My good friend Roberto Cesaro, a young italian writer and poet, has recently brought to my attention the ecological problem of the pointless deforestation on the Piave river in the Veneto region of the North East of Italy. In a section of the river called "Golena" the local government has decided to enact a plan of deforestation which involves cutting the trees which run along the river. The rationale for the tree cutting is flood prevention. If this was justified by engineering studies, and a substantial amount of people would loose their home and agricultural trade, then there would be a reasonable case for intelligent deforestation. Unfortunately, according to the assessment of many very well qualified and intelligent italian engineers (the experts which local government should trust), this is quite clearly not the case. The question is clearly political too, but I want to mainly stick to the scientific evidence on which the political decisions should be based.
Now, if you've been to the area (e.g. if you've looked out of the window from the Ryanair bus from Venice "Treviso" airport to Venice), you will know that the Veneto is very flat agricultural landscape, where, due to histortical deforestation, very few trees remain. A similar extremely tree-less morphology occurs in some areas of the South East of England, to make another example. From the point of view of biodiversity, the absence of trees can significantly affect the variety of species which inhabit a certain area. The ecology of the problem is complicated, but it is quite obvious that with no trees, birds can only nest on the ground, so fewer species will live in a tree-less area; or, without trees, there is less nutrient recycling and the soil grows poor, driving away all the species that depend on the various members of the food chain (e.g. mushrooms won't grow, as my friend Marco, a Veneto who lives in Cambridge, was lamenting). So this is bad for local biodiversity, since it can turn fertile land into a barren environment with no shelter for species. Thus ecologically, the case is clearly for not cutting trees, especially if the trees have been there a few years and they are no longer non-native "big weeds" dangerous for other trees or plants.
What about the engineering problem? I don't really have much understanding of the effect of trees in a flood. I think the local Veneto goverment's idea, that of their advisory panels of engineers (the other qualified and intelligent engineers who think the case is for cutting), is that since the flood frequency is increasing, if you make the river wider the carrying capacity of the river can be increased, reducing the risk of floods. I need to think about the physics of this for myself, but the wisdom of many other engineers is that this won't do anything, other solutions can be found, and the trees are being cut for no reason, with the significant ecological impact discussed above. The engineering case against cutting needs to be scientifically and politically unassailable. E.g. if the story reached EU level, international pressure could help put pressure on the local government to stop cutting the trees. More in future posts, but I include in the next two posts the text of the case (in Italian for the moment) made by the "Gruppo di Cittadini in Difesa del Piave" who believe (like me) that the trees should not be cut. Roberto and his girlfriend Giuliana have played a critical role in coordinating the protest campaign.
