|Biodiversity and Conservation|
source ref: biobook.html
|Chapter 1:Introduction, History of Life|
|Chapter 2:The Age of Mammals|
|Chapter 3: Extinction And deplition From Over-Exploitation|
|Chapter 4:Whaling And Fishing|
|Chapter 5:Overexploitation Threatening Living Species|
|Chapter 6:Global Patterns of Biodiversity|
|Chapter 7:Values of Biodiversity|
|Chapter 8:Endangered Species Conservation|
|Chapter 9:Exotic Introductions|
|Chapter 10:Forests and Deforestation|
|Chapter 11:Endangered Aquatic Habitats|
|Chapter 13:Protected Areas|
|Chapter 14:Habitat Pollution|
|Chapter 15:Captive Breeding and Reintroduction|
|Chapter 16:Human Population|
|ARGUMENTS FOR CONSERVATION
Biological Control Agents
Model Systems for Science
Question: What good are they?
Answer: What good are you?
(in reference to an endangered species of desert pupfish)
From Species in a Bucket by Edwin Philip Pister. Natural History, January 1993.
It is important to be able to clearly define the reasons for believing in conservation of biodiversity, if we are to justify it in the face of increasing threats to species survival. One way to identify the reasons is to look at what we derive from biological diversity, and what we will lose as a result of species extinction.
Animals. Only a couple of dozen animal species have been domesticated for food production. Virtually 100% of the protein from domesticated animals consumed by people comes from nine species: cattle, pigs, sheep, goats, water buffalo, chickens, ducks, geese and turkeys.
Fish are becoming a new kind of domesticated animal through the development of aquaculture techniques. Salmon are now being farmed in large steel/net cages that are moored in various estuaries and rivers in Norway, Canada, Chile, Spain, Scotland, and Ireland. Shrimp is being grown by aquaculture in many less developed countries including Thailand, Bangladesh, Ecuador and the Philippines. These shrimp farms often replace Mangrove Forests, so they have a serious environmental impact.
Many freshwater fish can be grown in ponds. Israel and China already get about half of their fish from aquaculture. The species most commonly grown in existing facilities is a cichlid called Tilapia. But there may be many other kinds of wild fish that could be grown by aquaculture. The huge, colorful and spectacular tridacna clam is now being farmed in Palau, and the farms are a popular tourist attraction.
Plants. Only a very small proportion of the world's plants have been used for food on a large scale. About 10-50,000 are thought to be edible, but only about 150 are used as human food. As economies have become more global, man has concentrated on fewer species so that today, 90% of the world's food comes from 15 species. Three of them - wheat, corn, and rice - supply two-thirds of this amount. Although there are over 10,000 species of cereals, no new ones have been brought into cultivation during the past 2000 years.
The dangers of relying on too few crops are illustrated by the Great Irish Potato Famine. Potatoes were introduced into Ireland from the New World in about 1600 and eventually most of the Irish people became dependent on this one crop. But then in 1845-1847, the wind-borne Potato blight fungus spread throughout the country and caused almost complete failure of the potato crop. It is estimated that 1 million people died of starvation, cholera and typhoid.
Bananas and plantains are a staple food crop for millions of people in the tropics, for example in large areas of West and Central Africa, where about 10 million tonnes are produced each year. The genus originated in the Asia and Pacific region, where there is still a rich source of diversity of wild species. Although bananas and plantains are best known as a food crop, the plant is used for many other purposes. Juice from the ripe fruit is used to make beer, unripe fruit is dried and made into animal feed, and the peels are used to make an antiseptic poultice for wounds. The plant fiber is made into a strong paper (used for bank notes), textiles, string, and for various handicrafts. The leaves are used as umbrellas and plates, and for making thatched roofs, for wrapping food, and many other uses. Starch is extracted from the plant and used for production of glue. In mixed farming systems, bananas are used as a shade plant for cocoa, coffee, black pepper and nutmeg, and in many countries the plant itself is used as an ornamental. Seeds from wild species are used for making necklaces and other ornaments. Banana sap can be used as a dye, and banana ash is used in making soap.
The vast store of species in the tropics is the obvious place to look for new potential crop plants. At least 1650 known tropical forest plants have potential as vegetable crops. The botanist N. Vavilov identified the major areas of high diversity of crops and of the origins of food crops around the world. Most of them are in developing tropical countries. The table shows some new tropical plant products that are gradually making their way on to the market, at least in health-food stores:
|POTENTIAL NEW CROPS FROM TROPICAL AMERICA|
|Buriti palm||Vitamin C-rich fruit, palm hearts,
oil, starch, wine, fiber.
"Biopiracy". Unscrupulous investors have been trying to patent genetic varieties, often when it is clear that they have not "invented" anything, but are simply taking advantage of traditional knowledge. For example, in 1994 the president of the U.S. seed company POD-NERS bought yellow beans in Sonora, Mexico. He brought them home, bred several generations, selecting for yellow seeds. In 1996 the company had produced a "uniform and stable variety with yellow seeds", and applied for a patent. In 1999 a U.S. patent (and Plant Variety Protection Certificate) was granted. In 1999 the company was suing Mexican bean exporters for patent infringement. There are hundreds of other cases of suspected biopiracy: search RAFI-USA for the latest news on this.
Wild plants are also important sources of genes that can confer useful properties on our conventional crops.
A wild relative of the potato was found in Peru, and when it was hybridized with the standard crop plant a variety was obtained that was resistant to potato blight.
A wild barley plant from Ethiopia provided a gene that protects the $160 million California barley crop from lethal yellow dwarf virus.
Rice grown in Asia is protected from the four main rice diseases by genes brought in from a wild species from India.
In both India and Africa, yields of cassava (tapioca) - one of the most important root crops throughout the tropics - were increased 18-fold because of disease resistance brought in from wild Brazilian cassava.
The sugar cane industry in the U.S. was saved from collapse by disease-resistance genes brought in from wild Asian species.
A wild tomato discovered in the Andes has been used to increase the sugar content of cultivated varieties, increasing their commercial value by $5-8 million per year.
Wild plant species usually have a great deal of genetic variability, so that markedly different strains can be developed by selective breeding from one species. This is an important reason for conserving not only species, but a good sampling of the genetic variability within species - i.e. samples from different locations, different subspecies, etc.
These genes from wild species usually have to be brought into the crop by hybridizing it with the wild species, then selectively breeding the hybrids. For this to work, the wild plant has to be closely enough related to the crop plant that it can be hybridized.
About 2.5 million entries are kept in 700 seed banks world wide, but there has been only limited success in using these wild species for crop improvement. Most of the successes have been in disease resistance, and this is because disease resistance is controlled by one or a few genes. This makes it very easy to transfer into a domestic species that can be hybridized to it:
|Parents:||RR x rr|
|Backcross (hybrid x parent):||Rr x RR|
But other characteristics, especially quantitative ones like annual yield or nutritional quality, are controlled by many genetic differences. One wild species may differ from a crop species in some genetic variations that increase yield and others that decrease it, their effects may be masked in the hybrid, and it is very difficult to capture the desired genes in the progeny of the hybrid. Therefore, a new trend in plant breeding is to try to map all of these genetic differences to their positions on the chromosomes. They are called Quantitative Trait Loci or QTLs. The idea is to carry out traditional hybridization and backcrosses, but to track the genetic differences at the DNA level rather than just measuring their effect on the plant (i.e. assess the genotype rather than the phenotype). This should make it possible to exploit much more of the useful genetic variations in wild species.
Another method of introducing desired genes into a species is by the newly developed technique of Genetic Modification (Genetic Engineering). If a desired gene from one species has been cloned, then by genetic engineering it can be transferred into another species. The gene has to be first inserted into an individual plant cell, and this cell is then grown into a clone in tissue culture, and the clone can be used to regenerate an entire transgenic plant. There are no serious barriers to this kind of gene transfer - the desired gene can come from another plant species or a different family, or from a bacterium or fungus or animal, or can be completely synthetic. Surprisingly, the way that genes are copied into RNA, and the RNA translated into protein, are practically identical in all species, so a foreign gene is usually functional. Furthermore, the protein produced by the foreign gene is also usually a functional product. For example, Monsanto is engineering crops to produce bovine growth hormone, which can be used to promote milk production in cattle, using a gene cloned from cattle. Transgenic sheep have been produced that synthesize a human protein for use in treating hemophilia.
An estimated 57 percent of the soybeans and 30 percent of the corn planted in the U.S. in 1999 were genetically modified (GM) (genetically engineered), either to resist pests or herbicides. As of February 1999, at least 64 GM crop varieties had been approved in the USA and Canada, 20 in Japan but only eight in Europe.
Many kinds of GM crops are being produced:
Insecticidal crops. Monsanto and Aventis CropScience have produced several GM crop varieties that make their own insecticide. This is done by transferring a gene from the naturally occurring soil bacterium Bacillus thuringiensis, that encodes an insecticidal protein called Bt toxin. Thus:
This reduces the need for pesticide spraying.
Roundup-ready crops. Several crops have been modified to make them resistant to the herbicide "Roundup" (glyphosate). This made it possible to use large quantities of Roundup around the crop to kill weeds without killing the crop.
Plants that taste better. Wheat and soy plants have been engineered to contain a gene from brazil nut plant that gives cereals produced from the plant a "nutty" flavor.
Plants that immunize. Australian scientists are trying to produce transgenic crops that produce a measles virus protein, so that children could be vaccinated by eating special varieties of rice or lettuce. The initial trials used tobacco plants, since the genetic methods had already been worked out with that plant. When fed to mice, the transgenic tobacco caused the mice to develop antibodies against the measles protein, and those antibodies then protect the mice against measles. Targets for development are plants that produce vaccines against cholera, tuberculosis and hepatitis, which kill millions of people every year including many children in developing countries.
Terminator technology. Another modification made in transgenic crops is called "terminator technology". It is a genetic modification that makes the plants grown from the transgenic seed sterile. This was promoted as a way to prevent the transgenic crop from hybridizing with other varieties. However, it was seen as a tactic by the seed companies to guarantee their markets. In response to public criticism, Monsanto has announced that it will no longer use this technology.
Increased crop yields. Global demand for food is expected to increase by ~50% in the next 20 years as a result of population growth and rising incomes. Its supporters argue that genetic engineering will contribute substantially to increased crop yields and so help increase the food supply. It can also increase the food value of crops: for example, a variety of rape seed (canola) has been genetically modified to contain high levels of beta carotene, which the body can convert into vitamin A. Canola oil from these plants could be made into a margarine that could provide enough beta carotene to prevent night blindness.
Reduced use of herbicides. The industry maintains that Roundup-ready crops will help farmers increase yields by improving weed control while reducing the total number of sprays needed to control weeds.
Reduced use of insecticides. Monsanto claims that their NewLeaf insect-resistant potato requires 40 percent less insecticide (for the Colorado potato beetle and aphids that transmit leaf roll virus disease) than other varieties.
Reduced soil erosion. When the crops planted are "Roundup-ready", the fields can be sprayed with Roundup and the weeds will be eliminated but the crop will not be affected. This eliminates the need for plowing, consequently there is less erosion and loss of topsoil.
Drought tolerance. Crops are being produced that are tolerant of drought, by incorporating genes from east that improve tolerance to high sodium.
Criticisms of GM crops
Some people object to genetic modification, believing it is unnatural and therefore wrong. Other criticisms are based on more practical considerations:
Health risks. GM crops may cause allergies. For example, Wheat and soy plants have been given a gene from the brazil nut plant to give them a "nutty" flavor , but this is the same gene that is responsible for allergies against brazil nuts, so the GM cereal may cause the same allergies! There have already been some examples of mistakes in identifying Genetically engineered crop plants. Studies of StarLink (insecticidal) corn show that it was not allergenic, as had been suspected but then an EPA report concluded that it may be. It was approved only for animal feed but was found to be contaminating several corn products sold to consumers.
Poisoning of wildlife. Pollen produced by the plant also contains the toxin, and this may be harmful to animals that feed on pollen. In field tests of Bt cotton, massive mortality of the bees around the test sites was observed.
Evolution of insecticide-resistant insect pests. The constant exposure to the insecticide may lead to faster development of resistance in the pest insects, than would be the case with an insecticide sprayed only when necessary. This could make the environmentally friendly Bt spray ineffective and force farmers to go back to more toxic chemical sprays. Bt-resistant insects have already been discovered in the US and elsewhere.
Contamination by Insecticide. The insecticide may be released into the soil and have harmful effects there, or contaminate streams. Bt toxin is known to be highly poisonous to fish.
Genetic contamination. There are two fears about genetic contamination. First, the herbicide-resistance genes may be transferred into other related wild species (e.g. sunflowers) by hybridization, producing herbicide-resistant weeds. Second, antibiotic-resistance genes have usually been used as genetic markers during the production of GM crops. They have no harmful effect on the plant, but there are fears that they could be captured by harmful bacteria, which would then be resistant to the antibiotic.
Loss of crop diversity. If the GM crops are successful, farmers are likely to become too dependent on a small number of GM varieties, leading to loss of non-GM varieties that could be have been useful in the future under changed conditions (e.g. drought or attack by presently unknown diseases or pests).
Conflict of interest. The company responsible for developing Roundup-ready crops was also selling Roundup. Terminator technology was widely believed to have been developed to provide a permanent market for the seeds, rather than to prevent genetic contamination.
65 plaintiffs including Greenpeace, the Sierra Club and the International Federation of Organic Agriculture Movements have filed a suit against the Environmental Protection Agency (EPA), demanding that the agency withdraw approval of all Bt plants and stop approving any new ones until it has done a complete assessment of their environmental impact.
Europe is considering a compulsory labeling system for foods containing products from genetically engineered crops. US biotech companies are frustrated with the resistance to GM crops in European countries, and claim that European governments are imposing non-tariff trade barriers that threaten to undermine the USA's $60 billion export trade in agricultural products. They have urged the US government to take their case to the World Trade Organization.
Food testing. Public fear of GM crops has led to calls for more complete testing of foods for health effects. But there are no good methods available. For example, to test for health effects of a GM tomato, biologists fed it to rats at a rate corresponding to 13 tomatoes per day, and were not able to demonstrate any difference between GM and conventional tomatoes - both groups of rats got sick! This is a general problem in food safety testing. It is very difficult to feed enough of the food product to any test animal to get a useful result. Instead, the usual procedure is to synthesize the suspect chemicals some other way (for example, produce them in transgenic bacteria) and then test the pure compound on animals. But this approach assumes that we know what chemicals need to be tested. We often do not know enough about how the biochemistry of the GM crop is altered to make this a safe strategy.
The Food and Drug Administration (FDA), which is responsible for certifying the safety of foods and food additives, has no authority over pesticides, so they refer matters concerning Bt to the EPA. But the EPA has been slow to recognize any dangers of GM crops. USDA is responsible for determining whether GM foods represent plant pests, and they have ruled many GM crops harmless.
StarLink, produced by Aventis CropScience, has been genetically altered to produce a protein, Cry9C, to repel pests. Because the protein may be a human allergen, it was barred from human food in 1998. Since then, Aventis has asked EPA to approve StarLink for human consumption. In September 2000, the altered corn was detected in Taco Bell taco shells being sold in grocery stores. Since then it has turned up in numerous other brands of taco shells, corn meal and corn flour. In February 2001, a group of Iowa farmers filed a class action suit in Des Moines, saying they were financially hurt because of consumer fears generated by StarLink.
Politicians debate genetically engineered seeds | Transgenic Plants and World Agriculture | Genetically Modified Trees Pose Concern | Key FDA Documents Revealing Hazards of Genetically Engineered Foods | Rachel's Environment and Health weekly #685 - Trouble in the Garden | Genetically modified world | Rural Advancement Foundation International | Biosafety talks conclude in surprising accord | Biotech Myths Exposed | PBS - harvest of fear
Value of genes. Genetic engineering only works with genes that have been isolated and analyzed at the molecular level, and the technology is still dependent on biological diversity to get the genes in the first place. All of the genetic variation present in wild populations is potentially useful for improvement of domestic animals and plants, and therefore should be preserved.
On many occasions, man has introduced exotic animals or plants that have become serious pests. Usually, the best control methods have been to find the natural antagonists of the species in its original home. For example:
Prickly Pear Cactus was introduced into Queensland, Australia, in the 19th century to provide cattle fences. It grew out of control, almost covering 100,000 square miles of land. Eventually a small moth was discovered in South America, whose caterpillars feed on prickly pear. It was introduced to Australia and quickly decimated the prickly pear, and ever since the prickly pear population has been low enough that it is not a major problem. Now we need something like that for Artichoke thistle, Pampas grass and Castor bean.
Introducing exotic species can, of course, cause problems of its own. Sometimes the organism introduced to control a pest can expand its host range and cause serious damage to native organisms. This happened with a weevil introduced to control thistles.
Rabbits were introduced from Europe to Australia and were a serious pest. They were brought under control using the myxomatosis virus.
Striga. In Africa, sorghum, millet and maize production can be reduced by as much as 70% by a parasitic weed called witchweed or striga. Striga is a parasitic plant that penetrates the roots of other plants, diverting nutrients from them and stunting their growth. Traditional weed control methods are ineffective in controlling striga but scientists have identified an African fungus that effectively eliminates the weed from cropland.
Cottony Cushion Scale was introduced here from Australia in the 19th century and almost wiped out the California citrus industry. Entomologists went to Australia and found a small beetle predator, the Vedalia. This was introduced and has kept the scale insect under control ever since.
Other insect pests including Sugarcane Weevil in Hawaii, Gypsy Moths, Browntail Moths and Alfalfa Weevils in the U. S., and Rhinoceros Beetles in Mauritius, have been controlled by introduced parasitic insects.
Scientists from the University of Illinois recently identified two species of parasitic wasps that may prove useful in controlling stable flies and house flies, two well-known pests in the midwest United States.
Gypsy moth larvae have been defoliating huge areas of forest in New England since they were accidentally introduced in 1869. The insecticide spraying programs have wiped out dozens of native moths and butterflies, probably doing more damage than the gypsy moth would have done. Now it is being controlled by a short-lived toxin (Bt) produced by a naturally occurring soil bacterium Bacillus thuringiensis, and a naturally occurring virus (marketed as Gypchek). A lethal fungus is also being tested.
A new strain of Bacillus thuringiensis might be able to kill more pest species than previously used strains, without harming beneficial insects.
All of these examples depended on the availability of wild species.
Pesticides. Many tropical
plants produce chemicals that deter herbivores. Tropical indigenous people have discovered
many of these plants, and use them as poisons or medicines:
i.Calabar bean was traditionally used as a poison in West Africa. Chemical studies of this plant led to the development of methyl carbamate insecticides.
ii. Daisy plants (Chrysanthemum cinerariaefolium) were first used centuries ago as a lice remedy in the Middle East, and this led to the discovery of pyrethrum insecticides. The seeds contain a natural insecticide called pyrethrin, a generic name for six related active compounds. It is one of the safer insecticides for several reasons: it decomposes rapidly in sunlight; it has few known effects on mammals; and insects do not develop resistance to it. It is used on foodstuffs, in head lice shampoos, and in many indoor insect sprays. 100,000 tons of mosquito coils made from pyrethrum are sold each year. Scientists have synthesized similar compounds called pyrethroids, but the chemical synthesis produces all geometric isomers of the compounds, many of which are ineffective and are difficult to separate from the active forms. The plant material contains only the active isomers.
iii. In South America, the natives use an extract of a forest vine to stun fish; this led to the discovery of rotenone, a biodegradable insecticide.
iv. The bacterium Bacillus thuringiensis produces toxic proteins that kill certain insects but are apparently harmless to humans. These are being produced and marketed as biopesticides. And Monsanto has engineered cotton plants that produce their own protein insecticide.
v. The Neem tree, in India, has been found to be a source of the insecticide azadirachtin, as well as fungicides, spermicide, and agents potentially valuable in birth control such as materials that prevent implantation or cause abortion. The tree has been used in traditional agriculture, medicine and cosmetics for centuries. However, recently companies from industrialized countries have been seeking patent protection, and 90 patents have been granted worldwide for "inventions" of products from Neem. A coalition or organizations has been fighting patenting of materials already in traditional use (biopiracy), and in 2000 they achieved their first victory in persuading the European Patent Office to revoke a patent from USDA and W.R. Grace on Neem tree fungicide on the basis that the product was already being used traditionally (in India) before the Company patented it.
Other tropical plants have been found to be toxic to leafcutter ants, mosquitoes, and other insects, and could lead to the discovery of other pesticides.
Medicines. The potential for discovering medicinal compounds in wild organisms is enormous, and provides one of the most powerful arguments for conservation of biological diversity. This is especially true of tropical forests.
The pharmaceutical industry is much more dependent on natural products than is generally realized. About a quarter of all prescription drugs are taken directly from plants or are chemically modified versions of plant substances, and more than half of them are modeled on natural compounds. About 121 prescription drugs are derived from higher plants. These include morphine, codeine, quinine, atropine, and digitalis. Yet fewer than 1% of rainforest plants have been tested.
MEDICINES FROM WILDLIFE
(from a list of 117)
|Immunosuppressant||Cyclosporin||Fungus, Tolypocladium inflatum|
|Contraceptives||Steroids||Fungus, Rhizopus nigricans|
|Anti-inflammatory||Cortisone and prednisone||Fungus, Rhizopus nigricans|
|Cholesterol lowering||Lovastatin||Fungus, Aspergillus terreus|
Central American frog
|+ (Indian fever bark)|
+ (arrow poison)
|Antispasmodics for intestinal disorders||Scopolamine, Hyoscyamine||Nightshade
|+ (arrow poison)|
|High Blood pressure||Reserpine||Rauwolfia
Why should plants make medicines? Wild plants have been evolving chemical defense mechanisms for millions of years. The chemicals that have evolved are highly specific toxins that attack herbivores at various different points in biochemical pathways. Although the chemicals are often toxic, sometimes if they are delivered in the right way or in the right dose, or altered chemically, they can be used to attack disease-causing agents or even cancer cells.
Many of these chemicals are derived from plants that had been used in traditional medicine. For example, Peruvian Indians had a cure for malaria; they used an extract of the bark of the Cinchona tree, and this led to the discovery and use of quinine as an antimalarial treatment. Many plants have been used traditionally because they are psychoactive. Of the 121 drugs mentioned earlier, 74% were identified through native folklore.
A Japanese company was recently awarded a patent on a chemical derived from the Congorosa bush, a plant that is native to Uruguay. The native people have known for centuries that the plant can be used to combat inflammation and as a stomach and liver analgesic, so they are very much opposed to paying a fee to a Japanese company for the right to continue these uses.
Natural products isolated from higher plants and microorganisms
Even compounds produced by insects and other invertebrates may be useful. Recently a protein isolated from the salivary gland of a biting sandfly was shown to have a very powerful vasodilation effect (this facilitates blood feeding by the insect when it is injected into the host).
i. Anti-cancer drugs. The rosy periwinkle was used in Cuba, the Philippines, and South Africa for the treatment of inflammation, rheumatism, and diabetes. In the late 1950s, vincristine and vinblastine were isolated from the periwinkle plant by Eli Lilly scientists and these chemicals were shown to have anti-cancer effects. Treatment with these drugs has increased the chances of remission to 99% in childhood leukemia and to 70% in Hodgkin's disease. Global sales of vincristine and vinblastine earn the Eli Lilly Company about $100 million each year.
|Cantharidin||Chinese Blister beetle||+ (abortifacient)|
|Podophyllum peltatum||+ (snake
bites, weakness, condyloma,
|Monocrotaline||Crotalaria spectabilis||+ (skin cancer)|
|Rosy periwinkle||+ (diabetes)|
|Taxol||Yew (Taxus brevifolia)||_|
In 1986, the National Cancer Institute started a new, extensive plant collection and screening program and has tested (on cultured cells) 35,000 species of higher plants as well as other organisms for anti-AIDS and anti-cancer activity. As of 1991, over 800 had shown some anti-HIV activity and 60 had shown anti-cancer activity (the HIV screens have been given higher priority). Plants used as medicines or toxins by forest people were 2-5x more likely to be active in these assays as other plants. This is a very preliminary result, and many more tests have to be done before any of these compounds will go into clinical trials. NCI estimates that of every 10,000 extracts tested, fewer than 10 will reach clinical trials. NCI is also supporting botanical exploration, research and training to increase the number of species to be tested. The collections have identified more than 40 new species of plants. NCI requires that if a pharmaceutical company receives a patent license, they have to share a percentage of the royalties with the country where the sample originated.
Chemists have devised ways of synthesizing many of the medicinal compounds found in plants. But it is usually (in about 90% of cases) cheaper to extract the natural product. In spite of this, pharmaceutical firms in the U.S. are doing very little to discover new drugs from higher plants. They are concentrating on other approaches; for example, using supercomputers to design new molecules.
An exception is Shaman Pharmaceuticals, a company set up specifically to identify and obtain medicinal compounds from tropical plants. Their program involves a serious effort to obtain not only materials but also knowledge from the people of the rain forest; they spend a lot of time interviewing forest people about medicinal uses of plants, then give much higher priority to testing those that have folk uses. They are screening for antiviral, antifungal, and sedative/analgesic activity. Out of the first 58 species screened, they found that 60% had activity in one of their screens, and 74% of their active samples correlated with the original ethnobotanical use. This is a much higher "hit" rate than then NCI rate, perhaps because of the different activities being screened for, and perhaps because they make greater use of ethnobotanical knowledge. This company is also dedicated to developing nondestructive harvesting methods and in providing benefits from any discoveries to the indigenous people who are the primary sources of the inventions. Merck & Co. have also set up an agreement with a research institute in Costa Rica to screen samples from micro-organisms, plants and insects from that country's forests. The institute will earn a share of any royalties on the sale of products derived from the project.
In 1982, the. e TRAMIL (Traditional Medicine for the Islands) research network was launched in the Dominican Republic to provide scientifically proven alternatives to patent drugs, which are becoming scarcer and more expensive due to increasing poverty and dwindling foreign currency reserves. The network which recognizes that many rural people are more familiar with medicinal plants aims to ensure the safety, efficacy, and accessibility of natural medicines. In this manner, TRAMIL hopes to preserve the diversity of plant species and indigenous knowledg
|Commercial overharvesting of some medicinal plants including
goldenseal root, American ginseng, and Echinacea, may be endangering the survival of these
species. American Indians have developed ways
of using these plants more sustainably.
In 1998, the Indian Council of Scientific and Industrial Research successfully challenged six patent applications on the medicinal properties of turmeric. The U.S. patent office ruled that turmeric's medicinal properties were part of the traditional Indian knowledge base and were therefore not patentable.
The Pacific Yew tree, a rare and slow-growing tree in the Pacific Northwest, is the only source of a drug called taxol, which appears to be very effective in treating ovarian cancer and has great promise for treating breast cancer as well. Each year, about 20,500 women are diagnosed with ovarian cancer and about half that number die from it. But it takes six Pacific yew trees to extract enough taxol to treat one patient. The National Cancer Institute has enough available to treat about 300 patients-not even enough to complete clinical trials. The yew tree is found only in old-growth forests, so it has now become a potential problem, along with the spotted owl, in trying to save these forests. Recently, chemists found ways of synthesizing taxol, but it is a very complicated process. Another more feasible solution is to chemically modify related compounds that are found in the English Yew, which is a widely planted ornamental plant and could produce a sustainable supply so that the Pacific Yew will not have to be harvested.
The taxol story will hopefully have a happy ending, and it teaches us that the forest (and other natural habitats) should be considered a source of knowledge about medicines, rather than a source of the medicines themselves.
ii. Antibiotics. Antibiotics are generally isolated from fungi (e.g. penicillin) or bacteria (e.g. erythromycin). However, a small group of antibiotics comes from marine animals- mimosamycin, that comes from a nudibranch (sea slug) and a sponge.
(about 1,000 now known)
Fertilizers. Recent research has led to the identification of species of bacteria from the deep ocean that are capable of fixing nitrogen, converting into a form that can be used as a fertilizer for crops.
Materials. Many organisms have evolved materials whose unusual physical properties may make them useful. They may be obtained from the wild or, better, copied by biochemists. In many cases, finding one useful material may lead to the discovery of many more, with subtle differences in physical properties, from related organisms.
i. Fibers. Silkworm silk has been used for hundreds of years in production of fabrics. Spider silk, which is chemically very similar to silkworm silk, comes in many different varieties (some species make seven different kinds - see slide) and has 5-10x the tensile strength of steel and some very unusual elastic properties. It has been used on a limited basis for fishing nets and for wound dressings, and for cross hairs in optical instruments. However, for other applications it cannot be obtained in large enough quantities from spiders. Therefore, the genes for spider silk have been placed in bacteria or animal cells, which then make the silk protein. However, they make it in a solution, and this has to be extruded (forced through a small orifice at high pressure) to force the protein molecules to line up into a fiber. Nexia Biotechnologies is now producing transgenic goats in which a gene for spider silk is expressed in large quantities in the mammary glands. They are now working on ways to spin it into fiber. The artificial silk has the potential to be strong enough to make bullet-proof vests, surgical sutures and artificial tendons.
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ii. Coatings. Shellac, a wax produced by insects that is harvested by hand from trees in India. 4 million pounds/year are harvested and used in varnishes, paints, stiffeners and other uses. Some related species of insects in the southwestern U.S. make colored waxes that were used by the Indians to waterproof and decorate baskets and to repair pottery.
The cuticles and eggshells of insects, crustaceans, and many other animals, and the seed coats and other protective layers on plants may have useful properties as waterproof coatings for other materials. Chitin (the carbohydrate part of cuticle, extracted from shrimp shells) is already used to make wool shrink-resistant.
Keratins (the protein of feathers and hair) is used as a coating for pills so that they survive the acid stomach but then release their contents in the alkaline intestine.
iii. Adhesives. Casein, a protein from milk, is already used extensively in glue manufacture as well as in plastics and paints.
At least two companies are now marketing a glue based on the adhesive used by marine mussels to hold themselves on rocks. This kind of glue will stick to animal tissue as well as to metals and other materials. It might be useful in surgery and in other places where glue needs to function in a wet environment or needs to join dissimilar materials like metal and bone. One company is extracting the glue directly from a gland in the mussel, the other is synthesizing a glue based on the composition of the natural adhesive. Unfortunately, the natural material is not well understood. However, there are hundreds of different kinds of mussel, and there may be many different versions of the glue to investigate.
iv. Biopolymers, especially moldable polymers, similar to plastics made chemically, have been produced in bacteria and theoretically could be produced in plants, so that the material could be grown as a crop.
v. Oils. About 20% of the petroleum used in this country is used for non-fuel purposes such as plastics, fertilizers, lubricants, and adhesives. The majority of these substances can now be synthesized from plant products. In fact, about 3 million tons of vegetable fats and oils are already used in these processes annually. Further development of these industries could help in reducing our dependence on non-renewable fossil fuels.
There are several promising tropical oil plants in South America, including:
Another very important plant is Jojoba, a desert plant of the southwestern United States and northern Mexico that produces a "liquid wax" (chemically different from an oil) that is almost identical to sperm whale oil, is very useful as a heat-resistant lubricant and has many other potential uses. Another desert plant, guayule, has a very high content of natural rubber and could help to relieve the dependence of this country on rubber grown in Southeast Asia.
Oil from the seed of India's Pongamia pinnata tree is being used as a substitute for diesel in electricity generation in rural areas of the country.
vi. Enzymes. Some of the bacteria-like organisms found near submarine hot vents (Archaea) can live at temperatures as high as 113oC and may be useful in the production of enzymes that are stable at high temperatures (for use in washing machines, for example).
Biomimetic materials science is the name given to attempts to mimic the materials found in nature. Much of it is funded by the Navy and the Air Force, because of the potential importance of lightweight but strong materials in aerospace engineering, and of underwater glues and coatings in marine engineering. It is necessary to understand not only the chemical makeup of the biological materials, but also the organization of different components within the material (e.g. calcite and proteins in sea urchin skeleton, or carbohydrate and protein in cuticle), which in nature is controlled by the cells producing the material.
Wild organisms carry out many functions in the environment that are vital to us, and that would be very difficult to do ourselves. Bees pollinate about a trillion apple blossoms each year in New York State.
Carpenter bees pollinate Brazil-nut trees. Bats pollinate wild bananas (not the cultivated ones that are parthenocarpic), breadfruit, guava and durian (Malaysian fruit). Wild micro-organisms biodegrade much of our garbage as well as fallen leaves and other dead animal and plant matter. Earthworms turn over soil and keep it aerated. Soil bacteria turn nitrogen into nitrate fertilizer. Plants use up carbon dioxide and produce oxygen, thereby slowing global warming due to CO2.
A few decades ago, the water in the Chesapeake Bay was clear because oysters were filtering out particles at a rate estimated to be the equivalent of the entire volume of the bay every three days. Because the oysters have been overharvested (99% gone) they are no longer able to keep up with the accumulation of silt and other particulates.
All of these services, and many more besides, are provided free of charge and usually taken for granted until they stop.
CO2 - 02 exchange
micro - organisms
Bioremediation (=phytoremediation if it is done by plants) refers to the use of organisms to clean up toxic wastes. Some plant species that live naturally on soils that are rich in heavy metals have evolved biochemical mechanisms for extracting those metals from the soil and accumulating them to very high levels in their tissues. They are called hyperaccumulators. Plants in the mustard family are especially promising. Some of them accumulate so much metal that it makes up 5% of their weight. This makes them toxic to insects, so it has probably evolved as a defense mechanism. The accumulated metals also makes them harmful or lethal to grazing animals including cattle and horses. Read how "locoism" may have played a part in General Custer's defeat at the battle of Little Big Horn. Plants have been found that hyperaccumulate copper, nickel, lead, cadmium, chromium, zinc, cobalt, mercury and selenium, so they are being planted on toxic waste sites where they remove the toxic metals from the soil. They can be burned in order to recover the metal in cases (copper and nickel) where the metal is valuable. With less valuable metals such as lead, the hyperaccumulating plants are much easier to dispose of than contaminated soil.
A simple use of phytoremediation has been used in California's San Joaquin Valley, where there is a problem with high levels of selenium in the soil. Growing mustard plants on the contaminated soil reduced selenium levels by 50% at depths down to 1m.
Other sites where this technique is being used include abandoned mines (zinc and lead); military sites (lead and cadmium); municipal waste dumps (copper, mercury, lead); and sewage dumps (all of these metals). Phytoremediation is potentially much more effective and less expensive than current methods which consist mainly of excavation and reburial.
Some of the metals that are toxic at high levels (e.g., selenium) are actually required by the body at low levels. So hyperaccumulating plants may also be useful in providing essential metals in the diet at the appropriate levels.
Some of the hyperaccumulating plants are difficult to grow and do not produce much biomass. Scientists are therefore identifying and cloning the genes responsible for hyperaccumulation and exploring ways of transferring them into common crop plants that would not have these drawbacks.
In a paper published in Nature in May 1997, a
group of 13 ecologists, geographers and economists estimated the economic value of these
environmental services at between $16 and $54 trillion per year. This estimate is based on
the cost of artificially providing the same services. The services they evaluated included
food production, raw materials, recreation and water supply, regulation of climate and
atmospheric gases, water cycling, erosion control, soil formation, nutrient cycling and
the purification of wastes. Also read the discussion of this paper.
Ecosystem Services: Benefits Supplied to Human Societies by Natural Ecosystems
"Miners use canaries to warn them of deadly gases. It might not be a bad idea if we took the same warning from the dead birds in our countryside" (H.R.H. the Duke of Edinburgh at the Wild Life Fund dinner, about 1963 in reference to DDT). Today, we might take the same warning from the forest dieback, the dead sea lions and dolphins on our beaches, and the missing amphibians. (See Lecture 14 for examples of the effects of chemical pollutants on wildlife.) If the environment is killing animals and plants, it might eventually kill us too. Pesticide levels in human milk are enormous. If we were egg-laying mammals we might be suffering from eggshell thinning caused by DDT by now.
The necessity of looking to wildlife species for warning signs becomes more evident when one considers that for 71 percent of the 3,000 highest-volume chemicals in the U.S. economy no human health-effect screening has ever been conducted. A 1984 report released by the National Academy of Sciences' National Research Council documented a lack of "even minimal" health screening tests for 78 percent of high-production-volume chemicals in the U.S. In July of 1997, the Environmental Defense Fund released a study entitled "Toxic Ignorance" that pointed to the lack of improvement in screening over the last 13 years. In conjunction with the report's release, the EDF called for commitments from the chief executive officers of the 100 top chemical manufacturers in the U.S. to complete preliminary health screening tests on each company's top-selling chemicals before the year 2000, and disclose the results to the public. According to the EDF study, the testing requested would cost between 1/10 of a cent to 2/3 of a cent per dollar of profit for the top 100 US companies, which made profits of $29.4 billion last year on $230.5 billion of chemical sales. In the meantime, the effects of these chemicals on wildlife, and on humans, remain unknown.
Wild species provide raw material for basic research. The object of basic research is simply to understand the natural world. Even though it often leads to material benefits, and is justified that way, the motivation is simply the challenge to know as much as possible about the natural world, and to understand how both living and non-living things work.
Wildlife is worth conserving because it is interesting, beautiful, spectacular, or contributes to landscapes that are interesting, beautiful, or spectacular. Wild animals and plants provide inspiration not only to biologists but also to millions of naturalists, explorers, painters, photographers, writers, poets and musicians. After Aldous Huxley read Rachel Carson's Silent Spring (about the loss of songbirds due to DDT), his comment was that "we are losing half the subject-matter of English poetry".
Enjoying wildlife is far from being restricted to poets, however. According to a survey conducted for the U.S. Fish and Wildlife Service, 77 million Americans participated in wildlife-related recreation in 1996. During that time, they spent $108 billion compared to only $81 billion on cars. Preserving the environment is healthy for the economy as well as for the soul.
John Muir, one of the founders of the Sierra Club, valued wilderness and wild creatures for their aesthetic qualities. He managed to convince President Theodore Roosevelt, the hunter, that our most beautiful areas should be protected, simply for aesthetic reasons. His work led to the establishment of Yosemite National Park and many other protected areas.
These arguments justify saving subspecies as well as species. Some of them justify preserving abundance as well as existence of a species. Of course, ecosystems are interesting too, and according to this view they should also be conserved. Some of the most interesting aspects of animal life (social behavior, migration, etc.) occur only in the wild, not in zoos. So this argument favors conservation in the wild.
We do not know what our value systems will be in the future, or what the value systems of our successors will be. Perhaps they will need vast quantities of some species that we now consider insignificant or even harmful. Many of the natural sources of medicines are, in fact, poisonous. Nobody could have predicted that bread mold would be the source of one of the most useful antibiotics; that armadillos would have been useful in medical research because they are the only experimental animal that can be infected with leprosy; or that the Madagascar periwinkle would be a source of an antileukemic drug, or that a heat-loving microbe living in a hot spring at Yellowstone National Park would provide a key ingredient in the DNA fingerprinting work was so important in the O.J. Simpson trial.
The main reason for preserving not only species but also genetic variability of not only wild species but also domesticated ones (and humans!) is so that we, and the other animals and plants on the planet, can adapt to unforeseen changing circumstances.
A relevant question that is now being asked is whether we should destroy the last remaining stocks of the smallpox virus. They are being kept in a freezer pending review of a decision made to destroy them in 1999.
In the future we may find new reasons for keeping ecosystems, not just species, alive. We could not learn about medicinal plants from chimpanzees if they are in a zoo - they have to be in an intact environment in the wild.
By allowing species to become extinct and by destroying ecosystems we cut off options that we are not capable of imagining; the responsible course is to keep as many options open as possible.
For additional reading, see "Do We Still Need Nature? The Importance of Biological Diversity".Biodiversity and its value (Biodiversity Series No. 1)
INTERNATIONAL SOCIETY FOR ECOLOGICAL ECONOMICS
The search for agricultural and medicinal uses for the world's biodiversity can be controversial. Legal and ethical issues surrounding the sharing of genetic resources and the profits realized from them remain unresolved. The United Nations Convention on Biodiversity addresses many of these issues and has been ratified by 170 countries. Some countries, including the United States, still refuse to sign the agreement, primarily because it contains clauses requiring profits from biodiversity be shared with the species' country of origin.
Finding useful drugs in wild plants and animals can be a mixed blessing. According to the World Health Organization the global trade was worth about $500 million a year in 1980, but by 2000, the larger European market alone may reach $500 billion. A 1998 study by TRAFFIC, the wildlife trade monitoring program of World Wildlife Fund and the World Conservation Union, identified 102 medicinal plant species (including the frankincense tree) and 29 medicinal animal species (including the green turtle, African rock python, and black rhinoceros) as priorities for early conservation and management action.