What is a weed?
A plant whose virtues have not yet been discovered.
Ralph Waldo Emerson (1803-1882)
Fortune of the Republic, 1878
The Truth about the Birds and the Bees
Disappearing pollinators.
Declining populations of pollinators can have economic effects on crops and environmental effects on ecosystems.
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Human activities such as agriculture, development, pesticide use, and hunting have placed the world's pollinators in jeopardy, and that spells trouble not just for the birds and the bees, but for the flowers and the trees--and for the human communities that depend on them.
Approximately 1,300 food crops worldwide, together with an estimated 90% of the 250,000 species of flowering plants, are fertilized by pollen- or nectar-gathering visits from over 20,000 species of insects, birds, bats, and monkeys, as well as one species of lizard, the gecko. Yet the only animal to receive serious attention for the vital role it plays in pollination has been the honeybee, the fruits of whose labors are an estimated $9 billion in U.S. crops. And honeybees are in trouble.
"The honeybee is the queen of pollination, but mites and invasion by African bees are causing problems," says Ron Bitner, a senior partner with International Pollination Systems, a company that markets pollinator species. Since the 1980s, wild and domestic hives in the United States have been decimated by a dual infestation of exotic parasitic mites--tracheal mites affect the respiratory tract of adult bees, and external varroa mites attack larval, pupal, and adult bees. The African bee is an aggressive variety of honeybee that was brought intentionally to South America, then escaped and spread as far as the U.S. Southwest. These bees compete with honeybees and other species for nectar, and have helped carry mites into wildlands and croplands, infecting other bees. "We're working with alkali and leaf cutter bees that are more efficient [than honeybees] in pollinating crops like alfalfa," Bitner says. "But they're not going to replace honeybees. It's not crunch time yet--we haven't seen a honeybee decline in California, for example. But if more goes wrong, [there] will be."
The decline in U.S. honeybee populations--down by 50% in the last 50 years, with 95% or more of wild hives destroyed in some areas--highlights the importance of the thousands of alternate pollinator species such as wild bees, flies, beetles, wasps, butterflies, and moths. Stephen I. Buchmann, an entomologist with the U.S. Department of Agriculture in Tucson, Arizona, and Gary Paul Nabhan, science director of the Arizona-Sonora Desert Museum in Tucson, cite figures in their 1996 book,
The Forgotten Pollinators, showing that the current rate of decline of honeybees, combined with declines in wild pollinators resulting from human activities, could cause up to $5.7 billion in annual losses to U.S. food crops.
The effects of human activities on tropical pollinators, which include 45 species of bats, 26 species of hummingbirds, 70 species of passerine birds (perching birds and songbirds), and several species of lemurs and monkeys, have also raised concerns among conservationists. Specifically, widespread development and deforestation have led to loss of habitat, the overuse and misuse of pesticides has contributed to species declines, and a popularized fear of vampire bats has resulted in the destruction of roosting caves. Scientists say that declines in pollinators in the tropics, particularly losses of bats, can cause a cascade of effects by reducing pollination and thereby stunting biodiversity. For example, each of the world's 750 fig species is pollinated by a single species of wasp. If the fig wasps in South American tropical forests were to disappear, a cascade effect could result in the disappearance of the monkeys that eat the figs, and the jaguars and other predators that prey on the monkeys. Cascade effects involving whole ecosystems have not been observed so far.
There could be human consequences as well. Bats are the major pollinators of over 100 medicinal plants, as well as over 450 economically important crops and plants used to produce fibers, dyes, and fuel valued at hundreds of millions of dollars, according to Barbara French, a biologist and information specialist with Bat Conservation International (BCI) in Austin, Texas. "Nectar-feeding bats that transport pollen are vital to the production of economically important bananas, mangoes, neem, and durian fruits," she says. "Bats also play a very significant role in insect control."
Until recently, many useful pollinators have been perceived as pests, especially bats, whose image as "vampires" and rabies carriers contributed to massive destruction of their roosts. Gaps in pollinator research haven't helped the situation. "There's been no concerted effort to collect data [on pollinators], except perhaps in agriculture, and there are few mechanisms for funding basic research," says David Inouye, a professor of biology at the University of Maryland at College Park. Funding cuts have led to the closure of four of the seven U.S. bee research labs over approximately the last 10 years.
But the future for pollinators is not entirely bleak. "We've recognized the problem [of declines in pollinator species] in time," Inouye says. Researchers are working with several substances that offer some promise against the killing mites that threaten some pollinators. The plight of such popular pollinators as hummingbirds and monarch butterflies also has helped increase the visibility of threats to pollinators. Monarch butterflies and some hummingbirds and bats are migratory, and they travel along a "nectar corridor" in which their arrival coincides with the maturation of the flowers upon which they feed. When these corridors are disrupted, the pollinators may starve. Also, migratory animals need a place that meets their food, shelter, and water needs in which to spend the winter. In the case of monarchs, traditional wintering sites in California and Mexico have been converted by development, deforestation, or agriculture. Thus, tens of millions of monarchs are restricted to 10 sites in Mexico (5 of them unprotected by regulations) and only 7 remaining sites in California. The butterflies are not yet endangered, but a major part of their life cycle is in jeopardy.
Outreach in elementary schools has improved the public's appreciation of bats. And BCI is working with mining companies to convert abandoned mines into roosts for hibernating bats, creating a human-animal partnership with mutual benefits. "This is a very important part of bat ecology," says French. "We protect [both] the bats and people with gates at the mine entrances. It gives a habitat for bats, and helps give mines a more positive image."
Pollinators may also benefit from the move toward more "natural" gardens in private homes that demand less pesticide use, as well as a 1994 Executive Memorandum issued by President Clinton that recommends the use of regional native plants, which often evolved with their pollinators in a mutually beneficial relationship, and integrated pest management, which features reduced use of pesticides on federal and federally funded properties. And science is beginning to do its part to protect pollinators, as well. In a paper published in the February 1998 issue of
Conservation Biology, Nabhan, Bitner, Inouye, and 19 other coauthors propose supporting animal pollinator services by promoting alternative pollinators, encouraging crop breeders to consider pollinator attraction in new varieties, preserving pollinator stocks, and researching ways of increasing pollination and creating pollinator habitats in agricultural areas.
Melanoma Vaccines
Researchers are making significant progress in developing innovative treatments for melanoma, a form of malignant skin cancer that is on the rise in the United States, according to the American Cancer Society. Melanoma begins in the melanocytes, the cells that produce the skin pigment called melanin. Researchers believe that exposure to ultraviolet light damages the DNA in these cells, which results in the development of melanoma.
Scientists have been working for years to develop vaccines that treat melanoma by stimulating the immune system to attack cancer cells. The body does not ordinarily attack melanoma cells because such cells are roughly 99% normal, says Philip Livingston, head of the cancer vaccinology laboratory at Memorial Sloan-Kettering Cancer Center in New York City. Researchers have sought to identify the differences that explain why some cells turn cancerous. "We've spent many years in the laboratory trying to define and isolate the genetic elements and the genes that code for what is different on a cancer cell compared to a normal cell that the immune system can recognize," says Steven Rosenberg, chief of surgery at the National Cancer Institute (NCI).
Livingston refers to these characteristic elements of cancer cells, which include proteins and antigens, as "handles." Researchers developing melanoma vaccines replicate these handles and combine them with immune boosters, or substances that the immune system recognizes and attacks. Theoretically, linking the handles with substances known to elicit an immune response will prompt the body to seek out all handles and therewith eliminate the cancer cells. Although the practical application of such vaccines is years away, scientists are making significant advances in the area. "This is a mammoth field," says Paul Chapman, an associate attending physician and head of the melanoma section at Memorial Sloan-Kettering Cancer Center. "There are many vaccines that are being tested, and all are equally promising."
Researchers at Memorial Sloan-Kettering are working on melanoma vaccines that contain one of three replicated chemicals--GM2, GD2, or GD3--that are located on melanoma cells and that have been found to be recognized by the immune system. The vaccines combine the chemicals with QS21, an immune booster from the South American soapbark tree, and KLH, an antigen produced by the mollusk
Megathura crenulata. Early results show an improvement in survival rates in some patients.
Rosenberg and colleagues at the NCI have chosen to work with cancer cell peptides that the immune system can recognize. They have modified the peptides so they can better bind to the immune cells--cytotoxic T lymphocytes--that attack melanoma cells. The modified peptides are then injected into the body. In a recent study published in the March 1998 issue of
Nature Medicine, Rosenberg and colleagues reported that, when administered with interleukin-2, a medication that boosts the immune system to help slow the growth of cancer, the vaccine caused an immune system response. They also found that 13 of 31 patients showed at least partial tumor shrinkage in the lung or skin, among other sites.
Another promising vaccine has been developed by Donald Morton and colleagues at the John Wayne Cancer Institute in Santa Monica, California. Morton collected blood, tissue, and serum samples from melanoma patients for many years. Study of these samples enabled him to identify three cancer cell lines that provoke strong immune system responses. Morton is working on a vaccine that uses radiated melanoma cells containing many different handles combined with bacillus Calmette-Guerin, a known immune booster. Morton is currently conducting worldwide clinical trials on the vaccine.
New Source of Fish Fears
In the Snook Nook bait shop in Jensen Beach, Florida, snapshots of anglers holding up their prize catches attest to the rich bounty for which the adjacent Indian River is famous. A few yards from the shop, in a cramped trailer owned by the Florida Department of Environmental Protection (DEP), is another photographic testament to the Indian River's fish. These close-up shots show fish with bloody, open sores reminiscent of those associated with the toxic dinoflagellate
Pfiesteria piscicida.
The sickened fish in the photos began appearing early this spring on the hooks of anglers fishing around the juncture of Florida's Indian and St. Lucie rivers, a brackish region known as the St. Lucie Estuary. At least 33 species of fish were affected. Although the lesions mimic those associated with the
Pfiesteria
outbreaks that have killed millions of fish in Maryland and North Carolina, the estuary apparently harbors a different culprit; nearly all the sickened fish in the estuary were found alive.
Water samples revealed the presence of
Cryptoperidiniopsis
("crypto"), one of 10 recognized
Pfiesteria-like species of microalgae. Karen Steidinger, a senior research scientist, and Jan Landsberg, a research scientist, both of the DEP's Florida Marine Research Institute in St. Petersburg, first identified crypto in 1997 in water samples taken from St. John's River near Jacksonville. Like
Pfiesteria, crypto is a heterotrophic dinoflagellate that feeds on microalgal prey. Crypto coexists with
Pfiesteria
in Maryland and North Carolina, but appears to live apart from any related species in Florida.
Whether it's causing the ulcers in the St. Lucie fish, though, is not clear. Of the 2,000 known species of dinoflagellates, about 65 have been shown to produce toxins. "There's no evidence [crypto] is toxic," says JoAnn Burkholder, an associate professor of botany and aquatic ecology at North Carolina State University in Raleigh, who in 1991 helped identify
Pfiesteria. "We don't understand much about toxin production in dinoflagellates." Whatever is plaguing the St. Lucie fish appears to act by destroying the protective mucous coat of the fish, inviting opportunistic bacterial and fungal infections.
Burkholder, Steidinger, and other researchers are scrambling to determine whether crypto is indeed toxic, and to solve the mystery of the sickened fish. "It's extremely important from a public health perspective to know what's out there, what are its toxins and their effects," Steidinger says. Sometime this summer, researcher Peter Moeller, project leader for the marine biotoxins program at the National Ocean Service in Charleston, South Carolina, expects to have preliminary results of bioassays he's conducting to determine crypto's toxins. His findings should aid in understanding both crypto and its cousins.
According to Daniel Baden, director of the NIEHS Marine and Freshwater Biomedical Sciences Center at the University of Miami in Florida, three toxins have been associated with
Pfiesteria-like dinoflagellates--a lipid-soluble lethal toxin, a water-soluble suspected neurotoxin, and a dermonecrotic toxin. Baden speculates that lesions found on fish killed by
Pfiesteria
may actually be caused by crypto. "People have been working with mixed cultures," he says, "but because the organisms were differentiated only recently, we haven't had time to ascribe specific toxins to specific organisms."
New water worries.
Cryptoperidiniopsis, a species of microalgae, may be causing sick fish--and concerns for human health.
Source: Florida Department of Environmental Protection.
Some researchers hope to ward off future outbreaks by determining what caused an ancient species of microalgae to strike here and now. "We believe crypto has been here hundreds, maybe thousands of years," says DEP marine biologist Ann Forstchen. Four times over the last 20 years, the St. Lucie Estuary has suffered outbreaks of fish disease. Each followed unusually high discharges from the St. Lucie Canal into the St. Lucie River, in which the South Florida Water Management District flushed fresh water from Lake Okeechobee through the canal to prevent flooding. "There's an apparent causal relationship between massive discharges and the outbreak of ulcers," says Dan Haunert, a lead scientist with the South Florida Water Management District. Nutrient runoff into the canal is believed to promote microalgal growth while the force of the discharges is thought to push the growth up from the bottom sediment.
Although studies are incomplete, crypto appears to have little, if any, effect on humans. Two months into the St. Lucie outbreak, the Florida Department of Health had received fewer than two dozen complaints from people who suspected they had been harmed by contact with the river water. "We haven't seen a clear association between exposure and illness," says epidemiologist Alan Rowan. "[People are] reporting various symptoms and they've had a wide range of exposures, from one day to five years. There may be alternative explanations."
As freshwater discharges dropped off in April, so did the number of diseased fish brought to the DEP's trailer outside the Snook Nook. Scientists believe the fish disease event may have run its course. But Forstchen expects it to return, just as she expects the periodic return of unseasonably heavy rains. "I don't think we'll be in a position to stop [outbreaks]," she says, "but we may be able to predict when they'll happen."
Lasers for Lungs
Lung cancer is one of the deadliest cancers in the United States, striking an estimated 190,000 people and killing 160,000 annually. Smoking is the major cause of lung cancer worldwide, but asbestos, air pollution, and radon appear to contribute to this disease. By the time cancers of the lung become visible through conventional diagnostics, they frequently are too far advanced to treat successfully. Now, Xillix Technologies Corporation of Richmond, British Columbia, has developed a technology that allows much earlier diagnosis of these dangerous cancers, possibly helping to save lives. The device was approved by the U.S. Food and Drug Administration (FDA) for use on lung cancers on 20 September 1996.
The lethal nature of non-small cell lung cancer (NSCLC) lies largely in the fact that, by the time the tumor becomes visible to the oncologist, it has spread too widely to be successfully surgically removed or irradiated. Chemotherapy also has had very limited success against lung cancer. Sixty-five percent of stage I cancers, 50-55% of stage II cancers, and 30% of stage III cancers are cured. But most lung cancers are not caught until stage 3 or 4, says Tracy Lee Weigel, an assistant professor of surgery and director of the LIFE-Lung Bronchoscopy Program at the University of Pittsburg School of Medicine in Pennsylvania. For all those diagnosed with NSCLC, she says, the five-year survival rate is about 13-14%.
The new technology, which Xillix calls the Lung Imaging Fluorescence Endoscopy bronchoscopic system, or LIFE-Lung, helps doctors detect lung cancers 1-2 years earlier than standard bronchoscopy, says Weigel. This can make all the difference in catching the disease in time. "We can [detect lung cancers] before they've broken through the basement membrane [of the lung], before they've gained access to the lymphatics and the bloodstream and develop the potential to metastasize," she says.
The LIFE-Lung works according to simple principals. Tissue fluoresces when illuminated with laser light, but the autofluorescent properties of normal and malignant tissues differ. A physician uses the LIFE-Lung bronchoscope--a laser hooked to a flexible fiberoptic endoscope--to shine light onto the lungs through the fiberoptic imaging bundle of the scope. The fluorescence given off by the illuminated tissue is relayed back through a second imaging bundle and observed directly by the physician. With the LIFE-Lung, healthy lung tissue appears green and abnormal tissue appears red. In clinical trials, the LIFE-Lung was "171% more sensitive in picking up abnormalities than white light," says Harvey Pass, a professor of surgery and oncology at Wayne State University in Detroit, Michigan, and program director for the Barbara Ann Karmanos Cancer Institute in Detroit. A similar device, which uses a computer algorithm to distinguish between the subtle differences in the wavelengths of fluorescent light given off by normal and malignant tissues, is in development at Oak Ridge National Laboratory in Tennessee.
Differential fluorescence does not replace biopsy, says Bergein F. Overholt, president of Gastrointestinal Associates in Knoxville, Tennessee, a company involved in the development of the Oak Ridge device, but it may help decrease the number of biopsies needed by allowing a physician to screen large swaths of tissue quickly, and guiding them to sites of malignancies. Biopsy, which is still necessary for confirmation of malignancy, becomes much less of a hit-or-miss proposition with the use of the LIFE-Lung.
Weigel asserts that differential fluorescence is currently too expensive to be practical for general screening. She estimates the cost of the procedure at $2,000, compared to the $40 cost of a chest X-ray, the current general screening method. She is testing the technique in the highest-risk patients: people who appear to be cured following successful resection of lung cancer but who have approximately a 5% annual chance of developing a second primary cancer, and people with emphysema, who have a 3-5% annual chance of developing lung cancer.
One of the biggest contributions differential fluorescence can make, says Weigel, is to render practical a new technique called photodynamic therapy. The 30-minute procedure begins 48 hours after injection of a photosensitized drug, Photofrin, which concentrates mainly in cancerous tissue. When activated by nonthermal, 630-nm red laser light, Photofrin destroys cancer cells, leaving healthy tissue relatively unharmed. "Photodynamic therapy is curative in over 90% of patients with early NSCLC," says Weigel. "The importance of differential fluorescence for photodynamic therapy is that it could tell the oncologist where to shine the laser to kill the cancer so that they are not, in effect, shooting in the dark." Photodynamic therapy was conditionally approved for treatment of early stage I lung cancers by the FDA in January 1998.
Weigel also thinks differential fluorescence will become useful for monitoring treatment of cancers to make sure the treatment is working. Doctors would simply use the device on patients who have undergone radiation or photodynamic therapy to make sure the cancer had disappeared.
Both Xillix and Oak Ridge National Laboratory are developing differential fluorescence to screen a wide variety of other cancers, notably of the gastrointestinal tract. Oak Ridge researchers successfully tested their device against esophageal cancer, a rare but increasing malignancy that afflicts 11,000 and kills 10,000 people in the United States annually. In clinical trials, specificity was 95-100%, says Overholt. Xillix also plans to target bladder cancer, cervical cancer, and head and neck cancers with its device, says Laurie McMichael, the company's manager of investor relations and communications.
The Animal and Plant Health Inspection Service (APHIS), a service of the U.S. Department of Agriculture (USDA), is responsible for maintaining the health of the United States' plants and animals and thereby contributing to the national economy and public health. This includes guarding against the importation of diseases and pests, controlling insect and plant diseases that do break out within the nation's borders, and providing protection for U.S. animals ranging from endangered wild species to laboratory rats to show dogs. The APHIS World Wide Web site, located at
http://www.aphis.usda.gov/, offers some insight into how the service discharges its responsibilities.
The Mission link on the main page leads to a narrative, peppered with hypertext, that describes the mission of the APHIS and how the service goes about carrying out its mission. Each link within the narrative leads to fact sheets and APHIS program pages, such as the Center for Veterinary Biologics home page, the National Biological Control Institute home page, and a fact sheet on how APHIS facilitates the safe export of agricultural products. The Activities link leads to a guided tour of APHIS's activities conveyed through pictures. The Organization link leads to an easily navigable table of the various offices within APHIS.
Under the Functions heading on the main page is a list of links to topics of care within the service. Each link leads to an outline of key APHIS links, as well as other Web sites related to the topic. For instance, the Excluding Pests link provides access to such sites as the APHIS Plant Protection and Quarantine home page; the APHIS Welcome to the United States site, which outlines customs requirements for importing fruits, vegetables, and plants; and the Meet Agriculture's Beagle Brigade! site, which tells how the USDA is using beagles to sniff out illegal fruit and meat arriving from overseas. Related Web sites listed under the Excluding Pests link include the home pages for the U.S. Customs Service and the U.S. Immigration and Naturalization Service.
The News & Information heading on the main page is the gateway to a wealth of information on such topics as APHIS publications, regulations, import-export rules, and congressional statements. The Publications link leads to a listing of all currently available APHIS publications, a vast library of brochures, fact sheets, and technical reports on topics ranging from the Africanized honeybee to water spinach. The Regulations link leads to a bank of all APHIS documents published within the past four months, as well as an archive of
Federal Register
notices dating back to 1995. This link also leads to a searchable online version of the 1998 edition of the
Code of Federal Regulations.
The Import-Export link found under the News & Information heading leads to a detailed listing of the rules on importing and exporting various plant and animal species and products. The listing succinctly describes the documentation that must accompany each import or export, and includes contact telephone numbers for more information about specific families of plants and animals. The Communications to Congress link on the main page leads to the most recent statements and reports presented before Congress by APHIS, such as a 20 May 1998 statement by APHIS acting administrator Craig Reed concerning the Plant Protection Act.
The Hot Issues heading on the main page covers links to plant and animal issues in the headlines. For instance, the Medflies in Florida link leads to updates on how various Florida counties are faring in the battle against the Mediterranean fruit fly, which threatens the state's agriculture industry (the state is releasing sterile fruit flies as well as applying the pesticide malathion in an effort to eradicate the imported pest). Another example is the Vesicular Stomatitis link, which leads to weekly updates and contact information regarding the outbreak of this viral disease that appeared among New Mexico horses in mid-May.
Last Updated: August 24, 1998