Climate change and new diseases threaten the limited varieties of seeds we depend on for food. Luckily, we still have many of the seeds used in the past-but we must take steps to save them.

Six miles outside the town of Decorah, Iowa in the USA, an 890-acre stretch of rolling fields and woods called Heritage Farm is letting its crops go to seed. Everything about Heritage Farm is in stark contrast to the surrounding acres of intensively farmed fields of corn and soybean that are typical of modern agriculture. Heritage Farm is devoted to collecting rather than growing seeds. It is home to the Seed Savers Exchange, one of the largest non government-owned seed banks in the United States.

In 1975 Diane Ott Whealy was given the seedlings of two plant varieties that her great grandfather had brought to America from Bavaria in 1870: Grandpa Ott’s morning glory and his German Pink tomato. Wanting to preserve similar traditional varieties, known as heirloom plants, Diane and her husband, Kent, decided to establish a place where the seeds of the past could be kept and traded. The exchange now has more than 13,000 members, and the many thousands of heirloom varieties they have donated are kept in its walk-in coolers, freezers, and root cellars the seeds of many thousands of heirloom varieties and, as you walk around an old red barn that is covered in Grandpa Ott’s beautiful morning glory blossoms, you come across the different vegetables, herbs, and flowers they have planted there.

"Each year our members list their seeds in this,"Diane Ott Whealy says, handing over a copy of the Seed Savers Exchange 2010 Yearbook. It is as thick as a big-city telephone directory, with page after page of exotic beans, garlic, potatoes, peppers, apples, pears, and plums-each with its own name and personal history .For example, there’s an Estonian Yellow Cherry tomato, which was brought to the seed bank by “an elderly Russian lady” who lived in Tallinn, and a Persian Star garlic from “a bazaar in Samarkand.”There’s also a bean donated by archaeologists searching for pygmy elephant fossils in New Mexico.

Heirloom vegetables have become fashionable in the United States and Europe over the past decade, prized by a food movement that emphasizes eating locally and preserving the flavor and uniqueness of heirloom varieties. Found mostly in farmers' markets and boutique groceries, heirloom varieties have been squeezed out of supermarkets in favor of modern single-variety fruits and vegetables bred to ship well and have a uniform appearance, not to enhance flavor. But the movement to preserve heirloom varieties goes way beyond the current interest in North America and Europe in tasty, locally grown food. It’s also a campaign to protect the world’s future food supply.Most people in the well-fed world give little thought to where their food comes from or how it’s grown. They wander through well-stocked supermarkets without realizing that there may be problem ahead.We’ve been hearing for some time about the loss of flora and fauna in our rainforests.Very little,by contrast,is being said or done about the parallel decline in the diversity of the foods we eat.

Food variety extinction is happening all over the world - and it's happening fast. In the United States an estimated 90 percent of historic fruit and vegetable varieties are no longer grown. Of the 7,000 different apple varieties that were grown in the 1800s, fewer than a hundred remain. In the Philippines thousands of varieties of rice once thrived; now only about a hundred are grown there. In China 90 percent of the wheat varieties cultivated just a hundred years ago have disappeared. Experts estimate that in total we have lost more than 50 percent of the world's food varieties over the past century.

Why is this a problem? Because if disease or future climate change affects one of the handful of plants we've come to depend on to feed our growing planet, we might desperately need one of those varieties we've let become extinct. The loss of the world's cereal diversity is a particular cause for concern. A fungus called Ug99, which was first identified in Uganda in 1999, is spreading across the world's wheat crops. From Uganda it moved to Kenya, Ethiopia, Sudan, and Yemen. By 2007 it had jumped the Persian Gulf into Iran. Scientists predict that the fungus will soon make its way into India and Pakistan, then spread to Russia and China, and eventually the USA.

Roughly 90 percent of the world's wheat has no defense against this particular fungus. If it reached the USA, an estimated one billion dollars' worth of crops would be at risk. Scientists believe that in Asia and Africa alone, the portion currently in danger could leave one billion people without their primary food source. A famine with significant humanitarian consequences could follow, according to Rick Ward of Cornell University.

The population of the world is expected to reach nine billion by 2045. Some experts say we’ll need to double our food production to keep up with this growth. Given the added challenge of climate change and disease, it is becoming ever more urgent to find ways to increase food yield. The world has become increasingly dependent upon a technology-driven, one-size-fits-all approach to food supply. Yet the best hope for securing our food's future may depend on our ability to preserve the locally cultivated foods of the past.

The long-standing debate about whether to fluoridate our drinking water continues Fluoridation is the addition of fluorine to public water supplies with the aim of reducing tooth decay. The fluorine, when mixed with water, becomes fluoride and the desired concentration of fluoride in public water is approximately one part per million, depending on the regional temperature and hence the amount of water people are likely to drink. Many studies, such as those by McClure in 1970 through to Burt in 1983, have shown that when children drink fluoridated water, their average rate of tooth decay seems greatly reduced. A typical figure claimed is 50 percent reduction. This apparently enormous benefit for children's teeth is the major argument in favor of fluoridation.

Three main grounds for opposition to fluoridation have been expressed. First, opponents claim the benefits are exaggerated or not established. Second, there are claims of health risks to pans of the population, for example, allergic reactions. It is also accepted that high levels of fluoride can cause discoloration of otherwise healthy teeth. Proponents do not consider this to be a problem in such small concentrations, whereas opponents disagree - especially because some people drink more water and obtain much more than the standard 1 milligram of fluoride per day. Third, fluoridation is thought to be an infringement on individual rights because it is compulsory medication of all members of a community.

An understanding of the fluoridation issue has important implications. If, according to the experts, fluoridation is unquestionably a beneficial and non-hazardous measure, then the wisdom of allowing the public to vote on, and reject it must be questioned.

Almost all studies that have been done have assumed that the scientific aspects of the controversy are unproblematic, and they have excluded science from sociological examination. The traditional view is that science is a special kind of knowledge, which is established through scientific methods and objectively applied by members of a scientific community. However, in recent years there has been a major challenge to this picture by a sociology of science that shows how scientific knowledge is socially negotiated, and inevitably linked to the values of the relevant parties, both scientists and nonscientists. These challengers do not see scientific knowledge as exempt from social inquiry.

Kuhn (1970) argued that scientific knowledge does not always develop as an orderly process, but is characterized by periodic revolutions. in which the methods of study and the assessment criteria change in a fragmented way. According to Kuhn, the shift from one scientific way of thinking to another is not made solely on the basis of clear rules of formal scientific practice, but can include social factors, though Kuhn has never developed a full analysis of what these might be. Collins (1975) took this concept further when he asserted that the outcome of experiments was not something whose meaning could be immediately comprehended, but rather something for interpretation, discussion between scientists, and reinterpretation in the light of other experiments.

One interpretation of this analysis of science is that traditional distinctions between facts and theories, and between scientific knowledge and values, can no longer be justified. Because social processes are involved at all stages of the creation, evaluation, and establishing of scientific knowledge, social values may also be involved.

In the same way as many scientists who study fluoridation have overlooked social values, sociologists have also downplayed an important part of the debate by ignoring the number of eminent scientists who have questioned aspects of fluoridation. An example is the study by Sutton in 1960, which analyzed the classic North American studies of the effect of fluoridation on tooth decay, and found that each showed significant methodological shortcomings. Sutton's detailed study throws doubt as to the extent of reductions in tooth decay from fluoridation. Yet Sutton's book is not cited in a single analysis of the fluoridation issue by any sociologist. In a situation of some scientific uncertainty, differences in values are highlighted. A supporter of fluoridation might argue. The evidence for the benefits of fluoridation is quite substantial, while the evidence for harm is limited and dubious. I think the likely benefits outweigh the possible dangers; hence I support fluoridation because it is the cheapest and easiest way to make sure every child reaps the benefits. An opponent might argue, 'Though the evidence for the benefits of fluoridation is substantial, there is some doubt about it. Since fluoridation is not necessary for good teeth, we should forego the benefits if there is some slight chance of harm. Some scientists claim that a small percentage of the population could be harmed by fluoride. Therefore I oppose fluoridation of water supplies and favor the voluntary use of fluoride tablets by those who want to take them.'

Both arguments consider the scientific evidence concerning fluoridation, but differ in their assessments of the social benefits and costs. This difference is not between rationality and irrationality but is a legitimate difference in values, for example, the positive value placed on good teeth, the negative value placed on possible health risks, and the social benefits or costs of compulsory or voluntary intake of fluorides.

From the sociological point of view, opposition to fluoridation is not necessarily irrational. Rather, claims to rationality and to scientific authority are better seen as part of a strategy to promote fluoridation than as incontrovertible statements of fact. Second, social values are likely to be bound up in any decision about fluoridation, so this is not an issue on which declarations by scientific experts ought to be considered the final word.