We all know about the major deserts of the world – the Sahara, the Gobi and the Chihuhuan – however few people know that there are ‘deserts’ in the ocean.

These deserts are sometimes referred to as the Earth’s ‘biological desert’ and are areas of nutrient-starved saltwater in the Earth’s oceans. These biological deserts are the least productive systems within our watery expanses and cover around 40% of the Earth’s surface. Global warming appears to be having a big effect on the deserts and they may become an area of the Earth that gets a lot more press in the near future.

With rising temperatures, it was expected that the biological deserts would expand however researchers have found that the watery deserts are growing much faster than global warming models predicted. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) is a sensor mounted on a spacecraft launched in 1997 that maps ocean colour around the world – green shows an abundance of plant lift thanks to the photosynthetic pigment chlorophyll, and this is the base of the food chain so large quantities of green areas are a good thing. (picture: NASA/GSFC/SeaWiFS)

Researchers tracked the changing size of the central region of the faint green in the subtropical areas of the North and South Pacific, North and South Atlantic and South Indian Oceans. The tracking showed that with the exception of the South Indian ocean, all the biological deserts had grown in size with a total expansion of around 6.6 million square kilometres – a rise of about 15%. With a non-localised trend that is happening in all four ocean basins, it suggests that global warming is the likely cause of the growth.

Gyre waters are strongly layered. This means that the wind does little to help the nutrients stored deep down come to the surface to help fuel plant and algae growth, and therefore help animal growth. As temperatures rise, this layering is strengthened which makes mixing the nourishment even harder. Although the gyre deserts were predicted to expand, they were not expected to expand as quickly as they have done – in the past 9 years, gyre deserts have grown between 10-25 times quicker than predicted.

The only question that remains is whether the real cause of the growth in the gyres is global warming, or whether the growth is part of a natural cycle that takes years to play out and will therefore shrink in size over the next few years.

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