman

To that end, the researchers will cut down individual trees in various spots within Guam’s forests, creating new gaps in the forest. They’ll also remove trees from locations on two nearby islands that are still brimming with birds. Then they’ll monitor how long it takes the spaces to fill in and take note of which seedlings thrive on Guam versus on the other islands. It may seem that to get their results they’re destroying what they’re trying to study, but in actuality they’re taking down a tiny percentage of the island’s trees–20 total.

Guam’s situation is similar to that of tropical regions worldwide. “Animals involved in seed-dispersal are in decline in a lot of tropical forests around the world right now,” the co-principal investigator of the study, Amy Dunham, said in a statement. “It’s very important to understand the implications of those declines.” So far scientists have looked into the role of endangered mammals like lemurs, giant tortoises (PDF) and African forest elephants (PDF) in seed dispersal, but the upcoming study will be one of the first to focus on endangered birds.

It’s also the rare study to examine what happens when seed dispersal completely ceases–Guam being the only place in the world to experience whole-island forest bird loss in modern times. “The situation on Guam–which is tragic–provides us with a unique opportunity to see what happens when all seed-dispersal services provided by animals are lost from an entire ecosystem,” Dunham said. 

The snakes, meanwhile, continue to dominate the island of Guam. The U.S. Department of Agriculture traps approximately 6,000 brown tree snakes each year, and yet there are still nearly two million slithering around the island. The snakiest patches contain 14,000 of the reptiles per square mile–one of the highest snake concentrations in the world.

In February, the Department of Agriculture embarked on a new tactic for tackling the snake problem: dropping dead mice laced with acetaminophen, which is fatal to them, into the jungle. ”We are taking this to a new phase,” Daniel Vice of the Department of Agriculture’s branch that focuses on wildlife services in Hawaii, Guam and other U.S. held Pacific Islands, said in a recent interview. “There really is no other place in the world with a snake problem like Guam.”

Wetlands, such as this marsh above, buffer communities against flooding. Photo by Flickr user daryl_mitchell

In the aftermath of Superstorm Sandy last fall, New York Governor Andrew Cuomo joked to President Barack Obama that New York “has a 100-year flood every two years now.” On the heels of flooding from 2011′s Hurricane Irene and Tropical Storm Lee, it certainly seemed that way. Given that climate change has sparked multiple major storms and raised sea levels, and that urban and agricultural development have impeded our natural flood-management systems, chronic flooding could be here to stay.

Wetlands, which include swamps, lagoons, marshes and mangroves, help mitigate the problem by trapping floodwaters. “Historically, wetlands in Indiana and other Midwestern states were great at intercepting large runoff events and slowing down the flows,” environmental engineer Meghna Babbar-Sebens of Oregon State University said in a recent statement. ”With increases in runoff, what was once thought to be a 100-year flood event is now happening more often.”

One key problem is that most of our wetlands no longer exist. By the time the North American Wetlands Conservation Act (PDF) was passed in 1989, more than half of the wetlands in the United States had been paved over or filled in. In some states, the losses are much greater: California has lost 91 percent of its wetlands, and Indiana, 85 percent. In recent years, scientists have been honing the art of wetlands restoration, and now a recent study published in the journal Ecological Engineering by scientists at Oregon State University is helping to make new wetlands easier to plan and design.

Scientists are using an Indiana watershed to study how wetlands can be created or restored to help stem the effects of climate change. Photo by Flickr user Davitydave

The research focused on Eagle Creek Watershed, ten miles north of Indianapolis, and identified nearly 3,000 potential sites where wetlands could be restored or created to capture runoff. Through modeling, the scientists discovered that a little wetland goes a long way. “These potential wetlands cover only 1.5% of the entire watershed area, but capture runoff from 29% (almost a third) of the watershed area,” the study authors wrote.

Their next step was to begin developing a web-based design system to allow farmers, agencies and others to identify areas optimal for new or restored wetlands and to collaborate in designing them. The recently launched system, called Wrestore, uses Eagle Creek as a test-piece.

A new web tool analyzes different components of a watershed; Indiana’s Eagle Creek Watershed steam network is pictured here. Map courtesy of Wrestore

The tool has a variety of functions: It helps identify a region’s rivers and streams, divides watersheds into smaller sub-watersheds and shows where runoff is likely to collect—places conducive to building wetlands. If a city wants to reduce flooding in its watershed, the site’s interactive visualization engine displays various conservation options and allows groups of city planners to collaborate on the design of new wetlands.

“Users can look at various scenarios of implementing practices in their fields or watershed, test their effectiveness via the underlying hydrologic and water quality models, and then give feedback to an ‘interactive optimization’ tool for creating better designs,” Babbar-Sebens, lead author of the study and the lead scientist on the web tool, told Surprising Science.

It provides an easy way for landowners to tackle such environmental challenges. “The reason we used a web-based design system is because it gives people the flexibility to try and solve their problems of flooding or water quality from their homes,” Babbar-Sebens said.

As the spring flood season approaches and environmental degradation continues throughout the nation, a new tool for mitigating wetland loss with targeted, minimal wetland gain is certainly a timely innovation. Babbar-Sebens and her team have been testing it out on Eagle Creek Watershed and will be fine-tuning it throughout the spring. ”There is a lot of interest in the watershed community for something like this,” she said.