Econ Papers Daily / 期刊论文
可再生自然资源、制度变迁与滞后效应
Renewable Natural Resources, Regime Shift and Hysteresis
摘要
Many of the world’s renewable resources are in decline. Optimal harvests with smooth recruitment is well studied but in recent years, ecologists have concluded that tipping points in recruitment are common. Recruitment with a tipping point has low-fecundity below the tipping point and high-fecundity above. When the discounted value of high-fecundity is sufficiently high, there is a high-fecundity steady-state. This steady-state is stable but in some cases, small perturbations may result in large, temporary reductions in recruitment and harvests. Below the tipping point, a low-fecundity steady-state need not exist. When a low-fecundity steady-state does exist, there is an endogenous tipping (Skiba) point: below, harvests converge to the low-fecundity steady-state and above, an austere harvest policy transitions the renewable resource to high-fecundity recruitment. If there is hysteresis in recruitment, the high steady-state may not be stable. Moreover, if the high-/low-fecundity differential is large then following a downward perturbation, fecundity optimally remains low.
中文摘要
世界上许多可再生资源正在衰退。具有平滑补充机制的最优采伐已有充分研究，但近年来生态学家得出结论，补充过程中的临界点十分常见。存在临界点的补充机制表现为：临界点以下繁殖力低，临界点以上繁殖力高。当高繁殖力的折现值足够高时，存在一个高繁殖力稳态。该稳态是稳定的，但在某些情况下，微小扰动可能导致补充量和采伐量出现大幅暂时性下降。在临界点以下，低繁殖力稳态未必存在。当低繁殖力稳态确实存在时，存在一个内生临界（Skiba）点：在该点以下，采伐量收敛于低繁殖力稳态；在该点以上，一种紧缩性采伐政策将使可再生资源转向高繁殖力补充。若补充过程存在滞后效应，高稳态可能并不稳定。此外，若高/低繁殖力差异较大，则在向下扰动之后，繁殖力最优地保持在低水平。