How can decentralized individual decisions inefficiently reduce the ability of biodiversity to mitigate ecological and environmental variability and then its “natural insurance” role? In this article we present a simple theoretical set-up to address this question and to evaluate some policy options.

We study a model of strategic competition among farmers for the conversion of a natural forest to agricultural land. Unconverted forest land allows to conserve biodiversity, which contributes to reducing the volatility of agricultural production. Agents' utility is given in terms of a Kreps Porteus stochastic differential utility capable of disentangling risk aversion and aversion to fluctuations.

We characterize the land used by each farmer and her welfare at the Nash equilibrium, we evaluate the over-exploitation of the land and the agents' welfare loss compared to the socially optimal solution and we study the drivers of the inefficiencies of the decentralized equilibrium.

After characterizing the value of biodiversity in the model, we use it to obtain a decomposition which helps to study the policy implications of the model by identifying in which cases the allocation of property rights is preferable to the introduction of a tax on land conversion. Our results suggest that enforcing property rights is more relevant in case of stagnant economies while taxing land conversion may be more suited for rapidly developing economies.

分散的个人决策如何低效地降低生物多样性减轻生态和环境变化的能力，进而降低其“自然保险”的作用？在本文中，我们提出了一个简单的理论设置来解决这个问题并评估一些政策选择。

我们研究了农民之间将天然林转变为农用地的战略竞争模型。未转化的林地可以保护生物多样性，这有助于减少农业生产的波动。代理的效用是根据 Kreps Porteus 随机微分效用给出的，该效用能够解开风险厌恶和波动厌恶。

我们在纳什均衡下描述每个农民使用的土地及其福利，与社会最优解相比，我们评估土地的过度开发和代理人的福利损失，并研究分散均衡效率低下的驱动因素。

在表征模型中生物多样性的价值之后，我们使用它来获得分解，通过确定在哪些情况下产权分配比对土地转换征收税更可取，这有助于研究模型的政策含义。我们的研究结果表明，在经济停滞不前的情况下，执行产权更有意义，而对土地转换征税可能更适合快速发展的经济体。