Appeltans, W.; Dujardin, F.; Flavell, M.; Miloslavich, P.; Webb, T.J. (2016). Biodiversity baselines in the global ocean, in: UNESCO-IOC et al.The open ocean: Status and trends. pp. 220-238
In: UNESCO-IOC; UNEP (2016). The open ocean: Status and trends. United Nations Environment Programme (UNEP): Nairobi. ISBN 978-92-807-3531-4. xxxiii, 331 pp.
This chapter provides baselines on what is currently known about the taxonomic, biogeographic, and conservation status of marine species using the world’s largest marine biodiversity database, the Ocean Biogeographic Information System (OBIS; iobis.org). The ocean may be home to one million or more species, with 230,000 so far described by science. The age of discovery continues, with the rate of description of new marine species higher than ever, suggesting that most will be discovered by the end of this century. The importance of species diversity for marine ecosystem functioning is well known. It is therefore important to know which species live where, why, in what abundance, and how these factors are changing through time. Despite increased biodiversity monitoring since the 1950s globally, with daily averages of 120 sampling events and 1 800 observations in OBIS, 98.7 per cent of the ocean volume can still be regarded as severely under-sampled and all we know of 62 per cent of all marine species might be based on a single record. Assessments of completeness based on nonparametric richness estimators confirm that many species remain to be sampled in most parts of the world’s ocean. For only 1.5 per cent of all marine regions, knowledge of species richness is >80 per cent complete. For >50 per cent of the ocean, however, no reliable estimate could be calculated and even in highly-sampled regions such as Europe, there are still many spots with over 30 per cent undiscovered or unreported species. When restricted to fish, completeness scores are higher globally, particularly in coastal areas, but not in open waters. Understanding where species occur is a necessary first step towards identifying areas of high richness, endemicity, or threat, and is thus essential for effective conservation planning. For those areas with sufficient data, several biodiversity indices agree that Southeast Asia, the Southwest Pacific, the Gulf of Mexico and the Caribbean Sea are notably rich in biodiversity. This agreement is encouraging given the significant gaps and biases in OBIS data. According to the Red List of the International Union for Conservation of Nature (IUCN), 17 per cent of marine species assessed are considered to be threatened with extinction and 20 are extinct. When plotted in OBIS, areas of greatest importance to species known to be threatened include the Caribbean and Atlantic Coast of the USA, waters between Eastern Africa and Madagascar, and the Indo-Pacific. However, considering that little is known of rare species, true rates of threat in marine species may be substantially higher, and spatially more distributed, than current estimates suggest. In addition, OBIS lists almost 500 species that have >10 observations but have not been recorded at all in the last 50 years. Monitoring ocean biodiversity is expensive and can be risky, and requires highly skilled people. Very few marine regions or taxonomic groups have benefitted from long-term monitoring programs; hence stocktaking remains far from complete. Publishing existing biodiversity data into open data repositories such as OBIS provides the most costeffective means to address this shortfall, and we hope that momentum in this direction can be maintained, alongside new efforts to discover and document the diversity and distribution of life in the ocean. In addition, we recommend focused efforts to monitor the abundance of key species at all trophic levels, potentially as part of a global initiative such as the Global Ocean Observing System (GOOS).
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