‘Agricultural Modifications of Hydrological Flows Create Ecological Surprises'

Stockholm Resilience Centre and Stockholm Environment Institute, Stockholm University, Stockholm, Sweden.
Trends in Ecology & Evolution (Impact Factor: 16.2). 05/2008; 23(4):211-9. DOI: 10.1016/j.tree.2007.11.011
Source: PubMed


Agricultural expansion and intensification have altered the quantity and quality of global water flows. Research suggests that these changes have increased the risk of catastrophic ecosystem regime shifts. We identify and review evidence for agriculture-related regime shifts in three parts of the hydrological cycle: interactions between agriculture and aquatic systems, agriculture and soil, and agriculture and the atmosphere. We describe the processes that shape these regime shifts and the scales at which they operate. As global demands for agriculture and water continue to grow, it is increasingly urgent for ecologists to develop new ways of anticipating, analyzing and managing nonlinear changes across scales in human-dominated landscapes.

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    • "There is a variety of different impacts on agriculture such as decrease of crop yields (Potop et al., 2010) or higher demands on irrigation and on stream ecosystems such as temporal loss of habitat for aquatic organisms or loss of stream connectivity (Lake, 2003). Moreover, the needs of sustainable stream ecosystem management can be opposite to human needs related mainly to agriculture and water supply (Baron et al., 2002; Gordon et al., 2008). It is assumed that some impacts of these changes can be partly mitigated by increasing the landscape retention capacity. "
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    ABSTRACT: The risk of increasing frequency and duration of dry periods has become much more discussed topic with respect to expected climate change. This can result in water scarcity for different purposes. Besides others, agriculture and river ecosystems can be mentioned as those which can suffer from droughts. The retention of the landscape is therefore still more accented. Increase of landscape retention capacity is considered as a good way to keep water in the landscape which can be then available during dry periods. Despite the most retention capacity consists in the soil, the volume of small water reservoirs must be considered as important in conditions of the Czech Republic. This results in increased demand for building new small water reservoirs spread in the landscape. However, there is a lack of suitable profiles for that due to relatively high population density in the Czech Republic. The restoration of extinct ponds is considered therefore as a good option for this purpose. The paper presents the results of GIS analysis of the volume of water which would be available in case of the restoration of extinct ponds in the catchment of the river Blanice (543 km2). For this purpose, detail elevation data were used to avoid unacceptable error in volume estimates due to the sizes of considered areas. The results of analyses show that there is considerable retention volume available which could be used either to improve hydrologic conditions in stream network or for agricultural use consisting mainly in irrigations. Additionally, the results were compared to discharge data for three profiles on main major stream channels. In general, the results show how the building of new small water reservoirs can be used to mitigate droughts.
    12/2015; 4. DOI:10.1016/j.aaspro.2015.03.010
    • "The intensification of agriculture during the last century has resulted in an increased application of nitrogen fertilizers to optimize yield (Gordon et al. 2008; Gruber and Galloway 2008). As nitrate (NO 3 -N) is highly soluble and mobile, excess NO 3 -N may be released to groundwater and surface waters , reducing water quality there (Ciarlo et al. 2007; Kröger et al. 2007; Gordon et al. 2008; Greenan et al. 2009; Seitzinger et al. 2010; Chintala et al. 2013). Denitrifying bioreactors within subsurface water pathways have proven to be effective tools for the mitigation of NO 3 -N loads in impacted groundwater or drainage water (Schipper et al. 2010a; Christianson et al. 2012b). "
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    ABSTRACT: A laboratory column experiment was conducted to test the efficiency of denitrifying bioreactors for the nitrate (NO3-N) removal in drainage waters at different flow rates and after desiccation. In addition, we investigated detrimental side effects in terms of the release of nitrite (NO2-N), ammonium (NH4-N), phosphate (PO4-P), dissolved organic carbon (DOC), methane (CH4), and dinitrogen oxide (N2O). The NO3-N removal efficiency decreased with increasing NO3-N concentrations, increasing flow rates, and after desiccation. Bioreactors with purely organic fillings showed higher NO3-N removal rates (42.6-55.7 g NO3-N m(-3) day(-1)) than those with organic and inorganic fillings (6.5-21.4 g NO3-N m(-3) day(-1)). The release of NO2-N and DOC was considerable and resulted in concentrations of up to 800 μg NO2-N L(-1)and 25 mg DOC L(-1) in the effluent water. N2O concentrations increased by 4.0 to 15.3 μg N2O-N L(-1) between the influent and the effluent, while CH4 production rates were low. Our study confirms the high potential of denitrifying bioreactors to mitigate NO3-N pollution in drainage waters, but highlights also the potential risks for the environment.
    Environmental Science and Pollution Research 05/2015; 22(17). DOI:10.1007/s11356-015-4634-0 · 2.83 Impact Factor
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    • "Synonymous with irreversible change. Multiple or alternative stable states Ecosystem states before and after a tipping point, often held to be maintained by feedback mechanisms (Scheffer et al., 1993; Gordon et al., 2008). Regime shift The process whereby an ecosystem changes from one alternative stable state to another. "
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    ABSTRACT: The concepts of ecosystem regime shifts, thresholds and alternative or multiple stable states are used extensively in the ecological and environmental management literature. When applied to aquatic ecosystems, these terms are used inconsistently reflecting differing levels of supporting evidence among ecosystem types. Although many aquatic ecosystems around the world have become degraded, the magnitude and causes of changes, relative to the range of historical variability, are poorly known. A working group supported by the Australian Centre for Ecological Analysis and Synthesis (ACEAS) reviewed 135 papers on freshwater ecosystems to assess the evidence for pressure-induced non-linear changes in freshwater ecosystems; these papers used terms indicating sudden and non-linear change in their titles and key words, and so was a positively biased sample. We scrutinized papers for study context and methods, ecosystem characteristics and focus, types of pressures and ecological responses considered, and the type of change reported (i.e., gradual, non-linear, hysteretic or irreversible change). There was little empirical evidence for regime shifts and changes between multiple or alternative stable states in these studies although some shifts between turbid phytoplankton-dominated states and clear-water, macrophyte-dominated states were reported in shallow lakes in temperate climates. We found limited understanding of the subtleties of the relevant theoretical concepts and encountered few mechanistic studies that investigated or identified cause-and-effect relationships between ecological responses and nominal pressures. Our results mirror those of reviews for estuarine, nearshore and marine aquatic ecosystems, demonstrating that although the concepts of regime shifts and alternative stable states have become prominent in the scientific and management literature, their empirical underpinning is weak outside of a specific environmental setting. The application of these concepts in future research and management applications should include evidence on the mechanistic links between pressures and consequent ecological change. Explicit consideration should also be given to whether observed temporal dynamics represent variation along a continuum rather than categorically different states. Copyright © 2015 Elsevier B.V. All rights reserved.
    Science of The Total Environment 02/2015; 534. DOI:10.1016/j.scitotenv.2015.02.045 · 4.10 Impact Factor
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