Catchment-Scale Analysis Reveals High Cost-Effectiveness of Wetland Buffer Zones as a Remedy to Non-Point Nutrient Pollution in North-Eastern Poland

Ewa Jabłońska,Dominik Zak,Carl C. Hoffmann,Marta Wiśniewska,Michael Trepel,Paweł Marcinkowski,Søren E. Larsen,Mateusz Grygoruk,Craig R. Walton,Wiktor Kotowski

doi:10.3390/w12030629

Abstract

Large-scale re-establishment of wetland buffer zones (WBZ) along rivers is regarded as an effective measure in order to reduce non-point source nitrogen (N) and phosphorus (P) pollution in agricultural catchments. We estimated efficiency and costs of a hypothetical establishment of WBZs along all watercourses in an agricultural landscape of the lower Narew River catchment (north-eastern Poland, 16,444 km2, amounting to 5% of Poland) by upscaling results obtained in five sub-catchments (1087 km2). Two scenarios were analysed, with either rewetting selected wetland polygons that collect water from larger areas (polygonal WBZs) or reshaping and rewetting banks of rivers (linear WBZs), both considered in all ecologically suitable locations along rivers. Cost calculation included engineering works necessary in order to establish WBZs, costs of land purchase where relevant, and compensation costs of income forgone to farmers (needed only for polygonal WBZs). Polygonal WBZs were estimated in order to remove 11%–30% N and 14%–42% P load from the catchment, whereas linear WBZs were even higher with 33%–82% N and 41%–87% P. Upscaled costs of WBZ establishment for the study area were found to be 8.9 M EUR plus 26.4 M EUR per year (polygonal WBZ scenario) or 170.8 M EUR (linear WBZ scenario). The latter value compares to costs of building about 20 km of an express road. Implementation of buffer zones on a larger scale is thus a question of setting policy priorities rather than financial impossibility.

Highlights

Human impact has significantly altered every major biogeochemical cycle [1]
In this paper we focus on nitrogen (N) and phosphorus (P) as main triggers of accelerating eutrophication of water ecosystems
We modelled environmental gains arising from catchment-wide implementation of wetland buffer zones (WBZ) and calculated costs and benefits of their creation in all ecologically suitable locations

Summary

Introduction

In this paper we focus on nitrogen (N) and phosphorus (P) as main triggers of accelerating eutrophication of water ecosystems. The disruption of their global cycles was considered among crossed planetary boundaries [2] as the second most serious global problem after the loss of biosphere integrity due to species extinction. After Haber’s discovery [3], the use of nitrogen fertilizers in agriculture increased worldwide from nearly zero to 100 Tg year−1 during the past century. The ability of streams to remove N from the biogeochemical cycle has been hindered due river training and drainage of riparian wetlands, adding another factor to the deterioration of quality of surface waters. The necessity of finding a systemic solution for this problem is acknowledged by both researchers and legislators

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Conclusion