At the end of 1996 the IUCN announced that 33,730 species of plant are threatened with extinction. Should we care?

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At the end of 1996 the IUCN announced that 33,730 species of plant are threatened with extinction.  Should we care?

“In one of our religious books it is written that the tree is like ten sons.

  It gives ten valuable things: oxygen, water, energy, food, clothes, timber,

medicinal herbs, fodder flowers and shade.”

(Chipko leader, Sunderlal Bahaguna)

        Plants are essential to life on earth.  They have the unique ability to fix carbon and synthesise all the primary metabolites essential for biosynthesis; for example, the 20 amino acids necessary for life.  About 4 million species on earth rely upon the 380,000 species of plant (consisting of 250,000 higher plants) for survival (Green Inheritance, 1984).  This number is not certain - estimates have been as low as 345,000 for species already named and described (Cronquist, 1981) and as high as 630,000 for species described plus an estimate of still unnamed and undescribed species (Schultes, 1972; Tippo and Stern, 1977).  As described by Bahaguna, plants provide for us in many ways.

On 8th April 1998 a major twenty-year study by botanists and conservationists was made public: on a worldwide scale one in every 8 plant species is presently facing extinction. The United States is the statistical leader among nations that harbours whole strains of soon-to-be-obliterated plants.  According to the World Conservation Union's Red List, nearly one in 3 plant species in the USA will soon no longer exist (of 16,108 species described).  However, Dr. Pimm said he thought that the plight of plant life in the U.S. seems more grim than in other nations because those surveys made for the report were better conducted on American soil than elsewhere.

Causes of extinction:

        There are several causes of extinction: loss of habitat; change in habitat quality; habitat fragmentation; persecution and exploitation of populations; and changes in the biotic environment (Global Biodiversity Assessment, 1995).  Any loss of habit increases the risk of extinction of some species, so the loss of biodiversity cannot be minimised by a careful consideration of single species.  A change in the habitat quality is not as extreme as complete habitat loss, but it can still have a significant effect on the mean and variance of population growth rate.  The most common cause for a change in the habitat quality is due to climate change (Kareiva et al., 1993).  An important factor to take into account is the versatility of a species, and its capability to evolve (Lynch & Lande, 1993) – alternatively the animal may be able to migrate to areas that are still favourable.  Habitat fragmentation can divide a single population, which can then lead to the extinction of one of those populations (as it is too small).  Persecution and exploitation of populations has been (and continues to be) a special threat to some species, especially large vertebrates.  The extinction of large mammoths may have been caused by human hunters some ten to twenty thousand years ago (Martin & Klein, 1984), and the loss of the do do is certainly due to human impact.  The final factor that can cause extinction is ‘interaction with alien species’ – the introduction of a non-indigenous species has caused widespread destruction of natural habitats (Simberloff, 1995).  Transportation of alien species has occurred in many parts of the world, in both the animal and plant kingdom – 822 species of Hawaii’s indigenous plants are threatened with extinction by lantana.

Value to Medicine:

        Over the period 1959-1973 an average of 25.36% of all prescriptions in the US contained one or more active principles derived from higher plants. The percent was never lower than 23.12 and never higher than 28.22, during any single year (Farnsworth & Morris, 1976).  Since 1977 the World Health Organisation (WHO) has accepted that traditional medicine has a role in primary healthcare.  In fact, 75-90% of the world rely on herbal medicine, yet herbalism has not been accepted as a conventional medicine in many developed countries (Plants & Society, 1996) – China has had a combination of traditional ways with Western medicine for many years.

        The rainforest still holds many secrets, many of which are held by members of tribes who live in them.  A single shaman on the Wayan tribe in the northeast Amazon may use over one hundred different species for medicinal purposes alone, and a great many of these are effective.  By 2050 there is a very real possibility that much of this knowledge will be lost, as younger members of tribes are not showing any interest in traditional ways.  Some tribal knowledge has been gained, and as the indigenous ‘discovered’ the properties of these plants, there should be a form of payment – all too often pharmaceutical companies exploit local people.  Not only is there a possibility of knowledge being lost, but also “tropical rainforests are of special concern since the widespread destruction of these ecosytems threatens to eliminate thousands of species that have never been scientifically investigated for medical potential” – since it is possible that there is a cure in the plant kingdom for every disease, it seems insane to destroy the one resource that least is well documented.

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Some examples of important discoveries from the plant kingdom:

  • Salicylic acid obtained from willow bark; once purified and modified aspirin is formed.
  • 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.
  • 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) ...

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