Preventing over-exploitation in a dynamic CPR game with heterogeneous players: A comparison of awareness, communication and advice in the lab

Rivalry in extractive CPR, like groundwater, implies that agents extract as muchas they need, and even more if they fear that others behave the same way (Gardner et al., 1990 ; Walker et al., 1990 and 2000), leading to the 'tragedy of the commons' (Hardin, 1968). Users depleting a groundwater CPR typically face two types of appropriation externalities (Gardner et al., 1997): a static externality, whereby individuals' extraction costs at any given date are affected by the total level of extraction at that date, and a dynamic externality, whereby the extraction cost any later date is affected by past cumulative extractions. Groundwater is a very important source of irrigation water, the latter representing more than 70% of the total water uses on earth (FAO, 2022). In North Africa half of the current groundwater water withdrawals exceed natural rates of water recharge (Mayaux et al., 2022). Maghreb Countries are highly dependent on their groundwater resources for their agricultural development. The public policies of the last decades triggered radical changes in newly irrigated areas (extension areas) and in traditional oases (Kadiri et al., 2022). This resulted in a quick intensification of local agriculture, like in Tunisia, where oases are currently facing sustainability concerns due to "uncontrolled expansion of irrigated areas, overexploitation of groundwater resources, and soil degradation" (Ghazouani et al., 2009 ; Mekki et al., 2013). In Tunisia, the Complex terminal aquifer in Kebili is under the threat of overexploitation, as its exploitation leads to a 1 meter lowering of the watertable/year. This is due to the combination of a very low level of water recharge and high level of water use for irrigation mainly ('Irigui et al., 2021). (French acronym for Agricultural Development Croups), which coexist with newly settled extension farmers. Many GDA farmers have also plots in the extensions, where, like the extension farmers they dig illicit private boreholes t