Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Proc Natl Acad Sci U S A. 2012 Apr 24;109(17):6484-9. doi: 10.1073/pnas.1114653109. Epub 2012 Mar 26.
Climate change is likely to alter the spatial distributions of species and habitat types but the nature of such change is uncertain. Thus, climate change makes it difficult to implement standard conservation planning paradigms. Previous work has suggested some approaches to cope with such uncertainty but has not harnessed all of the benefits of risk diversification. We adapt Modern Portfolio Theory (MPT) to optimal spatial targeting of conservation activity, using wetland habitat conservation in the Prairie Pothole Region (PPR) as an example. This approach finds the allocations of conservation activity among subregions of the planning area that maximize the expected conservation returns for a given level of uncertainty or minimize uncertainty for a given expected level of returns. We find that using MPT instead of simple diversification in the PPR can achieve a value of the conservation objective per dollar spent that is 15% higher for the same level of risk. MPT-based portfolios can also have 21% less uncertainty over benefits or 6% greater expected benefits than the current portfolio of PPR conservation. Total benefits from conservation investment are higher if returns are defined in terms of benefit-cost ratios rather than benefits alone. MPT-guided diversification can work to reduce the climate-change-induced uncertainty of future ecosystem-service benefits from many land policy and investment initiatives, especially when outcomes are negatively correlated between subregions of a planning area.
气候变化很可能改变物种和栖息地类型的空间分布，但这种变化的性质是不确定的。因此，气候变化使得实施标准的保护规划范式变得困难。之前的工作已经提出了一些应对这种不确定性的方法，但没有利用风险多样化的全部好处。我们采用现代投资组合理论（MPT）来优化保护活动的空间定位，以草原湿地地区（PPR）的湿地生境保护为例。这种方法在规划区域的各个子区域之间分配保护活动，以最大化给定不确定性水平下的保护回报，或最小化给定预期回报水平下的不确定性。我们发现，在 PPR 中使用 MPT 而不是简单的多样化，可以在相同风险水平下，每花费一美元实现的保护目标价值提高 15%。基于 MPT 的投资组合在收益方面的不确定性比当前 PPR 保护投资组合低 21%，或预期收益高 6%。如果回报是根据效益-成本比而不是仅仅是收益来定义的，那么保护投资的总收益会更高。当规划区域的各个子区域之间的结果呈负相关时，MPT 指导的多样化可以有效降低许多土地政策和投资计划未来生态系统服务效益的气候变化引起的不确定性。
