Smithsonian.com

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.