A strong Common Agricultural Policy is vital to maintain food security and tackle climate change, according to the president of European farmers' association Copa-Cogeca.
Gerd Sonnleitner warned that farmers across the world will face huge challenges in coming years as pressure on land and water resources increase.
"To weaken the CAP now would be like jumping ship just when a storm is brewing. We need a strong CAP more than ever," he said.
A strong CAP was vital to allow farmers in Europe to compete with nations like the USA, Brazil and China, which have many much larger farms than the UK, he added.
Without the CAP farming would have to undergo a huge structural revolution, said Mr Sonnleitner, speaking at the NFU Conference 2013.
"Farms in the more difficult areas would have disappeared altogether. Those that survived would have to compete with the huge farms that we see in our competitor countries," he added.
Food security could no longer be taken for granted, he said, even in Europe. And alongside competition for resources, farmers were starting to feel the first effects of climate change.
The economic position of farmers was the most important concern, said Mr Sonnleitner, as without a reasonable income, farmers could not provide services and modernise.
"This is why the maintenance of direct payments is so important and why farmers are totally opposed to any transfer of funds from the first to the second pillar," he added.
Strengthening farmers' position in the food chain was necessary to reduce dependence on direct payments, he said. While the appointment of a supermarket adjudicator in the UK was an important step, similar action at a European level should be next.
Secondly, the European Commission should ensure that greening economically benefits farmers, he said. "Greening is fine, providing it also contributes to growth. But the commission's own studies show their proposals will simply lead to higher farm costs and reduced production."
Another "major worry" for the union was simplification of the CAP, which may not allow for flexibility. "We need flexibility to take account of the diversity of European farming. But we must find ways of achieving this without imposing yet more controls and paperwork on farmers."
Lastly, Mr Sonnleitner warned delegates about trade distortions.
Under current CAP reform proposals, one member state could decide to pay their farmers a basic payment equal to around two-thirds of their first pillar funds, he said.
In contrast, another country could decide to shift 15% of their national envelope to the second pillar and/or redirect much of it to specific causes under the first pillar - to help areas with natural handicaps, young farmers, small-scale farmers and specific types of production.
"This could completely undermine our attempts to reduce the gaps between the different levels of hectare payments. It also risks putting many farmers at a completely unfair competitive disadvantage and undermining the single market," he warned.
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