It is currently a wildlife preserve, though urban development posed a serious threat to the lake and its environs during the 1980s and early 1990s.

[2] Østensjøvannet is well known for its birdlife, and over 200 different species of birds have been sighted at or near the lake, quite a significant number by Norwegian standards.

Abildsø gård, located on the lake's west side, was Norway's second farm school.

In 2002, the Oslo city council passed plans for the "Østensjøvannet Environmental Park", which in effect preserves the various habitats and "green areas" surrounding the lake.

[citation needed] Situated inside the Oslo city limits, surrounded on all sides by built-up areas, has put a considerable strain on the lake, both in terms of pollution (especially caused by leaks from less-than-perfectly maintained sewage systems) and plans for using the fields and forested areas surrounding the lake for various purposes, including housing, a cemetery and even a small golf course.