Mr Stevenson was speaking at a publication launch in Brussels
A Scottish MEP has condemned the "folly" of dumping hundreds of tonnes of healthy fish back into European waters during a time of food scarcity.
Conservative Struan Stevenson said 800,000 tonnes of fish is wasted, while agricultural land is dwindling rapidly.
Speaking at the European Parliament he said scientists and policy makers should work together more closely to solve the problem.
It comes as nets designed to reduce cod waste are trialled in Orkney.
Mr Stevenson said agricultural land equivalent to the size of Ukraine was being lost annually globally, while the population was rising.
He said: "This has to be at the top of our agenda.
"Deserts are spreading across the world. We are losing globally an area the size of Ukraine every year because of encroaching dry land and deserts.
"With rising world population levels we cannot afford to be losing agricultural land. It's causing major problems."
He said: "In European waters alone we are looking at 800,000 tonnes of healthy fish being dumped at a time of food scarcity.
"Scientists and policy makers must work more closely together."
He was speaking at the launch of "Desertification - socio economic, agricultural and forestry impacts and their political consequences".
Meanwhile preliminary trials by a fishing vessel in Orkney of a new type of net have found a reduction in the amount of small cod caught.
Skipper Tom Harcus designed the net which has a wider mesh size at the entrance of the trawl than conventional nets.
He said: "I expected there to be a reduction in the cod catch with the new net, but not to the extent that we found in these trials.
"These are very encouraging results and I believe that this type of trawl could play a very important role in fish stock conservation."
Mr Harcus plans to carry out more trials next year on smaller vessels.