Valuation of natural capital under uncertain substitutability

Natural capital is complex to value notably because of the high uncertainties surrounding the substitutability of its future ecosystem services. We examine a Lucas economy in which a consumption good is produced by combining different inputs, one of them being an ecosystem service that is partially substitutable with other inputs. The growth rate of these inputs and the elasticity of substitution evolve in a stochastic way. We characterize the socially efficient ecological discount rates that should be used to value future ecosystem services at different time horizons. We show that the inverse of the elasticity of substitution can be interpreted as the CCAPM beta of natural capital. We also show that any increase in risk of this beta reduces the ecological discount rate. If our collective beliefs about the elasticity of substitution of ecosystem services are Gaussian, the ecological discount rates go to minus infinity for finite maturities. In that case, a marginal increase in natural capital has an infinite value. We provide a realistic calibration of the model that is coherent with observed asset prices by using the model of extreme events of Barro (2006). The bliss maturity for infinite discount factors is less than 100 years in this calibration.     

关于水中总α总β放射性测量监测方法改进的探讨

目前国内关于水中总α、总β放射性测量相关标准还不够细化,操作规程在一些细节方面还存在部分问题,为减小实验误差,提高实验准确度,对监测方法进行了改进.对前期水中总α、总β放射性监测的实验过程进行经验总结,对实验条件进行优化改进,通过回收率和准确度对实验结果进行验证.对水中总α、总β放射性监测实验过程中的水样放置时间、蒸发...