* Top agricultural economist says world food supply not safe

* Says Africa farmers must access fertiliser, loans, markets

* Calls for smarter loans, more investment in agriculture

By Laura MacInnis

GENEVA, June 30 (Reuters) - Africa's farmers need help to access loans, fertiliser and export markets to avoid future food supply crises caused by climate change and commodities speculation, a top agricultural expert said on Tuesday.

Wheat, rice and maize prices have fallen sharply from their 2008 highs, when protests broke out across the developing world over unaffordable staple foods and countries imposed export bans to ensure their people had enough to eat. [ID:nN19448408]

Akinwumi Adesina of the Alliance for a Green Revolution in Africa, an aid group headed by former U.N. Secretary-General Kofi Annan, said commodity markets dampened by recession were serving to mask "the next storm".

"The global food supply remains far from secure," Adesina told the U.N. Conference and Trade and Development (UNCTAD).

"We have not yet tamed the forces of speculation, climate change will yet trample our farm fields, crop diversity remains under increasing threat," he said in a speech. "Global grain reserves may be replenished for the time being, but global food security remains a goal, not a reality."

One of the biggest problems, according to the agricultural economist from Nigeria, is the persistently paltry harvests from Africa's farms, most of which are tended to be "without access to basic farm inputs, finance or markets".

"While yields across the globe, especially in Asia and Latin America, have steadily increased, the yields of Africa have remained constant -- sitting at about one-quarter of the global average," Adesina said.

MORE FINANCING NEEDED

He called for international donor agencies and the banks and insurance providers active in the agricultural arena to step up their activity in Africa, and work to help farmers access small loans that meet their productive needs.

"Lack of access to finance is a major constraint to unlocking the potential of agriculture in Africa," he said.

The diversity of crops now being produced across the continent must also be preserved.

Plant diseases such as the blight that ruined Ireland's potato crop and caused famine are among the biggest risks to the global food supply, especially if major staples such as wheat or rice should be affected. [ID:nL21933129]

Adesina said the variety of foods being produced in Africa, often on the same farm -- with maize, groundnuts, rice, cowpea and sweet potato all grown in a cycle -- served as an important insurance that must be maintained however possible.

But he allowed that hefty costs may be involved in boosting the productivity and output of small-holder farms across the vast continent, which is highly vulnerable to extreme weather and the effects of climate change.

Citing figures from the International Food Policy Research Institute, the expert said that Africa will need $32 billion to $39 billion annually to achieve an agricultural transformation -- not including infrastructure costs. (Editing by Stephanie Nebehay)

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