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Maximizing US nitrate removal through wetland protection and restoration

Abstract

Growing populations and agricultural intensification have led to raised riverine nitrogen (N) loads, widespread oxygen depletion in coastal zones (coastal hypoxia)1 and increases in the incidence of algal blooms.Although recent work has suggested that individual wetlands have the potential to improve water quality2,3,4,5,6,7,8,9, little is known about the current magnitude of wetland N removal at the landscape scale. Here we use National Wetland Inventory data and 5-kilometre grid-scale estimates of N inputs and outputs to demonstrate that current N removal by US wetlands (about 860 ± 160 kilotonnes of nitrogen per year) is limited by a spatial disconnect between high-density wetland areas and N hotspots. Our model simulations suggest that a spatially targeted increase in US wetland area by 10 per cent (5.1 million hectares) would double wetland N removal. This increase would provide an estimated 54 per cent decrease in N loading in nitrate-affected watersheds such as the Mississippi River Basin. The costs of this increase in area would be approximately 3.3 billion US dollars annually across the USA—nearly twice the cost of wetland restoration on non-agricultural, undeveloped land—but would provide approximately 40 times more N removal. These results suggest that water quality improvements, as well as other types of ecosystem services such as flood control and fish and wildlife habitat, should be considered when creating policy regarding wetland restoration and protection.

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Fig. 1: Our approach to estimating wetland N removal across the USA.
Fig. 2: Wetland densities, N surplus magnitudes and wetland N removal across the contiguous US.
Fig. 3: Spatial relationships between N source areas and existing wetlands.
Fig. 4: Estimated N mass removal and costs for the three wetland restoration scenarios.
Fig. 5: Wetland restoration simulation results for a 10% increase in wetland area.

Data availability

Nitrogen mass balance data were obtained from the TREND-nitrogen dataset, available through the PANGAEA Data Publisher (https://doi.org/10.1594/PANGAEA.917583). The National Wetlands Inventory dataset was retrieved from US-FWS (https://www.fws.gov/wetlands). The Watershed Boundary Data set used for HUC-8 boundaries was retrieved from the USGS website https://www.usgs.gov/core-science-systems/ngp/ngtoc/watershed-boundary-dataset. USGS water quality data were retrieved from Oelsner et al.54Source data are provided with this paper.

Code availability

The MATLAB software used for the present analysis is available from Mathworks (https://www.mathworks.com/); R (version 3.5.2) used for geospatial analysis is available from the R Core Team (https://www.r-project.org/). Codes for the estimation of current wetland N removal, wetland restoration scenarios and cost analysis are available at https://github.com/landscape-ecohydrology/optimizing_wetland_restoration_in_nature.

References

  1. 1.

    Díaz, R. J. & Rosenberg, R. Introduction to environmental and economic consequences of hypoxia. Int. J. Water Resour. Dev. 27, 71–82 (2011).

    Article  Google Scholar 

  2. 2.

    Van Meter, K. J., Basu, N. B. & Van Cappellen, P. Two centuries of nitrogen dynamics: legacy sources and sinks in the Mississippi and Susquehanna river basins. Global Biogeochem. Cy. 31, 2016GB005498 (2017).

    Google Scholar 

  3. 3.

    Cheng, F. Y. & Basu, N. B. Biogeochemical hotspots: role of small water bodies in landscape nutrient processing. Wat. Resour. Res. 53, 5038–5056 (2017).

    CAS  Article  ADS  Google Scholar 

  4. 4.

    Mitsch, W. J. et al. Reducing nitrogen loading to the Gulf of Mexico from the Mississippi River Basin: strategies to counter a persistent ecological problem. Bioscience 51, 373–388 (2001).

    Article  Google Scholar 

  5. 5.

    Mitsch, W. J. & Day, J. W. Restoration of wetlands in the Mississippi–Ohio–Missouri (MOM) River Basin: experience and needed research. Ecol. Eng. 26, 55–69 (2006).

    Article  Google Scholar 

  6. 6.

    Verhoeven, J. T. A., Arheimer, B., Yin, C. & Hefting, M. M. Regional and global concerns over wetlands and water quality. Trends Ecol. Evol. 21, 96–103 (2006).

    Article  Google Scholar 

  7. 7.

    Cohen, M. J. et al. Do geographically isolated wetlands influence landscape functions? Proc. Natl Acad. Sci. USA 113, 1978–1986 (2016).

    CAS  Article  ADS  Google Scholar 

  8. 8.

    Thorslund, J. et al. Wetlands as large-scale nature-based solutions: status and challenges for research, engineering and management. Ecol. Eng. 108, 489–497 (2017).

    Article  Google Scholar 

  9. 9.

    Fennessy, S. & Craft, C. Agricultural conservation practices increase wetland ecosystem services in the Glaciated Interior Plains. Ecol. Appl. 21, S49–S64 (2011).

    Article  Google Scholar 

  10. 10.

    Altieri, A. H. et al. Tropical dead zones and mass mortalities on coral reefs. Proc. Natl Acad. Sci. USA 114, 3660–3665 (2017).

    CAS  Article  Google Scholar 

  11. 11.

    Fennel, K. & Testa, J. M. Biogeochemical controls on coastal hypoxia. Annu. Rev. Mar. Sci. 11, 105–130 (2019).

    Article  ADS  Google Scholar 

  12. 12.

    Creed, I. F. et al. Enhancing protection for vulnerable waters. Nat. Geosci. 10, 809–815 (2017).

    CAS  Article  ADS  Google Scholar 

  13. 13.

    Golden, H. E. et al. Integrating geographically isolated wetlands into land management decisions. Front. Ecol. Environ. 15, 319–327 (2017).

    Article  Google Scholar 

  14. 14.

    Marton, J. M. et al. Geographically isolated wetlands are important biogeochemical reactors on the landscape. Bioscience 65, 408–418 (2015).

    Article  Google Scholar 

  15. 15.

    Hansen, L. et al. Targeting Investments to Cost Effectively Restore and Protect. Report No. 183 https://www.ers.usda.gov/webdocs/publications/45347/51895_err183.pdf?v=0 (United States Department of Agriculture, 2015).

  16. 16.

    Brinson, M. M. & Eckles, S. D. U. S. Department of Agriculture conservation program and practice effects on wetland ecosystem services: a synthesis. Ecol. Appl. 21, S116–S127 (2011).

    Article  Google Scholar 

  17. 17.

    Zedler, J. B. Wetlands at your service: reducing impacts of agriculture at the watershed scale. Front. Ecol. Environ. 1, 65–72 (2003).

    Article  Google Scholar 

  18. 18.

    Zimmerman, E. K., Tyndall, J. C. & Schulte, L. A. Using spatially targeted conservation to evaluate nitrogen reduction and economic opportunities for best management practice placement in agricultural landscapes. Environ. Manage. 64, 313–328 (2019).

    Article  ADS  Google Scholar 

  19. 19.

    Moreno-Mateos, D., Power, M. E., Comín, F. A. & Yockteng, R. Structural and functional loss in restored wetland ecosystems. PLoS Biol. 10, e1001247 (2012).

    CAS  Article  Google Scholar 

  20. 20.

    Golden, H. E. et al. Non-floodplain wetlands affect watershed nutrient dynamics. Crit. Rev. Environ. Sci. Technol. 53, 7203–7214 (2019).

    CAS  Article  ADS  Google Scholar 

  21. 21.

    Jordan, S. J., Stoffer, J. & Nestlerode, J. A. Wetlands as sinks for reactive nitrogen at continental and global scales: a meta-analysis. Ecosystems 14, 144–155 (2011).

    CAS  Article  Google Scholar 

  22. 22.

    Czuba, J. A., Hansen, A. T., Foufoula-Georgiou, E. & Finlay, J. C. Contextualizing wetlands within a river network to assess nitrate removal and inform watershed management. Wat. Resour. Res. 54, 1312–1337 (2018).

    CAS  Article  ADS  Google Scholar 

  23. 23.

    Hansen, A. T., Dolph, C. L., Foufoula-Georgiou, E. & Finlay, J. C. Contribution of wetlands to nitrate removal at the watershed scale. Nat. Geosci. (2018).

  24. 24.

    Czuba, J. A. & Foufoula-Georgiou, E. A network-based framework for identifying potential synchronizations and amplifications of sediment delivery in river basins. Wat. Resour. Res. 50, 3826–3851 (2014).

    Article  ADS  Google Scholar 

  25. 25.

    Van Cleemput, O., Boeckx, P., Lindgren, P.-E. & Tonderski, K. in Biology of the Nitrogen Cycle 359–367 (Elsevier, 2007).

  26. 26.

    Ferris, J. & Siikamäki, J. Conservation Reserve Program and Wetland Reserve Program: Primary Land Retirement Programs for Promoting Farmland Conservation https://media.rff.org/documents/RFF-BCK-ORRG_CRP_and_WRP.pdf (Resources for the Future, 2009).

  27. 27.

    Rabotyagov, S. S. et al. Cost-effective targeting of conservation investments to reduce the northern Gulf of Mexico hypoxic zone. Proc. Natl Acad. Sci. USA 111, 18530–18535 (2014).

    CAS  Article  ADS  Google Scholar 

  28. 28.

    Van Meter, K. J., Van Cappellen, P. & Basu, N. B. Legacy nitrogen may prevent achievement of water quality goals in the Gulf of Mexico. Science 360, 427–430 (2018).

    Article  ADS  Google Scholar 

  29. 29.

    Van Meter, K. J., Van Cappellen, P. & Basu, N. B. Response to Comment on “Legacy nitrogen may prevent achievement of water quality goals in the Gulf of Mexico”. Science 365, eaav3851 (2019).

    Article  Google Scholar 

  30. 30.

    Hayes, D. J., Kling, C. L. & Lawrence, J. D. Economic Evaluation of Governor Branstad’s Water Quality Initiative. Report No. 16-PB 19 https://governor.iowa.gov/sites/default/files/documents/ISU%20CARD%20Economic%20Evaluation.pdf (Center for Agricultural and Rural Development, 2016).

  31. 31.

    Jones, C. S., Nielsen, J. K., Schilling, K. E. & Weber, L. J. Iowa stream nitrate and the Gulf of Mexico. PLoS One 13, e0195930 (2018).

    Article  Google Scholar 

  32. 32.

    Dahl, T. E. Wetlands Losses in the United States, 1780’s to 1980’s. https://www.fws.gov/wetlands/documents/Wetlands-Losses-in-the-United-States-1780s-to-1980s.pdf (U.S. Department of the Interior, Fish and Wildlife Service, 1990).

  33. 33.

    Ward, A. S. New Clean Water Act rule leaves U.S. waters vulnerable. Eos https://eos.org/opinions/new-clean-water-act-rule-leaves-u-s-waters-vulnerable (2020).

  34. 34.

    Tomer, M. D. & Nelson, J. A. Measurements of landscape capacity for water detention and wetland restoration practices can inform watershed planning goals and implementation strategies. J. Soil Water Conserv. (2020).

  35. 35.

    Salo, T. & Turtola, E. Nitrogen balance as an indicator of nitrogen leaching in Finland. Agric. Ecosyst. Environ. 113, 98–107 (2006).

    CAS  Article  Google Scholar 

  36. 36.

    Bouwman, A. F., Van Drecht, G. & Van der Hoek, K. W. Global and regional surface nitrogen balances in intensive agricultural production systems for the period 1970-2030. Pedosphere 15, 137–155 (2005).

    Google Scholar 

  37. 37.

    Byrnes, D. K., Van Meter, K. J. & Basu, N. B. Trajectories nutrient dataset for nitrogen (TREND-nitrogen). PANGAEA https://doi.org/10.1594/PANGAEA.917583 (2020).

  38. 38.

    Byrnes, D. K., Van Meter, K. J. & Basu, N. B. Long-term shifts in U.S. nitrogen sources and sinks revealed by the new TREND-nitrogen dataset (1930–2017). Glob. Biogeochem. Cycles (2020).

  39. 39.

    USDA – National Agricultural Statistics Service. Census of Agriculture. www.nass.usda.gov/AgCensus (2017).

  40. 40.

    NADP Total Deposition Science Committee. NADP total deposition maps. National Atmospheric Deposition Program http://nadp.slh.wisc.edu/committees/tdep/tdepmaps/ (2018).

  41. 41.

    USDA ERS. Fertilizer use and price. https://www.ers.usda.gov/data-products/fertilizer-use-and-price.aspx (2018).

  42. 42.

    Brakebill, J. W. & Gronberg, J. M. County-Level Estimates of Nitrogen and Phosphorus from Commercial Fertilizer for the Conterminous United States, 1987–2012. https://www.sciencebase.gov/catalog/item/5851b2d1e4b0f99207c4f238 (USGS, 2019).

  43. 43.

    U.S. Fish and Wildlife Service. National Wetlands Inventory https://www.fws.gov/wetlands/Data/Data-Download.html (2019).

  44. 44.

    Land, M. et al. How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review. Environ. Evid. 5, 9 (2016).

    Article  Google Scholar 

  45. 45.

    Fisher, J. & Acreman, M. C. Wetland nutrient removal: a review of the evidence. Hydrol. Earth Syst. Sci. 8, 673–685 (2004).

    CAS  Article  ADS  Google Scholar 

  46. 46.

    Spieles, D. J. & Mitsch, W. J. The effects of season and hydrologic and chemical loading on nitrate retention in constructed wetlands: a comparison of low- and high-nutrient riverine systems. Ecol. Eng. 14, 77–91 (1999).

    Article  Google Scholar 

  47. 47.

    Barton, L., McLay, C. D. A., Schipper, L. A. & Smith, C. T. Annual denitrification rates in agricultural and forest soils: a review. Soil Res. 37, 1073–1094 (1999).

    Article  Google Scholar 

  48. 48.

    Wu, Q. & Lane, C. R. Delineating wetland catchments and modeling hydrologic connectivity using lidar data and aerial imagery. Hydrol. Earth Syst. Sci. 21, 3579–3595 (2017).

    Article  ADS  Google Scholar 

  49. 49.

    Mishra, S. Uncertainty and sensitivity analysis techniques for hydrologic modeling. J. Hydroinform. 11, 282–296 (2009).

    Article  Google Scholar 

  50. 50.

    Muleta, M. K. & Nicklow, J. W. Sensitivity and uncertainty analysis coupled with automatic calibration for a distributed watershed model. J. Hydrol. 306, 127–145 (2005).

    Article  ADS  Google Scholar 

  51. 51.

    Van Meter, K. J. & Basu, N. B. Signatures of human impact: size distributions and spatial organization of wetlands in the Prairie Pothole landscape. Ecol. Appl. 25, 451–465 (2015).

    Article  Google Scholar 

  52. 52.

    Theriot, J. M., Conkle, J. L., Reza Pezeshki, S., DeLaune, R. D. & White, J. R. Will hydrologic restoration of Mississippi River riparian wetlands improve their critical biogeochemical functions? Ecol. Eng. 60, 192–198 (2013).

    Article  Google Scholar 

  53. 53.

    Tyndall, J. & Bowman, T. Nutrient Reduction Strategy Decision Support Tool https://www.nrem.iastate.edu/bmpcosttools/ (Iowa State Univ., 2016).

  54. 54.

    Oelsner, G. P. et al. Water-Quality Trends in the Nation’s Rivers and Streams, 1972–2012—Data Preparation, Statistical Methods, and Trend Results. Report No. 2017-5006 https://pubs.er.usgs.gov/publication/sir20175006 (USGS, 2017).

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Acknowledgements

The present work was financially supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) grant (reference number 386129293) for F.Y.C. and N.B.B., an NSERC graduate scholarship for F.Y.C., an NSERC Discovery Grant and an Ontario Early Researcher Award for N.B.B. and D.K.B., and by startup funds from the University of Illinois at Chicago for K.J.V.M. Additional funding support was received through the Global Water Futures project Lake Futures for N.B.B.

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Authors

Contributions

N.B.B., K.J.V.M. and F.Y.C. conceived the study. N.B.B., F.Y.C. and K.J.V.M. developed the wetland N removal models. F.Y.C. ran simulations for current wetland N removal, and K.J.V.M. carried out the wetland restoration simulations and cost analysis. D.K.B., K.J.V.M. and N.B.B. provided N input data for the model simulations. K.J.V.M. wrote the paper with direct contributions from N.B.B., F.Y.C. and D.K.B.

Corresponding author

Correspondence to N. B. Basu.

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The authors declare no competing interests.

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Peer review information Nature thanks Jacques Finlay, Patrick Inglett, John Tyndall and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 Nitrogen surplus distributions across US hydrologic regions.

a, Histograms of N surplus by hydrologic region. The counts in the histograms refer to individual HUC-8 watersheds within the hydrologic regions. b, Map of hydrologic regions defined by the USGS. Boundaries of the Mississippi River Basin are drawn in yellow.

Extended Data Fig. 2 Modelled N removal by hydrologic region.

The counts in the histograms refer to individual HUC-8 watersheds within the corresponding hydrologic regions. See Extended Data Fig. 1b for region locations.

Extended Data Fig. 3 Analysis of empirical data used by Cheng &Basu3 to develop the kτ relationship used in our study.

a, N removed at the individual wetland scale. Data were obtained from a global meta-analysis of 178 wetlands. b, N removal efficiency, ρ, calculated as the ratio between N removal and N inputs to the wetland. c, N removal-rate constant, k, estimated as a function of ρ and empirically based estimates of wetland residence times, τ, assuming that N removal within the wetland follows first-order kinetics. d, A strong inverse relationship was found between k and wetland residence time τ. This relationship between size and N removal-rate constants allows us, in this work, to more accurately upscale to the continental US scale than has previously been achieved.

Extended Data Fig. 4 Costs of wetland restoration.

a, b, Estimated costs for restoration of a 1-ha wetland in 48 states across the contiguous US on cropland (a) and pastureland (b). Whereas construction and maintenance costs are considered to be constant across states, land rental costs vary by state and by land use. Costs are annualized over a 50-year management horizon.

Extended Data Table 1 N surplus and wetland N removal magnitudes for a subset of nitrate-affected watersheds
Extended Data Table 2 Ranges of parameters used in the Monte Carlo simulations of wetland N removal

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Cheng, F.Y., Van Meter, K.J., Byrnes, D.K. et al. Maximizing US nitrate removal through wetland protection and restoration. Nature 588, 625–630 (2020). https://doi.org/10.1038/s41586-020-03042-5

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