Seabirds in danger
Norman Ratcliffe, who used to be a Senior Research Biologist for the RSPB explains how seabirds are in danger.
The effects of climate change
"Our seabirds are already being affected by climate change - in the North Sea, the temperature has risen by 1C in just 25 years.
Species we would never have expected off our shores are moving northward at a rate of 50km a year – warm water fish such as red mullet, sardines and anchovies, seahorses and squid. Familiar cold water fish, such as cod, are retreating northwards.
The chemistry of the seas is changing. As surface waters have warmed, their salinity has fallen.
The seas are also becoming more acidic, as they absorb half of humankind’s carbon dioxide emissions. Increased acidity is leading to a drop in numbers of phytoplankton, corals and shellfish which are unable to maintain their calcium-rich shells."
"At the top of the marine food web, seabirds are a visible sign of the changes taking place below the surface. They are sensitive to disruptions in the food chain. Sand eels are disappearing due to dramatic changes in their plankton diet. In turn, birds are not finding enough sandeel food to sustain them and their young.
Kittiwakes, arctic terns, guillemots and shags are among the seabirds which depend on sandeels for adult and chick food.
Sandeels are rich in oil and so highly nutritious. Without them, adult birds do not reach breeding condition and may fail to nest.
When sandeels are in short supply, there is not enough food for young birds and they fail to survive. The parents have to forage harder to try and make ends meet. They may try to switch to other prey, if available, but this may be less suitable for breeding and survival."
"As a result of this sandeel shortage, seabirds have failed to breed up and down the UK’s North Sea coast.
- In 2004, in Shetland, Orkney and Fair Isle, hundreds of thousands of seabirds failed to raise any young.
- Breeding failure was scarcely less dramatic further south, stretching right down to the RSPB nature reserve at Bempton Cliffs in Yorkshire. Entire colonies of seabirds did not return to their breeding grounds at all and those that did struggled to reproduce. Seabirds are long-lived, but successive years of failure on this scale is bound to lead to population declines.
- In 2005, seabird breeding failures spread for the first time to parts of the UK’s west coast. Breeding success continued to be poor for most species on Shetland in 2006 and 2007, though kittiwakes had moderate years.
- Guillemots fared poorly on the east coast, while other species seem to be doing all right. Breeding failures were evident on the west coast for many species in both 2006 and 2007, although they weren't so extensive as in 2005.
Our recent climate modelling work showing the future potential distribution of the UK’s breeding birds predicts seabird distribution as a whole could be strongly affected by warming by the end of the century. Many popular species such as guillemots and arctic terns could suffer significant retractions in range around UK coastlines."
Norman Ratcliffe, who worked as a Senior Research Biologist for the RSPB.