Basic environmental and geographic information
on the 2000 significant islands of the world
Originally published as: Dahl, Arthur Lyon. 1991. IUCN/UNEP Island Directory. UNEP Regional Seas Directories and Bibliographies, No. 35, Nairobi, Kenya. 573 p. and made available on line in 1998 at http://islands.unep.ch/isldir.htm
Much of the data in this directory is now more than 20 years old.
WCMC is working on a new Global Island Database which may be available at http://gid.unep-wcmc.org/ with over 180,000 islands. It complements but does not yet replace this directory
(listings accessing data sheets on 2,000 islands)
- Country list
- Alphabetical index of islands
- Low islands
- Raised coral islands
- Volcanic islands
- Continental islands
- Islands by conservation importance
- Islands by total endemic species
- Islands by number of endemic land birds
- Islands with protected areas
- Islands by population density
- Islands by human impact
- Important islands at risk
- Explanation of Island Indicators
- Model country and island entries
- Island Directory Field List (complete description of each field in the directory)
- References and sources
Islands have long been noted for their unique fauna and flora which are particularly vulnerable to disturbance and destruction by human activities. They are also of interest for the special adaptations of island societies, the difficulties of economic development in an island context, and the challenge of achieving sustainable development within limited island resources. With the increasing rate of global change, islands represent some of the most fragile and vulnerable resources on the planet.
This Island Directory assembles information on the significant islands of the world. It is intended to help those living on islands or involved in island development and conservation to understand the environmental problems of islands, to identify islands with special problems or under particular threat, and to compare and classify islands globally to show which islands may share common problems and be able to cooperate in solving those problems.
This Island Directory provides an annotated list of nearly 2,000 of the significant islands of the world. Several criteria were used to determine how much detail is provided for the selected islands. Islands over 17,000 square kilometres are too large to summarize in this directory format; each should have a book in itself, and receives only cursory treatment here. Only oceanic islands are included; those occurring in freshwater bodies have not been covered. Small islands are treated differently depending on their location. Small islands close to and not differing from nearby larger land areas are not listed separately, whereas remote islands of similar size are generally covered. Finally, islands in shallow water (with depths of less than 100 metres to an adjacent land mass) have only been islands since the last ice ages, with less opportunity to develop unique biological features, and are thus not treated in the same detail. In general, less effort has been made to collect and enter data for the lower priority islands (large, urban, or in shallow water) and many gaps in the information in this directory about these islands will be obvious.
The format has been designed to summarize many kinds of information to give an overview of the geographic, ecological and human interest of islands. Where the data available are sufficient, a variety of indicators are used to make listings and comparisons of islands easier. The size of each entry has been adjusted to the amount of data entered.
It will be apparent that the coverage in this directory is very uneven. Some regions and groups are covered in some detail, while for others it was not possible to obtain or enter much information with the resources available. One of the purposes of this Internet edition is to encourage the compilation of information to fill in the gaps in this directory. Similarly, some fields have been included in the database for which data do not generally exist, but which would be very useful for comparing islands or for responding to particular problems. Again it is hoped this will stimulate people to collect such information.
The deficiencies in the data available mean that many of the means for comparing and rating island characteristics in this directory cannot be used to their full potential at present. A zero value or the absence of an entry cannot be taken as meaning more than that the information was not available at the time of compilation. While the fact that certain islands stand out for their environmental importance in this directory is significant, the converse is not the case; island that do not stand out may only be poorly documented, not uninteresting. This problem should be diminished as more information is compiled.
The islands are grouped by ocean and country. Some appropriate information on each country or territory, such as the land area, sea area within the exclusive economic zone, population, population density and estimated growth rate, authority responsible for conservation/environment, and legislation for conservation, is provided under the country headings at appropriate places in the directory. Within these groupings, islands are listed in alphabetical order.
There is a page for each country or island territory (where this may have separate legal or administrative arrangements) (see model country page), and a page with entries for each island within the country (see model island entry). The country pages include a count of the number of islands by size, and a variety of demographic, economic, social and environmental statistics at the country level. There are text entries for administrative bodies, legislation and non-governmental organizations.
Several kinds of information have been collected for each island when available, as described below. A complete listing of all the fields in the directory is given in the Field List.
a) The present name in English, the official name if in another language, and significant former names if widely used in the literature.
b) Basic descriptive information
on each island, such as its geographic co-ordinates, land area (in square
kilometres) and maximum altitude or elevation (in metres), submerged area
the 100 metre depth contour (in square kilometres), length of shoreline (in kilometres), and isolation (distance to nearest equivalent or larger island, island group and continent).
c) The island type (continental, volcanic, atoll, low island, raised coral limestone, or some combination of these), age, geology and soil types.
d) Climate, rainfall, temperatures (maximum, minimum and mean; air and ocean).
e) The major natural and human catastrophic threats which could endanger an already vulnerable population or feature, such as cyclones (hurricanes or typhoons); volcanic eruptions; earthquakes, tsunamis (tidal waves), landslides and other effects of geological instability; severe drought; susceptibility to major fires; high risk of oil spills; etc.
f) The history of human occupation, historic and prehistoric populations and dates of colonization, present population (with the year of the census or estimate) and density (inhabitants per square kilometre). In the absence of a population figure, an island should be assumed to be inhabited unless otherwise stated.
g) Indicators of human impact,
such as urban areas, airports, types of economic activity and agriculture,
etc.; the state of resources (soil, water, etc.); and selected indicators
h) A brief list of the major ecosystem types or biomes on and around the island, where this information is available. For some areas these data are very incomplete, and the failure to mention an ecosystem does not mean that it is not present, but only not recorded.
i) Features of special interest for conservation, such as seabird rookeries, sea turtle nesting areas, marine mammal resting or breeding sites, lakes or other unusual habitats, active volcanoes, and other information on the island's conservation importance.
j) The size and diversity of the flora and fauna, such as the total numbers of species, at least in the best-known categories, where such figures were available.
k) The numbers of endemic species (those
species occurring only on a particular island or island group) in the best
studied plant and animal categories (plants, butterflies, land snails,
reptiles/amphibians, birds, mammals, and marine life), as a convenient
measure of evolutionary interest or uniqueness; also the number of species
classified as Endangered, Vulnerable, Rare and
Indeterminate, according to IUCN criteria.
l) The scientific and common names of endemic species and other species of special conservation interest, with brief information on their habitats and population sizes, and their status (Endangered, Vulnerable, Rare, Indeterminate, or K -insufficiently known). The status is capitalized if determined by the World Conservation Monitoring Centre or indicated in a Red Data Book, and in lower case if obtained from other sources. An asterisk (*) after the name shows that there is some question concerning the taxonomic status of the species.
m) Information on introduced biota, particularly alien or feral species or diseases known to be invasive on islands and to cause major conservation problems.
n) The names of terrestrial and marine protected areas on the island and their area in hectares. Recent official proposals for protected areas may also listed for some countries.
o) References to key papers with information on the island.
p) For islands with sufficient data, the entry in the
directory includes a series of indicators
used to evaluate certain island characteristics. These include the ecosystem
richness reflecting the number of types of ecosystems present, the species
richness based on the number of species, the individual island and
island group endemics, and the number
of special features, all
evaluated separately for terrestrial and marine areas. Other general
island indicators are the natural
vulnerability based on the kinds of risks of natural or human
catastrophes, the natural conservation status or protection
provided by the island's inherent situation, the reliability
the data on which the listing and evaluation are based, the human
threat measuring the pressure of the people on the land and
resources, the economic
pressure related to the level of development and material lifestyle
of the population, and three aggregate indicators for the potential for human
impact on the island, and for the terrestrial
importance and marine
importance of the island. The details of the basis for and
calculation of all of these indicators are given in the section: Explanation
of Island Indicators. The indicators are intended to put the
largely qualitative information about the islands into a form permitting
some comparisons between and rankings of the islands on a country,
regional or world basis.
- Basic information on each country or territorial entity is summarized in a country format of some 70 fields. Each country page includes a list of links to each island in that country or territory. The field list explains the contents of each field on the country page.
- Most of the detailed information in the directory is in the island format with 120 fields. All the islands within a country are grouped on the same page, so you can scroll between them. The country names on each island page are linked to the country page. The field list explains the contents of each field on the island page. The indicators are also explained separately.
- The indices and tables provide direct links to the country and island pages.
- A special feature of this directory is the "hot colons". The colon ( : ) between each heading and its contents is linked to the description of that heading in the field list, including explanations of the numerical values. Click on the colon and you have an immediate explanation of the content of the field. Then use "back" to return to the page.
This directory is a preliminary attempt to synthesize large amounts of information on an island by island basis around the world. Many entries are incomplete, or possibly even misleading if essential information, such as the human population or the fact that the island is inhabited, have not yet been entered. In addition, the following specific problems with data quality have affected the result and should be kept in mind particularly when using the directory to compare islands.
a) The quantity of available information is highly variable from one region or island to another. A few islands happen to have been studied in detail, perhaps by some scientific expedition, while others may never have been visited by a scientist. For many islands, even basic descriptive information is lacking in the sources available. Inevitably the better known islands stand out in such a survey, and this may in part be an artefact of the data available.
b) Most islands are still rather poorly known scientifically, partly because work on one island cannot be easily generalized to others. New species are still being discovered in obvious and well-known categories such as birds and reptiles. Other categories such as some types of insects have hardly been looked at at all.
c) Information on species is often only available at larger geographic scales such as island groups, countries or biogeographic provinces. This can make it difficult to know what specifically occurs on any given island. The regional distribution of many species is known or mapped, but islands are sufficiently variable that it is not possible to assume that a species occurs there just because the island is within the species' known range. Distributions can be highly irregular or spotty depending on chance dispersal or extinction and on local conditions.
d) The data may be patchy in different ways. An island may be well known for birds or land snails, but hardly at all botanically, or vice versa. This can have a particular effect on levels of endemism, which may vary greatly from one type of organism to another. Hopefully the gaps identified in this directory will encourage others to fill them.
e) The cross-checking of data from different sources has revealed many errors, to the point that it has sometimes seemed doubtful that the same island was being described. Even figures such as the island surface area or altitude have differed by up to 50%. The type of island or the existence of specific features also sometimes vary between sources. Some errors maybe obviously typographical or due to incorrect (or even double) conversion between units of measure, and these have been corrected where they were identified. In other instances, it has been impossible to determine which source of information is correct, and one has had to be chosen based on the probable reliability of the source. Unfortunately errors such as these tend to be perpetuated from one compilation or study to another, and some have probably be unwittingly carried over into this one where cross-checking with authoritative sources was not possible.
f) Much of the available information is seriously out of date. No island stays still in time, and conditions or features may change from the time when they were described. Many sources fail to give the dates for their data, and old information may be assumed to be current. Much island information dates from expeditions early in this century, or from World War II, and it will need to be confirmed or revised from up-to-date surveys before using it as the basis for important decisions or conservation actions. Dates have been added where known to the types of information in the directory where this may be critical, as with population figures or the status of a species.
In spite of all these problems and sources of error, it should be
possible to have reasonable confidence in the overall content of the
directory and the results of the review and analysis based on it.
Enough different types of information have been brought together to
diminish the impact of any single error or data variable.
This Island Directory is a product of the Island Database system of nearly 2,000 islands that was first developed in 1987-89 by Arthur Lyon Dahl under contract to IUCN - The World Conservation Union with the financial support of the United Nations Environment Programme (UNEP) and the assistance of the IUCN Task Force on Conservation of Island Ecosystems and the World Conservation Monitoring Centre. The database is still maintained by Arthur Dahl, but major parts have not been updated. It has been redesigned to generate all the pages of this directory directly in html.
Major contributions of data were made to the original database by the staff of the UNEP-World Conservation Monitoring Centre under the supervision of Jerry Harrison, by Timothy H. Johnson of the International Council for Bird Preservation (now BirdLife International), and by Christian Depraetere of IRD (formerly ORSTOM). Many others contributed in ways too numerous to mention.
A preliminary edition of this Island Directory was published by UNEP in
its Regional Seas Directories and Bibliographies series, No. 35 (573 pp.),
in 1991, but is now out of print. The directory was then made available on
the UNEP Islands Web Site (http://islands.unep.ch),
but this could no longer be maintained after the retirement of Dr. Dahl. A
new Global Island Database is being prepared and may be available at
and the contents of this directory have been transferred to them for
eventual incorporation in that database.
Dahl, Arthur Lyon. 1991. Island Directory. UNEP Regional Seas Directories and Bibliographies No. 35. UNEP, Nairobi (573 pp.)
Dahl, Arthur Lyon. 1986. Review of the Protected Areas System in Oceania. IUCN/UNEP, Cambridge and Gland (239 pp.)
The sovereignty of a considerable number of islands is subject to
disputes between Governments. Such disputes are noted in the entries
whenever possible. The information on administrative and legal
arrangements reflects the de facto situation where it is known.