Anemones on a sea mount - not known for their migratory habits
The weather forecast was ominous as we departed Aberdeen harbour, gales and high winds were ahead of us. But with the wind behind us, we've had a good night's sailing.
Just now we're close to Fair Isle, an isolated island halfway between Orkney and Shetland. It's famous for its knitwear, but also as a great place to see birds. Winds, location, and luck make it a common resting place for lots of unusual birds as they migrate, or are blown off course - and Fair Isle offers them a temporary and welcome shelter.
Islands offer unique opportunities for species - they are places where new ones often develop in isolation. And we don't need to restrict that definition to just islands as we know them, the same is true of places like mountain tops, and lakes. Think about it. Any habitat that is 'isolated' from another similar habitat is effectively an island to the plants and animals in it.
Of course some species roam widely. The arctic terns we have been seeing migrate pole-to-pole, and animals like whales can move great distances. Other species either don't get about so easily. Bottom-dwelling species like sea urchins and coral can't get out much, really!
Even under the waves the conditions are highly variable, and 'islands' exist for ocean species. It could be the type of terrain - rocky or sandy, for instance - or the depth, or the temperature, or the abundance of food. Many factors combine to limit the distribution of marine life.
Nowhere is that more evident in our oceans than on underwater mountains called sea mounts - these exist all over the world and, because they force water and nutrients upwards by just being there, are particularly rich in ocean life. They're also home to a large amount of species found nowhere else - about 15 per cent of the species on each sea mount can be found nowhere else. These are just one of the special habitats that we think a network of marine reserves must be protecting.
If you agree, write to David Miliband, environment secretary, and tell him to push for North Sea marine reserves.
