We tested how sediment trapping by hydroelectric dams affects tropical estuaries by comparing two dammed and two undammed rivers on Mexico’s Pacific coast. We found that dams demonstrably affected the stability and productivity of the estuaries. The two rivers dammed for hydroelectricity had a rapid coastal recession (between 7.9 and 21.5 ha year−1) in what should otherwise be an accretional coastline. The economic consequences of this dam-induced coastal erosion include loss of habitat for fisheries, loss of coastal protection, release of carbon sequestered in coastal sediments, loss of biodiversity, and the decline of estuarine livelihoods. We estimate that the cost of the environmental damages a dam can cause in the lower part of basin almost doubles the purported benefits of emission reductions from hydroelectric generation.

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El objetivo de este trabajo es dar conocer los representantes del género Ephedra en México y su distribución a nivel nacional. En el territorio de la República existen ocho especies de Ephedra en el norte y centro del país: Ephedra antisyphilitica, E. aspera, E. californica, E. compacta, E. nevadensis, E. pedunculata, E. torreyana y E. trifurca. Ephedra compacta es la única endémica de México y la de mayor distribución en su superficie. Se elaboró una clave, descripciones y mapas de repartición geográfica de las especies. Se encontró que las poblaciones de Ephedra en México se presentan entre los 0 y 2800 m de altitud, en matorral xerófilo, pastizal y bosque espinoso, principalmente.Palabras clave: distribución geográfica, Ephedra, México, taxonomía. ABSTRACTThis research seeks to determine the number of species of Ephedra in Mexico and their distributions in the national territory. Eight species of Ephedra are distributed in North and Central Mexico: Ephedra antisyphilitica, E. aspera, E. californica, E. compacta, E. nevadensis, E. pedunculata, E. torreyana and E. trifurca. Ephedra compacta is the only species endemic to Mexico and the one with the most widely distribution over the country. A key, descriptions for each of the species, and distribution maps are presented. Ephedra species are found between 0 and 2800 m above sea level, mostly in xerophytic scrublands, grasslands, and thorn forests.

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