Plants - How Could We Do Without Them?
Number 2 - January 2004
|This article appeared in Issue 2 of 'Cultivate' which had the theme of 'Plant use'. |
The following articles also appeared in that issue:
Plants - How could we do without them?
|Botanic gardens and the sustainable use of plants|
|Case study: |
Tam Dao National Park, Vietnam
For much of the world’s population, it is plants, in the form of fuel-wood or charcoal, that provide most household energy – not electricity; nine out of ten people live in informally built houses, often made from local plants; eight out of ten people consult traditional healers, who use edible wild plants and fungi as medicines and dietary supplements. We need plants for basic human activities –eating, washing and medicine, but also for shelter, amusement and transport.
When asked which plant species you would take to a desert island in the last issue’s poll – many of you identified plants which had multiple uses – aloe which has medicinal properties and bananas whose broad leaves and fibrous tissues can be used in making shelters. The wide range of uses of plants explains why, despite our dependence on only a few species for food, we need to be concerned about conserving diversity. In this article we take a brief look at some the less obvious uses of plants. We will start by looking at some of the ‘services’ plants provide to humankind before briefly covering a few of the more traditional but less recognised uses of plants. While we cannot hope to do justice to the amazing diversity of plants and their uses around the world, we hope this short article will provide some illustrations of just how dependant we are on plants, and how we use them in all aspects of our lives.
Forest canopies purify air by filtering particles and providing chemical reaction sites where pollutants are detoxified. Forest trees and other plants also store carbon and help to slow human-induced global climate change. Were it not for the carbon sink provided by plants, the rate of carbon dioxide accumulation in the atmosphere would be almost twice as fast as it is today – leading to rapid climate change.
Cleaning Toxic Soils
Soils in some areas are unusable as human activities have resulted in them becoming contaminated with heavy metals, radioactive elements and other toxins. Plants can be used to clean up such soils as they have the capacity to concentrate toxic elements in their tissues without harm. Mustard plants for example accumulate lead and certain ferns take up arsenic.
Plants provide natural protection for soils against erosion in several ways. Their leaves intercept raindrops, reducing the physical impact of raindrops, while their roots bind the soil, protecting it from being washed away by heavy rain. Plant cover also limits the drying effects of sunshine and helps to prevent soil being blown away by strong winds. Many of the deadly landslides associated with hurricanes and severe storms occur in areas where forests have been cleared and hillsides have been left bare.
Plants have formed the basis of traditional medicine for thousands of years. The first records are from Mesopotamia and date from about 2600BC, and include use of cedar, cypress, licorice, myrrh and opium poppy. Traditional medicine continues to be based on plants, with Indian medicine relying on around 7,000 different species. In 1990, Chinese doctors used 700,000 tons of plant material, and in 1994, China exported US$ 2 billion worth of plant drugs. In the USA, herbal medicines are worth around $1.6 billion annually. Several important drugs in modern medicine are derived from plants – the opium poppy is the source of morphine and codeine, and the Pacific Yew has been found to contain taxol, a novel drug used to fight cancer. Gardens in Britain provide 200 tonnes of native Yew clippings for the extraction of taxol.
One of the most successfully used plant products is the powder from pyrethrum flowers (Chrysanthemum cinerariaefolium). Pyrethroids act as insecticides, killing insects effectively before decomposing into harmless products. Neem is another plant-based insecticide used widely in India and Africa, especially for controlling insect pests in stored grain.
People use fibres from over 2,000 species – flax, hemp and cotton are amongst the best known and most widely used today. Before cotton was widely available in Europe, the fibres of the common stinging nettle (Urtica dioica) were used for making cloth. Even today, the leaves of many other well known plants which produce high-quality fibres, such as bananas and pineapples, are used in some countries for making clothes, ropes, handicrafts, mats etc. In the Pacific region, the bark of certain trees is collected, beaten and dried to make a cloth known as ‘tapa’ cloth, while in Africa and elsewhere, the leaves of palms, such as the raffia palm, are weaved into baskets, hats and a wide range of handicrafts. The leaves of the raffia palm are the largest in the entire plant kingdom – in some species stretching up to 25 metres in length.
Trees are essential to music! Musical instrument trees or tone-woods provide some of the most valuable timber in the forest products industry. Trees used to make musical instruments come from different types of forests - tropical, temperate and boreal - from all over the world. Current research has shown that there over 200 tree species used to make popular musical instruments, with over 70 of these species included in the World Conservation Union (IUCN) 2000 Red List of globally threatened trees.
Some examples include the African blackwood which is the preferred timber, for making oboes and clarinets. Possibly one hundred thousand of these instruments are being made from African blackwood each year. Pau Brasil is highly sought after for making bows for stringed instruments while Sitka spruce is considered to have excellent acoustic properties. The wood from cedar trees is another important tone-wood for soundboards of acoustic instruments and logs from these trees can reach $50,000. The trees that are sought after for tone woods are often several hundred years old, making conservation of the species a top priority. Despite restrictions in trade of many of these species, especially tropical species, such as mahogany and rosewood, demand is so high that illegal trade continues, threatening the long-term survival of some species. The SoundWood campaign is helping to address the problem of sourcing wood for instruments.
Plants have been used for cosmetic purposes since time immemorial. From the ancient Egyptians, who used olive oil perfumed with aromatic plants to keep their skin supple, to the modern day, plant extracts are widely used by men and women alike for cleansing and beautifying purposes. One of the oldest and best known plant oils is derived from lavender, the scientific name of which ‘Lavandula’ is derived from the Latin ‘lavare’, meaning to wash, after the widespread Roman practice of throwing lavender in their baths. Hair rinses and shampoos containing camomile (Chamaemelum nobile), are popular nowadays amongst those with blond hair. However, the importance of camomile was recognised by the Vikings who are known to have used the flowers to enhance their blonde locks. It was also honoured in their mythology, and was one of the 'sacred herbs' given to the gods by Wodan. Henna is another well-known, natural hair dye. Made from the crushed, dried leaves of the henna plant (Lawsonia inermis), it is one of the oldest known hair and body dies. The prophet Mohammed is said to have used it to redden his beard and it is still commonly used by women to colour not only their hair, but in some countries also their cheeks, hands, nails and feet.
There are countless other uses of plants – too many to record here. However, for those of you interested to read more, I can do no more than recommend the wonderful new edition of Anna Lewington’s book “Plants for People” recently published by Transworld publishers. Divided into chapters by the way plants serve us (e.g. plants that clothe us, plants that care for us) the book is lavishly illustrated as well as providing a fascinating read.