Environmental degradation and opportunities for riparian rehabilitation in a highly urbanized watershed: the Matanza-Riachuelo in Buenos Aires, Argentina.

GUIDA JOHNSON B; ZULETA G.; FAGGI A.

České Budějovice

Congreso; 8th European Conference on Ecological Restoration.; 2012

SER

Degradation imposed by human activities on rivers is still considerable in many parts of the world and that is the case of Matanza-Riachuelo watershed, one of the most polluted in Argentina. It is occupied by one of the 27 world’s megacities (Buenos Aires) downstream, while in the upper basin agriculture almost completely replaced natural grasslands. In order to evaluate the condition of streams and determine opportunities for rehabilitation, we conducted a stratified random sampling of 83 sites regarding anthropic impacts and riparian vegetation. We determined that 65% presented at least one sign of canalization: lower basin was associated with concrete slopes, middle basin with straighten banks and upper basin with mounds resulting from dredging. Other anthropogenic impacts were related to predominant land uses in each region: stormwater discharges in the lower basin, bridges and roads in the middle, and access of livestock to riversides in the upper. Regarding riparian vegetation, 45% of the identified species were exotic and three riparian communities were recognized: semi-natural banks, dominated by grasslands with equal cover of native and exotic species, “herbaceous” and “woody” river banks. The cover of exotic species in the last two doubled the natives. A detailed characterization of streams is appropriate in order to identify opportunities for rehabilitation according to the current state of degradation: from geomorphological “re-naturalization” of the sinuosity of streams to exotic species control and reintroduction of native plants. We discuss the potential of these techniques as part of the agenda of municipal authorities responsible for watershed management.