chapter - Atmospheric and Oceanic Science

The main services and problems of water resource
8.2.2. Environment and ecosystem vulnerabilities
The quantity and the quality of water have a direct relation and constitute a
very important factor for the biological diversity. Therefore, changes in the water
quality or its absence can cause negative impacts on biodiversity.
As an example, the potential problems in the biodiversity of Paraguay will be
discussed here. It includes numerous species of mammals, birds, fish, invertebrates,
plants and planktonic microorganisms that are distributed in a wide scale of terrestrial,
aquatic and marshy environments. Gamarra de Fox et al. (1997) estimate that
in this country there are l228 species of vertebrates among mammals, birds, reptiles,
amphibians and fish of which 50% would have conservation problems. It is
considered that 29 species of flora and forty of fauna are in danger of extinction.
The marshlands are particularly sensitive to the changes of the hydrology,
especially to the systems of shallow lagoons, which are strongly influenced by the
environmental conditions and by local climate changes. Since wetlands, reservoirs
and creeks are almost dry during extreme ebbs, the wild fauna dies, emigrates, or
develops other survival responses, being the fish, carpinchos (great South
American rodent), crocodiles (caymans) and herons among other species the most
affected by the lack of water. For example, the crocodiles is one of the key species
of commercial value of the Esteros del Iberá (wetlands of the Iberá). The crocodiles
are very territorial and tend to nest in very similar places year after year, for
what their nesting and survival are strongly dependent on water depth (Loureriro
da Silva et al. 2003).
In the case of the ichthyic fauna, if at the very moment of reproduction the
hydrometric levels are high enough, the juveniles enter and develop in the flood
valleys of the rivers, where they find shelter and food. On the contrary if during the
reproductive phase hydrometric levels are low, the juveniles would not have the
possibility of getting into the above mentioned zones, and as a consequence it is
very likely for this set of offsprings will not prosper. This happens especially in the
migrating species such as sábalo, surubi, bogas, gilded, bagres and therefore, the
variability and seasonality of the streamflows is of crucial importance for the population
of these species.
Under the Climatic Change scenario of increase of the variability of the rainfall
and therefore of the river flows, the effects on biodiversity and in the number
of subjects of important species of economic value would be significant. This scenario
is probable as will be discussed for the case of the navigation.
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