Export Coefficient Modelling of Nutrient Neutrality to Protect Aquatic Habitats in the River Wensum Catchment, UK

The pressure of nutrient pollution derived from wastewater treatment works and agricultural runoff is a reason for the decline in the ecological health of aquatic habitats. Projected residential development in catchments creates further nutrient loading that can be offset by nutrient management solutions that maintain ‘nutrient neutrality’ either onsite or elsewhere within the same catchment. This study developed an export coefficient model in conjunction with detailed farm business data to explore a nature-based solution to nutrient neutrality involving seven scenarios of crop conversion to mixed woodland or grazing grass in an area of intensive arable cultivation in the groundwater-fed Blackwater sub-catchment of the River Wensum, UK. When compared with the monitored riverine export of nutrients, the calculated nitrogen (N) and phosphorus (P) inputs under current land use showed that subsurface denitrification is removing 48–78% of the leached N and that P is accumulating in the field soils. The addition of 235 residential homes planned for 2018–2038 in the Blackwater will generate an additional nutrient load of 190 kg N a−1 and 4.9 kg P a−1. In six of the seven scenarios, the modelled fractions of crop conversion (0.02–0.21) resulted in the required reduction in P loading and more than sufficient reduction in N loading (196–1874 kg a−1 for mixed woodland and 287–2103 kg a−1 for grazing grass), with the additional reduction in N load above the requirement for nutrient neutrality potentially contributing to further improvement in water quality. The cost of land conversion is modelled in terms of crop gross margins and nutrient credits generated in the form of 0.1 kg units of N or P. For the range of scenarios considered, the annual cost per credit ranged from GBP 0.78–11.50 for N for mixed woodland (GBP 0.74–7.85 for N for grazing grass) and from GBP 160–782 for P for both scenarios. It is concluded that crop conversion is a viable option to achieve nutrient neutrality in arable catchments in eastern England when considered together with other nutrient management solutions

Biophysical suitability, economic pressure and land-cover change: a global probabilistic approach and insights for REDD+

There has been a concerted effort by the international scientific community to understand the multiple causes and patterns of land-cover change to support sustainable land management. Here, we examined biophysical suitability, and a novel integrated index of “Economic Pressure on Land” (EPL) to explain land cover in the year 2000, and estimated the likelihood of future land-cover change through 2050, including protected area effectiveness. Biophysical suitability and EPL explained almost half of the global pattern of land cover (R 2 = 0.45), increasing to almost two-thirds in areas where a long-term equilibrium is likely to have been reached (e.g. R 2 = 0.64 in Europe). We identify a high likelihood of future land-cover change in vast areas with relatively lower current and past deforestation (e.g. the Congo Basin). Further, we simulated emissions arising from a “business as usual” and two reducing emissions from deforestation and forest degradation (REDD) scenarios by incorporating data on biomass carbon. As our model incorporates all biome types, it highlights a crucial aspect of the ongoing REDD + debate: if restricted to forests, “cross-biome leakage” would severely reduce REDD + effectiveness for climate change mitigation. If forests were protected from deforestation yet without measures to tackle the drivers of land-cover change, REDD + would only reduce 30 % of total emissions from land-cover change. Fifty-five percent of emissions reductions from forests would be compensated by increased emissions in other biomes. These results suggest that, although REDD + remains a very promising mitigation tool, implementation of complementary measures to reduce land demand is necessary to prevent this leakage

Developing scenarios and visualisations to illustrate potential policy and climatic influences on future agricultural landscapes

The future evolution of our agricultural landscapes and countryside is the subject of considerable debate and policy discussion, alongside which is an increasing emphasis on the inclusion of public consultation and participation within planning and decision making systems. However, communicating different proposed policy options in a manner that facilitates informed decisions from stakeholders can be far from straightforward. This is particularly true with more abstract and uncertain issues such as potential impacts of climate change. Scenarios depicting the possible outcomes of policy options provide a useful tool to evaluate the potential consequences of choices. This paper documents an approach to constructing scenarios that can incorporate potential climate change impacts, and reflect the uncertainty in climate change projections due to different environmental policies. It describes the construction of scenarios using the Humberhead Levels in the UK as a case study and portrays the scenarios using two forms of visualisation—digital photo-montage and a real-time landscape model. The method is equally applicable to other study areas across Europe where suitable data are available. Preliminary reactions from an audience to scenario images are discussed, as well as the technical and practical challenges of using visualisation techniques to support decision making

Potential impacts on ecosystem services of land use transitions to second-generation bioenergy crops in GB.

We present the first assessment of the impact of land use change (LUC) to second-generation (2G) bioenergy crops on ecosystem services (ES) resolved spatially for Great Britain (GB). A systematic approach was used to assess available evidence on the impacts of LUC from arable, semi-improved grassland or woodland/forest, to 2G bioenergy crops, for which a quantitative 'threat matrix' was developed. The threat matrix was used to estimate potential impacts of transitions to either Miscanthus, short-rotation coppice (SRC, willow and poplar) or short-rotation forestry (SRF). The ES effects were found to be largely dependent on previous land uses rather than the choice of 2G crop when assessing the technical potential of available biomass with a transition from arable crops resulting in the most positive effect on ES. Combining these data with constraint masks and available land for SRC and Miscanthus (SRF omitted from this stage due to lack of data), south-west and north-west England were identified as areas where Miscanthus and SRC could be grown, respectively, with favourable combinations of economic viability, carbon sequestration, high yield and positive ES benefits. This study also suggests that not all prospective planting of Miscanthus and SRC can be allocated to agricultural land class (ALC) ALC 3 and ALC 4 and suitable areas of ALC 5 are only minimally available. Beneficial impacts were found on 146 583 and 71 890 ha when planting Miscanthus or SRC, respectively, under baseline planting conditions rising to 293 247 and 91 318 ha, respectively, under 2020 planting scenarios. The results provide an insight into the interplay between land availability, original land uses, bioenergy crop type and yield in determining overall positive or negative impacts of bioenergy cropping on ecosystems services and go some way towards developing a framework for quantifying wider ES impacts of this important LUC

Conservation tillage and soil health: lessons from a 5-year UK farm trial (2013-2018)

In 2010, the UK government launched the Demonstration Test Catchments (DTC) platform to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology whilst maintaining food production capacity. In this paper, we compare the impacts on soil health of two types of conservation tillage (direct drill and shallow non-inversion) against conventional mouldboard ploughing after five years (2013–2018) of adoption within the River Wensum DTC. Across the 143 ha conservation tillage trial area, temporal changes in the physical, chemical and biological condition of the soils were examined through the analysis of 324 soil samples, whilst the impacts on soil water chemistry were assessed through the analysis of 1176 samples of subsurface field drainage. Riverine water pollution was also explored through high-resolution (30 min) hydrochemistry measurements generated by an automated, in-situ bankside monitoring station located 650 m downstream of the trial area. Results revealed that conservation tillage did not significantly alter the soil physical, chemical or biological condition relative to conventional ploughing during the first five years. In addition, conservation tillage did not reduce nutrient leaching losses into field drainage and did not significantly impact upon river water quality, despite the trial area covering 20% of the catchment. Economically, however, conservation tillage yielded net profit margins 13% higher than conventional ploughing after five years of practice due to a combination of operational efficiency savings and improved yields. Overall, the results of this study demonstrate that conservation tillage alone is ineffective at improving the short-term environmental sustainability of farming practices in this lowland intensive arable setting and indicates that a broader, integrated approach to conservation agriculture is required incorporating aspects of cover cropping, crop rotations and precision farming techniques. The improvements in farm business performance do, however, demonstrate land managers can make important financial gains by converting to a conservation tillage system

The potential for bioenergy crops to contribute to meeting GB heat and electricity demands

The paper presents a model system, which consists of a partial equilibrium model and process-based terrestrial biogeochemistry models, to determine the optimal distributions of both Miscanthus (Miscanthus × giganteus) and short rotation coppice willow (SRC) (Salix. viminalis L. x S. viminalis var Joruun) in Great Britain (GB), as well as their potential contribution to meet heat and electricity demand in GB. Results show that the potential contribution of Miscanthus and SRC to heat and electricity demand is significant. Without considering farm-scale economic constraints, Miscanthus and SRC could generate, in an economically competitive way compared with other energy generation costs, 224 800 GWh yr?1 heat and 112 500 GWh yr?1 electricity, with 8 Mha of available land under Miscanthus and SRC, accounting for 66% of total heat demand and 62% of total electricity demand respectively. Given the pattern of heat and electricity demand, and the relative yields of Miscanthus and SRC in different parts of GB, Miscanthus is mainly favoured in the Midlands and areas in the South of GB, whereas SRC is favoured in Scotland, the Midlands and areas in the South of G