Juncus has a
cosmopolitan distribution, with species found throughout the world, with the exception of
Antarctica.
Juncus species often prefer wetland habitats, such as salt marshes and seeps.
Juncus species are important members of the ecosystems they inhabit, providing food and creating habitat for many other organisms, including microbes, insects, amphibians, fish, and birds. Certain species have also been shown to alter the often heavily waterlogged soils they grow in around their roots, increasing the oxygen concentration and changing the pH. Beyond this,
Juncus species across their range have been used in diverse ecological studies, including those relating to precipitation effects on marsh species, salt tolerance in brackish wetland plants, the effects of
Juncus presence on plant diversity, and the effects of wetland plants on microbial soil communities. ==Fossil record==