The Flora of Aruba, Bonaire and Curaçao
– by André van Proosdij
Botanical research on Aruba, Bonaire and Curaçao dates back to the late 19th century and still continues today. The large historical and recent botanical collections of the islands are now part of Naturalis Biodiversity Center and continue to be of great value for current and future research. New technologies and media enable the close cooperation between local professionals and volunteers as well as experts worldwide in collecting and identifying new collections. Recently, the latest edition of the Flora for Aruba, Bonaire and Curaçao was published, triggering local plant lovers to study the flora and discover even more new species.
The flora of Aruba, Bonaire and Curaçao comprises 569 indigenous and naturalised species. The flora is composed of South American, Central American and Caribbean floristic elements: species that naturally occur in one or more of these floristic regions. In addition to the indigenous species, 86 species are of foreign origin. These have been imported accidentally or on purpose by man, escaped from cultivation and finally managed to establish themselves in the ecosystem. Some of these have become invasive by turning into notorious weeds that outcompete other species and change the ecosystem. The three islands differ in floristic composition. Curaçao is the largest of the three islands, has the highest hills and receives the highest level of precipitation. Hence it is the most species-rich with 541 registered species. Aruba on the other hand is the smallest and driest of the three and consequently is relatively species-poor with 352 registered species. Bonaire is intermediate with a total of 387 registered plant species. Some species occur only on the ABC islands or even on one single island. A total of nine endemic species are known from Aruba, Bonaire and Curaçao together, but Aruba, with six endemics, has one more than each of the other two islands.
Table: Endemic plant species of the Leeward Dutch Caribbean Islands
| Aruba | Bonaire | Curaçao |
| – Agave arubensis – Agave rutteniae – Cynanchum boldinghii – Melocactus macracanthos – Melocactus stramineus – Melocactus x bozsingianus |
– Agave boldinghiana – Cynanchum boldinghii – Melocactus macracanthos – Maytenus versluysii – Myrcia curassavica |
– Agave boldinghiana – Cynanchum boldinghii – Melocactus macracanthos – Maytenus versluysii – Myrcia curassavica |
Research on the local flora started in the late 19th century with the work of W.F.R. Suringar and his son J. Valkenier-Suringar and was continued in the beginning of the 20th century by Isaac Boldingh. Boldingh collected thousands of plant specimens, which he used to write his ‘Flora of Curaçao, Aruba and Bonaire’ (1913) and ‘Flora of the Dutch West Indian Islands’ (1913). His work was continued by Fr. Arnoldo and Prof. Stoffers who both collected intensively during the second half of the last century. Stoffers’ ‘Flora of the Netherlands Antilles’ (1963-84) covers approximately half of the plant families. Arnoldo published the first 2 editions of the ‘Zakflora’ (pocket flora) of Aruba, Bonaire and Curaçao (1954 & 1964). In the late 1990s Van Proosdij revised the ‘Zakflora’ (2001), for which additional collections were made. Since then, the study on the flora continued resulting in new fieldwork and a new edition of the ‘Zakflora’ in 2012.
New technologies and media have created new opportunities for scientific research and collaboration on the flora, such as the ability to access collections housed by the New York Botanical Garden. Additionally it allows local naturalists to become more and more involved. Either alone or in hiking groups, they cross valleys and climb hills, taking pictures with digital cameras and collecting material from plants which they can’t identify. Usually the same day e-mails with images or links to online 
photo-libraries are shared leading to lively discussions and increased knowledge for all participants. Voucher specimens of all new discoveries are collected and deposited in Naturalis’ herbarium collections. Investing time and effort in training these local volunteers by means of a citizen’s science training program has paid off well: In 2013 alone this has resulted in several new records and species for the ‘Flora’. The research continues in close cooperation with local volunteers and international experts. Ambitions for the future include a ‘Flora for St. Maarten, Saba and St. Eustatius’ as well as online tools for plant identification.
