TY - JOUR

T1 - Multiple-year optimization of conservation effort and monitoring effort for a fluctuating population

AU - Yokomizo, Hiroyuki

AU - Haccou, Patsy

AU - Iwasa, Yoh

N1 - Funding Information:
This work was done by the partial support from a JSPS grant-in-aid in Scientific Research to Y.I. E.A. van Ast corrected the English. We are also grateful to the following people for their helpful comments: M. Durinx, J. Greenman, H. Hakoyama, H. Hirakawa, K. Kaji, H. Matsuda, J.A.J. Metz, H.P. Possingham, T. Saitoh, K. Sato, R. Schlicht, H. Seno, K. Tamada, H. Uno, T. Yahara, and K. Yamamura.

PY - 2004/9/21

Y1 - 2004/9/21

N2 - We consider optimal conservation strategies for an endangered population. We assume that juvenile survival is affected by unpredictable environmental fluctuation and can be improved by costly conservation effort. The initial population size is not accurately known at the time that the conservation effort level is chosen, but the uncertainty of its estimate can be reduced by a costly monitoring effort. In a previous paper, we analysed the optimal management strategy that minimizes a weighted sum of extinction probability and economic costs when only a single year is considered. Here we examine the case in which the conservation period lasts for several years by dynamic programming with incompletely observed process states. We study the optimal levels of the conservation and the monitoring efforts, and their dependence on the length of the conservation period and other parameters. The main conclusions are: (1) The optimal conservation effort in the first year depends on the accuracy of the information on the population size in the first year, but is almost independent of the accuracy of the information in later years. (2) When the risk of population extinction is small, the optimal conservation effort increases with the uncertainty of the population size. In contrast when the population is endangered, the optimal conservation effort decreases with the uncertainty of the population size. (3) The optimal conservation and monitoring efforts both increase with the length of the conservation period, provided that the population is relatively safe. However, if the population is endangered, both types of effort become smaller when the conservation period increases.

AB - We consider optimal conservation strategies for an endangered population. We assume that juvenile survival is affected by unpredictable environmental fluctuation and can be improved by costly conservation effort. The initial population size is not accurately known at the time that the conservation effort level is chosen, but the uncertainty of its estimate can be reduced by a costly monitoring effort. In a previous paper, we analysed the optimal management strategy that minimizes a weighted sum of extinction probability and economic costs when only a single year is considered. Here we examine the case in which the conservation period lasts for several years by dynamic programming with incompletely observed process states. We study the optimal levels of the conservation and the monitoring efforts, and their dependence on the length of the conservation period and other parameters. The main conclusions are: (1) The optimal conservation effort in the first year depends on the accuracy of the information on the population size in the first year, but is almost independent of the accuracy of the information in later years. (2) When the risk of population extinction is small, the optimal conservation effort increases with the uncertainty of the population size. In contrast when the population is endangered, the optimal conservation effort decreases with the uncertainty of the population size. (3) The optimal conservation and monitoring efforts both increase with the length of the conservation period, provided that the population is relatively safe. However, if the population is endangered, both types of effort become smaller when the conservation period increases.

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U2 - 10.1016/j.jtbi.2004.04.036

DO - 10.1016/j.jtbi.2004.04.036

M3 - Article

C2 - 15302548

AN - SCOPUS:4043179096

SN - 0022-5193

VL - 230

SP - 157

EP - 171

JO - Journal of Theoretical Biology

JF - Journal of Theoretical Biology

IS - 2

ER -