Many different species are relocating their habitats in response to global warming, and diseases are doing much the same.

Blue-tongue is one such disease that now poses an imminent threat to the UK. It was first described in South Africa and then spread through the tropics and sub-tropics.

Since 1999 it has spread from both Turkey and North Africa to the Mediterranean region as a result of climate change. Last year there were cases on farms in Holland, Belgium and Germany.

Blue-tongue is an insect-borne, viral disease, normally transmitted by mosquitoes and biting midges, that affects all ruminants. Although cattle are the main reservoir of the virus and important in the spread of the disease, sheep are the most severely infected and losses can reach 70% of the flock.

Some reckon it is only a matter of time before the UK suffers an outbreak, probably as a result of midges being blown across the channel.

The latest threat out of Africa is a new and virulent fungus that attacks a wide range of wheat varieties.

The wheat stem rust (Puccinia graminis), also known as wheat black rust, is capable of causing severe losses and can destroy entire wheat fields.

It is estimated that as much as 80% of all wheat varieties planted in Asia and Africa are susceptible to the new strain.

The spores of wheat rust are mostly carried by wind over long distances and across continents and have spread from East Africa to Yemen on the Arabian Peninsula.

The new pathogen first emerged in Uganda in 1999 and is called Ug99. It subsequently spread to Kenya and Ethiopia. It appears that the Ug99 strain found in Yemen is already more virulent than the one found in East Africa. There is a high risk that the disease could also spread to the Sudan.

Wind-borne pests and diseases can cause serious damage to crop production. In the late 1980s, a virulent strain of the yellow rust, a wheat disease similar to the stem rust, emerged in East Africa and crossed the Red Sea into Yemen. It then moved into the Near East and Central Asia, reaching South Asia in four years. Major yellow rust epidemics were recorded with wheat losses of more than $1bn £500m).

Based on the monitoring of the Desert Locust pathways, wind currents could carry Ug99 stem rust spores from Yemen northwards along the Red Sea to Egypt or through the Saudi Arabian Peninsula towards countries in the Near East.

"Global wheat yields could be at risk if the stem rust spreads to major wheat-producing countries", said leading specialist Dr Jacques Diouf of the Food and Agriculture Organisation of the United Nations (FAO).

"The fungus can spread rapidly and has the potential to cause global crop epidemics and wheat harvest losses of several billion dollars. This could lead to increased wheat prices and local or regional food shortages. Developing countries relying on wheat and without access to resistant varieties will be particularly hit", warned Diouf.