Programme for the Monitoring and Evaluation of Long Range Air Pollutants in Europe, National Crop Loss Assessment Network). However, these networks have been largely limited to monitoring the deposition of a specific chemical or class of compounds (e.g., acid deposition, ozone). For this reason, they have provided very limited information on the full suite of stresses and benefits experienced by an ecosystem from atmospheric deposition and, thus, on the long-term effects of this deposition. With the development of new deposition measurement techniques, it should be possible to design more comprehensive atmospheric deposition and exposure monitoring networks. Implementation of these networks for key ecosystems and biomes (e.g., at Long-Term Ecological Research sites) would provide a long-term record of atmospheric deposition; with co-located ecological monitoring, this record would no doubt prove useful in establishing causal relationships between atmospheric deposition and ecosystem vitality and succession.
Even with reliable and fully evaluated deposition measurement techniques, it will never be possible to measure dry and wet fluxes for all species of interest over all ecosystems of interest, over all time. For this reason, process-oriented field studies, involving observations of fluxes under a carefully selected range of conditions, have to be undertaken in order to identify the factors that control such fluxes. With these factors identified, algorithms and parameterizations describing deposition fluxes can be developed, tested by further observations, and incorporated into regional and global atmospheric chemistry models, as well as integrated atmospheric-biospheric response models.