heat wave. In the same way, if a forester chooses species resistant to climate change today, his future heirs will benefit from this choice because they will have wood to sell.

**However, circumstances do exist in which the private production of adaptation by households or firms (sometimes referred to as "spontaneous adaptation") risks being insufficient,** and where public intervention for adaptation is justified from the point of view of economic theory for reasons of equity and/or efficiency.  The list that follows is adapted from Lecocq and Shalizi (2007).

- **Poor dissemination of available information:** Experience suggests that information that exists on climate change, its impacts and on adaptation options is not available today in sufficiently large quantity, particularly in developing countries.  This creates asymmetrical situations in terms of information that may lead, on the one hand, to maladaptation situations (see Box n°1) and, on the other, may stand in the way of good market operation, create location advantages and produce new inequalities (between and within countries).  Public authorities and the international community have an important role to play in this case in the production of information (fundamental research, R&D) and in the dissemination of this information between countries and to households, firms and local communities within countries.  This point is developed in Section 2.2.1.

- **Barriers to collective action at the local level** : Adaptation often requires considerable cooperation between actors at the local level for the provision of local public goods (irrigation networks, seawalls, etc.).  This is particularly true for the management of transborder resources such as large drainage basins.  Public action and international coordination may be necessary to facilitate negotiations between concerned stakeholders.  Coordination support may be provided, for example, by the setting of standards and norms (Section 2.2.2), as well as by an action on institutions (Section 2.2.3) such as the creation of discussion forums or national or international mediation activities.

- **Decision routines and inadequate consideration of long-term consequences on private investment decisions:** Private investment decisions do not always adequately take long and very long-term consequences into account (for example, future snow conditions in medium-altitude ski resorts), which could justify public action.  In the same way, the provision of basic services by public authorities is often taken for granted, whereas major changes in climate conditions could make these services impossible or too costly (for example, access to water for agriculture on the long-term). This could justify a public action to make it easier to address this new situation.

- **External impacts** : Some adaptation actions are not profitable from the private point of view but may be for the community at large. For example, it may not be profitable for a homeowner to insulate his home to reduce energy consumption linked to airconditioning, whereas the collective benefit is considerable if a large number of homeowners do it.  In contrast, it may be profitable for a developer to build in a floodprone area, whereas the cost of flooding for the community is much greater (pressure on the healthcare system, temporary relocation of flood victims, etc.)<sup>(9)</sup> . **An optimal**

> 9 Many other examples of external impacts linked to adaptation actions exist.  Concerning water, for example, it may be economically viable to increase irrigation for agriculture, but the removal of additional water could have negative effects on other stakeholders (particularly electricity producers) and on ecosystems.  Once again, in relation to water, upstream actions involving drainage basins, particularly at the transnational level, can positively or negatively influence the situation downstream.  In the area of energy, the massive use of air-conditioning or the desalination of seawater can increase energy consumption and lead to tension between adaptation and mitigation.  In contrast, the reinforced insulation

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