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PART ONE
The Scope and Potential of Ex Situ Plant Conservation
Early perceptions of ex situ (off-site) plant conservation as a largely irrelevant novelty or possibly even a well-meaning but counterproductive distraction are giving way to a growing awareness that properly managed off-site collections can make the critical difference between extinction and survival. The diverse tools of ex situ plant conservation are a means to an endâsurvival in the wildâand a vital part of larger integrated conservation efforts.
Part I reflects the remarkable advances that ex situ plant conservation has made. Beginning with application to a small number of unusually threatened species and practiced as a standalone approach, and serving by default as a management cul-de-sac (see Chapter 1, this volume), ex situ plant conservation is increasingly being used to support the integrated conservation of regional plant diversity (Chapters 3 and 4, this volume). Over the almost 500-year history of the modern botanic garden, the classic venue for ex situ plant conservation, curatorial principles and professional codes evolved slowly until the last 40 years, when we have seen a dramatic revolution in both professional ethics and the application of conservation science (Chapter 1). As outlined in Chapters 1 and 3â5, this revolution has been driven in part by an internal recognition that ex situ conservation is a duty for botanic gardens and an external expectation by both the public and conservation agencies.
Set against the backdrop of an increasing appreciation of the sheer magnitude and increasing rate of species loss, the Endangered Species Act (ESA) in the United States and the ratification of the international Convention on Biological Diversity (CBD) can be viewed as two of the greatest external stimuli for ex situ plant conservation. The legal requirement of the ESA to recover threatened species in the United States provided impetus to try new approaches. More recently, and through the CBDâs national biodiversity strategies, has come explicit recognition that ex situ conservation is a legitimate and sometimes essential tool for species conservation and a valuable support to in situ conservation efforts. In turn, both of these extraordinary instruments are derived from decades of concern about the environment and from the intellectual and scientific frameworks developed by international agencies such as the World Conservation Union (IUCN), the International Plant Genetic Resources Institute (IPGRI), and Botanic Gardens Conservation International (BGCI). Whereas the international conferences of the 1970s by IUCN and others spurred the development of ex situ conservation in recent decades, the work of Vavilov and others in the early 1900s laid the strategic and scientific framework for ex situ plant conservation. It is on these foundations that national networks such as the Center for Plant Conservation (CPC; Chapter 4, this volume) and regional government agencies such as the State of Western Australia (Chapter 3, this volume) have advanced the field. The experience of both the CPC and Western Australia illustrates a growing mode of professional practice, an essentially collaborative ethic based on delivering services to conservation agencies with the objective of securing wild populations and holding viable insurance collections as a backup to wild stocks.
The ethical context of ex situ conservation, reviewed by Rolston in Chapter 2, is a dynamic and sometimes troubling view, but one that provides the intellectual and moral framework for much of plant conservation. Rolston explores the philosophical underpinnings of the commonsense recognition that biodiversity loss is to be avoided and that wild populations are inherently more valuable, and informative, than cultivated representations. Based on lessons learned in the zoo community, in Chapter 5 Stanley Price and colleagues advance the ethical debate beyond the immediate concerns about species conservation and show how ex situ efforts and institutions can be used to leverage support for habitat and ecosystem conservation, both locally and globally. These and other advances help to move us beyond the âput a plant in a pot and the species is savedâ stereotype toward a realization that ex situ activities are critical to integrated plant conservation. Success ultimately will be measured not just by the number of taxa stored safely but, more importantly, by how well ex situ efforts contribute to the overall effort to maintain biodiversity in the wild.
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Chapter 1
Ex Situ Methods: A Vital but Underused Set of Conservation Resources
MIKE MAUNDER, KAYRI HAVENS, EDWARD O. GUERRANT JR., AND DONALD A. FALK
Botanic gardens and other ex situ facilities such as seed banks are among the most extensive yet underused plant conservation resources in the world. For them to make a truly meaningful difference in how much plant diversity survives into the next century, ex situ plant conservation providers need to not only use the most effective and efficient means possible, but also increase their institutional capacity. In a sobering global review of the threats to biological diversity, Myers et al. (2000: 853) found that the ânumber of species threatened with extinction far outstrips available conservation resources, and the situation looks set to become rapidly worse.â This statement summarizes the challenge facing ex situ conservation at a time when the absolute need for in situ conservation has never been greater and the threats facing species diversity are increasing in type, severity, and scale.
The worldâs botanic gardens and other ex situ facilities, such as seed banks, are among the most concentrated sites of species richness on the planet, in effect artificial centers of species diversity. The worldâs 1,800 botanic gardens hold an estimated 2.5 million accessions of growing plants representing about 80,000 species (Wyse Jackson 2001). These vast collections have been accumulated over many decades and represent a huge investment in human resources and infrastructure. This book reviews the effective role of ex situ collections and assesses the values and limitations of ex situ plant conservation techniques.
The vast majority of ex situ samples, even those intended for conservation, have been collected on an ad hoc basis because they may be needed in the future for some unspecified purpose by an unspecified client. In addition, these collections are heavily skewed toward the cultivation of small and nonâgenetically representative samples of horticulturally amenable taxa and often suffer from poor documentation (Maunder et al. 2001b, 2001c). The majority of threatened species held in botanic garden collections are not specifically managed for conservation purposes and are characterized by a number of shared genetic and demographic characteristics (Box 1.1). However, the composition, status, and management of collections are rapidly improving as more facilities adopt conservation responsibilities. The recurring theme of this book is clearly outlined by Stanley Price et al. in Chapter 5: Where and how can ex situ investment make the most difference to in situ conservation?
Plant conservation facilities operate under the premise that they contribute conservation services to a variety of different clients. The primary role, retaining samples of wild plant diversity under artificial and accessible conditions, has been ratified in a number of professional guidelines (BGCI 2001) and international policy documents (IUCN/UNEP/WWF 1980, 1991; Glowka et al. 1994). However, these services are provided by a range of institutions and facilities of diverse historical heritage that share few common standards or protocols for the management, documentation, and display of threatened plant material. The majority of ex situ facilities were developed and still serve as facilities for growing and displaying token or at least genetically nonrepresentative samples of taxonomic diversity. The challenge is to use the most effective tools and processes and to serve these agreed roles of maintaining offsite collections and making them available for restoration and other conservation purposes.
The number of ex situ conservation facilities has increased dramatically in recent years (Wyse Jackson 2001), and they have become increasingly integrated under national and regional conservation initiatives. Nevertheless, many authorities hesitate to use them as a fundamental and effective component of plant conservation. This reluctance may originate from a number of perceptions. First, that ex situ conservation may undermine the integrity of, and need for, in situ conservation by devaluing wild populations and habitats. Second, it may reflect a lack of professional confidence in the technical ability of ex situ facilities to hold genetically diverse samples of threatened plant germplasm over extended periods of time. Much of the concern probably is based on a lack of understanding of what ex situ options exist and what their strengths and limitations are. For instance, storing seed is very different, in terms of both financial costs and biological risks, from maintaining a cultivated collection. Third, ex situ collections can be viewed as potential conservation liabilities, a source of new invasives and pathogens that can affect wild populations and habitats (Reichard and White 2001).
BOX 1.1
Characteristics of Threatened Plant Populations in Botanic Gardens
- Populations are small and often derived from a small number of closely related founder individuals.
- The cultivated stocks are subject to fluctuating population size as a result of changing horticultural fashions and episodic mortality events.
- Often little or no associated ecological or biological information is available to guide ex situ managers in cultivating and managing the stocks.
- There is little information on the history of the taxa in cultivation and often no satisfactory horticultural protocols.
- Individuals are scattered through a number of collections with varying horticultural and curatorial capacity and hence differing patterns of regeneration and mortality.
- Individuals are susceptible to artificial selection, genetic drift, inbreeding, and hybridization with congenerics.
- Persistence in collections is highest for horticulturally amenable taxa and particularly for taxa with display or commercial value.
Based on Maunder and Culham (1997).
Ex situ conservation at its crudest may temporarily hold token samples of wild plant diversity. At best it can play a critical role as one component of an integrated conservation response supporting a primary objective: the retention and restoration of wild plant diversity. However, to achieve this objective, improved working practices and facilities are needed. We contend that it is because ex situ tools are not widely understood that they are undervalued and therefore underused. Understanding and effectively communicating the relative conservation roles, values, opportunities, and challenges faced by seed storage and growing collections may be among the biggest challenges practitioners face. A major purpose of this volume is to explore the value, limits, and range of available ex situ tools.
The Plant Diversity Crisis
The old World Conservation Union (IUCN) survey of plant species conservation status indicates that about 33,400 plant species are threatened with extinction (Walter and Gillett 1998), or about 10 percent of the worldâs known 250,000â300,000 plant species. This IUCN survey records 380 plant extinctions (Walter and Gillett 1998), less than 1 percent of the recorded species of vascular plants. The plant extinctions recorded by the IUCN and World Conservation Monitoring Center (WCMC) reflect, in part, the geographic distribution of botanical knowledge and monitoring rather than actual rates of species loss. For the largest part of the planet there is no clear consensus on the rate of species and population loss, but this is improving as more IUCN Red Lists are undertaken. For example, in a review of recorded extinctions, rates of habitat conversion, and distribution of restricted endemic plant species for tropical Latin America, Koopowitz et al. (1994) produced estimates of recent extinctions that far exceed those the WCMC and IUCN record. This discrepancy is particularly notable for Brazil, where WCMC and IUCN recorded only five extinctions, whereas Koopowitz et al. estimate a loss since 1950 of about 2,200 species.
There is an acute need to act decisively, creatively, and effectively. Extinction rates for both species and populations are increasing as a result of human changes to habitats (Hannah et al. 1994; Hughes et al. 1997). This trend is accelerating as surviving wild areas become increasingly degraded through isolation, fragmentation, competition from invasive species, and climate change (Sala et al. 2000). The expected result, particularly in the endemic-rich hotspots (sensu Myers et al. 2000), will be many more plant extinctions.
The dearth of field survey work and the rapidity of habitat loss, particularly in the tropics, mean that many plant extinctions are likely to be identified only in retrospect, if at all. This raises the question, How should facilities, especially those in the high-diversity regions, most effectively allocate their limited resources? Should they focus a large proportion of their limited resources on managing a small number of threatened plant species, perhaps selected through an imperfect understanding of local conservation priorities? Or should they also use available resources for promoting and supporting the conservation of important habitat areas, such as recognized centers of plant diversity (Maunder et al. 2002; Chapter 5, this volume)? In addition to measuring yield from ex situ investment through increased taxonomic representation in cultivation or seed banks (e.g., scoring collections against national red lists), facilities could also score against quantitative assessments of genetic representation, contributions to implemented recovery plans, and the conservation of important plant habitats.
The Evolution of Ex Situ Plant Conservation
Botanic gardens, as scientifically organized plant collections, were originally initiated as repositories serving academic study, predominantly medical and theological (Prest 1981). In a time still dominated by an essentialist worldview dating back to Plato, curation was driven by the desire to accumulate t...
