Forgotten fronds of the fishes' nursery

World Atlas of Seagrasses
June 18, 2004

Our cultural heritage in the West leaves us singularly ill-equipped to deal fairly (and squarely) with seagrasses. No doubt we can plead, with some reason, that seagrasses do not rank highly in the scheme of things around our shores. The two species of seagrasses that are to be seen around British coasts and the North American seaboard are found infrequently by the average beachcomber and then only at muddy sites in turbid waters of estuaries and the like. But the same could be said of corals, and yet we all know a lot more about corals and the exotic nature of coral reefs. It must be admitted that seagrasses have had a fairly poor press until recently.

Is this as much the fault of scientists as anyone else? Probably. While Linnaeus recognised and named three of the 60 seagrasses, and while his admirer Erasmus Darwin, the grandfather of Charles, wrote in The Botanic Garden (1798): "Stretch'd on her mossy couch, in trackless deeps,/ Queen of the coral groves, Zostera sleeps", most botanists paid seagrasses scant due.

For example, when Captain Cook sailed into what was to be called Botany Bay in New Holland in 1770 and was so impressed by the activities of his botanist, Joseph Banks, that he named the bay after them, he nevertheless collected not a single seagrass. And this despite the fact that the bay was so rich in seagrasses, four species of them, that it supported a wealth of marine fish, including the abundant stingray (Cook's first choice of name for the bay). It was left to the redoubtable Robert Brown to name the first Australian seagrass, Posidonia australis , during the circumnavigation of Australia by Matthew Flinders in 1805 - the same plant that Cook and Banks must have waded through in order to land in Australia.

So why should we bother with seagrasses now? Well, over the final quarter of the 20th century it became very clear that seagrasses contributed in great measure to the coastal ecosystems of all the continents except Antarctica - much more than their 60 species would suggest. Seagrasses are not really grasses at all but belong to two (or possibly three) families of monocotyledons in which a few early members took to the sea some 60 million years ago. Today, however, in many regions of the world they are the dominant form of marine vegetation in shallow bays and estuaries, virtually defining the local ecosystem, providing support for much of the local biodiversity and acting as the major nursery grounds for many commercial fish.

And that is the problem. Humans have also sought out the same sites, although preferring the landward side. The result is that the low profile of seagrasses and the high impact of humans at these sites - from shipping, port development, industrial developments, sewage discharge (containing herbicides and insecticides), eutrophication and so on - have led to an unprecedented and largely uncharted demise of seagrasses around the world.

The World Atlas of Seagrasses attempts to redress this indifference. It is lavishly illustrated and embellished with maps, tables and fascinating trivia concerning every aspect of seagrasses. It is divided into a general section, the global overview and 24 regional sections covering every important region around the world, written by local experts. That may sound like a lot of sections, but when one realises that a section can cover an area as large as, say, South America, it is clear that many of these areas are treated in broad-brush style. Also, given the lack of previous focus on seagrasses in many parts of the world, these regions are inevitably poorly understood.

Nevertheless, the atlas is excellently produced and acts as an irreplaceable compendium of knowledge about seagrasses, so that even where our knowledge is thin, the book will act as a focus for showing where future studies should be targeted.

The book's sponsor, the United Nations Environment Programme, aims "to help decision-makers recognise the value of biodiversity to people everywhere, and to apply this knowledge to all they do". The World Atlas of Seagrasses should certainly become a bible for the large number of decision-makers who have responsibility for marine catchments.

Tony Larkum is professor of plant sciences, Sydney University, Australia.

World Atlas of Seagrasses

Author - Edmund P. Green and Frederick T. Short
Publisher - University of California Press
Pages - 298
Price - £39.95
ISBN - 0 520 24047 2

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