A recent international study claims that the dwindling numbers of several species of large predators, such as killer whales, lions, wolves, sharks and elephant-like megaherbivores, may be “humankind’s most pervasive influence on the natural world.”

The revelation is in contrast to the notion that top-tier consumers only affect the species they directly consume. In fact, the report claims that loss of these apex consumers has “far-reaching effects” on diverse ecosystem processes.

The report “Trophic Downgrading of Planet Earth,” a result of research conducted by 24 scientists, was recently published in the journal Science. It claims that the planet is currently in the midst of a mass extinction event characterized by the loss of “apex consumers in particular.”

Although mass extinction events have long been part of earth’s history of biodiversity, this report claims that this extinction event is caused largely by humans.

Thomas Schoener, a co-author of the report and a professor at UC Davis, explained the human contribution to the declining population of these predators.

“The loss of producers (plants etc.) can leave the rest of the food web precarious,” he said.

Schoener said that the loss of much of the earth’s flora was due to human-induced stressors and pointed out that tigers in India now number about 2,000 – down from 40,000 a century ago.

James Estes, co-author and a professor of biology at UC Santa Cruz added, “There are two main [causes] – direct persecution because of concerns over personal safety, wildlife, stock depredation; and habitat fragmentation, since most large apex consumers require large areas of habitat to maintain viable populations.”

The report states that apex consumers play a huge role in “top-down forcing,” a trickle-down effect of peak consumers which affects species ranked lower on the food chain, such as insects and plants, and ultimately the related ecosystem processes.

The report states that, “responses to the loss or addition of a species may require years or decades to become evident.”

The authors caution that “[we] often cannot unequivocally see the effects of large apex consumers until after they have been lost from an ecosystem.”

The report, which reviews a large body of steadily growing empirical data, describes several examples of perturbed trophic cascades and ecosystems, some of them affecting human beings in unprecedented ways.

In the 1800s, introduction of rinderpest in East Africa led to the loss of the megaherbivores wildebeest and buffalo. This resulted in increased plant biomass, thus fueling wildfires in the dry season. Wildfires cost billions of dollars every year in damages.

Eventually, rinderpest was eliminated from the region in the 1960s and the herbivore populations flourished, with fewer wildfires.

Nowhere is the impact of the loss of these consumers more conspicuous than on the Scottish island of Rùm. The island lost its wolf population 250 – 500 years ago resulting in an increased number of herbivores. The once forested island now stands treeless.

“I think this gives conservation a new momentum with regard to apex consumers. Such animals are now realized to have major ecological environmental impacts,” Dr. Schoener said.

Indeed, the magnitude of the report’s impact on conservation efforts across the globe can only be imagined.

“In order to realize the myriad influences of large apex consumers, conservation areas must be very large,” Dr. Estes said.

He later predicted a shift in the scale at which conservation must be attempted.

SASHA SHARMA can be reached at science@theaggie.org.

With the help of a UC Davis geologist, the landing site for Curiosity, the new Mars rover, will be Gale Crater – a giant basin that contains a 5 km high mountain. NASA officially declared this selection in a press conference at the Smithsonian Air and Space Museum on July 22.

Curiosity, the $2.5 billion rover, will be taking pictures and studying mineral samples from the layered rocks at the base of the mountain.

“These rocks record the environments in Gale Crater through tens to hundreds of millions of years. It’s this long record that was one of the main reasons Gale was chosen,” said Dawn Sumner, professor of geology at UC Davis.

Sumner, who was a co-chair of the Landing Site Working Group for the Mars Science Laboratory mission had to choose between four different landing sites. The selection process began March of 2009 and after months of weekly teleconferences, presentations and discussions, the group ultimately selected Gale for its diverse environments and interesting mineralogy.

Crusta, a real time Mars visualization program developed by UC Davis doctorate student Tony Bernardin, aided in Sumner choosing Gale Crater. The virtual program is very similar to Google Mars but allows for more exact and detailed images.

Anahita Yazdi, a junior aerospace and mechanical engineering major who has worked in the lab since her first-year, helped Sumner establish a computer system that would run Crusta properly. Yazdi hopes to work as an engineer in NASA someday.

“All of the four landing sites were incredible, but in terms of the geological features, Gale is like a novel that you can read the history of Mars. It’s all deposits, and deposits are basically the history of any globe,” Yazdi said.

Curiosity’s two-year trip will partly be spent looking for organic compounds in these deposits and characterizing any that are found. Organic compounds are the building blocks of life and may be evidence of a habitable environment on the red planet. Because the compounds are difficult to preserve in rock, researchers will be using other properties on the stones to try and understand how the compounds may or may not have been preserved.

One such researcher is UC Davis doctorate candidate Amy Williams, who is a member of Sumner’s Mars Science Laboratory. Williams is working on developing an analog model to compare mineralogical bio-signatures potentially formed on Mars to the ones found on Earth. These bio-signatures are formed when microbes alter the minerals they live on, e.g. by dissolving or precipitating it.

When Curiosity lands, the rover will take high-resolution pictures that will be compared to images of the analog system. The analog system is an acid-saline environment in Northern California, chosen for its similarity to Mars.

“If you see exactly the same features, it might be preserved microorganisms. [We] may say, ‘Wow, those look a lot like preserved microorganisms on Earth, we should look at these in even more detail'”, Williams said.

“It’s just plain fun – going to another planet (virtually) and seeing things no one else has ever seen before is exciting!” Sumner said.

The six-wheeled, car-sized Curiosity is set to launch from Florida on the Atlas 5 rocket between Nov. 23 and Dec. 18, and arrive at Gale Crater between Aug. 6 and Aug. 20, 2012. This mission will be the first astrobiology research on Mars since the Viking trip in 1976.

To watch Sumner’s video of the virtual landing site, go to www.youtube.com/crustamars.

EVA TAN can be reached at science@theaggie.org.

Two people with sleep disorders sharing a bedroom can make for interesting nights, to say the least.

I have chronic insomnia; there can be multiple nights in a row where I’m unable to fall asleep until four or five o’clock in the morning. Taking my prescribed sleeping pills once in a while helps but leads to sleep talking, such as the time I climbed into my loft bed and treated my roommate to a lengthy speech about the possible evolutionary origins of the fear of falling.

I have no memory of talking about this, but I did so coherently enough that she thought I was awake.

My sleeping problems are not too unusual. According to the National Center for Sleep Disorders Research at the National Institutes of Health, about 30 to 40 percent of adults say they have some symptoms of insomnia within a given year, and about 10 to 15 percent of adults say they have chronic insomnia.

Insomnia can be caused either by stress or by some kind of underlying medical condition. A traumatic event, such as divorce or death of a loved one, can make people toss and turn. Medical conditions such as pain, menstruation and side effects of medications can also make it difficult to fall asleep.

Insomnia can lead to sleep deprivation, a condition with which college students in particular are familiar. According to the most recent National College Health Assessment, more than half of surveyed UC Davis students don’t get enough sleep to feel rested, and nearly a fifth have a big or very big problem with sleepiness.

“Sleep deprivation causes stress, moodiness, accidents and immune system impairment,” said Dorje Jennette, a doctor of psychology at Counseling and Psychological Services (CAPS) at UC Davis.

My insomnia is exacerbated (if not caused) by my off-kilter circadian rhythm. The circadian rhythm is the body’s pattern of being asleep and being alert. Exposure to light sets off a process starting at the retina in the eye and going to a certain area of the brain called the supra-chiasmatic nucleus, which then controls the release of hormones and other functions that control how sleepy or awake we feel.

However, the circadian rhythm is not only controlled by whether there is light outside. When we stay up all night trying to finish a paper, the end result could be suffering through an early morning class with heavy eyes and a slow mind.

“With irregular sleep schedules, we’re effectively giving ourselves jet lag,” Jennette said.

We all love jet lag, don’t we?

Though my sleeping problems are intensely aggravating and necessitate a great deal of coffee in order to get to my classes, my roommate’s problems can be more frightening.

“Insomnia, nightmares, sleepwalking and I’ve had a few night terrors,” said Nicole Hooper, a junior chemistry major.

There are two main types of sleep, REM (rapid-eye movement) and NREM (non-rapid-eye movement). Adults spend 20 to 25 percent of their sleeping time in the REM stage through four or five cycles of the two types. During REM sleep, brain activity, heart rate and breathing are surprisingly similar to being awake. Nightmares occur during REM sleep, much like normal dreams, but they are typically much more vivid.

REM sleep is also characterized by temporary muscle paralysis. This is why people don’t typically act out their dreams or move in their sleep. When this process doesn’t work properly, the result is REM Behavior Disorder, where individuals begin acting out their dreams.

NREM sleep, on the other hand, is the deep sleep portion of the night. What few dreams that do occur are vague and disconnected. It’s also the stage at which sleepwalking and night terrors take place, but these are more common in children than adults.

The tips online of trying to get a good night’s sleep are things everyone has heard before: try to keep a regular sleep schedule even on weekends, avoid caffeine several hours before bed and try relaxation exercises or meditation. If the problems continue, talk to a doctor and they can prescribe medication or refer you to a sleep study.

Now, where did I put my bed-time tea…

AMY STEWART can be reached at science@theaggie.org.