The conservation of biodiversity and its sustainable management are internationally recognised as vital global concerns. Identification of the components of biodiversity and the they face are important steps in planning for conservation action. Tree species are ecologically, culturally and economically valuable components of biodiversity and their conservation is essential to the well-threatsbeing of people in all countries of the world. With increasing general pressures on ecosystems and selective pressures on species, it has become apparent that many tree species are threatened with extinction. Information on the degree and extent of threat has, however, previously been scattered and scarce. The World List of Threatened Trees presents the results of the first survey of the conservation status of trees species worldwide.

Assessment of the conservation status of the world's tree species is a major task given the overall number of trees believed to exist. The world's tree flora is estimated to total around 100,000 species. It is not yet possible to give a precise figure because definitions of the term "tree" vary as do species concepts. One definition of "tree" which is commonly followed in temperate regions is a woody plant growing on a single stem usually to a height of over two metres. This definition has been adopted by the IUCN/SSC Temperate Broadleaved Tree Specialist Group. The Group recently compiled a list of temperate woody plant genera and estimated the number of tree species within these genera. This was undertaken to establish the scale of the task of conservation evaluation for temperate tree species. The tentative result was that there are 21,000 species in plant genera which are predominantly woody and temperate in distribution (Hunt, 1996). The richness of the world's tropical tree flora is certainly much greater and is also in greater need of taxonomic attention. In reality we can only make an informed guess at the total number of tree species. Nevertheless there is an urgency to document all available information on the growing number of tree species which are of conservation concern.

In evaluating the global conservation status of tree species the new IUCN Red List categories and criteria have been followed. The general aim of the new IUCN system of categorising threat is "to provide an explicit, objective framework for the classification of species according to their extinction risk" (IUCN, 1994). The IUCN categories and criteria have been applied to a broad selection of restricted range and exploited tree species as part of a major collaborative information gathering and evaluation exercise. In pre-selecting tree species for conservation evaluation, species from all parts of the world and most taxonomic groups were considered. Certain taxonomic groups were, however, excluded for pragmatic reasons. These include tree ferns in the families Cyatheaceae and Dicksoniaceae, tree species in the cycad families Cycadaceae and Zamiaceae, and arborescent members of the Cactaceae family. It was anticipated that the conservation status of species in these families would be evaluated in parallel exercises by the appropriate SSC Plant Specialist Groups.

As part of the conservation evaluation, the taxonomy and nomenclature of each of the tree species categorised as globally threatened have been checked, wherever possible, against current literature or by appropriate experts. Supporting information has been collected on the distribution, threats, conservation measures, the habitat type of the species, the uses of the species, level of use and ecological information. This more detailed information is available in electronic form in the Tree Conservation Database supplementing the summary information on individual species provided in The World List of Threatened Trees.

Over 7300 tree species are documented as globally threatened in this publication (see Table 2), based on the 1994 IUCN categories and criteria. In addition, in the Appendices, supplementary lists of globally threatened trees are given. Appendix 1 is a list of Australian globally threatened trees prepared for this publication by Lyn Meredith, Threatened Species and Communities Section, Environment Australia. Appendix 2 provides a list of Japanese tree species taken from the 1997 Red List of Japanese Vascular Plants compiled by the Threatened Species Committee, Japan Society of Plant Taxonomists (Yahara, T. 1997). Unfortunately this publication was not available in time to prepare species summaries for inclusion in the main text of the book. Appendix 3 provides a supplementary list of tree species from other parts of the world which are included as globally threatened in the 1997 IUCN Red List of Threatened Plants but which have not yet been evaluated against the new IUCN categories and criteria. Generally this reflects lack of current information on the species concerned.

Taking all this information together, nearly nine percent of the world's tree flora is documented as globally threatened with extinction. Given the economic and local value of tree species and their role in defining ecosystems, this represents a profound diminution of the world's biodiversity. The availability, for the first time of consolidated tree species conservation information should have a significant impact on international conservation policy and planning. It is hoped that this book will highlight the need for sustained efforts to conserve maximum tree species diversity for the benefit of people worldwide.

Evaluating the global conservation status of the world's trees is clearly a major undertaking and has only been possible through collaboration with a wide range of experts and institutions with local knowledge of tree biodiversity. A full list of contributors is given in the acknowledgements section and the assessors of the conservation status of individual tree species are noted with the species summaries. The identification of a network of botanists willing to contribute their expertise to the conservation of tree species is in itself an important factor in the promotion of global biodiversity conservation.

The need for sound biodiversity information on which to base conservation policy is now widely accepted. The need for biodiversity information to support policy and management objectives for tropical forests is, for example, highlighted in Box 1. Biodiversity is generally considered at three levels: the ecosystem, species and genetic resource level. As a broad indicator of the expression of biodiversity on a global scale, ecosystems are generally considered and ecosystem diversity is taken as a measure of species and genetic diversity. This is partly because of the sheer complexity of biodiversity below the ecosystem level, the lack of consistent and comparable information for most groups of organisms and the need to make rapid progress in biodiversity assessment for conservation action. Species information can, however, when organised in a coherent manner, following accepted information standards, reinforce ecosystem information and provide a crucial link with information on the component genetic resources. Various recent initiatives (SBSTTA, 1996; Van Bueren and Duivendoorn, 1996) have recognised that tree species diversity in particular can be used as a surrogate for overall species diversity in forest ecosystems given the relatively good availability of tree species information. Information on the distributions and convergences of restricted range species can be used to determine patterns of biodiversity.

Information on the threat status of species is essential in planning for conservation and sustainable management of individual species and also for use as an indication of ecosystem status. Information on threatened species is becoming increasingly available, at least for selected taxonomic groups. For plants in general, many national lists of threatened species and plant Red Data Books have been produced and recently the first international Red List of plants was published by IUCN (Walter and Gillett, 1998). This global list represents many years of effort to record and collate the names, conservation status and distribution of rare and declining plants. The database from which the global list was produced and national Red Lists and databases vary in the extent to which they record habit. Information on the habit, in other words whether the plant is a tree, shrub or herb, can provide an important indication of the ecological role of the species. Information on tree species has been seen as a particular requirement to support forest conservation policy but has not, until now, been readily available at an international level.

Biodiversity information is needed to support the following policy and management objectives:

• Land use planning for conservation and sustainable use of forest land
• Designation and management of totally protected natural forest areas
• Protection and reintroduction of endangered species
• Support, adoption and documentation of indigenous management of tropical rain forests
• Use and valuation of non-timber forest products
• Sustainable timber production
• Rehabilitation and productive use of secondary forests

The starting point for the collection of information on the conservation status of trees has been data holdings in the Threatened Plants Database maintained by UNEP-WCMC. This records information on the distribution, global and national conservation status of plant species worldwide and has been used to produce the 1997 IUCN Red List of Threatened Plants. Important sources of conservation status information within this database include the IUCN/SSC Plant Specialist Groups, individual experts, national red lists and Red Data Books and, of major importance, the partner organisations listed in the acknowledgements section of this book.

Information on the conservation status of trees included in the Threatened Plants Database was derived from various studies in addition to the general information sources referred to above. The conservation status of temperate tree species was, for example, reviewed by UNEP-WCMC in collaboration with the International Dendrological Society (IDS) and a Threatened Temperate Tree List was published in 1990 (Lear, 1990). This was updated for an IDS Symposium held in 1994 (Lear and Hunt, 1996). Information on the conservation status of conifer species has been developed by the SSC Conifer Group (Farjon, Page and Schevellis, 1993, Farjon, 1996) and made available for incorporation in the Threatened Plants Database. Information on the conservation status of tropical timbers in trade was collected for the International Tropical Timber Organisation with data collection concentrating on timber species of Southeast Asia and Africa (Oldfield, 1991). Collection of data on trees of Latin America was subsequently undertaken by UNEP-WCMC with support from the UK Government.

When the tree species conservation survey was initiated, the Threatened Plants Database maintained by UNEP-WCMC contained records of about 5000 tree species, 4,000 of which are tropical and 1,000 temperate in distribution. Over 600 of these species were recorded as globally threatened using the old IUCN categories of threat. Initial tasks in preparation for The World List of Threatened Trees were to identify and flag tree species in the Threatened Plants Database and to add a significant number of tree species name and distribution records from various parts of the world. Main geographical areas for which tree name and distribution records were added initially include Ghana, Nigeria, East Africa, Madagascar and Indonesia. Additional tree species name and distribution records were added through the electronic data merges in preparation for the 1997 IUCN Red List of Threatened Plants. In the first year of data collection, tree species records were increased from 5000 to 14,000. A list of 3200 tree species recorded as globally threatened according to the old IUCN categories of threat was prepared for review at a Technical Workshop held in Wageningen in November 1995.

Following the Technical Workshop, a data collection form was designed for experts to provide updates to existing data holdings on tree species in the Threatened Plants Database, and to record new information on species of conservation concern. This is reproduced in Appendix 5. Species were selected for review if they were believed to be single country endemics, threatened in significant parts of their distribution ranges or known to be widely exploited.

Standard data collection forms were sent to over 300 botanists or foresters with expertise in a particular geographical area or taxonomic group of trees. In addition a series of meetings, workshops and interviews was held to discuss the conservation status of tree species and to assign the IUCN categories. Four international workshops were held. The first was the Technical Workshop held in Wageningen which was successful in refining the scope, objectives and methodology for data collection. Three regional workshops have subsequently been held in Zimbabwe, July 1996; Costa Rica, November 1996 and Viet Nam in August 1997. These workshops provided an opportunity for participants to present and discuss national case studies on the conservation status of trees, to discuss conservation status in relation to sustainability issues and to work on species conservation assessments in small working groups. Training in the application of the IUCN categories and criteria was provided. The conservation assessments focussed on relatively widespread, exploited species which are difficult to evaluate without information from a significant proportion of the species' range. The evaluations were based on preliminary species profiles prepared by UNEP-WCMC.

At the regional workshop held in Zimbabwe a draft list of globally threatened tree species occurring in Africa was reviewed. A follow-up meeting was held during the AETFAT Congress in February 1997 to review African data collection and hold an inaugural meeting of the SSC African Tree Specialist Group. Also following the Zimbabwe regional workshop, assessment of the conservation status of trees of Southern Africa was coordinated by Craig Hilton-Taylor of the South African National Botanical Institute. Data sheets for all tree species considered to be threatened in southern Africa were sent to 23 amateur and professional botanists situated in Namibia, South Africa and Swaziland. Documentation explaining how to fill in the data sheets and how to use the new IUCN Red List Criteria and Categories was provided. Each person was asked to fill in data sheets for those species which they were familiar with in the field. Eleven people responded. Information from the replies was combined with information from the National Botanical Institute's southern African Threatened Plants Database (SARARES) and information from the literature to obtain an overall assessment.

Discussions held with botanists at the Rijksherbarium, Leiden and Missouri Botanic Garden have also enhanced the tree conservation evaluation process. Botanists at the Rijksherbarium provided information on the taxonomy and conservation status of trees in Southeast Asia. Assistance provided by Missouri included information from various major checklist projects notably for Peru (Brako and Zarucchi, 1996) and Ecuador (Jorgensen and León, in prep.) and the facilitation of contacts with botanists working in many Latin American countries.

Collection of tree conservation information was also facilitated by collaborative arrangements with national agencies. These have both provided information for the global tree conservation dataset and stimulated the collection of data for national use. Examples include:

The SSC Plant Specialist Groups have been a major source of information and conservation evaluations for The World List of Threatened Trees. Members of the Conifer Specialist Group have used the standard data collection form to compile information on about 300 conifer species and have adopted this procedure for future updating of conservation status information. Members of the Temperate Broadleaved Trees Specialist Group have provided data on selected genera and have prepared detailed species case studies for publication in Broadleaves, the Group's newsletter. In addition over 300 palm species, identified as trees from an initial list of threatened palms, have been evaluated using the standard data collection form by members of the Palm Specialist Group, coordinated by Dr Dennis Johnson.

In order to supplement the information provided by experts, UNEP-WCMC has reviewed a wide variety of data sources including electronic databases, published Floras and Monographs, Red Data Books and grey literature. On the basis of this information, conservation evaluations have been undertaken by UNEP-WCMC for species apparently of significant conservation concern. Wherever possible these have been sent out for expert review. Compilers at UNEP-WCMC also recorded supplementary information on ecology and uses of species, drawing heavily for Southeast Asian species on the excellent PROSEA publications (Soerianegara and Lemmens,1993; Lemmens, Soerianegara and Wong, 1995).

Following the Technical Workshop in Wageningen, a new database was designed to record tree species conservation information, resulting from the completed standard data collection forms. Amendments to the species and distribution records were initially recorded in the Threatened Plants Database maintained by UNEP-WCMC, to ensure consistency with the broader global plant conservation dataset. Subsequently tree species scientific and common names, distribution records and in some cases use records were transferred electronically to a new Tree Conservation Database. The design of the Tree Conservation Database took into account a user needs survey of 500 organisations carried out prior to the Wageningen Technical Workshop, and discussions with FAO and IPGRI concerning tree conservation data management. The potential for harmonised data management with the following data management systems was an important consideration.

A further key consideration was the requirement for a distributed database which could be made widely available in support of tree conservation initiatives. The database has been implemented using the latest generation of Microsoft Windows based software. It is designed to be simple to use and intuitive in operation, as well as conforming to recognised Windows standards. The choice of software tool was further influenced by the ability to link with other applications, including mapping tools. In addition, a Windows-style searchable help system has been developed. The system is implemented in Microsoft® Visual Basic and Access.

The species summaries recorded in The World List of Threatened Trees have been derived directly from the Tree Conservation Database which also records a considerable amount of supplementary information on each tree species.

IUCN categories of threat have been in use for over thirty years and are widely recognised as a standard for indicating the conservation status of individual species. The revised categories and criteria published in 1994 (IUCN, 1994) were developed to make the threat categories more quantitative, objective and equally applicable to all higher taxa of plants and animals. Under the new system, a category can only be assigned to a species if one or more of five criteria apply. Thus in order to qualify as Critically Endangered, Endangered or Vulnerable, evidence is needed to demonstrate that a species is experiencing, to various degrees, at least one of the following:

Criterion A Population is seriously declining, or is expected to decline, at a defined rate.

Criterion B Population is localised, within defined limits, fragmented and declining.

Criterion C Population is small, according to specified numbers, and either declining at a defined rate or declining and with a specified population structure.

Criterion D Population is very small, according to specified numbers, and acutely restricted, within defined limits.

Criterion E Quantitiative analysis showing the probability of extinction.

The use of criteria helps both to guide the assessor and to give transparency to the evaluation process. The rules for applying the IUCN categories and criteria are set out with explanatory notes in Appendix 4. Various criteria can be applied to any one species. The extent to which different criteria have been used in the tree species evaluations is summarised in Table 1. The use of Criterion E has been negligible for trees.

At the outset of data collection for The World List of Threatened Trees experience with the application of the new categories was very limited. The new system differs quite radically in its method of application from the previous IUCN categories with which most botanists and conservation agencies have become familiar. Concerns were expressed initially about the applicability of the categories to tree species, mainly because of the lack of knowledge of reproductive biology and population numbers for the majority of tree species. Furthermore it soon became apparent that the longevity of tree species poses a particular problem in application of the categories, with regard to interpretation of rates of decline. Guidelines were prepared by Charlotte Lusty to assist expert evaluations for tree species and to help ensure consistency in application of the categories by different assessors, especially those working in isolation. The guidelines for trees were developed from recommendations made by William Hawthorne, following a detailed review of the application of the categories to Ghanaian tree species, and incorporated suggestions from other botanists using the categories for trees. The guidelines provide both assistance with interpretation of the criteria through suggested supplementary definitions of terms relevant to tree species and suggestions as to how different sources of information can be used to aid the evaluation process.

In order to qualify as globally threatened based on population reduction (A Criterion), the population of a species should have an observed, estimated, inferred or suspected reduction of at least 20 percent over the last 10 years or three generations. The expression of generation time as specified by IUCN, 1994 is the average age of parents in the population. Defining the generation time of a tree species is very difficult given that the capability of reproduction in tree species varies widely according to the age/size class of individuals. For evaluation purposes, the guidelines for trees suggest that where no information is available the generation time should be taken as 50 years for most tree species, 10-20 for pioneer species or small trees, 100 years or more for slow-growing trees. Following this estimation very many tree species potentially fall within at least the Vulnerable category given the rates of deforestation, and therefore implied population decline, or the rates of exploitation of mature timber trees, over the past 150 years.

Linking tree species distribution data with knowledge of the extent and decline of the ecosystem in which the species occurs has been the means by which the IUCN categories have been most commonly applied to trees. Criterion B and D are appropriately used for such cases where the threat status is based on the geographical restriction of species.

GIS (Geographical Information System) analysis of species distribution information has proved to be a very useful tool in applying Criterion B and Criterion D, Where species point localities, ideally based on verified specimen data, can be stored in a GIS, data can be very successfully manipulated to assess whether their AOO (Area of Occupancy) or EOO (Extent of Occurrence) are within the limits set by the Criteria B and D. David DuPuy and Jonathan Hughes have evaluated the conservation status of a subset of Madagascan leguminous trees in this way, combining species distribution data with vegetation and substrate data in a GIS application.

The guidelines encourage evaluators to use all available sources of secondary information to assess the situation faced by a particular species. In ideal circumstances information from verified herbarium specimens and field survey of populations would be combined with general knowledge of vegetation types and decline throughout the range of a tree species, together with information on levels of exploitation through time where appropriate. Where such information is not available, however, it has been possible, by examining geographical and altitudinal ranges, and habitat requirements of the species, to make preliminary evaluations of the conservation status.

In general the categories have not been applied using fully quantifiable information. This is fully compatible with the guidance provided by IUCN, 1994 which states that, the absence of high quality data should not deter attempts at applying the criteria, as methods involving estimation, inference and projection are emphasised to be acceptable throughout. Furthermore, given that data are rarely available for the whole range or population of a taxon, it may often be appropriate to use the information that is available to make intelligent inferences about the overall status of the taxon in question. In cases where a wide variation in estimates is found, it is legitimate to apply the precautionary principle and use the estimate (providing it is credible) that leads to listing in the category of highest risk.

Although the new IUCN Red List Categories are much more objective than their predecessors, there is inevitably considerable scope for subjectivity. Different expert assessors have applied the categories with differing levels of confidence with regard to available information and different degrees of optimism regarding future trends. This has even applied when different assessors looked at the same species, where some, for example, have used Data Deficient and others have applied Critically Endangered. Some assessors have felt that they should use Data Deficient unless there have been recent field assessments of the species. This approach may be more appropriate where there are active conservation monitoring programmes but generally a greater degree of inference has been necessary. In such cases of divergent views the compilers have acted as referees and applied the category which appeared more appropriate in consultation with the assessors.

The use of the Lower Risk categories has also varied according to the opinion of different assessors. It is not always clear how much inference is appropriate to decide whether a species is Lower Risk or Vulnerable, particularly with regard to Criterion A. The category Lower Risk: conservation dependent should only be used for those species where a species-specific conservation measure ensures that the species does not qualify for Vulnerable, Endangered or Critically Endangered. Inclusion in a protected area is considered to be a sufficiently secure conservation measure to prevent a species being in a higher risk category by some assessors but there has not been uniformity of opinion on this issue.

Some assessors have probably followed the IUCN rules more rigidly than others. After careful consideration, the compilers decided not to apply a blanket standardisation of the categories and criteria across all tree species following the application by experts, although in some cases adjustments to particular species have been made through consultation. The compilers do not have the intrinsic knowledge of species in particular geographic regions and taxonomic groups which may have contributed to the expert evaluations. The listing of species should be seen as a fluid process, with scope for re-evaluations of species as more information becomes available, and as further debate on the categorisation process takes place.

Particular mention needs to be made concerning the dipterocarp trees of southeast Asia. Over 250 of these species have been listed in the most threatened category of Critically Endangered, using Criterion A. The basis for this assessment is the very rapid rates of forest loss in southeast Asia. Criterion A measures decline rates for long-lived species, such as trees, over a period of three generations. This amounts to at least 150 years for the dipterocarp species. Thus over 250 species of dipterocarp are believed to have lost over 80 percent of their forest habitat over the last three generations and are therefore listed as Critically Endangered. These listings might seem somewhat out of place alongside most other species listed as Critically Endangered, which tend to occur in tiny populations, sometimes of only a small number of individual trees. However, it is very important to be clear that extinction times scale with a species' generation time, and not with absolute time. All other things being the same, a long-lived species takes longer to go extinct than a short-lived species. If one considers a time window that is short relative to the lifetime of the species, one might miss the fact that it is in trouble, even if it is heading inexorably to extinction. To take a simple example, if one counts the numbers of a short-lived species with four generations per year and declining at 50 percent per generation, the population will have declined to 6.25 percent of the starting number after one year. Conversely, a species with a long generation time (say 100 years), but also declining at 50 percent per generation will exhibit almost no detectable decline as measured over a one-year period. The listing of the dipterocarps is therefore more logical and appropriate than appears at first sight.

Nevertheless, there is controversy concerning the use of Criterion A in this manner, and this is being studied as part of the SSC's ongoing review of the Red List Criteria. Three areas are currently being considered for possible revision of Criterion A: a) whether or not there should be a maximum time-limit set for estimates of generation-time, to make inference and projection more restricted in time for long-lived species and therefore more reliable; (b) the extent to which listing should incorporate information on whether or not the decline is controlled or managed, and therefore how likely it is to continue into the future; and (c) whether or not the current decline rates specified in the criteria are appropriate.

The three year time period for preparation of The World List of Threatened Trees has allowed for rapid assembly and review of currently available information on the conservation status of trees. There are, however, clear information gaps. These result from lack of identified expertise on particular taxa or geographical areas or lack of time for information to be compiled where experts were contacted in the later stages of the data collection process. For some parts of the world and certain taxonomic families information is not yet available on which to base sound conservation assessments. The design of the data management system, the involvement of a wide network of experts and the further coordinated development of the SSC Plant Specialist Groups, with capacity to manage their own decentralised data, will allow continual updating of the global Tree Conservation Database.

In some cases it has been very difficult to apply categories because of taxonomic uncertainty. This is the case for example with the genus Ardisia in the family Myrsinaceae. In Panama, alone, about 110 species have been described mainly on the basis of original collections which often did not have flowers or fruiting material. There is a need for taxonomic revision taking into account the wealth of unverified herbarium specimens. The situation is similar for many other genera of trees.

Papua New Guinea provides an example of a biodiversity rich country which remains poorly explored. As outlined by Frodin (1997) a relatively intense phase of biological study took place within the country from 1946 through the 1980s. This generated various major publications on vegetation, biogeography and ecology but there has subsequently been a general decline in new research work and particularly in botanical exploration in Papua New Guinea (Conn, 1994). Frodin (1997) notes that at the present time, there is no crticial and effective study of trees for Papua New Guinea and little prospect of one without substantial outside support. Given the low current exploration rate and the serious research and documentation backlog in general the conservation status of tree species is one of "data deficiency". Enough is known, however, about certain timber species to apply the IUCN categories and criteria and species summaries are included in the book for such species.

In general there has been overwhelming support from the botanical community for the preparation of The World List of Threatened Trees. There have, however, been instances where botanists were reluctant to share unpublished information. This has resulted in some cases from a sense of frustration with the difficulty of securing resources for the publication of taxonomic work and equally with concerns about incorporating new species names which have not been previously validly published in the scientific literature. In other cases herbarium botanists did not feel they had sufficient field knowledge to make conservation evaluations.

Locating and compiling information on the conservation status of trees has proceeded rapidly in preparation of The World List of Threatened Trees but unfortunately it has not proved possible to develop or incorporate all the information located. More comprehensive evaluation of the conservation status of tree species for many countries would add significant numbers of species to the list of globally threatened tree species. Countries for which very little new information has been compiled include Cameroon, Dominican Republic, Fiji, Guatemala, Haiti, Korea, the Philippines and Thailand. In some cases this was because of lack of time to establish contacts within the countries.

Information on African tree species, compiled in the early stages of data collection, has been subject to a more extensive period of review. Less time was available to incorporate and review the more extensive tree data for other tropical regions. Examples of countries for which data has only been partially processed for this publication include Bolivia, Costa Rica, Japan, Mexico, Peru and Viet Nam. To provide one specific example, the specimen database provided by ECOSUR provided a very rich source of data. This database contains data from 14000 herbarium specimens for Mexican tree species, with information on vegetation type, associated genera, and altitude. For each tree species recorded in the database the new IUCN category was added by experts at ECOSUR and, with approval from CONABIO, this data was provided to UNEP-WCMC. Information has been added to the Tree Conservation Database for endemic trees of Mexico but there has been no time to seek information on the wider distribution and conservation status for non-endemic trees.

The main body of this book is the compilation of conservation summaries for the 7388 tree species which have been evaluated as globally threatened. The summaries are arranged alphabetically by genus. In order to reduce the size of the species accounts, scientific authorities for species names and common names are not given although these are recorded in the Tree Conservation Database.

The threatened tree species included are those which have been evaluated as Critically Endangered, Endangered and Vulnerable. Species which have been evaluated as Lower Risk: near threatened and Lower Risk: conservation dependent are also included because, in most cases, the supporting information suggests that these trees are of equal conservation concern to species in the Vulnerable category. Furthermore summaries are also included for species evaluated as Data Deficient where it is apparent that the species are in a precarious situation even though some verification is needed of the taxonomic status or further field investigation is desirable. Frequently these species have been referred to as threatened elsewhere in the literature.

For each species the following information is given:

Table 2. Summary of the number of tree species assessed according to the 1994 IUCN threat categories for inclusion in The World List of Threatened Trees.

Note: Numbers of species given in the supplementary tree species lists in the Appendices are also included to give a global total.

The reasons for the decline and rarity for these tree species are varied. In addition to the threats mentioned in the species summaries, supplementary threats to each species are recorded in the Tree Conservation Database. In general, the threatened status of tree species results from processes of habitat modification and destruction. Specific threats may also result from direct exploitation of the species for timber or other products at rates which are unsustainable. The threats most commonly recorded in the Tree Conservation Database are summarised in Table 3.

Threats have been recorded primarily as a basis for determining the required actions needed to reverse the decline of individual species. The threats to tree species are based on personal observations and assumptions and there will be a bias according to the geographical areas where most species information has been collected. The relative importance of different threats implied by the above table should therefore be read with a degree of caution. It is interesting to note, however, the perceived impact of felling as a major threat to tree species. This threat includes both clear felling and selective felling. The fact that over 1000 tree species are considered to be globally threatened as a result of felling reinforces the need for timber harvesting regimes to be managed on a sustainable basis taking into account the impact on non-commercial species.

Information on use and level of use of tree species is recorded in the Tree Conservation Database. The information collated on globally threatened tree species illustrates that 25 percent have at least one recorded use. The use data remains incomplete but nevertheless Table 4 indicates the utility value of the tree species which are threatened with extinction.

The assignment of conservation categories can be an important step in deciding priorities for conservation action. As has already been noted a particularly wide range of tree species fall within the Vulnerable category as a result of the decline of their forest ecosystems over the past 150 years and the longevity of individual trees within this time frame. Furthermore, the rate of exploitation of mature individuals of timber species over this period inclines the species to the Vulnerable category. It is suggested that in developing priority conservation actions for tree species based on the categories of threat, the development of sustainable use rather than protection mechanisms per se should be the focus for economically valuable species which are categorised as Vulnerable based on levels of exploitation.

Most of the species categorised as Vulnerable are those which have a restricted range and are found in habitats which are fragmented and declining (Criterion B); or have very small and restricted populations (Criterion D). For these species in situ protection is particularly important either within areas set aside for conservation or as protected stands within areas, for example, of agricultural or forestry land use. Clearly where the locations of restricted range and threatened tree species converge, these sites should be protected to conserve the maximum number of threatened trees.

Tree species which are Critically Endangered or Endangered are those for which remedial conservation action should be a priority to prevent further decline towards extinction. Where more widespread species fall into these categories because of the rates of decline (Criterion A), however, as with the dipterocarp species, sustainable use initiatives may be equally appropriate. Information in the species summaries indicates those species for which immediate rescue attention is needed.

Measures to secure the conservation of tree species include research into the reasons for decline, protective legislation, in situ protection within designated conservation areas, management of populations in their natural habitats, ecological restoration measures, control of invasive species, and ex situ conservation in botanic gardens, arboreta and seed banks. Where in situ and ex situ conservation measures are already known to be in place for globally threatened tree species, this information is recorded in the Tree Conservation Database. It is apparent, however, that the majority of globally threatened species are not subject to any specific conservation measures.

It is also apparent that many more tree species will be evaluated and recorded as globally threatened as more information becomes available. The preparation of botanical checklists is a very important step in the evaluation of conservation status. There is also a great need for more field data on the conservation status and distribution of tree species.

Major efforts are needed to prevent tree species extinctions. The primary focus for action needs to be at a national level through the actions of government agencies, NGOs and local resource managers. International conservation instruments should reinforce these efforts and provide a broader policy context for activities on the ground.

International policy for the conservation and sustainable use of forest biodiversity has generally concentrated on ecosystem prioritisation and action. In order to prevent the loss of tree species diversity there is a need to shift the emphasis towards a complementary species-based approach. The World List of Threatened Trees and Tree Conservation Database provide the information resource to start doing so. The information now available can be used to refine implementation of policy through, for example, the selection of conservation sites based on tree species diversity and threat, the development of species indicators of ecosystem condition and the development of sustainable use initiatives for economically valuable components of forest biological diversity.

The objectives of CBD are the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilisation of genetic resources. Biological diversity, as defined by this Convention, includes diversity within species, between species and of ecosystems. Forest biodiversity is recognised as a current priority.

Forests are the most biologically diverse terrestrial ecosystems. Although still rich in absolute and relative terms, the biological diversity of all types of forests has been diminished by the impacts of human societies. Those impacts are greater now than at any time in human history and they are still increasing. They are eroding contemporary forest biological diversity and challenging the processes which maintain it in forest communities and their constituent populations. (SBSTTA, 1997).

Parties to the Convention have agreed that the ecosystem approach to the conservation of forest biodiversity should be the primary framework of action to be taken under the Convention. Within this framework priority activities relating to tree species include:

1. assessment of methodologies which improve the long-term persistence of genetic variability within and between the populations of forest species
2. development of methodologies for reporting on the distribution of fragile species.

More broadly, Article 7 of the Convention calls for the identification by Parties of components of biodiversity important for conservation and sustainable use having regard to:

Article 17 of the Convention calls for the facilitation of the exchange of information, from all publicly available sources, relevant to the conservation and sustainable use of biological diversity, taking into account the special needs of developing countries.

Actions to be taken to conserve biological diversity, in accordance with the provisions of CBD, include the development of national strategies, plans or programmes for the conservation and sustainable use of biological diversity (Article 6); establishment of protected area systems where special measures need to be taken to conserve biodiversity (Article 8); adopt measures for the ex situ conservation of components of biodiversity, preferably in the country of origin (Article 9); promote and encourage public awareness and education on the importance and measures required for biodiversity conservation.

The main objective of CITES is to protect species of wild fauna and flora against overexploitation through international trade, by means of international cooperation. Species which are covered by the provisions of the Convention are included in appendices. To qualify for Appendix I, taxa must be "threatened by extinction" and "are or may be threatened by trade". Species included in Appendix II are those which " although not necessarily now threatened with extinction, may become so unless trade in specimens of such species is subject to strict regulation in order to avoid utilisation incompatible with their survival".

In 1994, the Parties adopted new criteria for amendment of Appendices I and II, and specified information requirements for amendment proposals (Wijnstekers, 1995). The CITES listing criteria were developed at the same time as the development of the 1994 IUCN Red List Categories and are loosely related to them.

The CITES appendices include around twenty tree species which are traded internationally as timber. They also include other tree species which yield medicinal products or which are in genera listed because of the threat from commercial horticultural collection, for example succulent Euphorbia spp. and Aloe spp. The provisions of the Convention and subsequent guidance on species listing do not generally distinguish between different species groups in their application. There has, however, been international debate about the suitability of the Convention as a tool to help conserve particular species groups. Increased interest in the use of CITES for timber species over recent years has contributed to this debate. Various amendment proposals have been submitted to CITES for timber species and have been considered by the Parties at the Eighth and Ninth Conferences, prior to the adoption of the 1994 amendment criteria.

The CITES Timber Working Group (TWG) was formed at the Ninth Conference of the Parties to review implementation issues relating to timber species, notably the control of parts and derivatives of listed species, and relationships with other international organisations dealing with the conservation and sustainable use of timber. The final report of TWG was endorsed by the Tenth Conference of the Parties in Harare, June 1997.

In its final report the TWG recommended that: many internationally traded timber species, boreal, temperate and tropical, can be managed on a sustainable basis through the application of appropriate silvicultural techniques, but that for other timber species such knowledge is currently lacking; and that there may be timber species which are under threat because of detrimental levels of use and international trade.

Consequently the TWG recommended that: The range states should pay particular attention to internationally traded timber species within their territories for which knowledge of biological status and silvicultural requirements indicates concern.

The preamble of the ITTA, 1994 which came into force on 1 January 1997 notes the commitment of all members, made in Bali, Indonesia, in May 1990, to achieve exports of tropical timber products from sustainably managed sources by the year 2000. One of the objectives of the Agreement is: To encourage members to develop national policies aimed at sustainable utilization and conservation of timber producing forests and their genetic resources and at maintaining the ecological balance in the regions concerned, in the context of tropical timber trade.

With regard to cooperation and coordination with other organisations, Article 14 of the Agreement states that the Council (ITTC) shall make arrangements for consultation and cooperation with the United Nations and its organs, intergovernmental organizations including CITES and NGOs. The Organization (ITTO) shall, to the maximum extent possible, utilize the facilities, services and expertise of existing intergovernmental, governmental or non-governmental organizations, in order to avoid duplication of efforts in achieving the objectives of the Agreement.

At an international level, mechanisms for promoting the conservation of individual tree species and areas of maximum tree species richness and diversity within forest ecosytems, need to be developed. The CBD is currently the most appropriate policy instrument given the commitment of parties to the conservation of biological diversity, the sustainable use of its components and the fair and equitable sharing of the benefits arising out of the utilisation of genetic resources. Furthermore CITES can be used to ensure that commercially valuable globally threatened trees are traded internationally at sustainable levels and ITTA can be used to ensure that sustainable forest management and trade in forest products promotes the conservation of tree species.

The emphasis on implementation of CBD, CITES species selection and ITTA policy development and projects is at a national level with international exchange of information, financial support and technical expertise where appropriate. Subsets of information from the Tree Conservation Database will be made available as tools for the development of national threatened tree lists on which to base national policy and action. Convergence of national and international systems for collection of information and categorisation of threat needs to be considered further identifying, for example, which data elements are common requirements and guidelines for rapid collection of such data. There is a need for flexibility and incremental development of conservation information systems based on available knowledge.

The sharing of information between scientific and conservation institutions is important to build on the results of the tree species conservation assessments and fill in current gaps on tree species information as new scientific data becomes available. Baseline field survey is urgently required for many areas and the collection of additional distribution data for species known or suspected to be of concern. The spatial accuracy of current data can be significantly improved, and the application of the IUCN threat categories reinforced, by the use of GIS linking herbarium, species inventory and forest cover data. Enhanced use of distribution data will be particularly valuable in planning in situ conservation measures for trees.

Research is urgently needed on the population biology and autecology of globally threatened tree species. For practical application, research and information exchange are also needed on aspects of sustainability relating to tree species utilisation, particularly for those species categorised as Vulnerable. Silvicultural research and exchange of information on silvicultural techniques should be components of this. The links between forest certification initiatives and the sustainability of tree species should also be considered further.

Collaboration with international, regional and national agencies is essential in collecting information on the conservation status of trees. The preparation of The World List of Threatened Trees has fostered good links with international and national organisations, IUCN/SSC Specialist Groups and individual experts. Further collaboration with IPGRI and FAO in relation to information systems for tree species and their genetic resources (in turn linking with ICRAF and CIFOR) will be very valuable. National herbaria are an essential source of primary information on the conservation of tree biodiversity. Networking of information and expertise needs to be maintained and developed.

A strong message to emerge from the preparation of The World List of Threatened Trees is that tree species are threatened with extinction throughout the world. Numerically more species are threatened in tropical regions reflecting the greater tree species richness in these regions. Nevertheless, the potential for tree species loss is a universal problem and needs to be tackled in all countries and at all levels. Information products are needed to convey the information in this book to a wide audience including the managers of natural resources in rural communities. Local people may not always appreciate that a species they harvest has a narrow geographic distribution and is wholly dependent on local wise use for its conservation.

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Document URL: http://www.unep-wcmc.org /trees/Background/intro2.htm
Revision date: 05 September 2007 | Current date: 09 May 2008

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