History is about change and fundamental changes have, sooner or later, global impacts. From the Western political perspective the event that deserves to rank as the most important change of the last quarter of the 20th century is the demise of the Soviet Union. This choice is obvious given the extraordinarily high stakes involved in the superpower rivalry that could have escalated into a global thermonuclear war. Those historians who prefer to trace great socio-economic changes to their technical foundations would single out the emergence and a rapid post-1980 diffusion of a new information society based on increasingly more powerful yet more affordable integrated circuits. These technical advances changed the world through ubiquitous microchips (be it in household appliances or in passenger cars), personal computers, Internet, cellular telephony and the ever-morphing universe of consumer electronics. But if one looks for a change that made the greatest difference in lifting the quality of life for the largest number of people then the choice falls inevitably on China's post-1979 agricultural transformation.

　　This process was not only a key to economic advances in the world's largest nation but it also greatly enhanced the world's existential security and political stability. This accomplishment was long overdue but once new policies were in place their effect was rapid. China, India and Japan began their post-WWII development with a remarkably similar per capita food availability, but intially it was only Japan whose sustained advances made it possible to reach, by 1970, a high-level of average food supply. India could not achieve a clear food production breakthrough for decades, and after less than a decade of improving food supply China experienced the tragedy of the great 1959-1961 famine. Although a prompt recovery followed, by the late 1970s China's average per capita food supply was only marginally higher than in 1958 and rations were barely above the subsistence level.

　　Then the reforms ended urban food rationing, brought welcome dietary improvements (more cooking oil, meat and fish), and since 1997 China's average per capita food availability has been higher (in terms of total food energy) than the Japanese mean. But there are notable qualitative differences between the typical food intakes in the two nations and Japanese access to food is highly equitable while China's increasing urban-rural and coastal-interior inequities make all of its national averages less representative than they were a generation ago. But even when this is taken into account and when the Chinese total is slightly reduced because of questionable meat statistics a very remarkable fact remains: for some years China, the world's most populous country, has been able to provide its citizens, on the average, nearly as much food as Japan, one of the world's richest nations with less than one-tenth of China's population. Moreover, about half of Japan's food consumption is imported, compared to only about 5% of China's.

　　This, and not its burgeoning exports of consumer goods or its large foreign reserves, is modern China's greatest achievement, the foundation of its economic pyramid and an extremely valuable contribution to global stability. But this remarkable accomplishment is based on imperiled environmental foundations, and today's productivity will become unsustainable without major adjustments. Agriculture is best defined as a complex management of man-made ecosystems whose goal is to maximize yields of plant species grown directly for food or for animal feed. As such, it depends on adequate and sustained provision of many environmental services, ranging from precipitation to microbial cycling of plant nutrients in agricultural soils. Most of you are well aware of these matters and you will hear much more about some of them in detail later during this meeting. What I want to do, based on some three decades of studying these environmental foundations in China and around the world, is to stress three major concerns.

　　Contrary to a widespread consensus that sees water as the paramount limiting factor of China's economic development I put conservation of arable land ahead at the first place. Two considerations with a common denominator justify this primacy. First, China's very low water costs and wasteful irrigation practices offer enormous opportunities for improved efficiency of water use in cropping, and better agronomic choices can be of additional help. Second, reuse of water can be greatly increased because water pollution can be greatly reduced by relying on well-known physical, chemical and bacterial controls. China's water shortages can be effectively addressed by using appropriate water management methods and water pollution controls and hence they could be greatly eased by determined deployment of technical fixes. But their diffusion is predicated on a politically unpopular and economically contentious commitment to further substantial increases of water prices: China's water is still grossly undervalued.

　　In contrast, once a fertile field is paved over to become a site for a new factory, new suburb or a new highway it is extremely unlikely that these infrastructures will be removed and the space be reclaimed as a highly productive cropland. And although China's stock of arable land is considerably larger than was officially admitted until a 1999, and although the prospects for further yield increases are fairly good both for grain staples and speciality crops, China's per capita availability of good-quality cropland is low enough (just around 0.1 ha) to justify the strongest possible protection. Virtually all of China's most productive alluvial land should be permanently reserved for agriculture and it should be impossible to circumvent by any means the necessary laws mandating this protection.

　　My second major concern is China's dependence on nitrogen fertilizers and its management. Other populous modernizing Asian countries share China's need for greatly improved water management (particularly India and Pakistan), permanent preservation of the best arable land (especially Indonesia, Bangladesh and Vietnam) and better agronomic practices but China is unique in its intensity of crop fertilization. Although the country cultivates less than 10% of the world's arable land it has been recently applying nearly 30% of the world's nitrogenous fertilizers. Nationwide annual mean is now in excess of 170 kg N/ha of arable land, and in several rice-growing provinces the mean is well above 300 kg N/ha. In contrast, applications in other countries with intensive cultivation are much lower: Japanese mean is now less than 100 kg N/ha, Indonesian average is just 65 kg N/ha.

　　Close to 75% of all nitrogen needed to produce China's crops originates in synthetic ammonia, and because no less than 90% of the country's dietary protein supply is derived from domestically grown crops (the rest comes from aquatic food, meat and dairy products derived from grasslands, and from grain imports) this means that almost 900 million Chinese are now consuming food whose proteins were synthesized by crops from inorganic nitrogen applied in synthetic fertilizer. And this extraordinarily high dependence continues to rise as China's use of green manures has been declining and as crops stalks and straws, rather than being properly recycled into soil, are increasingly burned in fields (this indefensible practice further lowers organic matter content of China's soils). Moreover, as more cities install sewers and as animal production gets increasingly concentrated in large facilities, nitrogen in human and animal wastes is merely dumped into streams and lakes rather than being properly recycled.

　　In Western countries about half of the applied nitrogen never gets to crop roots as it escapes into streams, groundwater and the atmosphere, but China's average utilization ratio is much lower, largely because as much as 75% of all nitrogen applied as urea is lost in rice farming. This means that each year more than 15 million tonnes of wasted fertilizer nitrogen (more than the total US applications) leave China's field, and improperly handled organic wastes add to this pollution. This wasted nitrogen causes environmental problems that range from polluted drinking water to more nitrous oxide, a potent greenhouse gas, in the atmosphere, but its main imoact is that it fertilizes ecosystems that are harmed by it: China's lakes, ponds and rivers, as well as shallow coastal waters. Excessive nitrogen causes abundant growth of algae whose eventual decay creates waters devoid of oxygen that kill many aquatic species.

　　My third major concern is the effect of high, semi-permanent and extensively distributed concentrations of photochemical smog on China's crop yields. Again, photochemical smog –- which originates in emissions of nitrogen oxides, unburned hydrocarbons and carbon monoxide (the first two pollutants mostly from vehicles, power plants and refineries, the last gas mostly from vehicles) and produces a number of highly reactive gases, above all ozone –- is a worldwide problem that is present, year-round or seasonally, in any polluted and sunny location. But again, China's challenge is unusual. In the US or Brazil or France the most productive farming regions are either distant or upwind from major urban and industrial areas and the crops are not affected by high levels of smog. In contrast, China's large urban and industrial areas are either close neighbors or are located directly in the areas of intensive crop cultivation. As the areas affected by photochemical smog expand they will cover more of China's prime farmland and affect its productivity.

　　This harmful process is already well underway as increasing ozone levels are reducing China's yields of both spring and winter wheat, corn and soybeans. Acuteness of this concern is particularly justified given China's strategy of vigorous automobilization. This a risky play: by copying Japanese and South Korean experience China's car industry may become a leading wedge of industrial modernization and the country may become a significant car exporter –- but promoting mass car ownership, rather than rapid mass transport and dense urban subways, may substantially reduce China's crop harvests because of high ozone levels that will repeatedly cover extensive areas of the country's eastern provinces.

　　China that fails to pay determined and sustained attention to these four key factors –- to generally recognized water problems, to strict preservation of its good farmland, to the most efficient management of agricultural nitrogen, and to dangers of photochemical smog –- will not have the South Korean or Japanese luxury of relying on food imports to such an extent as these countries do. South Korea has been recently importing 65% of its cereal, and nearly 90% of its edible oil consumption; Japanese imports have supplied nearly 75% of all cereals, nearly all edible oils as well as 40% of all fish. If China were to buy two-thirds of its recent annual grain consumption abroad all of the grain recently traded on the world market would not suffice.

　　Consequently, for China no other set of strategic decisions is more important than taking the steps needed to assure the perpetuation of highly intensive domestic food production. This will be a difficult but by no means an impossible task. The needed remedies will require the state acting as a resolute protector of the environment. Both from fundamental biophysical and long-term historical perspectives there is no better way to use state's institutions and its legal system than to assure an intergenerational transfer of irreplaceable natural foundations for feeding a prosperous population. China, in spite of its numerous constraints, can do it but in order to succeed the essential policies must be as resolute, sustained and far-reaching as if not only the country's prosperity but its very survival depended on them: because it will.