Tufts OpenCourseware
Author: One Health Students

Fall 2008
Gretchen Kaufman, DVM
Cummings School of Veterinary Medicine at Tufts University

1. Environmental Health Perspective – Student Work

... collect information on impacts of dairy farming on the environment - use engineering perspective to document how these things are assessed, what information is available (or not), and various mitigating methodologies that can be employed to control the impact.

1.1. Basic Concepts

  • Air pollution

  • Water pollution

  • Soil impacts

  • Impacts on wildlife

  • Ecosystem disruption

Indicators of Environmental Health

The primary concept around measuring health is using measurements, both subjective and objective, as indicators. Assuming that a measurement is both accurate and reliable it can be used to indicate level of health. The use of indicators to assess health requires that there is an established link between a condition (health level) and the indicator. Indicators of environmental health can be taken from a wide spectrum and be highly variable. We have chosen to divide indicators into three general categories:

  1. Ecological Criteria

    1. Biodiversity

    2. Population size

    3. Health of living organisms

    4. Sentinel species

    5. Presence of pathogenic organisms

  2. Chemical Criteria

    1. Nutrient and mineral content of environmental media

    2. Presence of toxic compounds

  3. Physical Criteria

    1. Soil quality

    2. Surface water turbidity

    3. Surface water dissolved oxygen

    4. Odor

    5. Ability of environmental cycles to function

1.2. Disciplinary Gaps and Research Questions from the Environmental Health Perspective

  • Limited Information on New England. There is a lot of information on global farming, and farming in the United States. However, it is difficult to find New England specific farming data and statistics.

    • Method: Conduct an extensive literature review and data acquisition initiative to identify and collect any sources of data that may be available.

    • Method: Gather field data from New England stakeholders using qualitative methods such as focus groups, key informant interviews, and surveys.

    • Hypothesis: Farming practices and environmental impacts vary to a great extent across geographic and societal boundaries. New England farming practices are generally similar to other parts of the United States, but it faces a unique set of challenges.

  • Gap: Limited research comparing conventional and organic farming, and even more limited research comparing the two in New England.

  • Question: What are the key environmental differences between organic and conventional farming? Which form emits more pollution into the atmosphere? Which form pollutes the water more? To what degree does organic farming improve soil conditions compared to conventional farming practices?

    • Method: Conduct an extensive literature review and data acquisition phase. Use Meta-Analysis and other statistical methods to determine what differences, both in farming methods and environmental impacts, exist between organic and conventional types.

    • Hypothesis: Organic dairy farms are significantly different in the range and severity of the environmental impacts they cause, when compared with conventional farms.

  • What exactly is environmental health? What are the boundaries generally accepted when determining environmental health?

    • Defining the health of the environment is a difficult challenge because it is a philosophical, as well as scientific, question. Defining disciplinary boundaries will be essential to assessing the health of the environment. An accepted definition and limits on what can be used as indicators are essential in order to make the task of quantifying environmental health possible.

    • Methods: Bring together a multidisciplinary team of stakeholders, professionals, and policy-makers who have a vested interest in defining the health of the environment. Conduct an open discussion and workshop between all parties with the goal of forming a working definition of environmental health and a list of the most important/relevant indicators to be used as metrics.

  • How sustainable is organic farming?

    • Method: Choose an accepted definition of sustainability and evaluate how organic farming methods and environmental impacts are meeting or not meeting this definition. It may be useful to use a single farming operation as a case-study and evaluate all aspects of sustainability, or it may be useful to evaluate one aspect (e.g.: a particular farming process or practice) of multiple farms for sustainability.

    • Hypothesis: Although widely viewed as being "green" and "sustainable," organic farming operations have yet to achieve a goal of total sustainability. There are certain practices and methods that must be modified in order for organic operations to become truly "sustainable."

  • How feasible is organic farming? How much are people willing to pay to help the environment?

    • Methods: Conduct randomized surveys to try and determine how highly organic farming, sustainability, and environmental preservation and improvement rate to the general population.

    • Method: Conduct a cost-benefit analysis to determine is "going organic" is feasible for farms.

    • Hypothesis: Due to recent media attention and a growing movement of health and environmentally conscious citizens, people are more willing to support organic farms. "Going organic" is a delicate balance for the farms who still need to maximize profits while bettering the health of the environment.

  • What are the most common environmental impacts of the dairy farm? What are the most severe environmental impacts of the dairy farm?

    • Method: Conduct literature review and field work (measurements of environmental indicators on different farms coupled with stakeholder interviews and surveys) to get an idea of the most pertinent environmental health issues associated with dairy farming.

    • Hypothesis: Habitat alteration, water pollution, and soil degradation are likely to be the most recurrent environmental problems because they are easily observable and can occur regardless of size or type of farm. These three problems are difficult to manage simply because of the nature of agricultural land use and dairy farming methods.

1.3. Terms

The variety of different species, the genetic variability of each species, and the variety of different ecosystems they form.

Pore space in soil is reduced and density is increased as soil particles are forced together, which makes it difficult for plants to place roots.

Dissolved oxygen
The amount of oxygen freely available in the water, necessary for aquatic life and the oxidation of organic materials.

Ecological integrity
The ability of an ecosystem to function healthily and continue to provide natural goods and services and maintain biodiversity.

Ecological service
Ecological functions of healthy ecosystems which serve all living organisms through purification of air and water, maintenance of biodiversity, decomposition of wastes, soil and vegetation generation and renewal, pollination of crops and natural vegetation, groundwater recharge through wetlands, seed dispersal, greenhouse gas mitigation, and aesthetically pleasing landscapes.

A biotic community and its surroundings, part inorganic (abiotic) and part organic (biotic), the latter including producers, consumers, and decomposers. The components of an ecosystem are highly interdependent.

Ecosystem disruption
An event that results in displacement or discontinuity within an ecosystem, thus impairing the ability for that system to function properly.

Any liquid flowing out of the ground or from an enclosure to the surface flow network, typically the liquids discharged from domestic, industrial and municipal waste collection systems or treatment facilities.

Particles and gases released into the atmosphere as byproducts.

Environmental health
The physical, chemical, and biological processes and interactions between living and non- living worlds that influence social, physical, and emotional well being.

Process of bodies of water receiving excess nutrients that stimulate excessive plant growth (such as algae), reducing dissolved oxygen as plants decompose, which can cause other organisms to die from the low levels of dissolved oxygen.

Greenhouse gas
A gas, such as water vapor, carbon dioxide, methane, chlorofluorocarbons and hydrochlorofluorocarbons, that absorbs and re-emits infrared radiation, warming the earth's surface and contributing to climate change.

Habitat alteration
Any change in the structure or function of a habitat, often induced by human activities.

The food, water, and shelter suitable for the survival and reproduction of an organism or the organisms' population.

A measurable variable (or characteristic) that can be used to determine the degree of adherence to a standard or the level of quality achieved.

Land use
The human modification of the natural environment or wilderness into the built environment, such as fields, pastures, and settlements.

A substance assimilated by living things that promotes growth, including nitrogen and phosphorus.

Fine liquid or solid particles, such as dust, smoke, mist, fumes, or smog, found in air or emissions.

An essential and distinguishing attribute of something or someone. A characteristic property that defines the apparent nature of something.

The portion of precipitation or irrigation water that moves across land as surface flow and enter streams or other surface receiving waters. Runoff occurs when the precipitation rate exceeds the infiltration rate. Runoff carries contaminants from the land surface into receiving waters.

The process of sediment being carried into and deposited in surface waters. Sedimentation can smother benthic organisms and increase turbidity, thus degrading surface water habitats.

The process of sediment being carried into and deposited in surface waters. Sedimentation can smother benthic organisms and increase turbidity, thus degrading surface water habitats.

Sentinel species
Species used as an indicator of overall environmental conditions, particularly contaminants

An organized assembly of resources and procedures united and regulated by interaction or interdependence to accomplish a set of specific functions.

Harmful, destructive, or deadly to an organism.

A measure of the amount of light intercepted by a given volume of water due to the presence of suspended and dissolved matter and microscopic biota. Increasing the turbidity of the water decreases the amount and depth of light that penetrates the water column.

1.4. Stereotypes about Environmental Health

  • People that work in Environmental Health are tree huggers.

  • Environmental Health is only concerned with the health of the soil, air, and water.

  • People that work in Environmental Health are always in crisis mode.

  • People that work in Environmental Health are more concerned with protecting the environment than protecting humans or animals.

  • Not concerned with individuals, only populations.

  • More concerned with cost-benefit analysis than ethical and moral considerations.

  • Too much weight on modeling, assumptions, balancing uncertainties, and other probabilistic assessments.

  • Only concerned with systems for primary prevention.

1.5. Environmental Health Perspective Presentation Materials

1.6. Environmental Health Perspective Annotated Bibliography

Ali I, Morin S, Barrington S, Whalen J, Bonnell R, Martinez J. Surface irrigation of dairy farm effluent, part I: nutrient and bacterial load. Biosystems Engineering. 2006 Oct 13; 95(4):547-556.
Summary: This study looked at the characteristics of dairy farm effluent from different sources and storage systems. The management of effluent is important on dairy farms because it can contain high concentrations of nutrients, bacteria, dissolved solids, and other contaminants which may be harmful if discharged directly into the environment. Furthermore, since it is generally rich in nutrients, a common practice is to capture the effluent and use it for surface irrigation of forage crops. The research presented in this article shows that the total solids, nutrient load, and bacterial count of effluent vary considerably depending on the type of management system used. Effluent containing milk house waste water, manure runoff, or a mixture of both contained a relatively low nutrient load. On the other hand, when runoff and waste water were stored along with solid manure, the effluent tended to have higher nutrient loads, bacterial counts, and total solids.

Relevance: This research is relevant to our project because it shows how different engineered systems and farming practices can have an impact on the outputs that would go into the environment. Understanding how different methods impact the characteristics of dairy farm effluent is important to making decisions about how to apply the appropriate technologies. For instance, if discharging to the environment, the effluent should be as clean as possible to reduce environmental impact. On the other hand, if using the effluent for crop irrigation, the concentration of nutrients should be high to cut down on application rates and reduce cost. Better understanding how engineering/farming practices influence the outputs of the dairy farm will allow people to make decisions which are more sustainable and cause less impact on the environment.

Altieri M, Nicholls C, Soil fertility management and insect pests: harmonizing soil and plant health in agroecosystems, Soil Till. Res. 2003; 75:203-211.
Summary: This article summarizes the cultural methods such as crop fertilization that can affect susceptibility of plants to insect pests by altering plant tissue nutrient levels. It mentions how research indicates that a crop plants resistance to insect pests and diseases is tied to optimal physical, chemical and mainly biological properties of soils. Good soil fertility is typically seen through soils with higher organic matter and more active soil biology. When crops are grown it soil with good fertility, they typically have a lower abundance of insect herbivores, which may attributed to lower nitrogen content in organically farmed crops. Also, this article addresses how conventional farming uses agrochemicals, and excess use can cause nutrient imbalances and lower pest resistance. This article concludes with the consensus that more studies need to be done to compare pest populations on plants treated with synthetic versus organic fertilizers are needed.

Relevance: In conclusion, understanding why organic fertilization may improve plant health may lead us to new and better integrated pest management and integrated soil fertility management designs.

Arnon S, Dahan O, Elhanany S, Cohen K, Pankratov I, Gross A, Rohen Z, Baram S, Shore LS. Transport of testosterone and estrogen from dairy-farm waste lagoons to groundwater. Environ Sci Technol. 2008; 42:5521-5526.
Summary: This study evaluated whether waste lagoons were effective in blocking the transport of common hormones associated with dairy farms (testosterone and estrogen) from entering groundwater. The study utilized environmental sampling and analysis coupled with computer modeling programs to try to explain the presence of hormonal contaminants in soil and groundwater. The study found that hormones do end up at fairly deep groundwater levels, contrary to other studies and opinions. The discussion section speculates as to why hormones may be transported into the groundwater. The contaminant levels were below the Lowest Observable Effects Level (as determined by toxicological studies) for ecological receptors, but it should be noted that there is a great degree of uncertainty around this value, especially for chronic low-level exposure, and that environmental and public health implications should still be of concern.

Relevance: This type of research illustrates the concept of environmental systems and the interrelatedness of human practices, animals, and impact on the environment. This study is also an example of a common form of contamination (hormones) coming from dairy farms that could have potential impact on environmental and human receptors. Finally, this research shows that an established farming method (waste lagoons) may not be an effective mitigation technology for reducing environmental impact from dairy waste.

Birkhofer K, Bezemer T. Martijn, Bloem J, Bonkowski M, Christensen. Soil Biology & Biochemistry, ScienceDirect. Sep 2008; 9(40):2297-2308.
Summary: This article discuss organic farming and how it may contribute to future agricultural production through improved soil quality and pest control, which would reduce the environmental impacts of conventional farming. This paper investigates soil chemical, as well as below and above ground biological parameters of two organic and two conventional wheat farming systems. These systems primarily differ in fertilization and weed management strategies. Management related differences between "herbicide-free" bio organic and bio dynamic systems and conventional systems with or without manure and herbicide application within a long-term agricultural experiment are analyzed.

Bolan NS, Wong L, Adriano DC. Nutrient removal from farm effluents. Bioresource Technology. 2004 Mar 6; 94:251-260.
Summary: This study examined the efficiency of a two-pond system in removing nutrients during treatment of dairy farm effluent. The researchers also looked at methods to produce an effective, yet inexpensive, nutrient trap that could be recycled as a source of nutrients or soil mulch after use. Concentrations of chemical oxygen demand, biological oxygen demand, nitrogen, phosphorus, and potassium were monitored over a period of seven months. Nutrient retention by two porous materials (zeolite minerals and bark) were examined both in the laboratory and in the two-pond field system. The study found that the widely-used two pond system was inefficient at removing nutrients which act as pollutants when discharged to the environment. Both the bark and zeolite materials were able to remove substantial quantities of nitrogen, phosphorus, and potassium from the effluent. These materials would be placed into the second pond of the system to remove excess nutrients and make effluent clean enough for discharge. The nutrient-enriched materials can then be used as a source of fertilizer and soil conditioner for crops.

Relevance: Illustrates how a relatively simple addition to a commonly-used system to treat effluent can reduce potential environmental impact by removing excess nutrients. The use of local materials (bark and zeolite) and their recycleability as fertilizers after use makes this a good example of a somewhat sustainable practice.

Bosch DJ, Wolfe ML, Knowlton KF. Reducing phosphorus runoff from dairy farms. J Environ Qual. 2006 Apr 26; 35:918-927.
Summary: This study provides an assessment of the impacts of alternative phosphorus reduction practices on phosphorus concentrations in runoff and on net financial returns of dairy farms. Applying methods to reduce phosphorus runoff is beneficial to the environment, but it can impose costs on dairy farms. Phosphorus control practices evaluated included: dairy herd nutrient management, crop nutrient management, and runoff and erosion control. Different farm scenarios were designated and computer modeling was used to predict phosphorus runoff. The results show that in general herd nutrient control strategies can reduce phosphorus load while having minimal impact on the economic returns of farms. These strategies are successful because they reduce phosphorus concentrations in manure and runoff potential while simultaneously increasing milk output and returns per cow. The study also points out that the size and type of the farm has a great impact on the financial returns due to balancing different expenses and externalities with the costs of implementing phosphorus control methods.

Relevance: This article points out that there are economic considerations to any environmental control technology. "Animal nutrient control strategies should be an important part of pollution control policies and programs for livestock intensive watersheds," but there must be a balance between cost-effectiveness and environmental benefit for it to be feasible. It is important to look at engineered systems from an interdisciplinary perspective that incorporates both science and economics.

Cederberg C, Mattsson B. Life cycle assessment of milk production-- a comparison of conventional and organic farming. Journal of Cleaner Production. 2000; 8:49-60.
Summary: This study performed a Life Cycle Assessment (LCA) on organic and conventional milk production for farms in Sweden. This evaluation paid particular attention to "substance flows in concentrate feed production" and the flow of nutrients on the farms. The LCA found that the more low-input agricultural systems (organic farms) had greater environmental benefits. The main benefits pointed out in this article are reduced pesticide and nutrient (phosphorus) use. On the other hand methods to reduce environmental impacts such as acidification, global warming, and eutrophication need to be implemented for both farming systems. The article points out that it is important to assess environmental performance and land-use both quantitatively and qualitatively since there are great differences in resource allocation and "material and energy flows" between conventional versus organic systems.

Relevance: This article is very useful because it provides a clear example of a Life Cycle Assessment which is directly related to our project. The LCA method is a great way to show how various inputs are processed and turned into outputs in a system. Applying the LCA approach to environmental health would be beneficial because it allows for evaluation of an entire complex system. An LCA can also provide an illustration of how inputs, processes, and outputs are all interconnected and how they in turn can influence/impact indirect environmental factors.

D'Antonio , D. Tilman, J. Fargione,B. Wolff, A. Dobson, R. Howarth, D. Schindler, W. H. Schlesinger, D. Simberloff, D. Swackhamer. Forecasting Agriculturally Driven Global Climate Change. Science. 13 April 2001; 5515 (292): 281 - 284. Cited in PubMed; PMID: 11303102.

Summary: The article addresses the global environmental impacts agriculture will have in the future as agriculture expands and population increases, which creates a higher demand for food. It mentions the effect increased agriculture will have on natural ecosystems, and how much nitrogen and phosphorous driven eutrophication would increase. Pesticide use would increase and habitats would be destructed, which would decrease biodiversity and lead to ecosystem simplification. Agriculture has the potential to have massive, irreversible impacts on the environment. The article discusses the main trends that must be mitigated if we hope to mitigate the harm agriculture poses to the environment.

Relevance: This article is relevant to the environmental sector of One Health because it discusses the impacts human can have on the environment. It mentions how biodiversity will be affected and how climate change will occur as agriculture continues to increase and sustainable alternatives remain costly or infeasible.

Duxbury J. The Significance of Agricultural Sources of Greenhouse Gases. Nutrient Cycling in Agrosystems. 13 March 1994; 38(2)151:163.
Summary: This paper discusses the impact land development for agriculture and agricultural practices have had on greenhouse gas emissions. Specifically, it analyzes the emissions of carbon dioxide, methane, and nitrous oxide. Over the last 150 years, the cumulative emissions of carbon dioxide associated with land clearing for agriculture are comparable to those from combustion of fossil fuel. Extension of the analytical approach to projected future emissions of greenhouse gases indicates that agriculture will become a less important source of radiative forcing in the future. Technological approaches to mitigation of agricultural sources of greenhouse gases will probably focus on reducing methane and nitrous oxide. Carbon dioxide emissions are believed to be primarily associated with deforestation.

Fatta D, Monou M, Voscos C, Kythreotou N, Stylianou C. Minimization of the diffuse pollution caused by dairy farms in Cyprus through the development of guidelines for their sustainable operation. Water Science and Technology. 2007; 56(1):89-97.
Summary: This study was conducted to develop guidelines for the management of impacts caused by dairy farm operations on the island of Cyprus.
Relevance: This is a good case study for showing the evaluation of dairy farms as an environmental problem and how to form policies to mitigate those problems. The article explains both the negative impacts of dairy farms on the island as well as a description of technologies and methods for controlling those impacts. In order to form effective environmental management policies, a complete exploration of the problem, along with possible solutions, must be explored.

Fisher PMJ, Scott R. Evaluating and controlling pharmaceutical emissions from dairy farms: a critical first step in developing a preventative management approach. Journal of Cleaner Production. 2008; 26:1437-1446.
Summary: This article summarized research that was conducted in Australia, which evaluated the extent of pharmaceutical pollution into aquatic environments. Each pharmaceutical evaluated was known to be used in dairy herd management. The study found that the chemical compounds in question are finding their way into the environment surrounding the farm operations. The article concludes that enacting a focused water quality monitoring program and making some simple changes to farm management practices will likely be able to lessen the extent and magnitude of the problem.

Foley J, Defries R, Asner G, Barford C, Bonan G, Carpenter S, Chapin F, Coe M, Daily G, Gibbs H, Helkowski J, Holloway T, Howard E, Kicharik C, Monfreda C, Patz J, Prentice I, Ramankutty N, Snyder P. Global Consequences of Land Use. Science. 2005 July 22; 309(5734):570-574. Cited in PubMed.
: This article focuses on land use and how it is considered a global environmental issue. Worldwide changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter for a growing population. Global croplands, pastures, plantations, and urban areas have expanded in recent decades, accompanied by large increases in energy, water, and fertilizer consumption. These expansions are coupled with losses of biodiversity. These changes may undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, and regulate climate and air quality. We need to do a careful benefit costs analysis of what our land use is doing to the environment.

Gomiero Energy and Environmental Issues in Organic and Conventional Agriculture. Critical Reviews in Plant Sciences. 2008 June 01; 27(4):239-254.
Summary: This article talks about the growing population and the scarcity and decreasing quality of land. This paper mentions the need to develop more ecological agricultural practices in order to preserve agroecosystems health. Practices also need to deal with the limitation of energy from fossil fuels. This paper reviews a number of studies comparing the performances of conventional and organic farms in terms of energy use, carbon dioxide emissions, and other environmental issues. Overall, it was found that organic agriculture results in less energy demand compared to conventional agriculture, which means less carbon dioxide will be used. Also, there are other environmental benefits such as preserving and improving soil quality, increasing carbon sink, minimizing water use, preserving biodiversity, and diminishing the use of harmful chemicals. The paper states that more research needs to be done to investigate the potential reduced environmental impacts organic farming may have on the environment.

Hajkowicz SA, Wheeler SA. Evaluation of dairy effluent management options using multiple criteria analysis. Environmental Management. 2008 Jan 10; 41:613-624.
Summary: The research presented in this article utilizes a method called Multiple Criteria Analysis (MCA). MCA is a framework that uses computer modeling and algorithms to combine multiple environmental, social, and economic objectives in order to form appropriate policy decisions. This application of MCA looked at how to manage dairy farm effluent in an area of South Australia where contamination by effluent was leading to environmental, human health, and tourism impacts. Of the 11 options and 6 criteria examined by MCA, the model selected "partial rehabilitation of dairy paddocks with the conversion of remaining land to other agriculture" as the most feasible option to managing the effluent problem.

Relevance: Shows how dairy farm effluent can have substantial impact on the environment and local communities. It is important to look into management strategies from many different angles to find the most fitting option. MCA is a useful tool for combining different disciplines and information sources together in order to make the most appropriate/best policy decisions.

Havlikova M, Kroeze C, Huijbregts MAJ. Environmental and health impact by dairy cattle livestock and manure management in the Czech Republic. Science of the Total Environment. 2008 Feb; 396:121-131.
Summary: This study evaluated the potential human and environmental health impacts of dairy farms in the Czech Republic. Special attention was paid to how livestock and manure were managed at different farms. A variety of health and environmental impacts were evaluated including: acidification, eutrophication, human toxicity, and contribution of greenhouse gases. The study found that the severity of impacts varied greatly depending on dairy cattle intensity and the location of the farm (e.g.: high human population density, nitrate vulnerable zones, etc.). The study is a good model because it estimates the potential human and environmental health impacts from dairy farming on a national level, rather than quantifying the health effects from a single farm. The results are useful for people to help identify areas where pollution from dairy farms is of critical concern, where pollution reduction plans should be targeted.

Habteselassie MY, Miller BE, Thacker SG, Stark JM, Norton JM. Soil nitrogen and nutrient dynamics after repeated application of treated dairy waste. Soil Sci. Soc. Am. J. 21 June 2006; 70:1328-1337.
Summary: This article summarized research assessing the effects of treated dairy-waste on a variety of soil and crop yield parameters in a silage cornfield. The study found that the three different treatment methods, ammonium sulphate fertilizer, dairy-waste compost, and liquid dairy-waste, all resulted in varying degrees of nitrogen dynamics in soil and crop yield. In general it was found that the organic form of nitrogen found in the compost was not as quickly available for plant uptake, but it continued to mineralize and remain in soils for longer periods of time. Understanding the nitrogen dynamics of different fertilizers is important to optimize nitrogen release timing for plant demand, and to lower post-harvest nutrient surpluses which can lead to excessive nitrate accumulations. This type of research is highly useful for dairy farms that want to use animal waste a source of fertilizer for their pastures and silage crops.

Hole D, et al., Does organic farming benefit biodiversity?, Biol. Conserv. 2005;113-130.Cited in PubMed; PMID.
Summary: This article assesses the impacts that organic farming has on biodiversity, relative to conventional agriculture. The comparison of the impacts of organic and conventional farming is done through a comparative study of the two systems. This comparative study is through a review of comparative studies of the two systems, in order to determine whether it can deliver on the biodiversity benefits its proponents claim. A lot of organisms are identified, such as birds, mammals, invertebrates, and vegetation that benefit from organic management through increases in species richness. Also, various management practices are introduced that have potential to benefit farmland wildlife.

Jarvis S, Pain B. Greenhouse gas emissions from intensive livestock systems: their estimation and technologies for reduction. Clim Change 25 October 1993; 27:27-38.
Summary: This article addresses intensive agricultural systems and how they contribute to inefficiency and leakage of materials into the wider environment. Specifically, it discusses how animals are potential sources of two important greenhouse gases, methane and nitrous oxide. Because of the complexity of the processes involved and because of the numerous interactions, there is a need to consider the potential for release of these two gases on an integrated, whole farm basis in order to ascertain the impact of management systems. This paper mentions gaps in existing knowledge and options to reduce emissions.

Kolodziej EP, Harter T, Sedlak DL. Dairy wastewater, aquaculture, and spawning fish as sources of steroid hormones in the aquatic environment. Environ. Sci. Technol.
Summary: The research presented in this article evaluated a suite of steroid hormones in aquatic environments near dairy farms, aquaculture facilities, and spawning fish. The dairy waste lagoon contained endogenous estrogens and androgens. A nearby groundwater well showed that these compounds were naturally attenuated before reaching the subsurface. On the other hand, surface waters and drainage, likely impacted by animal wastes, showed sporadic presence of steroidal compounds (near or below 1 ng/L). The results show that dairy wastewater can result in detectable concentrations of steroid hormones in surface waters, but that the concentrations vary temporally and spatially.

LeJeune JT, Kauffman MD. Effect of sand and sawdust bedding materials on the fecal prevalence of Eschericia coli O157:H7 in dairy cows. Applied and Environmental Microbiology. 2005 Jan; 71(1):326-330.
Summary: Farming practices can have a substantial impact on the presence of pathogens on the farm. This study evaluated how sand and sawdust bedding material influenced the prevalence of E coli O157:H7 (highly pathogenic to humans) in cows on the farm. Samples of bedding material found that E coli O157:H7 persisted in higher amounts in used sawdust bedding, as compared to sand bedding. The overall herd level prevalence of the pathogen was higher for animals housed in sawdust bedding than sand bedding (3.1 versus 1.4%). Overall, this study indicates that sawdust betting is more capable of housing E coli O157:H7, thus resulting in higher infection rates in cows. This study shows how barn management and animal husbandry practices can have an impact on the presence of a pathogenic organism.

Maeder P, et al. Soil Fertility and Biodiversity in Organic Farming. Science. 31 May 2002; 296: 1694.Cited in PubMed; PMID: 12040197
Summary: This article gives an understanding of agroecosystems and expresses it as a key determination factor for effective farming systems. The article reports results from a 21 year old study of agronomic and ecological performance of bio dynamic, bio organic, and conventional farming systems. The report showed that crop yield were 20% lower in the organic systems. This reduction in crops including a 34% reduction in energy and fertilizer use, and a 97% reduction in pesticide use.

McDowell RW. Phosphorus and sediment loss in a catchment with winter forage grazing of cropland by dairy cattle. Journal of Environmental Quality. 2006 Mar 1; 35:575-583. 2004; 38:6377-6384.
This study looked at the impact of winter grazing dairy cattle on the loss of phosphorus and sediment from land to surface waters. Samples were taken upstream and downstream of a field that was utilized for winter grazing. The results show that the impact of winter grazing on P losses was minimal, but suspended sediment load was increased by an average of 75%. This article shows how farming practices and herd management can have impacts on the environment surrounding the farm.

Monaghan RM, de Klein CAM, Muirhead RW. Prioritisation of farm scale remediation efforts for reducing losses of nutrients and faecal indicator organisms to waterways: a case study of New Zealand dairy farming. Journal of Environmental Management. 2008; 87:609-622.
Summary: This article looked at how various Best Management Practices (BMPs) in New Zealand worked to mitigate the effect of nutrients and fecal bacteria into surface waters. Various BMPs were described and modeled. Simulations were then ran for different case-study farms with the various BMP options. The model looked at both pollution mitigation and cost-effectiveness. The results show that BMP options can have substantial differences in effectiveness and cost. It is important to choose BMPs appropriately to deal with different types of pollutants, catchment (surface water) characteristics, and the "physical resources and management systems of farm businesses." Since there are many options available it is important to understand the how different practices work (in terms of cost and function) so that financial and environmental goals can be met.

Rabaud NE, Ebeler SE, Ashbaugh LL, Flocchini RG. Characterization and quantification of odorous and non-odorous volatile organic compounds near a commercial dairy in California. Atmospheric Environment. 2003; 37:933-940.
Summary: This article summarized research that was conducted at an industrial dairy facility in Northern California. Air sampling was carried out near the facility using sorbent tubes to identify and quantify volatile organic compounds in the air. Each the concentration of volatile organic compounds in each tube was analyzed and correlated with odor. A total of 35 different compounds were identified with varying concentrations. Few of the compounds identified exhibited offensive odors. Compounds with offensive odors were found at very low concentrations. Variables such as sampling location at the dairy, temperature, and humidity had no observable effect on the results of the analysis. This article shows that dairy facilities can emit a wide array of volatile organic compounds into the air, but that their concentrations may be quite low and not result in bad odors.

Ramirez CA, Patel M, Blok K. From fluid milk to milk powder: Energy use and energy efficiency in the European dairy industry. Energy. 2006; 31:1984-2004.
Summary: This paper looks at energy consumption and energy efficiency for the dairy industry within four European countries. Change in energy efficiency was monitored by measuring the energy use per ton of milk processed and also by comparing actual energy use with the amount of energy that would have been used if no changes in efficiency had been made over time. The results showed that energy efficiency has been improving over time in Germany, the Netherlands, and the United Kingdom, but that France has not made any progress. The data also showed that the three improving countries have converged towards lower values in their energy efficiency indicators. It is unclear why the French dairy industry is not becoming more energy efficient. This article shows that energy is an important input into the dairy system. A better understanding of energy will hopefully make farms more sustainable, and further reduce their environmental impact.

Reganold J, Elliot L, Unger Y. Long-term effects of organic and conventional soil erosion. Letters to Nature. 26 November 1987; 330:370-372.
Summary: This paper discusses how conventional, intensive tillage farming systems have greatly increased crop production and labor efficiency. It addresses the concern about the energy intensive nature of these systems and the adverse effects they may have on soil productivity and environmental quality. This concern has led to an increase interest on organic farming systems, in hopes that organic farms will help reduce some of the negative effects conventional farms have on the environment. This paper compares the long term effects of organic and conventional farming on properties of the same soil. The study indicates that in the long term, the organic farming system was more effective than the conventional farming system in reducing soil erosion and thus maintaining soil productivity.

Diaz R, Rosenberg R. Spreading Dead Zones and Consequences for Marine Ecosystems. Science. 2008; 321:926-929.Cited in PubMed; PMID.
Summary: This article addresses the issue of expanding dead zones in the coastal oceans and their adverse effect on ecosystems. The formation of dead zones has increased in speed due to eutrophication fueled by runoff of fertilizers and the burning of fossil fuels. These pollutants enter the water ways, causing an excess of nutrients, and rapid plant growth - namely algae. As the algae dies and decomposes, it uses up dissolved oxygen that other organisms need to survive. Dead zones have now been reported from more than 400 systems and affect a total area of more than 245,000 square kilometers.

Rumberg B, Mount GH, Filipy J, Lamb B, Westberg H, Yonge D, Kincaid R, Johnson K. Measurement and modeling of atmospheric flux of ammonia from dairy milking cow housing. Atmospheric Environment. 2008; 42:3364-3379.
Summary: This study aimed to determine the concentration and atmospheric flux of ammonia (NH3) emissions from dairy cow housing. Measurements of NH3 concentrations and flux were taken at the edge of cow stalls. An emissions model was constructed that "calculated liquid NH3 concentrations in urine puddles, NH3 volatilization, theoretical and empirical mass transfer to the bulk atmosphere, and NH3 transport." The total ammonia emissions of the dairy (185 cows) was found to be 7400 kg, which is equal to 40 kg of NH3 per cow each year. The model results were found to agree with the nitrogen mass balance of the dairy. The model showed that emissions were temperature dependent and was also highly sensitive to urine puddle pH. The results of this study are useful because it is important to understand the dynamics of atmospheric emissions at dairy farms in order to get an idea of potential environmental and health impacts. Farmers and stakeholders must also to know what steps could be implemented or corrected in to better mitigate these impacts.

Sawant AA, Hegde NV, Straley BA, Donaldson SC, Love BC, Knabel SJ, Jayarao BM. Antimicrobial-Resistant Enteric Bacteria from Dairy Cattle. Applied and Environmental Microbiology. 2007 Jan; 73(1):156-163.
Summary: This article presented research on the molecular epidemiology of "antimicrobial-resistant gram-negative enteric bacteria in the feces of healthy lactating dairy cattle." A total of 213 cattle on 23 farms were surveyed. Nine species of bacteria were isolated, with the most common being Escherichia coli. Isolates of bacteria exhibited a wide range of microbial resistance. Tetracycline resistance was the most predominant of resistance determinants. Subtypes of E coli were found to be confined mostly to individual herds, with similar subtypes between individual cows within the herd. The study concludes that "commensal enteric E coli from healthy cattle can be an important reservoir for tetracycline and perhaps other antimicrobial resistance determinants." This type of research is valuable to gain an understanding of the prevalence and characteristics of antibiotic and other antimicrobial resistant bacteria on dairy farms. Drug resistant bacteria may pose a threat to animal, human, and environmental health.

Shi-ming M, Joachim S. Review of History and Recent Development of Organic Agriculture Worldwide. Agricultural Sciences in China. 3 April 2006; 5(3):169-178
Summary: This paper addressed the history of the organic farming worldwide. The main stages of: emergence, expansion, and growth are discussed. There is some feedback from people involved with different stages of the development of organic farming.

Schnitkey G, Mirand M. The Impact of Pollution Controls on Livestock- Crop Producers. Journal of Agricultural and Resource Economics. 1993; 18(1):25-36.
Summary: This paper illustrates a model of a livestock-crop producer. This model is used to examine the long term effects on phosphorus runoff and how to optimize livestock production and manure application practices. The study shows that quantity restrictions and taxes on phosphorus application reduce livestock supply and impose greater costs on livestock-crop producers and on crop-only producers. If restrictions are place on manure application, phosphorus runoff levels are minimally affected.

Ullman JL, Mukhtar S. Impact of dairy housing practices on lagoon effluent characteristics: implications for nitrogen dynamics and salt accumulation. Bioresource Technology. 2007; 98:745-752.
Summary: This article presents research that was conducted on eleven different dairy operations in central Texas. Analysis for fifteen physicochemical parameters was conducted at anaerobic waste lagoons on each farm. Characteristics of the farms were also recorded to determine if housing practices had an effect on the lagoon effluent. It was found that there were significant differences in a variety of parameters depending on the type of farm. Differences were associated to cattle activity and the efficiency of waste transport into the lagoons. The data shows that there is a possible difference in nitrogen dynamics between lagoon types, which could have an influence on volatilization of ammonia. An understanding of nitrogen dynamics of lagoons is important for farms which intend to utilize the waste as a fertilizer, in order to prevent salt-stress impact and protect soil resources. The more information that is available on dairy waste management will help farmers make informed decisions on what practices best suit their needs, and will hopefully maximize revenue while minimizing environmental and health impacts.

Uri, Noel. Agriculture and the Environment. Nova Science Publishers. 1999;1-211.
Summary: This book gave an overview of the different effects agriculture has on the environment. Everything was addressed from the use of fertilizers to animal manure. It addresses the life cycle of a farm, beginning with the need for land and ending with the closing of the farm. All of the farm processes and management tactics are considered and analyzed, reaching the conclusion that more sustainable methods need to be researched.

Relevance: This book was applicable to the One Health class, particularly my discipline because it gave a great overview of how agriculture impacts the environment and to what extent different processes damage the environment. It helped me grasp a general understanding on many complex topics.

Vance, Carroll. Symbiotic Nitrogen Fixation and Phosphorous Acquisition: Plant Nutrition in a World of Declining Renewable Resources. Plant Physiology. October 2001; 127:390-397.Cited in PubMed; PMID: 101104.
Summary: This article discusses how due before the Green Revolution it was thought that food products would not be able to keep up with population growth. However, food production has exceeded population growth due to the unprecedented use of fertilizers and expanded the use of irrigation. The cost of this increases food population is the Earth's sustainability as the increase use of nitrogen and phosphorous fertilizers has causes air and water quality to degrade. Additionally, the use of water irrigation has causes soil salinization and depletion and ground and surface water supplies. We need to find a buffer against food insecurity that will not deplete natural resources, decrease biodiversity, and lead to unsustainability.

Relevance: When examining the environmental impacts of agriculture, nitrogen and phosphorous pollution is the back bone to many of the problems. The pollution these two chemicals cause in the air and water harms every form of life and it is crucial to find a more sustainable way to farm so less nitrogen and phosphorous is formed.

Walk ST, Mladonicky JM, Middleton JA, Heidt AJ, Cunningham JR, Bartlett P, Sato K, Whittam TS. Influence of antibiotic selection on genetic composition of Escherichia coli population from conventional and organic dairy farms. Applied and Environmental Microbiology. 2007 Oct; 73(19):5982-5989.
Summary: This study evaluated how antibiotic use influenced the genetic composition of E. coli populations on conventional and organic dairy farms. Data from 30 conventional and 30 organic dairy farms was used to build a log-linear model that assessed the association between farm type, age of cattle, bacterial phenotype (resistant versus susceptible), and the genetic composition of E.coli populations. Results show evidence for clonal resistance (ampicillin resistant bacteria) and genetic hitchhiking (tetracycline resistant bacteria), and discovered a statistically significant association between low multidrug resistance and organic farms. The study shows that organic farming practices (highly restricted antibiotic use) change the frequency of resistant strains and impact the overall genetic composition of resident E.coli.

Relevance: This study shows that antibiotic use can have an influence on the characteristics of bacteria populations on a farm. Organic (very limited antibiotic use) appears to have reduced impact on local bacteria compared to conventional methods that use antibiotics freely to treat cattle. This study is a good example of how a single input can have profound unintended consequences once entered into an environmental system.

Wheeler S. What influences agricultural professionals' views towards organic agriculture? Ecological Economics. 15 March 2008; 65(1):145-154.
Summary: This article addresses organic agriculture as a farming system that is considered to have potential of having beneficial impacts on the sustainability of agriculture. Research was conducted to study the attitudes of consumers and farmers and what factors influence the willingness of consumers to pay organic premiums and what factors influence farmers to adopt organic farming. This study recorded the results of a telephone survey done in 2004, where 185 agricultural professionals were asked about their views on organic farming. The study in this article shows the relationship between increased knowledge and experience and how they influence the person's attitudes towards organic agriculture. In the end, this study states that professionals with increased organic knowledge and experience are more likely to have a preference towards about organic agriculture.