The Witi protection zone is a cantonal agricultural and conservation zone north of the Aare river between Grenchen and Solothurn in the Swiss canton of Solothurn. "Witi" is the Solothurn dialect and means "wideness".
The zone was established by law in 1994. It is located in an area of scenic beauty, is a migratory bird and waterfowl reserve of international importance and is home to Switzerland's hare chamber, an above-average population of hares. The largest area of this is the Grenchenwiti. The protection zone may only be used extensively for agricultural purposes. There are also conflicts of use in the area of recreational activities, which are being attempted to be resolved through regulation in the sense of a compromise (concentration of recreational use). In certain areas, the protection of nature takes priority, and attempts are being made to consistently enforce this.
The Witi landscape is originally a product of the last ice age, when the entire area was covered in ice by the Rhone glacier. When the lake receded due to warming, Lake Solothurn was formed around 12,000 years ago, the level of which was around 20 metres above today's Witi. When Lake Solothurn retreated, the Witi remained as the lake bed alongside the Aare. Until the Jura water correction, the area was a frequently flooded floodplain and swamp landscape where agriculture was only possible under difficult conditions.
Between 1980 and 1995, 97 breeding bird species were observed in the Witi, 37 of which were on the Swiss Red List of endangered species, as well as 150 migratory and winter guest species. Due to the frequent pools of water in the cultivated land, the Witi developed into the third most important wader resting place in Switzerland. It is noteworthy that the majestic osprey is also observed relatively frequently, preferably in spring, as a migrant; some of the birds even spend the night in trees along the banks of the Aare. The black stork is also an irregular migrant, although the animals occasionally and temporarily stay in the white stork enclosure of the Altreu stork settlement. The nightingale, which is notable for its beautiful song, is also a frequent breeding bird in the Altreuer Witi.