Editing Suez Canal (section)

== Environmental impact ==
{{Main |Lessepsian migration}}
The opening of the canal created the first salt-water passage between the Mediterranean Sea and the Red Sea. Although the Red Sea is about {{cvt|1.2|m|ft|0}} higher than the eastern Mediterranean,<ref>Madl, Pierre (1999). [http://biophysics.sbg.ac.at/lm/lesseps.htm Essay about the phenomenon of Lessepsian Migration] {{Webarchive|url=https://web.archive.org/web/20160731063505/http://biophysics.sbg.ac.at/lm/lesseps.htm |date=31 July 2016 }}, Colloquial Meeting of Marine Biology I, Salzburg, April 1999 (revised in Nov. 2001).</ref> the current between the Mediterranean and the middle of the canal at the [[Bitter Lakes]] flows north in winter and south in summer. The current south of the Bitter Lakes is tidal, varying with the tide at Suez.<ref name=rsp/> The Bitter Lakes, which were hypersaline natural lakes, 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.<ref>{{Cite book |last=Nations |first=Food and Agriculture Organization of the United |url=https://books.google.com/books?id=jR4_EAAAQBAJ&dq=The+Bitter+Lakes,+which+were+hypersaline+natural+lakes,+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.&pg=PA32 |title=Non-indigenous species in the Mediterranean and the Black Sea |date=2021-07-29 |publisher=Food & Agriculture Org. |isbn=978-92-5-134775-1 |language=en}}</ref>

The Red Sea is generally saltier and less nutrient-rich than the Mediterranean, so that Erythrean species will often do well in the 'milder' eastern Mediterranean environment. To the contrary very few Mediterranean species have been able to settle in the 'harsher' conditions of the Red Sea. The dominant, south to north, migratory passage across the canal is often called [[Lessepsian migration]] (after Ferdinand de Lesseps) or "Erythrean invasion". The recent construction by the Egyptian government of a major canal extension – allowing for two-way traffic in the central section of the canal and finally implemented in 2015 – raised concerns from [[marine biologist]]s, who fear that it will enhance the arrival of Red Sea species in the Mediterranean.<ref>Galil and Zenetos (2002)</ref>

Exotic species from the Indo-Pacific Ocean and [[introduced species|introduced]] into the Mediterranean via the canal since the 1880s have become a significant component of the Mediterranean ecosystem. They already impact its ecology, endangering some local and [[endemism|endemic]] species. Since the piercing of the canal, over a thousand species from the Red Sea—plankton, seaweeds, invertebrates, fishes—have been recorded in the Mediterranean, and many others will clearly follow. The resulting change in biodiversity is without precedent in human memory and is accelerating: a long-term cross-Basin survey engaged by the [[Mediterranean Science Commission]] recently documented that in the first twenty years of this century more exotic fish species from the Indian Ocean had reached the Mediterranean than during the entire 20th century.<ref>Atlas of Exotic Fishes in the Mediterranean Sea. 2nd Edition. 2021. (F. Briand Ed.) CIESM Publishers, Paris, Monaco 366 p.[https://ciesm.org/catalog/index.php?article=2021]</ref>

Historically, the construction of the canal was preceded by cutting a small fresh-water canal called [[Sweet Water Canal]] from [[Nile Delta|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.<ref>Britannica (2007)</ref> However the [[Aswan High Dam]] construction across the Nile, which started operating in 1968, much reduced the inflow of freshwater and cut all natural nutrient-rich silt entering the eastern Mediterranean at the [[Nile Delta]].