Ecosystems containing many different plant species are more productive and better able to deal with stresses such as climate extremes, pests, and disease. Those are the findings, published in last week’s issue of Nature, of University of Minnesota ecologist David Tilman and colleagues Peter Reich and Johannes Knops.
It sounds familiar, doesn’t it? The debate about whether or not diversity stabilizes ecosystems has been going on for 50 years! But Tilman’s experiment is the first to collect enough data, over enough time and in a controlled environment, to confirm the hypothesis.
Tilman, Reich, and Knops spent 12 years studying 168 9-meter-by-9-meter experimental plots at the Cedar Creek Long-Term Ecological Research (LTER) site near Cambridge, Minnesota. Each plot was randomly planted with 1-16 perennial grasses and other prairie plants. Over the 12 years of the study, temperatures and rainfall varied, but the plots with more species and more root mass did better than the others. (Why root mass? Roots store nutrients and provide a buffer against climate variations. And perennial prairie plants have far more root mass than annual plants, such as corn and other crops.)
So what does it mean?
Two things. First, biodiversity does matter when it comes to healthy ecosystems. Second, biodiversity is decreasing worldwide as human populations increase and forests and prairies have been replaced with farm fields, buildings, and roads. Tilman thinks that increasing diversity may be the key to both restoring ecosystems and meeting the energy needs of people around the world.
In a National Science Foundation press release, Tilman said:
”Diverse prairie grasslands are 240 percent more productive than grasslands with a single prairie species. That’s a huge advantage. Biomass from diverse prairies can, for example, be used to make biofuels without the need for annual tilling, fertilizers, and pesticides, which require energy and pollute the environment. Because they are perennials, you can plant a prairie once and mow it for biomass every fall, essentially forever.”
The number of butterflies migrating through California has dropped to a forty year low, according to researchers at the University of California, Davis. One-half of the usual species of butterflies have not appeared this season, and other species have been observed in very low numbers. Climate change related to global warming and habitat destruction may be the cause.
Global warming is the increase in the Earth’s average temperature over recent decades primarily attributable to human activities.
Habitat destruction is a change in land use in which one habitat is replaced with another. The plants and animals which previously used the site are destroyed or displaced in the process.
A mild winter in Northern California has caused many species to not end their winter dormancy at the right time. This means that many butterflies emerged too late in the season. The proper climate for breeding was disrupted by a wet spring.
In Southern California, an unusually dry desert left little food for caterpillars of some species to feed on. A late snow in the Sierra Nevada may have killed many insects used for food.
Some species of butterflies that breed several times a year may rebound from these events, but for other species the effects may be devastating for up to a decade.
Read the original press release here.
Imagine that you are on a glacier and all around you thousands of black worms rise up out of the ice. It sounds like a scene from a science fiction movie, but it isn't. The worms are ice worms, and they're real.
Ice worms are extremophiles, animals that thrive in conditions that most creatures would not be able to survive, such as volcanos, glaciers and deep in the ocean. Ice worms live in glacial ice. They average around 1 cm long and 1 mm wide, and eat snow algae. Ice worms are the opposite of worms like earthworms, in that instead of becoming less active as temperature decreases, ice worms become more active with cooler temperatures. And there are a lot of them. One glacier can have an ice worm density of 2600 worms per square meter.
The ideal temperature for an ice worm is zero degrees Celsius, or 32 degrees Fahrenheit. This ability of ice worms to thrive in such extreme temperatures is the focus of a three year $214,206 NASA grant. Researchers hope ice worms can help unlock the secrets of how life might survive on distant ice worlds such as Europa.
Ice worms actually disintegrate through the process of autolysis when they are exposed to temperatures greater than 5 degrees Celsius. (Autolysis in cell biology refers to the destruction of a cell by its own digestive enzymes.) With the glaciers that are the only habitat for these organisms slowly melting due to global warming, ice worms are losing their habitat. If you consider that there are over 7 billion worms in one glacier, their impact on ecologies that are influenced by the glaciers must be significant, both in terms of biomass and in terms of nutrient processing. There is a lot more to learn about these organisms, and the role they play in the ecosystem.
For a time ice worms were believed to be mythical creatures — there is even an amusing poem that features the ice worm. I never knew these things existed — pretty amazing worm, I think.
It seems like science fiction, or some bizarre insect zombie movie, but...
Scientists have been researching the parasitic relationship between grasshoppers and the nematomorph hairworm (Spinochordodes tellinii). The hairworm lives and breeds in fresh water, but spends a part of its life eating the insides of live grasshoppers and then brainwashing the grasshopper into committing suicide by hopping into a pool of water and drowning. The hairworms, several times the length of the grasshopper at the time of the unfortunate incident, then emerge and continue their lifecycle in water. A team of researchers at the French National Center for Scientific Research is studying just how the hairworm manages to take over the body of the grasshopper.
This is just one example of a parasite seemingly taking over its host to produce specific results. In Costa Rica, there is a wasp whose larva lives inside the body of an orb-weaving spider. The evening before the larva kills the spider, the larva somehow manages to reprogram the web building activity of the spider so that it creates a durable platform for the larva to pupate on, instead of its usual temporary web. Studies show that if the larva is removed from the spider before the larva kills the spider, the spider will return to its usual web building activities within a couple of days.
And, if you think about it, the rabies virus makes animals so rabid that they want to bite others — which transmits the virus.
University of Minnesota professor Marla Spivak studies honeybees. She's fighting a parasite that has killed up to half of all North American bees in the last year.
Spivak leads a bee-breeding program that produces queen bees that remove larvae infested with Varroa sp. mites from their hives. (The mites suck blood from the bees, especially developing ones, weakening them and shortening their lifespan. Infested emerging bees may be missing wings and legs. And an untreated infestation can kill an entire honeybee colony.)
Humans used two chemicals against the mites for years, but the mites have recently become resistant to both and have made a big comeback, destroying honeybee colonies across the country. But beekeepers using Spivak's queen bees have experienced only minor losses.
Don't think humans depend on bees? Think again. Honeybees pollinate about a third of our diet and dozens of agricultural crops. The mite problem affects even the dairy industry, since the cattle feed crops alfalfa and clover are honeybee pollinated, not wind pollinated like most grasses.
Many, many "pest" species are developing resistance to the chemicals we use to control them. Do you worry about this trend? Do you see alternatives to chemical pest control? Would you be willing to pay more for food products that are chemical free?
"Mad cow disease"-also known as bovine spongiform encephalopathy (BSE)-is a fatal brain disorder in cows. It's spread by contact with brain or other nervous-system tissue from an animal with the disease. An animal can be infected but not have any symptoms for years. But once the disease is active, it kills brain cells, leaving large, spongy holes. It also causes large clumps of abnormal proteins in the brain and quickly kills the victim.
Scientists still don't know for sure what causes mad cow disease. But the most likely theory is that abnormal proteins called prions (PREE-ons) damage nerve cells, causing loss of brain function and eventual death.
You can read more about prions and how scientists think they might cause mad cow disease:
Scientists think mad cow disease came from a similar disease in sheep called scrapie. We used to feed cows meat and bone meal-from other cows, but also animals such as sheep-leftover after processing for human consumption. Cows ate food contaminated with scrapie and developed BSE. At the time, people thought that neither scrapie nor BSE affected us, so meat from BSE-infected cows got into the human food supply. People who ate the infected meat-probably hamburger or other processed meats-developed a disease similar to the cows'.
You can find out a lot more about mad cow disease and its human manifestation:
The US government has made some rules to try and protect people here from the disease. It has banned the import of cud-chewing animals (cows, sheep, goats) and products made from them from Europe. It prohibits the use of any mammal products in food for cows. Cows with unidentified neurological disorders cannot be eaten. Drug companies can't use animal tissues from countries with mad cow disease when they make vaccines or other products. And people who spent more than six months in the UK (where the mad cow disease epidemic was first identified) between 1980 and 1986 are not allowed to donate blood.
Do the new rules make you feel safer about eating meat? Have you changed any of your eating habits since mad cow reports came out in the media?
One of the ongoing debates in science is: where the heck did birds come from? Bird bones are fragile and don't often become fossils, so there's not a lot of evidence. And when a new bird fossil is found, there's always a lot of debate over how it fits into the puzzle.
Researchers at the Mayo Clinic have found a way to use measles to fight cancer.
Viruses are parasites. To reproduce, they seek out sites on a healthy cell, get inside, and then take over the host's cellular machinery. For years, researchers dreamed of using viruses to hijack cancer cells.
The Mayo team knew that measles kills most cancer cells, too. But to use the virus as an anti-cancer treatment, they had to change the virus so it wouldn't attack healthy cells. They eliminated the virus's ability to bind to its natural receptors, and retargeted it to zero in on ovarian cancer cells.
In lab animals implanted with human cancer cells, the virus hunted down and destroyed only infected cells. Clinical trials on patients with ovarian cancer began last summer, but it will be at least three years before the treatment is approved for use in hospitals.
In August 1995, schoolchildren found deformed frogs in a wetland near Henderson, Minnesota. Some frogs had extra legs, others no legs at all. Some had missing or extra eyes, toes, or feet. And some also had problems with their internal organs. By the fall of 1996, there were over 200 reports of freakish frogs, from two-thirds of Minnesota's counties. Deformed frogs have since been found in 44 states.
Courtesy Minnesota Pollution Control Agency
A 1997 study raised frogs in the lab, mixing pure water with water from two Minnesota sites that had lots of deformed frogs. The more pond water that was used, the more likely the lab frogs were to be deformed. Water from sites with healthy frogs produced healthy animals in the lab. The scientific conclusion was, "There's something in the water." But what could it be? Since then, several researchers have been hunting for the cause.
Scientists have proposed several explanations for the deformities. It may be parasites, chemicals, ultraviolet light, or some combination of the three. Lab studies have shown that all of these factors, alone or in combination, can cause some deformities. But no single cause seems to explain it all. The research doesn't yet add up to a neat and tidy answer, so scientists continue to puzzle out the story.
Who cares about frogs? You should. If there's something wrong with the water, it may eventually hurt all of us. But it will hurt frogs first. Frogs have thin skins, and easily absorb any contaminants in the water. Frogs seem to be in trouble all around the world. There are more and more reports of deformities. And some species have disappeared, or no longer live in their old habitats. It's a wide-spread problem that may affect us all.