( CNN ) -- Last week , I sat down with colleagues and students to an early Thanksgiving meal prepared by my university 's cafeteria . Along with our winter greens , butternut squash , brussels sprouts with apples and bacon , and pumpkin grits , we ate a roasted `` heritage breed turkey . '' Accolades ensued : `` To me , all turkeys taste the same—except for this one—I can tell the difference , '' said William Payne who works in the medical school . The local greens from Georgia farms were `` really , really tasty , '' said a first-year student from the Atlanta area and her friend from Tianjin , China . The meal was Emory University 's fourth Heritage Harvest Feast . The turkey that had everybody talking was a Narragansett , a heritage breed native to Rhode Island . Along with Bourbon Reds , Narragansetts have been saved from extinction by farms like the Good Shepherd Poultry Ranch in Kansas , where Emory 's turkey 's come from , and by the efforts of the American Livestock Breeds Conservancy , a nonprofit dedicated to conserving rare breeds of livestock . The Heritage Harvest Feast is not only an occasion for thanks and a good meal , but it also is part of a commitment to building a more sustainable food system . Sustainability depends on variety . To preserve variety , we need to grow it and want to eat it ! Thanksgiving advice , recipes , solidarity and sanity . Genetic variety in our food system is the result of thousands of years of farmer and consumer choices , in itself a precious human heritage . Adapted to local climates and all kinds of diseases and pests , the seeds and breeds that have survived until the present day are often hardier , more resilient—and can be more nutritious as well . As our planet warms and growing seasons shift , new patterns of flood , drought , frost and pests will stress our food system . When farmers plant large tracts of one variety -- perhaps one that is bred to grow faster , is suited to mechanical harvest and travels well -- or consumers demand only one breed of animal , our food supply is vulnerable . In the 1970s , for example , a disease wiped out more than 50 % of the corn crop in some states , because those areas were planted to one single corn variety . Crop uniformity is the enemy of resilience . The hardy traits of older , heirloom varieties provide a safety valve . They allow us to breed new , more resilient crops using traits we do n't even know we need until disaster strikes . But can we count on those genetic riches surviving today ? Around the world , the loss of species to extinction is progressing faster than ever . And this loss includes our seed varieties . Studies using USDA crop lists from 1903 estimate that only 6-7 % of the nation 's named commercial varieties remained available by the 1980s . We lost , for example , 86 % of our apple varieties and 92 % of our lima beans . Cary Fowler and Pat Mooney in `` Shattering : Food , Politics , and the Loss of Genetic Diversity '' report that 93 % of our lettuce varieties , 81 % of our tomatoes , 93 % of our carrots and 91 % of watermelon varieties are extinct . To be sure , commercial seed catalogs now list many new hybrid crop varieties . But these hybrid seeds do not contain the range of genetic variability of the older , open-pollinated seeds ( that is , plants pollinated by birds , insects or wind that `` breed true '' ) that reflect centuries of selection . This is a staggering loss of our precious genetic heritage . The best guarantee of a safe food supply as we head toward an uncertain global future is a large number of diverse food producers growing a wide variety of healthy seeds and breeds . But to save this rich biodiversity—of potatoes or turkeys—there needs to be a market . Fortunately , there is a growing awareness of the importance of heirloom varieties , and local farmers markets and even some grocery stores feature multiple varieties . Savoring distinct flavors in special types of vegetables , fruits and meats encourages us to recognize , enjoy and support farmers who are preserving variety . iReport : Who 's at your Thanksgiving table ? That 's why Cora and her husband , Simon , ( who came from the chemistry department to our early Thanksgiving dinner ) grow a garden with heirloom vegetable varieties . And they order a heritage breed turkey for Thanksgiving even though it costs more . They are willing to spend extra money because , says Cora , `` it 's tastier , and we 'd rather eat meat less often and not get mass-produced and flavorless turkey . '' So , as you plan your feasts this holiday season , can you add an heirloom vegetable ? Try a local specialty ? Seek out a heritage breed ? Our food future may depend on it . The opinions expressed in this commentary are solely those of Peggy F. Barlett .
Peggy Barlett : Early Thanksgiving dinner drew raves for tasty heritage turkey served . She says a sustainable food system needs diversity , preservation of old varieties . She says new weather patterns will stress crops ; old varieties provide growing options . Barlett : Majority of food plant varieties are lost ; help save the rest by providing demand .