Abstract
This paper introduces a framework for extending global climate and socioeconomic scenarios in order to study agricultural nutrient pollution on an individual catchment scale. Our framework builds on and extends Representative Concentration Pathways (RCPs) and Shared Socioeconomic Pathways (SSPs) at the spatial and temporal scales that are relevant for the drivers of animal husbandry, manure recycling and the application of inorganic fertilisers in crop production. Our case study area is the Aura river catchment in South-West Finland, which discharges into the heavily eutrophic Baltic Sea. The Aura river catchment has intensive agriculture — both livestock and crop production. Locally adjusted and interpreted climate and socioeconomic scenarios were used as inputs to a field-level economic optimisation in order to study how farmers might react to the changing markets and climate conditions under different SSPs. The results on economically optimal fertilisation levels were then used as inputs to the spatially and temporally explicit nutrient loading model (VEMALA). Alternative manure recycling strategies that matched with SSP narratives were studied as means to reduce the phosphorus (P) overfertilisation in areas with high livestock density. According to our simulations, on average the P loads increased by 18% during 2071–2100 from the current level and the variation in P loads between scenarios was large (from −14% to +50%). By contrast, the nitrogen (N) loads had decreased on average by −9% (with variation from −20% to +3%) by the end of the current century. Phosphorus loading was most sensitive to manure recycling strategies and the speed of climate change. Nitrogen loading was less sensitive to changes in climate and socioeconomic drivers.
Highlights
There is a consensus across Baltic Sea countries to reduce nutrient loading in order to retain the good environmental state of the sea (HELCOM, 2007)
As an extension to the work of Booth et al (2016) and Olesen et al (2019), we focus more on the interactions between economic drivers within socioeconomic narratives and their implications for nutrient loading with fertiliser, crop yield and the scale of animal husbandry at the catchment scale
Agricultural total phosphorus (TP) and total nitrogen (TN) loading in the future climate will firstly depend on C-induced runoff changes, which vary from a relatively small decrease to a large increase, depending on the climate model and Representative Concentration Pathways (RCPs)
Summary
Precipitation is projected to increase in most climate scenarios, winter runoff is expected to increase and spring runoff will decrease in most of Finland (Veijalainen, 2012) Together these developments will lead to increasing nutrient leakage from forest and agricultural soils and the surfaces of built areas. We study an animal husbandry–dominated catchment because there is a high need and potential to reduce the nutrient surpluses caused by manure inputs into the Baltic Sea basin (Svanbäck et al, 2019) To this end, we extend the SSP narratives and their earlier extensions to the national level by downscaling the SSP narratives and climate scenarios to a catchment scale. The obtained optimal fertiliser input paths are used as inputs to a spatially and temporally explicit nutrient-loading VEMALA model (Huttunen et al, 2016), which simulates total phosphorus (TP) and total nitrogen (TN) future nutrient loading pathways in different scenarios
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