The opening of the Suez Canal in 1869 created the first salt-water passage between the Mediterranean and Red seas. The Red Sea is about higher than the eastern Mediterranean , so the canal serves as a tidal strait that pours Red Sea water into the Mediterranean. The Bitter Lakes, which are hypersaline natural lakes that form part of the canal, blocked the migration of Red Sea species into the Mediterranean for many decades, but as the salinity of the lakes gradually equalised with that of the Red Sea, the barrier to migration was removed, and plants and animals from the Red Sea have begun to colonise the eastern Mediterranean. The Red Sea is generally saltier and more nutrient-poor than the Atlantic, and the direction of flow is generally from the Red Sea to the Mediterranean, so the Red Sea species have advantages over Atlantic species in the salty and nutrient-poor eastern Mediterranean. Accordingly, most Red Sea species invade the Mediterranean biota, and only few do the opposite. This migratory phenomenon is called Lessepsian migration (after Ferdinand de Lesseps) or "Erythrean invasion". The construction of the Aswan High Dam across the River Nile in the 1960s reduced the inflow of freshwater and nutrient-rich silt from the Nile into the eastern Mediterranean, making conditions there even more like the Red Sea, worsening the impact of the invasive species.

Invasive species originated from the Red Sea and introduced into the Mediterranean by the construction of the canal have become a major component of the Mediterranean ecosystem, and have serious impacts on the Mediterranean ecology, endangering many local and endemic Mediterranean species. Currently about 300 species from the Red Sea have been identified in the Mediterranean Sea, and there are probably others yet unidentified. The Egyptian government's intent to enlarge the canal have raised concerns from marine biologists, fearing that this will worsen the invasion of Red Sea species in the Mediterranean. .

Construction of the Suez Canal was preceded by cutting a small fresh-water canal from the Nile delta along Wadi Tumilat to the future canal, with a southern branch to Suez and a northern branch to Port Said. Completed in 1863, these brought fresh water to a previously arid area, initially for canal construction, and subsequently facilitating growth of agriculture and settlements along the canal. 


Canals dug by Necho, Darius I and Ptolemy
Suez Crisis
Old Cairo to the Red Sea
Environmental impact