The wetland at Is-Simar is one of the few remaining habitats of its type in the Maltese islands. Such habitats are therefore the only refuge left for a number of endangered or rare species such as the killifish (Aphanius fasciatus) and various species of flora. Six bird species have so far been recorded to breed at Is-Simar. In the vicinity of the wetland area, one finds other important habitats such as the olive grove and garigue which besides their ecological value on their own merits are also important in supporting the diversity within the wetland.

The surrounding embankment is planted with various species of indigenous trees, both along the path and also overlooking the marshland. It is gradually forming a thick hedgerow and is eventually turning into a rich habitat for several species of flora and fauna.

Before the conversion into a nature reserve in 1992, Is-Simar was an abandoned area primarily due to human disturbance. The original marshland vegetation was completely degraded where only a small remnant remained.

Mepa scheduled Is-Simar as an Area of Ecological Importance and Site of Scientific Importance as per Government Notice No. 1070/06 in the Government Gazette dated December 19, 2006, followed by a minor revision in 2008 (G.N. No. 371/08).