In an address to more than 170 people at the University of Otago's 44th Foreign Policy School Prof Watson, who is chief scientific adviser in the United Kingdom Department of Environmental, Food and Rural Affairs, said in the longer term advanced biotechnologies might be needed, but the risks and benefits needed to be fully understood.
Safety had to be the priority and the approach had to be evidence-based and case-by-case.
People needed to be open to the potential benefits and research, which was open and transparent, should continue.
There was also a need to be absolutely sure, if GM crops were to be planted, that they could co-exist with organic agriculture without cross-pollination, he said.
People buying food in supermarkets would also need to be sure of what they were buying with enforceable GM labelling rules.
Europe would not "go down the GM route" unless the consumer could see some benefits to it.
Keynote speaker MP John Hayes, who addressed the gathering on Friday, said he supported genetic modification as he did not see there was another way to increase food production sufficiently to cope with the looming food crisis.
GM plants were already growing on about 10% of the world's crop areas although they were largely banned in Europe and Africa, Mr Hayes said.
Prof Watson was one of several speakers at the school who emphasised the importance of the participation of the small-scale farmer in improving food security.
Difficulties for such farmers included lack of access to finance and technology and getting their goods to markets.
Prof Watson, who is a former chairman of the Intergovernmental Panel on Climate Change, said climate change posed both challenges and opportunities to agriculture.
There would be a need for adaptation including changing such things as crops and planting times, breeding new varieties which could cope with temperature change, drought, increased pests and salinity.
Mitigation of climate change effects would also be required and providing payments to farmers for maintaining and enhancing their environment was one of the options for action suggested.
