The turkey and ham many are eating this holiday season don't just appear magically on the table. Most are the end product of an increasingly global, industrialized system that is resulting in costly environmental degradation. Better understanding of the true costs of this resource-intensive system will be critical to reducing its negative effects on the environment, says an interdisciplinary team of researchers led by Stanford University's Rosamond Lee Naylor, Walter Falcon, and Harold Mooney.

"Losing the Links Between Livestock and Land" appears in the Policy Forum in the Dec. 9 issue of Science. It represents a synthesis of research by professors at Stanford University, the University of Virginia, the University of California at Davis, the universities of Manitoba and British Columbia in Canada, and the United Nations LEAD (Livestock Development and Environment) program within the Food and Agricultural Organization of UN.

"Sixty years ago, the link between the livestock production and consumption was much more clear and direct, with most consumers getting their meat and dairy products from small, family-owned farms," says lead author Naylor, an economist. Co-author Falcon agrees. "When I was growing up in Iowa, almost all farmers kept both chickens and pigs."

Today, meat consumption has sky-rocketed, and large-scale intensive livestock operations provide most of those products, both in the U.S. and around the world.

Particularly striking is the growth in demand for meat among developing countries, Naylor notes. "China's meat consumption is increasing rapidly with income growth and urbanization, and it has more than doubled in the past generation," she says. As a result, land once used to provide grains for humans now provides feed for hogs and poultry.

Numerous factors have contributed to the global growth of livestock systems, Naylor notes, including declining feed-grain prices; relatively inexpensive transportation costs; and trade liberalization. "But many of the true costs remain largely unaccounted for," she says. Those costs include destruction of forests and grasslands to provide farmland for corn, soybeans and other feed crops destined not directly for humans but for livestock; use of large quantities of freshwater; and nitrogen losses from croplands and animal manure.

Nitrogen losses are especially problematic, says James Galloway of the University of Virginia. "Once nitrogen is lost to the atmosphere or to water, it can have a large number of sequential environmental effects. For example, ammonia emitted into the atmosphere can in sequence affect atmospheric visibility, forest productivity, lake acidity and eventually impact the nutrient status of coastal waters."

Naylor cited Brazil as a specific example of the large impact on ecosystems and the environment. "Grasslands and rainforests are being destroyed to make room for soybean cultivation," she said. The areas are supplying feed to the growing livestock industry in Brazil, China, India and other parts of the world, leading to "serious consequences on biodiversity, climate, soil and water quality."

Naylor and her research team are seeking better ways to track all costs of livestock production, especially the hidden ones related to ecosystem degradation and destruction. "What is needed is a re-coupling of crop and livestock systems," Naylor said. "If not physically, then through pricing and other policy mechanisms that reflect social costs of resource use and ecological abuse."

Such policies "should not significantly compromise the improving diets of developing countries, nor should they prohibit trade," Naylor added. Instead, they should "focus on regulatory and incentive-based tools to encourage livestock and feed producers to internalize pollution costs, minimize nutrient run-off, and pay the true price of water."

She cited efforts in the Netherlands to track nitrogen inputs and outputs for hog farms as one approach. In the U.S., the 2002 Farm Bill provided funds for livestock producers to redesign manure pits and treat wastes, but she notes that much greater public and private efforts are needed to reduce the direct and indirect pollution caused by livestock.

In the end, though, it may be up to consumers to demand more environmentally sustainable approaches to livestock production. "In a global economy with no global society, it may well be up to consumers to set a sustainable course," she added.

Seed funding for the research was provided by the Woods Institute for the Environment, which supports interdisciplinary approaches to complex environmental issues. Naylor, Falcon and Mooney are affiliated with the institute and with the Center for Environmental Sciences and Policy in Stanford's Freeman Spogli Institute for International Studies.

In addition to Naylor, Mooney and Falcon of Stanford and Galloway of Virginia, co-authors are Henning Steinfeld of the United Nations Food and Agriculture Organization; Galloway; Vaclav Smil, University of Manitoba; Eric Bradford, University of California at Davis; and Jacqueline Alder, University of British Columbia.

SEATTLE - There are a billion hungry people in the world. Fifteen thousand children-the equivalent of five times the victims of the World Trade Center bombings-die each day of hunger. Yet it doesn't have to be this way. We can end hunger-if we make a commitment to doing so. The new one-hour documentary Silent Killer: The Unfinished Campaign Against Hunger shows how it can be done. Shot on location in the United States, South Africa, Kenya, Rome, Mexico and Brazil, Silent Killer examines both the problem of hunger and solutions. The documentary and its companion Web site (www.SilentKillerFilm.org) will provide viewers with inspiration and information to become part of the effort to end hunger.

Produced by Hana Jindrova and John de Graaf (Affluenza, Escape from Affluenza), in association with KCTS/Seattle Public Television, Silent Killer will air on several California public television stations as follows:

KTEH/ San Jose: Sunday, October 16 at 5:00 p.m. (please confirm).

KOCE/ Huntington Beach: Sunday, October 23 at 4:00 p.m.

KQED/ San Francisco: Wednesday, November 2 at 11:00 p.m., repeating on

KQED Encore (Digital Channel 189), Thursday, November 3 at 10:00 p.m.

KVCR/ San Bernardino: Thanksgiving evening, Thursday, November 24 at 8 p.m.

KVIE/ Sacramento: Airdate and time to be announced.

KCSM/ San Mateo: Airdate and time to be announced.

(For all other stations, please check local listings).

Narrated by National Public Radio's Scott Simon, the film begins in South Africa's Kalahari Desert, where razor-thin Bushmen use the Hoodia cactus to fend off hunger. But now, a drug firm has patented the Hoodia's appetite-suppressant properties and is using it to make a diet product for obese Americans and Europeans. Hoodia is a metaphor for a world where some people die from too much food, but millions more die from too little.

We discover how serious the problem is in Kenya as we meet Jane Ininda, a scientist who is trying to make agriculture more productive in her country, while her own brother, Salesio, barely survives the drought, poor soils and pests that constantly threaten his crops. Through powerful stories, we come to understand the dimensions of the hunger crisis.

At the World Food Summit in Rome, we learn how activists have been working to end hunger since President John Kennedy declared war on it in 1963. But today, America's commitment to food security is less clear. In fact, world financial commitments to hunger research are now in decline.

But Silent Killer does not leave viewers feeling helpless. A visit to Brazil finds a nation energized by a new campaign called FOME ZERO-Zero Hunger. In the huge city of Belo Horizonte, we meet a remarkable leader and see how, under the programs she supervises, the right to food is guaranteed to all. In the countryside, we are introduced to the Landless Peasants' Movement, which is giving hope to millions of hungry Brazilians.

Can we end hunger, or will it always be with us? Why should we try? What will it take? What are we doing now? Can biotechnology play a role, and if so, how? Is hunger just a problem of distribution, or do we still need to produce more and better crops? These are the questions considered in this exquisitely photographed documentary.

EXPERTS featured in Silent Killer: The Unfinished Campaign Against Hunger and available for press interviews include:

David Beckmann - President, Bread for the World. Since 1991, Reverend David Beckmann has served as president of Bread for the World, a Christian group that lobbies the U.S. government for policy changes to end hunger in the United States and around the world.

Per Pinstrup-Andersen - World Food Prize Laureate 2001. A native of Denmark, Per Pinstrup-Andersen is the H.E. Babcock Professor of Food, Nutrition and Public Policy at Cornell University. He also serves as the chairman of the Science Council of the Consultative Group on International Agricultural Research.

Chris Barrett - Development Economist, Cornell University. Dr. Barrett is a professor of applied economics and management at Cornell University. His focus is on rural communities, primarily in Africa, concentrating on the dynamics of poverty, food security and hunger.

Walter Falcon - Development Economist, Stanford University. Dr. Falcon is the Farnsworth Professor of International Agricultural Policy at Stanford University (emeritus), co-director of the Center for Environmental Science and Policy, and former director of the Stanford Institute for International Studies.

PROGRAM TIE-INS: October 16 is the 25th observance of World Food Day-a worldwide event designed to create awareness, understanding and year-round action to alleviate hunger. (See www.worldfooddayusa.org.) In addition, October 24 is the 60th anniversary of the founding of the United Nations and its first agency, the Food and Agriculture Organization (FAO).

CREDITS: Silent Killer was produced by Hana Jindrova and John de Graaf in association with KCTS/Seattle Public Television and is narrated by NPR's Scott Simon. Writer: John de Graaf. Photographers/Editors: Diana Wilmar and David Fox. Composer: Michael Bade. Executive Producer: Enrique Cerna, KCTS. Funding was provided by The Rockefeller Foundation.

DISTRIBUTOR: Silent Killer is presented nationally by KCTS/Seattle Public Television and is distributed by the National Educational Telecommunications Association (NETA).

WEB SITE: See www.SilentKillerFilm.org for more information about the film, including a full transcript, in-depth interviews with film characters and experts on hunger, a guide for teachers, a list of hunger facts and myths, a detailed "Take Action" section and additional resources. Color images from the film are posted on the site for press use, along with an online press kit.

Senior fellow and contributing author, %people1%, comments in <i>Nature</i> on the release of the Millennium Ecosystem Assessment--a four year endeavour that explores the link between human well-being, the status of ecosystems and their sustainable use.

How can ecosystems provide sustainable services to benefit society?

Four years in the making, the Millennium Ecosystem Assessment (see Nature 417, 112-113; 2002) is released this week (starting 30 March). This gigantic endeavour explores the link between human well-being, the status of ecosystems and their sustainable use.

What has this assessment taught us about developing our planet, and will it, or should it, be continued? To answer the first part of this question, the assessment is an invaluable record of where we stand now, and why. But for it to be useful, the answer to the second part of the question must be 'yes'. We need to take a consistent approach to measuring the status and trends of the world's ecosystems. To take one example, the Convention on Biological Diversity has set the target of reducing the rate of global loss of biodiversity by 2010. But the data to evaluate whether this goal is being met are not readily available, as biological diversity is more than just an enumeration of species present or absent - it includes parameters such as the populations of species and the ecosystems in which they reside. In addition, biodiversity is just one of the many aspects of change in ecosystems and their related functions assessed in the Millennium Ecosystem Assessment. Only from a periodic audit of the state of our natural resource base can we determine if we are indeed approaching sustainability.

At present, there are no formal plans to repeat the Millennium Assessment. There should be, and we hope that the informal discussions among the current sponsors will bear fruit from the seeds sown by the many smaller, ongoing sub-global assessments that were stimulated by the assessment.

Achievements and goals

The Millennium Ecosystem Assessment took a new pathway of evaluating the status of the Earth's human support systems. Rather than the standard environmental audit, the new assessment places audits of numbers of organisms and so on into the context of how ecosystem changes have affected human well-being, and how they may do so in the foreseeable future. It had to find a link between the status of biotic systems and the status of individuals in various societies in the world to estimate the capacity of ecosystems to provide services that benefit society. Many of these links are obvious, but others have not been appreciated, nor have all these linkages been quantified. In essence, we had to make a large leap from the current styles of evaluations of status and trends in ecosystems to an entirely different approach - an ecosystems services database related to how ecosystems and societies operate, and how they interrelate.

Current status of ecosystems

Human societies have made marked progress in increasing provisioning services, such as crops and livestock, to meet the demand of a growing population (see Box 1). Food is more abundant and cheaper than in the past. Despite these dramatic accomplishments, there are still more than 850 million undernourished people, and some advances in production are at the cost of other services essential for human well-being, such as ocean fisheries, wood for fuel, genetic resources and - perhaps the most important - fresh water. It is the poor in many nations that are most directly dependent on services from ecosystems, and the degradation of these systems can exacerbate their poverty. Millions of people face the reality of the declining availability of cheap protein from local fisheries, inadequate water for sanitation or live on degraded landscapes.

There are a number of issues that cloud the goal of sustaining a high level of provisioning services. The use of fertilizer in agriculture has greatly increased to meet food demand, but at the cost of polluting off-site unmanaged ecosystems, such as groundwater, rivers and coastal fisheries. In many regions, water for irrigation is being pumped from groundwater and in some cases from fossil sources. Rivers are dammed and diverted for irrigation, altering ecosystems that depend on this water - causing the loss of many of the services they provided.

Further, we are diminishing crucial 'regulating' services responsible for climate, erosion, air- and water-quality control, as well as for the regulation of pests and natural hazards. We are losing these services due to massive land-surface conversion, atmosphere alteration, eutrophication, overharvesting and the impact of invasive species. The Millennium Assessment concluded that 60% of the ecosystem services evaluated were either being degraded or being used unsustainably.

As an example, cultivated systems (areas where at least 30% of the landscape is in croplands, confined livestock production or freshwater aquaculture) now cover a quarter of the Earth's surface, partly by conversion of temperate grasslands, Mediterranean-climate forests and many tropical ecosystem types. Forests have essentially disappeared from 25 countries, with 9.4 million hectares being lost annually from the Earth's surface. Historically important fisheries have collapsed or are overfished, one third of the mangrove forests for which there are historical data have been lost, as have 20% of the coral reefs, with a further 20% degraded. Nearly 40% of the rivers of the world have been fragmented. Species and populations of species are being lost at unprecedented rates, while at the same time the global biota is becoming homogenized owing to the introductions of alien species to new regions. These examples represent major losses of pieces of the biosphere machinery, which have a serious impact on the delivery of ecosystem-regulating services - impacts such as greater prevalence of infectious diseases in disrupted ecosystems, adverse effects on local climates by ecosystem modification, and the loss of flood protection (as in the recent tsunami in Indonesia).

What we can do

The drivers of change in ecosystems and their services will continue in direction and intensity. So how can these trends be reversed to achieve sustainability and to relieve the negative impacts of the loss of services to society, particularly to the disadvantaged? New pathways and approaches can and must be taken. But these are major initiatives, which will mean profound changes in the way global society operates. As learned in the Millennium Assessment, favourable responses need to take place at all levels, from the local to the global. Global mechanisms do not necessarily solve local problems, yet are an important part of the overall solution. At the same time, local players and solutions can feed into regional and global approaches. The players at these different levels address different decision-makers, who can collectively put in place the major changes that are needed for ecosystem sustainability.

The Millennium Assessment examines the merits of options for mechanisms and policies, to accomplish the goal of maintaining and enhancing the delivery of ecosystem services to society. Some of these require major reorganization in the way we do business. At present, our organizational structures address separately the issues of a single resource, such as agriculture, fisheries or the environment. There is little interaction within and between each issue, and much less again with trade and the treasury bodies. The lesson of the Millennium Assessment is that all these resource issues are interrelated: action on one issue has consequences for another. It is crucial to address how to minimize the trade-offs (biodiversity or clean water for agricultural yield), either on-site or by managing landscapes. One important example of how this process can work is the EU system of directives for nitrate accounting on landscapes.

Some institutional innovations are moving towards more integrated views of issues and responses to them. For example, Britain has a government department for Environment, Food and Rural Affairs. These are all closely interrelated domains, but in other countries are often handled by competing agencies. Elsewhere, interagency groups are evolving to address central issues such as climate change, but their effectiveness is hampered by competitiveness and politics. We need new kinds of institutions in better positions to achieve sustainability of ecosystems that provide for human well-being.

We must also try to improve the economics. Although provisioning services are enmeshed in the local (and increasingly global) marketplace, regulating services are not. We must accelerate our ability to value ecosystem-regulating services at the national level, as well as the ecosystem services that provide crucial cultural amenities, and ensure that these values are considered in decision-making.

Some progress is being made. Costa Rica has established a system of conservation payments, under which contracts are brokered between international and domestic 'buyers' and local 'sellers' of sequestered carbon, biodiversity, watershed services and scenic beauty. On a global scale, the Ecosystem Marketplace consortium is beginning to track transactions, pricing trends and buyers' requests on the carbon, water and biodiversity markets. It is predicted that the global carbon market will reach US$44 billion by 2010.

We need to eliminate the subsidies that promote the excessive use of ecosystem services and evaluate more carefully the trade incentives that damage ecosystem services. We must work harder to educate the public on the strong links between sustainable ecosystems and the lives of humans. The role of new technologies in more efficient use of natural resources is crucial and needs more incentives.

There is plenty that can and needs to be done to deal with the crisis that has already enveloped us. The path is open for scientists to quantify, to a much greater extent, the way in which the operation of ecosystems is directly linked to human well-being, and hence model the course of human activities on future outcomes of the delivery of these services. The Millennium Assessment is certainly providing a strong stimulus for such studies.

Millennium Assessment

Acknowledgements. We thank the scientists, reviewers and members of the review board who provided input to the Millennium Ecosystem Assessment, and the sponsors of this work.