Heather Meek leafs through the seed catalogue she wrote on the family computer, on winter nights after the kids went to bed. Selling seeds is more than just an extra source of income on [her] organic farm an hour northwest of Montreal. For Meek and partner Frederic Sauriol, propagating local varieties is part of a David and Goliath struggle by small farmers against big seed companies. At stake, they believe, is no less than control of the world's food supply. Since the dawn of civilization, farmers have saved seeds from the harvest and replanted them the following year. But makers of genetically modified (GM) seeds -- introduced in 1996 -- have been putting a stop to that practice. The 12 million farmers worldwide who will plant GM seeds this year sign contracts agreeing not to save or replant seeds. That means they must buy new seeds every year. Critics charge such contracts confer almost unlimited power over farmers' lives to multinational companies whose priority is profit. They say GM seeds are sowing a humanitarian and ecological disaster. Worldwide, GM crops have grown 67-fold in 12 years, now covering 690.9 million hectares in 23 countries. Alexander Muller, assistant director of [the] Food and Agriculture Organization, warned that loss of agricultural biodiversity threatens the world's ability to survive climate change. "The erosion of biodiversity for food and agriculture severely compromises global food security," [he said]. Muller's words resonate with farmers Meek and Sauriol, whose four daughters help with the painstaking work of cleaning seeds over the winter. "Growing seed is a big job," says Meek. "But if you don't grow your seed, you lose your power."