The philosophical framework in which most botanic gardens operate now places a high value on maintaining what measure of biodiversity exists today. This can be seen as a direct outgrowth of concerns about the natural world which began to develop during the early twentieth century as the damage resulting from industrialization, population growth, and uncontrolled exploitation of natural resources became apparent. Rather than being motivated primarily by a desire to study God in nature, scientists and others began to think that nature was intrinsically valuable, over and above whatever link it might have with a deity or what economic advantage it might bring to human society. Often work begun by botanic gardens directly led to better understanding of the wonderful interplay of organisms in ecological systems, with far reaching philosophical and scientific repercussions.
Take for example the huge water lily Victoria amazónica, grown by many botanic gardens today. When it was first described in the early nineteenth century by plant explorers who found it in British Guyana, the accounts caused a sensation: in addition to having lovely flowers, its leaves grew up to 6 ft in diameter, and were strong enough to support an adult man. Seeds were sent back to Europe several times, but it was not until 1849 that Kew was able to raise plants to the stage where they could be set out in ponds. Of these, three flowered, the first being one in Duke of Devonshire's garden at Chatsworth. The one at Kew bloomed the next year after being installed in a special glasshouse, and some 30 000 visitors came to marvel at the flowers and the leaves. The craze was not confined to England: the Hortus Botanicus (Figure 6) at Leiden succeeded in getting a plant to flower in 1872, and kept one alive during the coldest days of World War II when there was only enough fuel to keep the water lily greenhouse heated. Early pictures from both the Singapore Botanic Gardens and the Missouri Botanic Garden feature the plant too.
But the story of Victoria amazónica does not end with special ponds and crowds of visitors. One of the oddities of the flowers is that when they are dissected in the wild, a particular sort of beetle (Cyclocephala hardyi) is often found inside. For a long time botanists suspected that the beetles pollinated the plant but were not sure how. The mystery was only unraveled in the 1970s when Ghillean Prance, Kew's director from 1988 to 1999 but then a research biologist for the New York Botanical Garden, spent nights standing hip deep in Brazilian ponds, watching the
flowers open and beetles flie in and out. He found that the beetles were attracted to the fragrance of the opening flowers, crawled inside to feed, and were trapped there when the flowers closed as dawn approached. The next evening the beetles, sticky from feeding, crawled back out as the flowers opened again, picking up a load of pollen as they passed. Then they flew away to repeat the process in another flower, and incidentally pollinate it. In so doing they demonstrated the complexity of ecosystems and the intricate way plants and animals are interrelated.
Much of botanic gardens' present-day work in the field, the laboratory, and in the gardens themselves is designed to study these kinds of relationships. Botanic gardens today also actively work for conservation of species by propagating plants and collecting and storing seeds. According to the World Conservation Union, 34 000 taxa around the world are considered threatened with extinction. Of them 10 000 threatened species - or about a third - are growing in one or more botanic gardens. In some cases, the collection of plant specimens comes just in the nick of time. The canyon in Chiapas, Mexico where botanists in the late 1990s found Deppea splendens, a shrub with lovely two-inch orange flowers hanging in long clusters, has since been cleared for cornfields: the plant is thought to be now extinct in the wild. But seeds from the shrub flourished in the San Francisco Botanical Garden, and cuttings from the plants are even sold by the Friends of the Garden at their annual sale.
Perhaps the biggest conservation project is Kew's Millennium Seed Bank. The £ 80 million (US$ 160 million) undertaking is housed in new facilities at Kew's Wakehurst auxiliary garden south of London. Its aim is to collect seeds from 24 000 species of plants from all of the world by 2020, and to keep them in secure locations so that they can be used at a later date. When seeds are dried so that they contain only 5% moisture, about 80% of them can successfully be held at -20 °C for periods of up to 200 years. A portion of all seeds will be held in their country of origin in order to avoid repeating 'theft' of plants like that which occurred during the great period of European colonialism. Fortunes were made then by European exploiters of coffee, rubber, and other plants but the countries of origin received no compensation.
As part of the effort to compensate for damage done in the past and to preserve remaining biodiversity, Botanic Gardens Conservation International has set a series of targets to be met by 2010. The overall aims are general - things like protection of plant diversity, conservation of endangered species in botanic gardens and in their native habitat, and public education about the importance of plant diversity. Specific goals in the 20-item to-do list are quite specific, though. For example, at least 10% of each of the world's ecological regions are to be effectively conserved, and the number of trained botanic garden staff working in conservation, research, and education should be doubled. In addition, international databases of such things as which endangered species are cultivated in what botanic garden and what plant introduction has become invasive in what range are under development. Many botanic gardens are already promoting awareness ofthe problems posed by invasive species through such things as the St. Louis Declaration on Invasive Plant Species, developed at a conference organized by the Missouri Botanical Garden in 2001.
Several new botanic gardens have also been established recently with the principal aim of protecting unique and relatively untouched environments. One of them is the Alice Springs Desert Park in central Australia, opened to the public in 1997, which preserves a section of that continent's desert. Another is the Bafut Botanic Garden in northwest Cameroon, also opened in 1997, a savanna botanic garden and forest reserve.
In addition, two other new botanic gardens point the way to reclaiming landscapes destroyed by human carelessness and greed. The first is the Eden Project in Cornwall UK, where a former clay pit has been transformed into a botanic garden with several distinct ecosystems represented in geodesic buildings sunk into the former mine landscapes. The other is the Maharashtra (Mahim) Nature Park in Mumbai, India, where 15 ha of former garbage dump have been reclaimed. The reconstructed forest is now home to 380 varieties of plants, 84 varieties of birds, and about 34 kinds of butterflies.
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