GREENING THE GARDENS

Forest and Bird, Volume 19, Issue 3, 1 August 1988, Page 25

GREENING THE GARDENS

by Dr

Botany Division, DSIR.

David Given,

Botanic gardens and Conservation

I has long been realised that preservation of species under threat should primarily be sought in areas of natural habitat. But conservation in botanic gardens as specimens and plantations, in seed banks, and in experimental gardens is increasingly seen not just as a back-up but as necessary in its own right. Each has its own unique contribution to conservation. To many people the botanic garden is an enigma — part pleasure garden and part recreation park — or perhaps somewhere to take chattering children on a Sunday afternoon. The problem of how people perceive botanic gardens was addressed by Winifred Blunt. In writing of the Royal Botanic Gardens at Kew, England, she observed that, "... to the botanists, Kew is a scientific institution, but one whose work is sometimes hindered and whose funds are excessively squandered to provide ignorant Londoners with a day in the fresh air among flowers whose names they neither Know or greatly wish to know"’.

Many varied roles

Botanic gardens have many varied roles. It is hard to find a simple definition, or single characteristic by which to define them. In general it may be said that plant collections in botanic gardens are managed in a scientific way and have a particular purpose other than simple pleasure and amenity. Their purpose can be educational, economic, taxonomic, medicinal, to encourage introduction of new exotic species, or to advance the conservation of rare and endangered species. Botanic gardens have been in existence for a long time. The earliest medicinal gardens were established in the 16th century in Europe, and today there are probably about 1400 of them worldwide. Most are in the northern temperate regions, especially Europe, North America and the USSR. The number of botanic gardens in the tropics is far fewer. However, during the last decade over 100 new gardens have been established, many in tropical or subtropical regions. Some are very small, perhaps only a few hectares in area. In contrast others cover many tens of hectares, employing not only scores of gardening staff but also supporting large scientific laboratories. In North America, for example, the Missouri Botanical Garden, has probably the largest concentration of scientists working on the immense flora of the tropical Americas. The largest herbaria in North America are mostly maintained by botanic gardens. Similarly, the Royal Botanic Gardens at Kew has not only 85,000 living accessions, but also a herbarium of over six million plant specimens. New Zealand botanic gardens are rather more modest in size and range of activities. Although most cities and some smaller centres have public gardens, only two (Dunedin and Christchurch Botanic Gardens) have a full-time botanist, and few would claim to put priority on the systematic and scientific collection of plants. Our New Zealand gardens have developed rather different traditions from those of many countries. Almost all are funded by municipal authorities rather than central government. Despite periodic calls for a national botanic garden

or a national network of gardens, this has not eventuated. Perhaps the period of provincial government early in colonial history stifled the development of a national botanic garden. Certainly, the development of gardens separate from museums and universities has persisted up to the present. Consequently a defined research function or long-term association with research, educational and conservation agencies has rarely been developed. It is therefore not surprising that some of the chief aims of many overseas botanic gardens are passed over or ignored in New Zealand. Sometimes they tend to be seen as options which are good to consider when times are prosperous but are not to be seen as basic functions. This may well apply to the role of gardens in biological conservation.

Five main reasons

There are five main reasons for growing plants in botanic gardens for conservation: to have as many species as possible in cultivation as an insurance against their loss in the wild, to ensure the preservation of a wide range of diversity of plant species as well as diversity within species, to have plants available for study without having to take scarce specimens from the wild, to educate people to the needs of the plant world, and to propagate and maintain species for exchange and for reintroduction into the wild. Implementing these functions might not appear to be a problem until one realises that there are currently about 240 plant species at risk in New Zealand. Of these, just over 20 are critically endangered and may be at risk of becoming extinct in the wild. To rescue such species demands not just the cultivation of a few specimens but if possible the capture of a sizeable proportion of the remaining genetic variation in the species. Most species are highly variable, and maintenance of variation is often the key to long-term survival. The occurrence of variation in the species is well demonstrated by the endangered kaka beak (Clianthus puniceus). This is currently being studied by Forest Research Institute and Botany Division, DSIR. Although the species is now very rare in the wild, with perhaps fewer than 200 wild plants known, the species shows considerable variation. Flower colour varies from white through pink to deep red. Plants can be erect to spreading and from two to perhaps as much as six metres high. Stems can be green or purplish. There is also variation in flower and leaflet size. Several other endangered plants found in New Zealand are now known in the wild only from single plants. The Three Kings Islands endemics, Tecomanthe speciosa and Pennantia baylisiana are examples of sin-gle-plant species, and the recently rediscovered Kermadec Islands koromiko (Hebe breviracemosa) is another. The last of these species was believed to be extinct for several decades until, following removal of goats from Raoul Island, a single plant was found. Cuttings from this have now been propagated and are growing in a number of experimental and botanic gardens throughout New Zealand. If it were not for horticultural techniques and garden-based plant

collections there would still be only one Kermadec Islands koromiko, and the species would be in dire straits. Of course, not all plant species have horticultural appeal. Species such as kaka beak and the Chatham Island forget-me-not are not likely to be absent from horticultural collections they are outstandingly attractive. In contrast, other critically rare plants such as Hydatella inconspicua (an obscure water plant) or Lepidium kirkii (a small herb of Central Otago salt pans) have little appeal to gardeners and gardens. Both are small and dull by comparison. Such plants do have to be brought into cultivation but perhaps as part of scientific collections held by experimental gardens or universities. Hydatella has actually been grown for some years in a high school biology department.

Critically threatened species

In conserving critically threatened species three main choices are generally available. These are whether to immediately conserve the plant in the wild, possibly manipulating the wild habitat and its remnant populations, to concentrate on growing the plant away from its wild habitat and propagate increasing numbers of plant in gardens, or to use habitat restoration perhaps on an entirely new site. The second and third choices require ex situ generally botanic garden based techniques, even when the ultimate aim is to put plants back into the wild. Each approach has its own hazards. For example, taking seed or propagating material from an endangered species on a small island, growing large numbers of plants, and later replanting it into the wild sounds simple. But it is necessary to ensure that the plant material actually comes from the island, that it is not just from a single individual (unless that is all that exists), and that

in the process of propagating it diseases are not acquired in the nursery and transferred back to the original site. Thus there is need for extreme care in documenting plants, in garden hygiene and in selecting good sampling techniques. The stumbling block uppermost in most people’s minds will be finance and resources, particularly skilled staff. In one recent survey of botanic gardens the comment was made that *’. . . local authorities are very much restricted by the limitations of their rate-derived budget . . . and

most Council Parks Departments will plead workload’’. This needs to be overcome, perhaps by pooling resources, each botanic garden being modest in its conservation programme and being prepared to work cooperatively with other people and institutions with differing areas of expertise. As an example Botany Division, DSIR, now has an office at the Christchurch Botanic Gardens. Although much remains to be done, there are very significant advances being made. The Nature Conservation Council has undertaken a survey of New Zealand threatened plants in cultivation the first step towards a co-ordinated network of national collections of these plants. Collections of rare species are now maintained at several gardens with an ongoing policy of maintaining these in cultivation. In these collections importance is placed on growing plants of known origin. Threatened plants are being grown for long-term research at the experimental gardens of Botany Division, DSIR, Lincoln, and long term seed storage of some critically threatened species is under way.

International level

At the international level an important step has been the formulation of a Botanic Gardens Conservation Strategy. This was launched at a conference on Botanic Gardens and the World Conservation Strategy, and its objects are encapsulated in the Declaration of Gran Canaria. One of the first steps has been the setting up of a Botanic Gardens Secretariat. Several New Zealand gardens are participating in this programme. As a country with a long tradition in horticulture and conservation, there are strong arguments for greater New Zealand support of these moves. The Timaru Botanic Gardens under the direction of the late Graeme Paterson has

provided an outstanding example of a successful conservation and education programme achieved on a modest budget. Over a period of several years, more than 100 threatened species native to New Zealand have been put into cultivation at the gardens. Stock plants have been propagated and made available to other gardens, schools, and research and conservation organisations. One of the features at Timaru is an educational display on conservation, incorporating living examples of endangered species and explaining why they are at risk. One of the more interesting overseas rarities in the Timaru Gardens is the inland sand thrift (Armeria maritima subsp. elongata) which in Britain is now known from only a handful of sites. From a small number of seeds collected in England, Graeme Paterson raised seedlings which have now led to a vigorous population of more than 100 plants, half way round the world from their point of origin. Growing the sand thrift far away from its native home as a conservation exercise, may set the stage for conserving other northern temperate plants. In the last few years, several reports have advocated use of New Zealand as a kind of "Noah's ark"’ for threatened plants and valuable cultivars from around the world.

Calls for this have been precipitated by increasing levels of pollutants (especially heavy metals and acid rain) in northern hemisphere countries.

In Europe the problem is particularly acute. New Zealand's isolation and relative freedom from pollution may be instrumental in giving its botanic gardens a pivotal role in world conservation. A Noah's Ark rescue programme must not be at the expense of our own flora. There are still many species not well represented in our botanical gardens. Gardens, in co-op-eration with research organisations are well placed to solve biological problems which hinder management of the New Zealand flora. This includes such matters as seed longevity, breeding systems and precise soil requirements. Botanic gardens should be closely linked with reserve management, not just supplying plants for population or vegetation restoration, but also applying horticultural expertise to management in the wild. Botanic gardens are an essential link between people and plants. For the city dweller in particular they provide a window to give glimpses of nature. They open our minds to the immensity and variation of that most essential part of the biosphere the world of plants. #& Dr David Given is the author of Rare and Endangered Plants of New Zealand, and is at present preparing a book for the IUCN on conserving the world’s plants.