Ecosystem loss assessment following hydroelectric dam flooding: The case of Yacyretá, Argentina

• We assessed ecosystem loss due to the Yacyretá dam flooding, Argentina.
• We compared two land use maps: pre (1987) and post (2011) dam flooding.
• Water bodies increased by 15% in detriment of wetlands, grasslands and native forests.
• Ecosystem loss differs in type and magnitude up and downstream of the dam.
• Results can help improve the current network of compensatory reserves.

The Yacyretá dam is one of the most important hydroelectric projects in La Plata Basin. As a consequence of the filling of the reservoir to its final height of 83 m, approximately 1,076 km2 of terrestrial and riparian ecosystems were flooded in Argentina and Paraguay. In order to evaluate the ecosystem loss due to this impounding, we generated two maps of land use/land cover from Landsat satellite images: 1987 (prior to the dam) and 2011 (after the final height was reached). We applied a post classification method and tested the gain, loss, and net change of natural and anthropic ecosystems in the study area with a cross tabulation matrix. Water bodies were the land cover type that showed the greatest degree of change, increasing 14.8% between periods. This was in detriment of, primarily, wetlands by 7.5%, grasslands by 4.0%, and native forests by 2.8%. However, sandbanks presented the highest probability of transition to another land class and, thus, correspond to the most vulnerable land cover in the study area. Also, we detected a differential ecosystem loss, both in type and magnitude, up and downstream of the dam. Our work is the first one to address ecosystem loss in the Yacyretá area and our results should help to improve management policies, such as the design of the current network of compensatory reserves.