Science Strategy
Mission & Subject Matter
Kew's Mission – The mission of the Royal Botanic Gardens, Kew, which has been agreed by the Board of Trustees and the staff, is:
"To inspire and deliver science-based plant conservation worldwide, enhancing the quality of life"
Importance of Plant Diversity - Plants provide the autotrophic foundation of virtually all terrestrial ecosystems, transforming the sun's energy into chemical energy, that ultimately fuels almost all animals – including ourselves. In the process, plants fix carbon dioxide from the air and liberate oxygen – thereby playing a significant role in controlling the composition of our atmosphere. As primary producers, plants are fundamental to the functioning of the vast majority of the earth's ecological systems. For all practical purposes - 'All Life Depends on Plants'. In addition, because of the close association between plants and some of the more diverse groups of terrestrial organisms, such as insects, the diversity of plants is probably one of the best available predictors of the total diversity of living organisms across ecosystems. With current levels of knowledge, plants provide a useful and practical scientific basis for defining priority areas for conservation.
Plants have had a strong influence on the direction and development of human civilisation, not only through the clear relationship between the development of agriculture and the elaboration of complex human societies, but also through the enormous utilisation of diverse plant products for many different purposes in different parts of the world.
Plant diversity is of direct economic importance for two main sets of reasons: i) actual or potential uses of plant species; and ii) the contribution of diverse vegetation to the support of other biodiversity and the provision of ecosystem services (see below).
Actual or Potential Uses of Plant Species - Just three species of grass – wheat, rice and maize – provide more than half the human direct plant-derived dietary energy. With the addition of sorghum, millet, potatoes, sweet potatoes, soybean and sugar this increases to 75%. Thirty crops provide 95% of the human direct plant-derived energy. Thus, at first sight, human utilisation of the plant kingdom for food seems relatively narrow. However, this belies the situation in many parts of the world.
Around the world, more than 7,000 plant species are cultivated and collected by humans for food, while in total more than 30,000 species are thought to be edible. Furthermore, the greatest reliance on the greatest diversity of plants for food – and for many other purposes – is in those developing areas of the world, where poverty is rife. In these areas the absence of other resource alternatives, combined with increasing population pressures, mean that native plants are heavily used for many purposes (e.g. food, fuel, medicine) and at the same time current and future levels of use pose substantial threats to plant diversity. Ironically, overuse to meet the urgent short-term needs of day-to-day survival is helping to eradicate the same plants on which the medium- and long-term survival of many poor people depends.
Beyond the direct use of plants for food or their indirect use as fodder, the utilisation of plant diversity for structural and domestic materials, firewood and decorative materials and many other purposes and in many cultures throughout the world is vast. Moreover, it is estimated that 75% of the world population obtain their primary source of medicine from plant species. Thousands of species are utilised in the traditional medicines of India, China and many other populous countries – and the use of these plants in the West is also increasing. Many western medicines also contain plant products or were originally developed from botanical sources.
Plant Diversity, Ecology and the Provision of Ecosystem Services - The conservation of plant diversity is fundamental to the conservation of other biodiversity. For example, among all the species so far described about one quarter are plant feeding insects. Thus, in broad terms, loss of plant diversity means loss of animal diversity.
It is also now widely accepted that ecosystems contribute a great range of services that typically are not accounted for in most standard economic models. In addition to the obvious contribution of net primary productivity – of which humans are estimated to have coopted 40% of that produced on land – ecosystems contribute to: i) prevention of flooding; ii) development and retention of soils; iii) provision of pest control; iv) pollination services; v) climate regulation at a variety of scales, and many other natural processes. The Millennium Ecosystem Assessment has done much to raise awareness of the consequences of ecosystem changes and the resulting effects on ecosystem services for human well-being.
There is increasing evidence that degraded, species-poor ecosystems do not provide ecosystem services so effectively. As early as 1872 Darwin suggested that greater plant diversity in a given area would lead to greater primary productivity, but only in the last two decades has this and related issues been pursued in a rigorous and experimental way. Tilman (1999) reviewed theory in this area and concluded that biodiversity can be one of several significant factors governing a range of ecosystem attributes including: productivity, stability, nutrient dynamics and vulnerability to invasions by exotic species. The predictions that emerged from these relatively simple models are that greater biodiversity should generally: i) increase community stability through time, ii) decrease stability at population level through time, iii) increase community productivity or standing crop, iv) increase ecosystem utilisation and stores of limiting nutrients, and v) decrease the probability of invasions by exotic species.
These conclusions based on theory are being tested, and have received some support from experimental studies, albeit with some notable exceptions (Kinzig et al., 2002). A recent review of the scientific literature in this area (Hooper et al., 2005) concluded with certainty that more species are needed to insure a stable supply of ecosystem goods and services as spatial and temporal variability increases, which typically occurs as longer time periods and larger areas are considered.
Status and Prospects of Plant Diversity - Conservative estimates of the total diversity of land-plants comprise about 320,000 species of which about 260–270,000 have been described (May, 2000; Tudge, 2000). Other more radical estimates suggest much larger numbers of up to 500,000 (Hammond, 1995; Govaerts, 2001, 2003). The discrepancy between numbers of described species and estimated total diversity is even higher in the case of the fungi: some 85,000 species have been recognised and described to date out of an estimated total of 500,000 (May, 2000) or 1,500,000 (Hawksworth, 1991), but again some radical estimates point to much higher numbers and suggest there could be as many as 3,000,000 fungal species (Hawksworth, 1991).
For flowering plants an estimated 240-400,000 species have been described out of a total diversity that may be as high as 450-500,000. An estimated 170,000 of these species are found in the tropics (Linares, 2000) as contrasted to a native flora of the British Isles of about 1,400 species. The World Conservation Union (IUCN) currently lists less than 3% of the world's known plant species as threatened with extinction.
Rates of discovery of new species while making inventories of tropical areas give some indication of the diversity that is lost when unexplored habitat is destroyed. On average about 1 in every 100 flowering plant specimens collected in the tropical rainforests represents a species new to science (Cox, 2000). When collecting is carried out by regional specialists, aware of what has already been collected for their area, this figure may rise to 5% and, for particularly diverse regions, novelty rates as high as 9% are still not unknown. Almost 2,000 new species of plants are described each year, mostly from the tropics. Thus the loss or serious degradation of habitat in tropical areas results in the potential extinction of completely unknown plant species as well as others which, although known to science, have not yet been safeguarded by in situ or ex situ conservation.
The rates of loss of biodiversity are now high and many scientists hold that we are witnessing a human-driven "sixth extinction" (Leakey & Lewin, 1996; Pimm & Brooks, 2000). Surveys of many groups of organisms reveal rates of extinction at least several hundred times the rate expected from study of the geological record (Pimm & Brooks, 2000). For plants, accurate data are sparse but in some situations estimates suggest that the average rate of extinction is 0.5% of all plant species per century, but half of all those extinctions occurred in the last century (Cox, 2000). In the face of these effects, there is a clear scientific imperative to continue to collect samples of plant diversity which may otherwise be lost forever. Now is not the time to stop collecting. "..Unlike the rest of science, the study of biodiversity has a time limit." (Wilson, 1992).
Users of Information on Plant Diversity - External users of information on plant diversity are varied and widespread, ranging from scientists based in educational institutions, botanical institutions, the private sector and government departments, to horticulturalists, the business community and the general public. In broad terms, our users are:
i) Scientific Community: systematists, other biologists, other scientists;
ii) Conservation Community: UK-based non-governmental organisations (NGOs), overseas NGOs;
iii) Horticultural Community: horticultural professionals, horticultural NGOs, amateur gardeners;
iv) Business Community: plant-related businesses, other businesses;
v) General Public: professionals, community organisations, schools;
vi) UK Government: Defra, other Government departments and agencies;
vii) European Governments;
viii) Other Governments: developed world, developing world.