We analyze the implications of transboundary pollution externalities on environmental policymaking in a spatial setting, in which pollution diffuses across the global spatial economy independently of the specific location in which it is originally generated. This framework gives rise to a simple regional optimal pollution control problem allowing us to compare the global and local solutions in which, respectively, the transboundary externality is and is not taken into account in the determination of the optimal policy by individual local policymakers. We show that it is not obvious that transboundary externalities are a source of inefficiency per se since this is strictly related to the spatial features of the initial distribution of pollution. If the initial pollution distribution is spatially homogeneous then the local and global solutions will coincide and thus no efficiency loss will arise from transboundary externalities, but if it is spatially heterogeneous the local solution will be suboptimal and thus a global approach to environmental problems will be needed to achieve efficiency. From a normative perspective, in this latter (and most realistic) case we also quantify the amount of policy intervention needed at local level in order to achieve the globally desirable goal of pollution eradication in the long run. Our conclusions hold true in a number of different settings, including situations in which the spatial domain is either bounded or unbounded, and situations in which macroeconomic–environmental feedback effects are taken into account.

我们分析了跨界污染外部性对空间环境中环境决策的影响，其中污染在全球空间经济中扩散，独立于其最初产生的特定位置。该框架产生了一个简单的区域最优污染控制问题，使我们能够比较全球和本地解决方案，其中，个别地方决策者在确定最优政策时分别考虑和不考虑跨界外部性。我们表明，跨界外部性本身并不明显是低效率的根源，因为这与污染初始分布的空间特征密切相关。如果最初的污染分布在空间上是同质的，那么局部和全局解决方案将重合，因此跨界外部性不会引起效率损失，但如果它在空间上异质性，局部解决方案将是次优的，因此需要对环境问题采取全局方法以达到效率。从规范的角度来看，在后一种（也是最现实的）情况下，我们还量化了地方层面所需的政策干预量，以实现全球长期根除污染的理想目标。我们的结论适用于许多不同的环境，包括空间域有界或无界的情况，以及考虑宏观经济-环境反馈效应的情况。