INHABIT project

When assessing the deviation from 'natural conditions' - that is the actual impact - we should act considering at least some important elements.
It is possible that indicators and biological metrics commonly used, e.g. for the official WFD water bodies classification, are affected by both anthropogenic factors (impacts) and habitat factors (effects of natural variations). In this case, the availability of information on habitat and on the relations that connect habitat to biocoenoses and to pressures will allow to discern and quantify impacts from natural variability factors. This is crucial to plan actually useful measures and to evaluate their effectiveness.

• It is likely that different aspects of habitat simultaneously affect aquatic biocoenoses; they should therefore simultaneously evaluated in order to understand the potential of the community and the real effects of pressures.
  
  
• WFD explicitly refers to changes in the abundance of observed taxa. This should express the "quantity" of each taxon. It is therefore obvious that, in order to assess the ecological status when impacts causing the reduction of habitat availability are observed (and not necessarily or not only habitat quality - such as the reduction of flow in the river bed), the associated decrease in the overall abundance should be considered. In other words, it will not be sufficient to evaluate the depletion of taxa (through the evaluation of taxa density), but it may be necessary to assess biological quality through a quantitative factor (e.g. observed compared to expected abundance).
  
  
• Given the importance of habitat quantity, as well as habitat quality, for biotic communities, the use of simple methods able to directly relate quantitative (e.g. water discharge and actual availability of habitat) and qualitative (e.g. ecological status or a related biological component) aspects, should support effective management of water resources.

• It is known that biological elements show a - often relevant - natural variability, even in the absence of anthropogenic disturbances. As previously mentioned, a part of this variability is related to changes in the characteristics of habitats present, which will be more or less suitable to organisms potentially present. In order to reduce variability in the definition of biological reference conditions, these should be quantified by directly considering habitat factors (commonly only partially and roughly included in typological factors, e.g. ‘standard’ and large scale WFD typologies).
  
  
• In the absence of relevant pressures, the presence of a 'good quality' for certain aspects of habitat (e.g. number and diversification) can compensate limiting conditions for other aspects (e.g. extreme conditions); consider, for example, Mediterranean rivers during the summer. Similarly, optimal habitat conditions can mitigate, at least partially, the impact of important alterations (e.g. pollution, reduction in water discharge/level). The knowledge of the most important habitat factors for biological communities and how they are expressed in the environment at the time when the survey is carried out, is therefore very important in the interpretation of the biological data, also in relation to the actual occurrence of impacts.
  
  
• It is desirable that biological metrics dedicated to the assessment of the effects of habitat alteration due to defined pressures (water abstraction, agricultural or artificial land use, presence of artificial structures, reservoir management, etc.), are applied together with those commonly in use, in order to improve available information for defining RBMPs measures and to evaluate their effectiveness. In particular, this will be useful for the selection of additional - and relatively inexpensive – measures, complementary to those already planned and primarily focused on improving quality of aquatic and riparian habitats.

Further details are available in the description of I3 activity group.