Kew shows Africa’s plant wealth

[Image] Kew’s Dr Rhian Smith gathers a
specimen of Isoetes eludens from
its rocky habitat in South Africa.
(Image: Stephen Hopper, Kew)

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East and tropical Southern Africa yielded the greatest number of new plant species in 2009, according to the Royal Botanic Gardens, Kew, which celebrated 250 years of existence last year and has just released its anniversary report.

The leafy bounty of almost 300 new species included palms and rainforest trees, rare orchids, fungi, wild coffees, and an aquatic plant related to ancient ferns.

Plants were discovered in wild and fascinating areas all over the world, from Madagascar, Iran and Borneo, to Brazil, Cameroon, South Africa and Western Australia. Scientists believe that a third of the new discoveries are endangered.

A whopping 67 new species were discovered in Tanzania – more than in any other country – while 33 each were found in Madagascar and Uganda, 25 in Kenya, 16 in Cameroon and Zambia respectively, 13 in Malawi, seven in Mozambique and six in Zimbabwe.

Four species were discovered in Ethiopia and Somalia, three in Sudan, two each in Nigeria, Angola, South Africa and Congo, and one each in Burundi, Namibia and Botswana.

The East African finds are part of two long-standing Kew programmes that focus on the flora of that region. It is estimated that eventually the Flora of Tropical East Africa and Flora Zambesiaca databanks will hold around 12 500 species and 10 000 species respectively.

The full list of 292 new discoveries is available on the Kew website, and can be seen in a special Google Earth layer.

South African discoveries

One of the two new species found in South Africa is a tiny aquatic plant Isoetes eludens, just 5cm in height. It lives in temporary rock pools and is so named because it eluded discovery for many years.

The minute specimen was found by Kew director Prof Stephen Hopper himself in a small rock pool, just 15cm deep, at 1 284 m above sea level in the Kamiesberg Mountains in Namaqualand – this is its only known habitat.

Kew botanists have highlighted the discovery as indicative of the huge diversity of the Cape province’s famous floral life, much of which has yet to be documented.

But the little plant, part of an ancient family known as quillworts, may be at risk from climate change, as the temporary rock pools in which it thrives are in danger of drying up should rainfall decrease. The shallow pools are known by the local Nama people as !gau. Scientists have dated quillwort fossils to more than 150-million years ago.

The other South African discovery, Dioscorea strydomiana, is a member of the yam family. This critically endangered plant is on the verge of extinction, with just two populations left in the wild.

Botanists have a particular interest in D. strydomiana because indigenous people view it as a cancer cure. However, this has resulted in over-harvesting of the tuberous plant, and although the tuber grows back prolifically each year its numbers continue to decline.

Botanical diversity

Hopper said that over 2 000 new plant species are discovered each year, a significant 10% of which is contributed by Kew.

“These new discoveries highlight the fact that there is so much of the plant world yet to be discovered and documented,” he said. “Without knowing what’s out there and where it occurs, we have no scientific basis for effective conservation. It is vital that these areas of botanical science are adequately funded and supported.”

Prof David Mabberley of the world-famous Kew Herbarium acknowledged the role that international collaboration played in the discovery of new species. “We are currently working with 100 countries around the world,” he said.

Kew’s Breathing Planet programme, a 10-year floral conservation strategy introduced in 2009, aims to accelerate the discovery and description of new species, as well as protect and restore vulnerable habitats while conserving the livelihoods of people, such as medicinal healers, who depend on plants.

During 2010, the International Year of Biodiversity, the institution will educate the public on the importance and value of plant biodiversity. Art exhibitions, horticultural displays and other educational activities are on the agenda for the upcoming months.

Diversity of plant life

Other interesting finds include three new species of towering rainforest trees that were found in the Korup National Park in southwest Cameroon. One of them, Berlinia korupensis, is critically endangered because of human encroachment on the park.

In Madagascar, Kew botanists discovered 20 new palms. This is important because 90% of Madagascar’s 188 palm species, including the 20 new species, are threatened because of habitat destruction and commercial use of the plants.

The island is also home to seven newly discovered wild coffee species, which hold important commercial implications.

Fourteen new species of indigo, the plant from which the valuable blue dye is extracted, came to light in Southern tropical Africa. An alarming 78% of these are threatened.

On other continents scientists found a new legume genus in the Rio de Contas mountain range in Brazil, and three new species of orchid on Mount Kinabalu in Borneo, while the Australian-born Stephen Hopper discovered a tiny species of eucalyptus in his homeland. The dwarf tree stands just 1m high.

Centre of botanical learning

The famous botanical gardens and research institute is situated on 132 exquisitely landscaped hectares in the borough of Richmond upon Thames in southwest London.

It houses the world’s largest collection of living flora – some 30 000 different plants – and its herbarium holds over 7-million dried specimens. Kew keeps a massive fungal collection of over 1.2-million specimens.

The institution also administers a National Trust estate, known as Wakehurst Place, in West Sussex. Here visitors will find the Millennium Seed Bank, the largest of its kind on the planet. To date, this facility has collected and documented seed from about 30 000 flowering plants, but this is only a paltry 10% of the world total. The goal is to have a quarter conserved by 2020.

Kew was inscribed as a world heritage site by Unesco in 2003.