Six coastal canaries

With so much climate change scepticism around, it is useful to have indicators that anyone can observe and which will point directly to rises in overall temperature. The “canaries” concept is one that fits this particular bill.

Canaries as indicators of danger

In times gone by, coalminers used to take caged canaries down the mine with them, not for the company but as a safety device. It was known that canaries were highly susceptible to gas poisoning, so if your canary fell off its perch you knew that there was methane gas seeping into the mine and it was high time that you moved to somewhere safer. (The canaries often recovered when taken to a place with better air, although this was not always the case).

The United Kingdom’s National Trust has taken the “canary” concept a stage further by announcing a set of six “coastal canaries” that, should their populations show a sudden decline (or in one case a rise), will provide a warning that global warming has reached a dangerous level. These are species that are highly dependent on such things as sea temperatures and weather patterns for their survival and which will react most quickly when these factors change.

Six coastal canaries

The canaries chosen by the National Trust are:

1.       .Glanville fritillary butterfly. The range of this butterfly has got gradually smaller over the years, and it is now confined to the western chalk cliffs of the Isle of Wight. It will therefore be relatively easy to spot its complete disappearance, should that occur.

2.       Oysterplant. Grows on shingle beaches in northern England, Scotland and Northern Ireland. It will suffer if the sea becomes more saline or if higher sea levels mean that it has to spend more time submerged.

3.       Cliff tiger beetle. As cliffs crumble as a result of rising sea levels and increased storm activity, it becomes necessary to carry out more cliff stabilisation projects. This disturbs the cliff tiger beetle, which can only fly short distances and will find it difficult to find new hunting grounds.

4.       Puffin. Warmer seas are affecting populations of sand eels, which supply the puffin’s chief source of food. They breed in cliff-top rabbit burrows which can flood if there are too many heavy rainstorms.

5.       Little tern. This bird breeds on beaches just above the high-water mark. Too many exceptionally high tides and summer storms will have a significant effect on the little tern’s breeding pattern.

6.       Triggerfish. Aptly named for this purpose, the triggerfish is a warm water species that is beginning to be seen in greater numbers in British waters, notably off North Wales. There are other “trigger” species for the same reason, such as basking sharks, certain species of jellyfish, and zebra mussels, all of which are being seen more frequently.

As climate change continues to affect the coasts of the United Kingdom, many species will doubtless be affected. The above “canaries” are likely to be only the first of many.

© John Welford

Kiritimati's corals are dying

Kiritimati is one of the world’s largest coral islands, located near the centre of the Pacific Ocean and part of the island nation of Kiribati (formerly the Gilbert Islands). It is also one of the Line Islands, which is one of the world’s longest island chains. The name Kiritimati is a re-spelling of Christmas, which was the name given to the island by Captain James Cook when he landed there on Christmas Eve in 1777, although he was not the first European to discover it.

Despite being created from coral, the phenomenon known as coral bleaching threatens the future of the island in terms of its ecology and economy. It has been estimated that 95% of its coral reefs may die within the next few years, and it could take decades for them to recover, if they ever do. A recent survey has shown that 80% of the giant table-top corals around the island are already dead and another 15% are dying.

The problem is that rapid increases in water temperature cause the tiny algae that nourish coral and give it its colour to be expelled, leaving behind ghostly white skeletons that are subject to disease and erosion. The algae are at the base of the food chain of a coral reef, so without them there are no fish, which are unable to escape to other islands because of Kiritimati’s remoteness. Without the fish, there is no livelihood for the human population of the island.

At the heart of the problem is the El Nino phenomenon, which is a periodic shifting of warm water within the Pacific Ocean that has worldwide consequences for weather patterns. El Nino events have been known about for centuries and can be expected every three to seven years, but their intensity has been increasing in recent decades, with global warming being a prime suspect. The warming of the ocean around Kiritimati, for example, has been measured at around 3.5⁰ C.

Short-term rises in water temperature can lead to the temporary bleaching of coral, from which a relatively rapid recovery can be expected as things return to normal in non-El Nino years. However, it is expected that future El Ninos will be more intense and more frequent, which means that coral reefs will find it very hard to recover.

Coral bleaching is a worldwide phenomenon, with the Caribbean being another region that has suffered badly. However, the problem at Kiritimati is particularly bad and few scientists are optimistic about its prospects if ocean temperatures continue to rise, as seems likely given current trends.

© John Welford