  ÃstensjÃ¸vannet is a lake in oslo, capital of norway. it is well known for the wide variety of birds and other wildlife that can be found there. it is surrounded by the ÃstensjÃ¸ borough. 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. == the name == ÃstensjÃ¸vannet ("ÃstensjÃ¸ lake") is named after the old ÃstensjÃ¸ farm (norse austansjÃ³r). the first element is austan 'east of', and the last element is sjÃ³r 'sea, lake'. the farm is situated on the lake's east side. the last element is the finite form of vann 'water; lake'. the meaning of the name is then 'the lake belonging to the farm ÃstensjÃ¸'. == wildlife == ÃstensjÃ¸vannet 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. other wildlife is regularly sighted at the lake, but the variety of species is not much different from surrounding places, such as Ãstmarka. fishing during the summer is forbidden, while ice-fishing is allowed. == cultural history == finds in the area suggest that people may have been living in the area as far back as the stone age. farming in the area started around 500 ad. at various locations surrounding the lake, there are burial mounds from the viking age. abildsÃ¸ farm, located on the lake's west side, was norway's second farm school, and is where minna wetlesen started europe's, and possibly the world's first "household"-school where girls and young women could learn about running a household and performing the various tasks related to it. == environmental issues == 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. the lake itself has been a wildlife preserve since 1992, while abildsÃ¸ farm was preserved by the norwegian riksantikvar in 1997. june 11, 2002, the oslo city council passed plans for the "ÃstensjÃ¸vannet environmental 
Lakes_of_Oslo Nature_reserves_in_Norway