Effects of different ammonia emission reduction strategies from livestock farming on ambient ammonia concentrations in nature areas: a series of scenario analyses

Excessive nitrogen deposition is a major problem in nature areas, causing soil acidification and eutrophication, which reduces biodiversity. In the Netherlands, most nitrogen originates from ammonia emissions related to agriculture. This study investigates how various ammonia emission reduction strategies affect spatial patterns of livestock-related ambient ammonia levels, focusing on nature areas near a livestock-dense region. The aim is to provide insights into effects of interventions on environmental exposure levels and efficiency of mitigation strategies. Using dispersion modeling, annual average patterns of ambient ammonia levels were estimated per scenario, considering emissions from approximately 4500 farms. Results indicate that scenarios involving significant reductions in ammonia emissions (54–86 %), achieved through technical or management modifications or farm removal, result in substantial reductions (62–87 %) in ambient ammonia levels within nature areas. Targeted strategies aimed at specific sectors that contribute most to ammonia levels in nature areas achieved relatively modest absolute reductions (8–13 %) but generally higher efficiency compared to more generic approaches. Scenario efficiency, defined as the ratio between emission/concentration reduction, varied considerably from 0.5 to 1.3. This variations underscores the importance of assessing spatial ammonia patterns rather than focusing and relying solely on emission reduction expressed in terms of total mass. The efficiency of reduction strategies depends on the geographical distribution of (sector-specific) farms near nature areas, and emission height from these farms. Therefore, combined strategies explicitly targeting these factors, such as integrating spatially focused measures (e.g., zoning) with generic emission reductions, are expected most effective in reducing ammonia concentrations in nature areas.