Estimating nitrogen risk to Himalayan forests using thresholds for lichen bioindicators

Himalayan forests are biodiverse and support the cultural economic livelihoods of their human communities. They bounded to south by Indo-Gangetic Plain, which has among highest concentrations atmospheric ammonia globally. This source excess nitrogen pushes northwards into Himalaya, generating concern that will be impacted. To estimate extent is impacting we focussed on lichen epiphytes, a well-established bioindicator for pollution. First, reviewed published literature describing thresholds (critical levels loads) at epiphytes affected, identifying mean confidence intervals based previous research conducted across diverse set biogeographic ecological settings. Second, used estimates from previously chemistry models (EMEP-WRF UKCA-CLASSIC) projected Himalaya with contrasting spatial resolution timescales characterise model variability. Comparing epiphyte critical loads projections, created preliminary impacted nitrogen; this equated c. 80–85% 95–98% respect total deposition, respectively. Recognising lichens one most sensitive bioindicators pollution, our new synthesis studies topic generated risk nitrogen. desk-based study now requires verification through biological surveillance, provide key recommendations.