Some examples of important discoveries from the plant kingdom:
- Salicylic acid obtained from willow bark; once purified and modified aspirin is formed.
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Witch hazel (Hamamelis virginiana) is a shrub or small native tree of Eastern North America – the leaves, twigs and barks have been used to prepare infusions to treat various aches and pains.
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Quinine comes from the Cinchona trees of the Andes, and is still the most effective anti-malarial agent; it is obtained from their bark, which is stripped off, thus leading to the tree’s eventual death.
Other discoveries (from the rainforest) include cardioactive agents (Aladesnmi & Llesanmi, 1987); antiviral agents (Wachsman et al., 1987); anti-implantation agents (Kong et al. 1985) and immunostimulants (Wagner et al., 1985).
Another example of the use of plants is for contraception – one of the oldest known effective plants for birth control was called silphium, a member of the Ferula genus. This plant was used well before 370 B.C. – apparently it was extremely effective and was used to extinction by the third or fourth century A.D.
Value of Plants in the Medicine industry:
There is a lot of money in the medicine industry, especially in research. The following is a calculation of the monetary value of plants in the developed world in the 1970s (US):
Since the total number of new and refilled prescriptions dispensed each year from community pharmacies in the US was known, the number containing plant-derived active constituents could be calculated. The resulting number could then be multiplied by the average prescription price for each year, which would give a dollar value at the consumer level for plant-derived prescriptions in the US. As many prescriptions in the US are dispensed from locations other than community pharmacies (eg hospital out-patient services, government agencies, mail-order services, etc) a reasonable factor to account for the total plant-derived drug market was determined to be 2 (Farnsworth and Morris, 1976). Thus in 1973, 1.532 billion new and refilled prescriptions were dispensed from community pharmacies. At an average cost to the consumer in that year of $4.13 per prescription, a dollar value of $6.327 billion (at the consumer level) for the market could be calculated. Thus, in 1973 the 25.2% of prescriptions found to contain active principles derived from plants, could be estimated at $1.594 billion. Multiplying this number by the factor of 2 gave a total value for plant-derived drugs in the United States during 1973 of about $3.188 billion. They may account for large revenue, but little of this money is ‘ploughed’ back into nature for its restoration and survival.
An additional 300 or so species of flowering plants are sold as herbal teas in the United States, mainly through health food outlets. According to FDA regulations, all of these herbal teas are considered to be ‘foods’ and not ‘drugs’ but it is obvious that the consumer purchases herbal teas because it is believed that they produce therapeutic effects. In 1979 the market value for herbal teas sold in health food outlets in the US was $150 million (Anonymous, 1980). Since these 300 or so species of flowering plants entering into the herbal tea market are not recognized as ‘drugs’, they were also not used in the calculations that follow.
If 5,000 species of flowering plants have been thoroughly examined on a worldwide basis as sources of useful drugs, and only 40 of these plants are currently used in the US as sources of drugs, it follows that for every 125 plants subjected to a thorough pharmacological examination one will eventually become important in medicine. It has been projected that 10% of all species of higher plants in the US will become extinct by the year 2000 AD (if appropriate measures are not taken to prevent this from happening) and this would involve 2,067 species. Thus it can be calculated that 2,067/125 = 16 species of useful drug plants will have been eliminated through extinction from the flora of the US.
Agriculture and Food:
Only 30% of the earth’s surface is land, and of this 12% is arable – fourteen crops account for 80% of the world’s food production (Roberts, 1998). While the human population is increasing (currently nearing 6 billion) the arable land area is decreasing (due to many areas becoming more arid and infertile). There is a tremendous strain on the land to produce sufficient yield to feed the population. To prevent world famine crop strains will need to be improved, increasing productivity and reducing susceptibility to disease and pests. Many wild relatives survive by doing just that, and this is due to the greater genetic variation in the wild – genetic resources must be conserved and made available to breeding programs to produce new and improved strains (Conserving the wild relatives of crops, 1988).
Farming today is designed for maximum yield per acre, and this is obtained by selecting the best seed and sowing fields of monocultures. This inbreeding to produce a high yielding seed reduces the genetic diversity of a crop, and is an ideal breeding ground for an opportunistic pathogen. The Irish potato famine of 1845 was due to this problem – all the potatoes grown in Ireland at that time were descended from an original stock from America. Phytophora infestans was able to infect all potatoes, leading to the death of over one million people.
Species in the wild have been used many times before, crossed with a domestic variety to produce an improved plant. The tomato plant of today (Lycopersicon esculentum) is a compilation of many plants: resistance to the fungus Fusarium oxysporum was obtained from L. pimpinellifolium; the genes used to adapt the fruit stalk for mechanical harvesting from L. cheesmanii; a more intense colour from L. chmielewskii; and finally increased beta carotene and vitamin C content (from L. hirsutum and L. peruvianum respectively). A wild species on the Galapagos islands can be crossed with a domestic tomato plant to convey salt resistance too (Green Inheritance, 1984). These modifications improve not only the aesthetic properties for the consumer, but also the nutritional value and even enabling plants to be grown in previously inhospitable soils.
Since Haber designed the aptly named ‘Haber process’ to produce ammonia, fertilizer has been applied to crops to increase the yield. The unfortunate consequence of excessive application is eutrophication (once the fertilizer is washed into streams). There is a species of South American grass that can form a symbiotic relationship with nitrogen-fixing bacteria; if this property could be introduced into wheat, then fertilizer application would be reduced and the wheat could be grown on poorer soils (Plant Extinction, 1990).
There are more than just those improvements mentioned above too. Some wild plants produce insecticides – these are secondary products which reduce a plant’s palatability – approximately 400,000 plants produce them. The accumulation of alkaloids or saponins produces a repellant bitter taste; cyanogens are toxic, and neem oil affects the hormonal balance and life cycle of the attacking insect. Pyrethrin, extracted from Chrysanthemum cinerariifolium, is an especially effective insecticide. It is a member of the pyrethroids that is broken down by sunlight; it has a very specialised mechanism that penetrates the cell membrane of the insect, blocking open the sodium channels, which disrupts the nervous system – it is dependent on the principle that pyrethroids are more soluble in fats than water. The most important additional advantage is that it is non-toxic to mammals and plants, and is biodegradable (unlike DDT). Acacia trees also release toxic chemicals in response to predation from giraffes – a pheromone is released (via a reaction mechanism) that causes all surrounding trees to produce this chemical too.
Solanum berthaultii, a wild potato from Bolivia, exhibits some remarkable characteristics. One of a farmer’s many problems is the aphid, often the cause of virus transmission – this species of potato plant is covered with sticky hairs that trap aphids, and it also releases a warning ‘pheromone’ that is identical to that produced by aphids themselves if alarmed. Many of these examples described will be advantageous not only to the specific species, but also to other wildlife – there will be a reduced need for insecticides, saving both the farmer money and the unnecessary death of many useful insects in the wild.
Crossing to improve a plant’s characteristics use to be a fairly random procedure – the staple plant is crossed with the appropriate strain showing the favourable trait. The problem encountered is that many undesirable characteristics are also introduced, so backcrosses are performed with the original staple plant, selecting each time for the characteristics desired, until the appropriate plant is obtained. Genetic engineering is opening up many possibilities, as specific genes can be introduced immediately; if genes from wild relatives are introduced then there will be no qualms from the public either – genetic engineering is encountering many problems due to some crops being “given a gene from a rat or a scorpion or a fish” (New Scientist, 23/10/98) – genetic engineering using wild relatives is only ‘speeding up the process of selective breeding’.
Plants in Industry:
Wood is the most obvious product from plants, and is of great importance. For many years it has been used in construction and for the production of paper. Trees grown in sustainable reserves are usually monoclonal (as with crops), so they are very vulnerable to disease and pests. It is important to maintain the genetic diversity of trees to protect the wholesale destruction of the crop. Cotton and linen, from the flax plant Linum, are more popular than their synthetic counterparts due to their ‘more comfortable feel’ – cotton is very efficient at wicking moisture away from the skin (a failure of nylon).
Natural rubber is a product from the latex of Castilla species, and the rubber tree Hevea brasiliensis. It is more expensive than the synthetic version, but is also longer lasting due to its superior quality – the market is split fairly evenly between the two at present.
Other species produce biocrude, which is a more viscous form of latex due to the lower water content. Euphorbia lathyris produces 50 barrels of biocrude per hectare per year; as oil prices continue to rise there may be more interest in this product as a renewable alternative.
Many of Brazil’s vehicles now use ‘Gasohol’ as their combustible fuel; this consists of 20% ethanol with 80% petrol. Aside from the obvious advantage of a lesser dependency on fossil fuels, there is also the benefit of less pollution – the alcohol leads to cleaner burning with fewer unburnt hydrocarbons being released into the atmosphere, and little/no carbon monoxide. Substitutes for diesel have been found from the copariba tree (Copaifera) and vegetable oils.
Aesthetic Uses:
The tropical rainforest is once again responsible for many other products: ranging from plants for cleansing, to coloured and sweet-smelling products (eg soaps, shampoos, toothpaste, creams and lotions, dyes, oils and incense to name a few). Chocolate, tea coffee, alcoholic beverages, perfumes and cosmetics are all derived from plants. The beauty of the flowers from many plants is also highly prized – much money is spent on gardens; there seems to be a human need for nature – “the further we are separated from our cities and civilisation, the more we fill our flats with plants” (Genetic Inheritance, 1984).
In-situ and Ex-situ:
As Whitmore expressed in 1975, one “must maintain the full genetic diversity of animal and plant species, especially those which occur at very low density”. To obtain this genetic diversity many more ‘in-situ’ areas need to be established. As has been described above, there are possibly many more plants to be discovered – there may also be medicinal features not yet discovered, and wild relatives of crop must be kept alive so that they can continue to evolve developing new traits and defences against new pathogens. Measures must be taken to prevent extinction of these wild relatives, such as setting aside reserves. This has been instigated to some extent – Special Sites of Scientific Interest (SSSI) in the UK and National Parks in the US are a start, but they are generally too small, and do not support a sufficiently diverse ecosystem. Some species can be conserved ‘ex-situ’ as dried seeds in seedbanks (or their genes in genebanks). This is effective for many species for a few years, but after this time the seeds must be sown otherwise they will lose their viability. Disadvantages of ex-situ storage include the inability for evolution to take place, some plants not producing seeds, and some producing recalcitrant seeds (which cannot be dried) (Green Inheritance, 1984).
Brazil – a case study:
Mahogany (Swietenia mahogani & S. macrophylla) is a highly valued wood, not only by the developed world, but also by the indigenous people of the state of Para, Brasil. The local tribes use this wood to construct canoes, but since it was discovered by Spanish explorers it has been used for furniture in the rest of the world. Commercially it is quite expensive, priced at $320 a tree – unfortunately only a small fraction of this money is being paid to the indigenous people ($20 per tree). Even this was not always paid by the logging companies – by March 1990, the Xikrin tribe (of Para) were suffering from alcoholism, prostitution, venereal disease and social breakdown (Vidal & Giannini, 1992). Due to this lack of payment from the loggers, there has been a constant extraction of trees from the state of Para, without any rejuvenation projects.
The scale of the problem is so huge that Brazil has listed this species as Vulnerable in the Annex of Convention on Nature Protection and Wildlife Preservation in the Western Hemisphere. S. macrophylla is also classified as a high priority species for genetic resource conservation by the International Board for Plant Genetic Resources. The reason these species are on these lists is not that they are near extinction (yet); it is that they are being removed at such a fast rate. For four months a year the trees are removed, 6 logs per lorry forty times a day. If this wasn’t a sufficient problem, every time a mahogany tree is cut down 28 other trees are seriously damaged: most are toppled or uprooted. 1450m2 of forest are affected by the cutting of every tree (Verissimo et al., 1992). The usual effect of removing forest is the loss of flora too – there can be a total disappearance of forest species, except for a few migratory species which occur sparsely (World Conservation Strategy, 1980).
Unless rejuvenation projects can be established mahogany will not continue to be a commercially viable product from Brazil. As of yet little is known about Brazil and its ecosystem – a problem encountered by Dr Brown (Oxford University) is that 99% of the seeds from mahogany trees are being eaten from the forest floor, thus preventing any reseeding and natural regrowth (it is not known by what species of animal – at present it is assumed to be a small rodent). Associated with the logging of the trees is the installation of roads though out Para, enabling easy access to previously impassable forest – more farms have been established, removing more of the rainforest that once stood.
Opposing views:
There is a policy called the ‘Triage policy’ which is based on logic that “some species will almost certainly go extinct whether or not we try to save them; other species may go extinct if we do nothing to help them but may survive if we do something; still others will probably survive if we do nothing”. This allegedly supports the notion of ‘live and let live’, yet Lovejoy (1980) states that “triage is both unworkable and misleading in its apparent common sense”.
It is obvious that the rate of extinction is hundreds of times higher than the natural background rate that prevailed, before the beginning of rapid human population growth (a few thousand years ago). This is the real reason why there are so many plants nearing extinction: due to pressure by population expansion on the land. If the population growth rate can be reduced, then maybe some plant preservation could take place.
Many people see the expenditure of vast amounts of money on nature reserves to be inappropriate, especially when one considers that up to 95% of all plants are not near extinction. In addition, when there are so many famine related problems in the world, surely the most important task is to produce as much food as possible, and if a few plants become extinct along the way then it is an unfortunate consequence.
The plants of the world are also extremely important to many countries’ economies. The exportation of mahogany from Brazil is the second biggest industry in the country (mining being the first) – if the mahogany trees are not cut down to be sold then an economy crashes (but the eventual problem still remains that at the rate the trees are cut down, this is a finite source of income).
Summary:
As can be seen by my proportionately biased argument, there are many reasons why we “should care”. “It is within the power of people, as intelligent beings, to modify their ways to avoid the unnecessary destruction of variety” – so much of the extinction of plant species is due to man, and his impact on nature. Mass extinction has occurred in the past of different species (eg the death of the dinosaurs), but this is situation is different: we have a choice about whether or not to save our ‘green heritage’ – the public needs to be made aware of the possibility that by 2050 up to 60,000 species may be extinct (IUCN, 1980)…
“nothing stimulates interest and concern like scarcity.”
References:
“Global biodiversity assessment”; Heywood; 1995
“Conserving the wild relatives of crops”; Hoyt; 1988
“Conservation of medicinal plants”; Akerele et al.; 1991
“World conservation strategy”; IUCN; 1st draft 1978
“Caring for the earth…”; IUCN/UNEP/WWF; 1991
“Plants and society”; Levetin & McMahon; 1996
“Economics and biological diversity”; McNeely; 1988
“Conservation biology”; Spellerberg; 1996
“Is using medicinal plants compatible with conservation?”; Sheldon; Plant talk; 1998
“Plants, people and culture, the science of ethnobiology”; Balick & Cox; 1996
“Green Inheritance”; Huxley; 1984
“Plants for people”; Lewington; 1990
“Plant extinction”; Koopowiti et al.; 1984
“Standards for ecologically responsible forest use”; Hammond; Global biodiversity; 1994
“The conservation of plant biodiversity”; Frankel et al.; 1997
Various internet sources; especially Friends of the Earth.
