| 1. |
- Braakhekke, Maarten C., et al.
(författare)
-
Nitrogen leaching from natural ecosystems under global change : A modelling study
- 2017
-
Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 8:4, s. 1121-1139
-
Tidskriftsartikel (refereegranskat)abstract
- To study global nitrogen (N) leaching from natural ecosystems under changing N deposition, climate, and atmospheric CO2, we performed a factorial model experiment for the period 1901-2006 with the N-enabled global terrestrial ecosystem model LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator). In eight global simulations, we used either the true transient time series of N deposition, climate, and atmospheric CO2 as input or kept combinations of these drivers constant at initial values. The results show that N deposition is globally the strongest driver of simulated N leaching, individually causing an increase of 88% by 1997-2006 relative to pre-industrial conditions. Climate change led globally to a 31%increase in N leaching, but the size and direction of change varied among global regions: Leaching generally increased in regions with high soil organic carbon storage and high initial N status, and decreased in regions with a positive trend in vegetation productivity or decreasing precipitation. Rising atmospheric CO2 generally caused decreased N leaching (33% globally), with strongest effects in regions with high productivity and N availability. All drivers combined resulted in a rise of N leaching by 73% with strongest increases in Europe, eastern North America and South-East Asia, where N deposition rates are highest. Decreases in N leaching were predicted for the Amazon and northern India. We further found that N loss by fire regionally is a large term in the N budget, associated with lower N leaching, particularly in semi-arid biomes. Predicted global N leaching from natural lands rose from 13.6 TgNyr-1 in 1901-1911 to 18.5 TgNyr-1 in 1997-2006, accounting for reductions of natural land cover. Ecosystem N status (quantified as the reduction of vegetation productivity due to N limitation) shows a similar positive temporal trend but large spatial variability. Interestingly, this variability is more strongly related to vegetation type than N input. Similarly, the relationship between N status and (relative) N leaching is highly variable due to confounding factors such as soil water fluxes, fire occurrence, and growing season length. Nevertheless, our results suggest that regions with very high N deposition rates are approaching a state of N saturation.
|
|
| 2. |
- Harrison, John A., et al.
(författare)
-
Global importance, patterns, and controls of dissolved silica retention in lakes and reservoirs
- 2012
-
Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 26:2, s. n/a-n/a
-
Tidskriftsartikel (refereegranskat)abstract
- Lentic water bodies (lakes and reservoirs) offer favorable conditions for silica (SiO2) burial in sediments. Recent global estimates suggest that (1) lentic SiO2 trapping is a globally important SiO2 flux, and (2) through reservoir construction, humans have dramatically altered river dissolved SiO2 (DSi) transport and coastal DSi delivery. However, regional to global scale patterns and controls of DSi removal in lentic systems are poorly constrained. Here we use 27 published lake and reservoir DSi budgets to develop insights into patterns and controls of lentic DSi retention and to develop a new, spatially explicit, global model of lentic DSi removal called SiRReLa (Silica Retention in Reservoirs and Lakes). In our analysis, lentic DSi removal (kg SiO2 yr−1) was significantly and positively related to DSi loading (P < 0.0001; r2 = 0.98), and DSi removal efficiency was significantly and positively related to water residence time (P < 0.0001; r2 = 0.68). In addition, DSi settling rates were, on average, 6.5-fold higher in eutrophic systems than in non-eutrophic systems (median settling velocities: 11.1 and 1.7 m yr−1 for eutrophic and non-eutrophic systems, respectively; P < 0.01). SiRReLa, which incorporates these insights, performed quite well in predicting both total DSi removal (kg SiO2 yr−1; Nash Sutcliffe Efficiency (N.S.E) = 0.88) and DSi removal efficiency (% Si removed; N.S.E. = 0.75), with no detectable bias in the model. Global application of SiRReLa confirms that lentic systems are important sinks for DSi, removing 89.1 Tg DSi yr−1 from watersheds globally, roughly 19–38% of all DSi inputs to surface waters. Small lakes and reservoirs (<50 km2) were critical in the analysis, retaining 81% (72 Tg DSi yr−1) of the globally retained total. Furthermore, although reservoirs occupy just 6% of the global lentic surface area, they retained approximately 35% of the total DSi removed by lentic systems. Regional hot spots for lentic DSi removal were identified and imply that lentic systems can remove the vast majority of DSi across a large fraction of Earth's land surface. Finally, a sensitivity analysis indicates that future improvements in DSi trapping and transport models should focus on improving estimates of DSi input to surface waters.
|
|
| 3. |
- Harrison, John A., et al.
(författare)
-
Modeling phosphorus in rivers at the global scale: recent successes, remaining challenges, and near-term opportunities
- 2019
-
Ingår i: Current Opinion in Environmental Sustainability. - : ELSEVIER SCI LTD. - 1877-3435 .- 1877-3443. ; 36, s. 68-77
-
Forskningsöversikt (refereegranskat)abstract
- Understanding and mitigating the effects of phosphorus (P) overenrichment of waters globally, including the evaluation of the global Sustainability Development Goals, requires the use of global models. Such models quantitatively link land use, global population growth and climate to aquatic nutrient loading and biogeochemical cycling. Here we describe, compare, and contrast the existing global models capable of predicting P transport by rivers at a global scale. We highlight important insights gained from the development and application of these models, and identify important near-term opportunities for model improvements as well as additional insight to be gained through new model analysis.
|
|
| 4. |
- Janssen, Annette B. G., et al.
(författare)
-
Exploring, exploiting and evolving diversity of aquatic ecosystem models : a community perspective
- 2015
-
Ingår i: Aquatic Ecology. - : Springer Science and Business Media LLC. - 1386-2588 .- 1573-5125. ; 49:4, s. 513-548
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.
|
|
| 5. |
- Metson, Genevieve, 1988-, et al.
(författare)
-
Socio-environmental consideration of phosphorus flows in the urban sanitation chain of contrasting cities
- 2018
-
Ingår i: Regional Environmental Change. - Heildelberg : Springer. - 1436-3798 .- 1436-378X. ; 18:5, s. 1387-1401
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding how cities can transform organic waste into a valuable resource is critical to urban sustainability. The capture and recycling of phosphorus (P), and other essential nutrients, from human excreta is particularly important as an alternative organic fertilizer source for agriculture. However, the complex set of socio-environmental factors influencing urban human excreta management is not yet sufficiently integrated into sustainable P research. Here, we synthesize information about the pathways P can take through urban sanitation systems along with barriers and facilitators to P recycling across cities. We examine five case study cities by using a sanitation chains approach: Accra, Ghana; Buenos Aires, Argentina; Beijing, China; Baltimore, USA; and London, England. Our cross-city comparison shows that London and Baltimore recycle a larger percentage of P from human excreta back to agricultural lands than other cities, and that there is a large diversity in socio-environmental factors that affect the patterns of recycling observed across cities. Our research highlights conditions that may be "necessary but not sufficient" for P recycling, including access to capital resources. Path dependencies of large sanitation infrastructure investments in the Global North contrast with rapidly urbanizing cities in the Global South, which present opportunities for alternative sanitation development pathways. Understanding such city-specific social and environmental barriers to P recycling options could help address multiple interacting societal objectives related to sanitation and provide options for satisfying global agricultural nutrient demand.
|
|
| 6. |
- Mooij, Wolf M., et al.
(författare)
-
Modeling water quality in the Anthropocene : directions for the next-generation aquatic ecosystem models
- 2019
-
Ingår i: Current Opinion in Environmental Sustainability. - : Elsevier BV. - 1877-3435 .- 1877-3443. ; 36, s. 85-95
-
Forskningsöversikt (refereegranskat)abstract
- Everything changes and nothing stands still (Heraclitus). Here we review three major improvements to freshwater aquatic ecosystem models - and ecological models in general - as water quality scenario analysis tools towards a sustainable future. To tackle the rapid and deeply connected dynamics characteristic of the Anthropocene, we argue for the inclusion of eco-evolutionary, novel ecosystem and social-ecological dynamics. These dynamics arise from adaptive responses in organisms and ecosystems to global environmental change and act at different integration levels and different time scales. We provide reasons and means to incorporate each improvement into aquatic ecosystem models. Throughout this study we refer to Lake Victoria as a microcosm of the evolving novel social-ecological systems of the Anthropocene. The Lake Victoria case clearly shows how interlinked eco-evolutionary, novel ecosystem and social-ecological dynamics are, and demonstrates the need for transdisciplinary research approaches towards global sustainability.
|
|
| 7. |
- van Grinsven, Hans J. M., et al.
(författare)
-
Losses of Ammonia and Nitrate from Agriculture and Their Effect on Nitrogen Recovery in the European Union and the United States between 1900 and 2050
- 2015
-
Ingår i: Journal of Environmental Quality. - : Wiley. - 0047-2425 .- 1537-2537. ; 44:2, s. 356-367
-
Tidskriftsartikel (refereegranskat)abstract
- Historical trends and levels of nitrogen (N) budgets and emissions to air and water in the European Union and the United States are markedly different. Agro-environmental policy approaches also differ, with emphasis on voluntary or incentive-based schemes in the United States versus a more regulatory approach in the European Union. This paper explores the implications of these differences for attaining long-term policy targets for air and water quality. Nutrient surplus problems were more severe in the European Union than in the United States during the 1970s and 1980s. The EU Nitrates and National Emission Ceilings directives contributed to decreases in fertilizer use, N surplus, and ammonia (NH3) emissions, whereas in the United States they stabilized, although NH3 emissions are still increasing. These differences were analyzed using statistical data for 1900-2005 and the global IMAGE model. IMAGE could reproduce NH3 emissions and soil N surpluses at different scales (European Union and United States, country and state) and N loads in the Rhine and Mississippi. The regulation-driven changes during the past 25 yr in the European Union have reduced public concerns and have brought agricultural N loads to the aquatic environment closer to US levels. Despite differences in agro-environmental policies and agricultural structure (more N-fixing soybean and more spatially separated feed and livestock production in the United States than in the European Union), current N use efficiency in US and EU crop production is similar. IMAGE projections for the IAASTD-baseline scenario indicate that N loading to the environment in 2050 will be similar to current levels. In the United States, environmental N loads will remain substantially smaller than in the European Union, whereas agricultural production in 2050 in the United States will increase by 30% relative to 2005, as compared with an increase of 8% in the European Union. However, in the United States, even rigorous mitigation with maximum recycling of manure N and a 25% reduction in fertilizer use will not achieve the policy target to halve the N export to the Gulf of Mexico.
|
|
