Accounting for the uncertainty in nitrogen deposition estimates in support of policy

Woodward, Huw ORCID: https://orcid.org/0000-0001-8994-8057; Fonseca, Elizabeth Ramos ORCID: https://orcid.org/0000-0001-8159-1372; Oxley, Tim; Rowe, Ed C. ORCID: https://orcid.org/0000-0003-4784-7236; Vieno, Massimo ORCID: https://orcid.org/0000-0001-7741-9377; Nemitz, Eiko ORCID: https://orcid.org/0000-0002-1765-6298; ApSimon, Helen. 2025 Accounting for the uncertainty in nitrogen deposition estimates in support of policy. Environmental Research, 121519. 10.1016/j.envres.2025.121519

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Official URL: https://doi.org/10.1016/j.envres.2025.121519

Abstract/Summary

•Deposition of reactive nitrogen (Nr) onto sensitive habitats in exceedance of Critical Load (CL) thresholds can drive biodiversity loss and affect ecosystem function. Nr deposition is a highly complex process that is difficult to measure and model, leading to large uncertainties. •We assess the implications for policy development and target setting of the large range in estimates provided by different modelling approaches. •We considered three UK models (UKIAM, EMEP4UK, CBED), used to inform national policy and responses to the UN-ECE Air Convention. We used a scaling method to project the range in current estimates to future scenarios, and a risk-based approach to provide a probabilistic assessment of exceedances. We considered two future scenarios, a 2040 baseline and a 2040 high ambition technological measures scenario, in relation to a 2018 baseline. •The 2018 baseline CL excedances are highly dependent on the model used – Average Accumulated Exceedance of 1.3-9.1 kg.N.ha-1.yr-1 across all habitats. The relative reduction in exceedances for future scenarios also depends on the model, with a range of 30-66% achieved by 2040 for the high ambition scenario, posing a challenge for target setting. Despite this, it’s clear that a much greater level of ambition is required to protect the majority of habitat areas. Our risk-based approach shows that implementing only technological measures is likely to leave most areas in exceedance in 2040. •This uncertainty in the assessment of Nr deposition and the benefits of abatement measures poses a challenge for policy development that is not unique to the UK.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.envres.2025.121519
UKCEH and CEH Sections/Science Areas:	Land-Atmosphere Interactions (2025-)
ISSN:	0013-9351
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	nitrogen, deposition, air pollution, critical load, habitat, biodiversity, policy
NORA Subject Terms:	Ecology and Environment Atmospheric Sciences
Date made live:	08 Apr 2025 09:29 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539222

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.envres.2025.121519

UKCEH and CEH Sections/Science Areas:

Land-Atmosphere Interactions (2025-)

ISSN:

0013-9351

Additional Information. Not used in RCUK Gateway to Research.:

Open Access paper - full text available via Official URL link.

Additional Keywords:

nitrogen, deposition, air pollution, critical load, habitat, biodiversity, policy