Ocean meadows threatened by development

November 7, 2003 - Human beings are air-breathing landlubbers, and that biological constraint shapes the way we see the world, our priorities and values. Water covers more than 70 per cent of the earth, but it is an alien, mysterious - indeed, many would say forbidding and inhospitable - world.

Cut off from air, we would perish in just a couple of minutes, so we maintain tenuous airways to keep us alive as we explore the aqueous environment. Our windows into the water world are tiny and we catch brief glimpses of the enormous diversity that exists there. We are almost as ignorant of the ecology of forest canopies and of the enormous diversity at the microscopic level in the soil that sustains us.

If we don't know what we have, we don't know what we're losing. So the purpose of a much-needed project called the international Census of Marine Life is to document as many species as possible over a 10-year period. According to a progress report released recently by the Census, more than 210,000 marine species, including 15,000 different types of fish, have thus been identified.

And the work is just beginning. Scientists believe that there may be over two million marine species in our oceans and researchers with the Census hope to at least make a pretty big dent in that number by the time the project wraps up in 2010.

It's an inventory that's desperately needed. Recent surveys of some of the most productive parts of our oceans, like coral reefs and seagrasses, show steady declines. For example, studies have found that 30 per cent of the world's coral reef ecosystems are badly damaged, and many may not survive at all unless action is taken quickly to protect them.

Seagrass ecosystems are also under threat. Although not well known, seagrasses are critical to the health of marine ecosystems. They are also fascinating, partly because they are not grasses at all. They are actually the only flowering plant to have returned to the sea after having evolved on land.

About 60 types of seagrass, some just a few centimeters long, others extending several meters, form meadows that extend in range from frigid Arctic waters to warm tropical seas. Individual plants may live for 1,000 years, and some beds span several thousand square kilometers. Across the globe, seagrass meadows cover about 177,000 square kilometers of coastal waters - larger than all the Maritime provinces combined.

These meadows serve vital functions that help maintain the health of the oceans as a whole. They provide food and shelter for thousands of species, including endangered manatees, dugongs and sea turtles. They also act like nurseries or safe havens for important commercial fish species to reproduce and grow. In addition, seagrass meadows physically protect coastal shorelines from erosion and aid coral reefs by filtering sediment and nutrients.

Although seagrasses may be the most widespread shallow marine ecosystems in the world, they are among the least protected. And according to the recently completed World Atlas of Seagrasses, a project funded by the United Nations, meadows are in serious decline. In the past 10 years alone, 15 per cent of the world's total seagrass area has been lost.

Threats vary from region to region, but generally the decline is attributed to a combination of sewage and chemical pollution, invasive species, poor fishing practices and destructive dredging and land reclamation projects. Because the global importance of seagrasses is not well understood, meadows are often disregarded in fisheries management and coastal development plans.

The good news is that seagrass meadows can often recover. For example, after a new sewage processing system was installed in Boston Harbour, seagrasses returned for the first time in 200 years. Unfortunately, such stories are currently the rare exception rather than the rule. And unless we start protecting these overlooked, but vital ecosystems, our oceans will continue to become impoverished and we could lose many species we already know are endangered, as well as some we have yet to discover.

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