1. Comparing the Environmental Impacts of Pasture-Based and Confinement-Based Dairy Systems in Nova Scotia (Canada) Using Life Cycle Assessment.
Arsenault, N., Tyedmyers, P., Fredeen, A. 2009. International Journal of Agricultural Sustainability 7(1):19-41.
This study conducts a life cycle assessment (LCA) to compare environmental impacts between grazing and confinement dairy systems in Nova Scotia, Canada. Data on material and energy inputs and outputs are compared for 11 categories, such as the use of concentrate feeds, N fertilizers, transport fuels, and land-use footprint. Surprisingly, grazing cows for five months per season (typical grazing periodicity in Nova Scotia) showed little overall environmental benefit compared to confinement. The authors conclude these findings are due to the greater amount of land (footprint) utilized by grazing verse confinement systems. While the conclusion suggests there’s little difference between energy inputs and outputs between the two different grazing systems, the study fails to include an ecological integrity index to compare the external environmental impacts between confinement and grazing.
2. The Impacts of Grazing Animals on the Quality of Soils, Vegetation, and Surface Waters in Intensively Managed Grasslands.
Bilotta, G.S., R.E. Brazier, Haygarth, P.M. 2007. Advances in Agronomy 94:237-280.HYPERLINK “http://www.sciencedirect.com/science?_ob=ShoppingCartURL&_method=add&_udi=B7CSX-4NR6454-6&_acct=C000050221&_version=1&_userid=10&_ts=1301514659&md5=93af254f256c3106854d2ad074616e53”
This paper conducts a literature review concerning the impacts of grazing on soil and water quality. The review concludes well managed grazing has beneficial soil and water quality impacts, but intensive grazing can have negative soil water quality impacts. Causes and consequences of degradation are discussed and solutions to problems proposed.
3. Farm returns to carbon credit creation with intensive rotational grazing.
Bosch, D.J., Stephenson, K., Groover G., Hutchins, G. 2008. Journal of Soil and Water Conservation 63(2):91-98.
This study compares carbon sequestration rates between rotational and conventional grazing systems. Carbon sequestration rates increase for intensive rotational grazing; however, current carbon offsets under rotational grazing do not warrant financial carbon-credit incentives enough to switch from conventional to managed grazing in Eastern USA livestock operations.
4. Environmental Impacts of grazed pastures.
Eriksen, J., Ledgard, S., Lou, J., Schils, R., Rasmussen, J. 2010. Grassland Science in Europe 15:880-890.
This study examines cycling rates and residence times for nitrogen (N) and methane (CH4) between grazed and confined livestock operations. The study concludes N in animal excreta can be high in localized patches which under poor management can increase the risk of N losses to waterways and the atmosphere; however, under good grazing management N can be recycled between forage and livestock to form a closed loop that decreases N loss. Management strategies to induce closed N loop cycling are discussed. Also, the research shows grazing can reduce CH3 emissions. In conclusion, good pasture management can reduce negative environmental impacts associated with N and CH4 loss from pasture systems compared to confinement systems.
5. Soil Carbon Sequestration in Grazing Lands: Societal Benefits and Policy Implications.
Follett, R.F., Reed, D.A. 2010. Rangeland Ecology & Management 63(1):4-15.
This study examines the potential for pastures to act as a carbon sink. Carbon sequestration rates are tested in both grazed and un-grazed grasslands. Evidence suggests good pasture management offers a viable option to sequester and store atmospheric CO2. The authors conclude by suggesting that because grazing can sequester and act as a long term sink for CO2, and the numerous other positive environmental benefits associated with grazing, government environmental and agricultural agencies should establish policy and programs to encourage grazing.
6. Grazing Impacts on Soil Carbon and Microbial Communities in a Mixed-Grass Ecosystem.
Ingram, L.J., Stahl, P.D., Schuman, G.E., Buyer, J.S., Vance, G.F., Ganjegunte, G.K., Welker, J.M., Derner, J.D. 2008. Soil Science Society of America Journal 72(4):939-948.
This study examines the effects of different grazing intensities on soil carbon, nitrogen, and microbial communities. Treatments include no grazing, light grazing, and continuous grazing. Results show soil carbon increases in un-grazed and lightly grazed treatments, soil nitrogen levels increased in un-grazed and lightly grazed treatments and declined in continuously grazed treatments. The only change in microbial community composition occurs in continuously grazed treatments and only after prolonged drought. The authors’ conclude the relationship between grazing, soil carbon storage, and soil nitrogen are complex and change according to the spatial and temporal scale of observation. Likewise, soil microbial composition seems to be more influenced by abiotic factors, such as climate, than by biotic factors such as grazing; however, the complex array of feedbacks constraining microbial community configuration is difficult to understand in short time periods in small plots.
7. Grazing: A Natural Component of Grassland Ecozone Riparian Systems
LaForge, K. 2004. Agriculture and Agri-Food Canada, Prairie Farm Rehabilitation Administration document
The author concludes grazing ungulates are a natural feature of riparian grassland ecosystems. Unmanaged grazing can degrade riparian ecosystems, but properly managed grazing can mimic patterns of native grazing ungulates and improve riparian health and function. Good management requires developing site specific grazing plans.
8. A Framework to Predict the Effects of Livestock Grazing and Grazing Exclusion on Conservation Values in Natural Ecosystems in Australia
Lunt, I.D., Eldridge, D.J., Morgan, J.W., Witt, G.B. 2007. Australian Journal of Botany 54(4):401-415.
Australian grasslands are unique in that they evolved in absence of large grazing herbivores. Introduced livestock have severely damaged many Australian landscapes; however, livestock are still used in some regions to maintain ecological integrity. This paper constructs a framework to inform natural resource managers on when grazing might be beneficial or detrimental to any particular landscape. The framework suggests grazing exclusion for intact ecosystems with shallow soils. The framework also suggests grazing be employed on lands that require biomass control, where grazing can prevent invasion by undesirable species, and when grazing can enhance biodiversity.
9. Grass Versus Trees: Managing Riparian Areas to Benefit Streams of Central North America.
Lyons, J., Trimble, S.W., Paine, L.K. 2000. Journal of the American Water Resources Association 36(4):919-930.
Forestation is common conservation practice along riparian areas in agricultural lands in central North America. Trees and shrubs can provide benefits to streams, but this type of management removes agriculture land from production. This paper examines the potential benefits of grassy riparian buffer strips. The study concludes grassy riparian buffer strips might be more effective in reducing erosion and trapping sediments than wooded buffers. Maintenance of grassy riparian vegetation requires management such as mowing, haying, or grazing to promote dense turfs. The authors suggest grassy buffer strips have potential to restore degraded stream ecosystems while still producing agricultural products.
10. Influence of Intensive Rotational Grazing on Bank Erosion, Fish Habitat Quality, and Fish Communities in Southwestern Wisconsin Trout Streams.
Lyons, J., Weigel, B.M, Paine, L.K., Undersander, D.J. 2006. Journal of Soil and Water Conservation 55(3):271-276.
This paper examines the potential for rotational grazing to rehabilitate degraded stream banks in agricultural regions of Central, North America. This study compares stream banks managed by grassed buffer strips, rotational grazing, continuous grazing, and wooded stream banks for their ability to reduce erosion and enhance fish biotic integrity indexes. Results indicate grassed buffer strips and rotational grazing provide effective management strategies to rehabilitate stream banks, reduce sediment inputs, and enhance fish biotic integrity indices.
11. Pathways of Grazing Effects on Soil Organic Carbon and Nitrogen.
Pineiro, G., Paruelo, J.M., Oesterheld, O., Jobaggy, E.G. 2010. Rangeland Ecology and Management 63(1):109-119.
This paper examines the impacts of grazing on the ability of soil to sequester atmospheric CO2. Results indicate carbon sequestration is more complex than can be explained by any one general model. Carbon dioxide sequestration rates are influenced by many factors including the nitrogen cycle, precipitation patterns, and soil bulk densities. Still, the authors’ conclude, in most cases, well managed grazing can increase both pasture productivity and CO2 sequestration rates, especially in conjunction with management procedures that impose strong controls on nitrogen cycling.
12. Grazing Can Reduce the Environmental Impact of Dairy Production Systems.
Rotz, C.A., Soder, K.J., Skinner, R.H., Dell, C.J., Kleinman, P.J., Schmidt, J.P., Bryant, R.B. 2009. Forage and Grazinglands.
This study compares the environmental footprint of three different Pennsylvania dairy operations: 1) total confinement based production, 2) summer pasture – winter confinement production, and 3) summer pasture and winter forage production. Results indicate the summer pasture and winter forage production system had the lowest environmental impacts, reducing soil erosion by 87%, sediment bound and soluble phosphorus losses by 80%, and reducing carbon output by 80%. The authors conclude environmental benefits of grass-based dairy systems should be used to encourage expansion of pasture/forage dairy operations.