The sea is called "dead" because its high salinity means no macroscopic aquatic organisms such as fish or water plants can live in it, though minuscule quantities of bacteria and microbial fungi are present.

In times of flood, the salt content of the Dead Sea can drop from its usual 35% salinity to 30% or lower. In the wakes of rainy winters the Dead Sea temporarily comes to life. In 1980, after one such rainy winter, the normally dark blue Dead Sea turned red. Researchers from Hebrew University found the Dead Sea to be teeming with a type of algae called Dunaliella. The Dunaliella in turn nourished carotenoid-containing (red-pigmented) halobacteria whose presence is responsible for the color change. Since 1980 the Dead Sea basin has been dry and the algae and the bacteria have not returned in measurable numbers.

Many animal species make their homes in the mountains surrounding the Dead Sea. A hiker can see camels, ibex, hares, hyraxes, jackals, foxes, and even leopards. Hundreds of bird species inhabit the zone as well. Both Jordan and Israel have established nature reserves around the Dead Sea.

The delta of the Jordan river was formerly a veritable jungle of papyrus and palm trees. Flavius Josephus described Jericho as "the most fertile spot in Judea". In Roman and Byzantine times sugarcane, henna, and sycamore all made the lower Jordan valley quite wealthy. One of the most valuable products produced by Jericho was the sap of the balsam tree, which could be made into perfume.

By the nineteenth century Jericho's fertility was a thing of the past.