Variable flooding conditions, associated with seasonal flooding or daily tidal fluctuations, create a complex mosaic of wetland and aquatic habitats. Although wetlands occupy only a small area in comparison with terrestrial habitats, they support a large number of rare plant and animal species in relation to their size. By itself, the network of protected areas is not sufficient to maintain the overall biodiversity of the St. Lawrence. This network not only covers a relatively limited area but will always contain major gaps. Indeed, it is already impossible to find habitats of adequate size available for conservation purposes in the most urbanized regions.
Natural communities are dynamic.
They undergo rapid changes when they are subjected to natural disturbances and evolve gradually in response to factors such as climate change or plant succession. To prevent the net and irreversible loss of biodiversity, not only must the most vulnerable species be protected but, more importantly, the physical conditions and ecological processes under which all the species in the community have evolved must be maintained. Corridors are not only required at present for the movement of species with large home ranges but are essential for ensuring gene flow between populations. This helps avoid the isolation and subsequent extirpation of populations of specialist species, which may not be able to adapt to future conditions in the existing protected sites. It has been known for some time that all organisms and ecosystems cannot be preserved under satisfactory conditions for the long term based solely on the existence of the classical type of protected areas, although this usually has been the only approach used up to now.