ALMOST 70 countries have agreed a plan to protect one of Europe's rarest species of geese, but some Scots experts say scientists are ignoring a key threat.

About 50% of the world's population of Greenland white-fronted geese winter in Scotland, with an estimated 5000 spending more than six months on Islay.

The species is on the International Union for Conservation of Nature's "red list". Scientists say there is increasing evidence that spring snow in west Greenland is affecting breeding.

As a result, a plan for greater protection has now been signed under the African-Eurasian Waterbird Agreement, which brings together representatives of 67 governments and organisations every three years to discuss conservation needs.

Professor Tony Fox, from Aarhus University, Denmark, an authority on the Greenland white-fronted goose, said the population "in recent decades has been exposed to unprecedented environmental change".

However, Islay's farmers argue that climate change may not be the most important reason for the species's decline. They say that the white-fronted geese are now joined by 45,000 barnacle geese, which deny them the best grazing.

Gill Johnstone, Islay's representative of the National Farmers' Union Scotland, said: "We have been saying for a long time that the sheer growth of the barnacle population helps explain the decline of the white-fronted geese."

A spokeswoman for Scottish Natural Heritage said: "We have no evidence the Greenland white-fronted geese are suffering because of the numbers of barnacle geese on Islay. In autumn 2010 they came back to Scotland with the best breeding figures in 15 years which suggests they are not leaving Scotland in bad condition. But something could be happening on the way to the Arctic"