As shown there are quite a lot of methods in use, some of them well adjusted to special questions others related to more general tasks. As already mentioned in the introduction some techniques are not mentioned here or they are not presented in detail. The main focus of this presentation is on the frequency resp. ecological approach for air quality assessment with lichens. It terms out that both methods have their assets and drawbacks; however, to enhance the comparability between surveys in europe (or at least in central europe) a uniform methodology is urgently needed otherwise bioindication as a powerfull tool will not get the attention it owes. In other words, we need to harmonize the different techniques everywhere in use in order to establish bioindication/biomonitoring with lichens as an additional tool beneath technical measurements on a european scale.
According to this, we should keep the words by Louis Le Bois (quoted from http://www.bgbm.de/ial/321/forum.html) in mind:
„...at the end, I do not see any relevant differences between the two methods: the frequency data deriving from the [VDI] can be (almost always are!) organized into a matrix of species and relevés, which can be processed exactly as a matrix of phytosociological relevés. The two approaches should not be used together, they should be merged into a single methodology.“
In fact, there are already attempts to create a europeanwide "guideline" for bioindication combining both approaches; due to the high variability within europe resulting in different nation-specific demands the european guideline will be a framework leaving freedom for national adjustment.
Today, under the impression of short budgets, bioindication is sometimes faced with rejection as e.g. local authorities are not willing to pay for "weak" biological data. Often "hard facts" provided by analysing machines are preferred. But just today is the right time to use bioindicators to detect the impacts caused by the complex "cocktail" of pollutants. Additional to technical measurements we need knowledge about the effects of traffic, industrial and aricultural emissions which can be best obtained by organismns.
Roofing a method for bioindication with lichens under the EC will bring this technique to a high standard which in turn will hopefully enhance the acceptance of this approach at administrative bodies.