http://www.diva-portal.org This is the published version of a paper published in Journal of Environmental Management. Citation for the original published paper (version of record): Lind, L., Hasselquist, E M., Laudon, H. (2019) Towards ecologically functional riparian zones: A meta-analysis to develop guidelines for protecting ecosystem functions and biodiversity in agricultural landscapes Journal of Environmental Management, 249: 1-8 https://doi.org/10.1016/j.jenvman.2019.109391 Access to the published version may require subscription. N.B. When citing this work, cite the original published paper. Permanent link to this version: http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-75700 Journal of Environmental Management 249 (2019) 109391 Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Review Towards ecologically functional riparian zones: A meta-analysis to develop guidelines for protecting ecosystem functions and biodiversity in T agricultural landscapes ⁎ Lovisa Linda,b, , Eliza Maher Hasselquista, Hjalmar Laudona a Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 901 83, Umeå, Sweden b Department of Environmental and Life Sciences, Karlstad University, 656 37, Karlstad, Sweden ARTICLE INFO ABSTRACT Keywords: Riparian zones contribute with biodiversity and ecosystem functions of fundamental importance for regulating Agricultural flow and nutrient transport in waterways. However, agricultural land-use and physical changes made to improve Buffer zone crop productivity and yield have resulted in modified hydrology and displaced natural vegetation. The mod- Ecological functional riparian zones ification to the hydrology and natural vegetation have affected the biodiversity and many ecosystem functions Riparian zone provided by riparian zones. Here we review the literature to provide state-of-the-art recommendations for ri- Vegetation parian zones in agricultural landscapes. We analysed all available publications since 1984 that have quantified Water services provided by riparian zones and use this information to recommend minimum buffer widths. We also analysed publications that gave buffer width recommendations to sustain different groups of organisms. We found that drainage size matters for nutrient and sediment removal, but also that a 3 m wide buffer zone acts as a basic nutrient filter. However, to maintain a high floral diversity, a 24 m buffer zone is required, while a 144 m buffer is needed to preserve bird diversity. Based on the analysis, we developed the concept of “Ecologically Functional Riparian Zones” (ERZ) and provide a step-by-step framework that managers can use to balance agricultural needs and environmental protection of waterways from negative impacts. By applying ERZ in al- ready existing agricultural areas, we can better meet small targets and move towards the long-term goal of achieving a more functional land management and better environmental status of waterways. 1. Introduction (Jakobsson, 2013). Alterations of the landscape hydrology have led to changes in the natural water and nutrient balance that has contributed The riparian zone forms a natural buffer between the surrounding to loss of important riparian habitat and downstream eutrophication land and waterways, and thus, the protection and management of near (Kiffney et al., 2003; Lam et al., 2011). stream areas have important implications for water quality and biodi- Agriculture is one of the largest sources of nitrogen (N) and phos- versity (Renouf and Harding, 2015). Riparian zones are the interface phorus (P) to rivers and lakes (Carpenter et al., 1998; Hanifzadeh et al., between the aquatic and the terrestrial ecosystems that connect and 2017), and it only takes a few percent cover of agricultural land in an help regulate the ecological functions of both systems (Gregory et al., otherwise forested landscape to increase the nutrient leakage 1991; Naiman and Décamps, 1997). Since humans started intensive (Sponseller et al., 2014). However, the loss of nutrients is also corre- farming, society has made large-scale changes to the hydrology of lated with variations in discharge (Mander et al., 2000). Sufficient streams and rivers to create conditions for cultivation, often at the ex- drainage is important to sustain high productivity in agricultural land, pense of both riparian zones and their downstream waterbodies. Wet- and tile drainage (underground pipes) is still the most common method lands have been drained, lakes have been lowered and rivers straigh- of achieving this (Gökkaya et al., 2017). Through the underground tened with the aim of increasing the agricultural land available and its pipes, water is transported from the soil profile to main conduits and efficiency. For example, in Sweden alone, a total of 600 000 ha of further on to wells, streams or open ditches. The pipes can also be in- marshes and bogs have been drained and, 2500 lakes have been low- stalled in systematic networks, i.e. tile drainage systems. A study of the ered, of which 25% were completely drained, for agricultural purposes Shatto Watershed district in Indiana, USA, showed that 79% of the ⁎ Corresponding author. Department of Environmental and Life Sciences, Karlstad University, Karlstad,656 37, Sweden. E-mail address: [email protected] (L. Lind). https://doi.org/10.1016/j.jenvman.2019.109391 Received 28 January 2019; Received in revised form 24 July 2019; Accepted 10 August 2019 Available online 21 August 2019 0301-4797/ © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). L. Lind, et al. Journal of Environmental Management 249 (2019) 109391 agricultural land in the district was tile drained (Gökkaya et al., 2017). specific decisions regarding the function and design of riparian zones in This practice has comes at a cost to the environment as tile drainage agricultural landscapes, we provide a framework for working towards systems reduce the retention time of water in the soil, thereby creating achieving these goals by implementing small steps on the way to ERZ. a shortcut for nutrients into streams and rivers, which also affects the Specifically, we asked the following questions: 1) Is there an optimal quality of drinking water resources (Tiemeyer et al., 2006; Hanifzadeh width for riparian buffer zones in agricultural landscapes that achieves et al., 2017). Grazing in the riparian zone can also lead to lower water different types of ecosystem functions, such as filtering nutrients and quality, soil erosion, unstable soils, and drier, warmer conditions in the sediments, shading to buffer water temperature, organic material, in- riparian zone (Hughes et al., 2016; Belsky et al., 1999). One of the stream wood, and biodiversity? (2) When buffer zones cannot be wide transport routes of pollutants to water bodies is through surface runoff. enough due to landscape constraints inherent to cultivated areas, are Runoff is usually limited to specific locations (e.g. erosion prone soils, there ways we can increase the efficiency of the buffer? (3) Does the tractor tracks, and areas around the drainage wells) and to storm events ability of riparian zones to reduce different types of negative impacts on (Frey et al., 2009). Soil properties also influence the risk of overland water quality depend on stream size, soil type, vegetation cover, or flow and stable clay soils have higher risk of surface runoff than slope of the near stream area? Moreover, we suggest applying the new structurally weak and silty soils (Nolan et al., 2008). Areas with tile concept of ERZ in the agricultural landscape and suggest ways to im- drainage systems, a high groundwater level, and/or dense soils with prove the quality of the riparian zone to benefit various ecosystem high clay content therefore offers fast transport routes for pollutants functions and biodiversity goals in a ‘step-by-step ERZ framework’. For into neighboring waters (Lewan et al., 2009). each step, new functions of the riparian zone are introduced as the Both tile drainage and drainage ditches reduce the retention time of width increases. water in the soil, but it is still possible to manage the riparian zones to achieve some level of riparian protection. In fact, this is required ac- cording to a number of local, national and international agreements. 2. Methods Preventing further eutrophication and degradation of marine and freshwater ecosystems is included in, for example, the Baltic Action To answer if there are optimal widths to achieve different ecosystem Plan 8 (Ejhed et al., 2014), the EU Water Framework Directive functions or biodiversity goals, we first analysed results and re- (European Commission, 2000) and the Clean Water Act (33 U.S.C. commendations in 52 published peer-reviewed studies, from years 1984 §1251 et seq. (1972)). Few countries have national regulations of buffer and onwards (first year of study we encountered that provide sufficient widths, for example Germany and Switzerland (5 m wide), but most are information) (Appendix A1). Secondly, we reviewed the literature to still lacking such regulations and therefore provide little practical gui- outline the specific functions and characteristics that need to be con- dance that can force practitioners to implement riparian buffers. sidered when designing effective riparian buffers. The ecosystem Buffer zones or riparian zones are commonly thought to be effective functions or biodiversity